| Name | Notes |
|---|---|
| stonewort | Chara spp. (characeae) |
| Key criteria: | Freshwater algae. Tolerates brackish water. brackish |
| no common name | Audouniella (acrosiphoniaceae) |
| Key criteria: | filamentous epiphytic red algae epiphyte |
| no common name | Batrachospermum (batrachospermaceae) |
| Key criteria: | Freshwater filamentous red algae. ~ |
| scorpion tailed saltmarsh weed | Bostrychia scorpioides (rhodomelaceae) |
| Key criteria: | Small turf-forming species that occurs in salt marshes where it is easily recognizable. It is widespread in the area but as shown here rare on some eastern coasts of England and Scotland probably because of the lack of suitable environments. Upper intertidal. upper intertidal intertidal marsh |
| no common name | Grateloupia dichotoma (halymeniaceae) |
| Key criteria: | Small dichotomously branched flattened fronds. In south-western Britain found in subtidal gullies or cobble to 10 m. Despite repeated searching no genuine plants have been found in Ireland. subtidal |
| no common name | Gracilariopsis longissima (gracilariaceae) |
| Key criteria: | Medium-sized species with flexible branches and general elongated morphology. Readily confused with G. gracilis. Probably widely distributed. ~ |
| no common name | Hildenbrandia spp. (hilenbrandiaceae) |
| Key criteria: | A dark red encrusting algae ~ |
| pepper dulse | Osmundea pinnatifida (rhodomelaceae) |
| Key criteria: | Large (to 15 cm) turf-forming species with compressed regularly branched axes which is confined to the intertidal zone of sheltered to exposed coasts. Grows on bedrock with turf of other algae. Its abundance and wide distribution are reflected in the large number of records shown. intertidal rock sheltered exposed |
| brittle fern weed | Osmundea oederi (rhodomelaceae) |
| Key criteria: | Lower intertidal. Epiphytic on Fucus. epiphyte lower intertidal intertidal |
| no common name | Lemanea (lamaneaceae) |
| Key criteria: | Freshwater red algae. On streams on rocks in flowing water. Epilithic. epilithic rock |
| no common name | Lemanea fluviatilis (lamaneaceae) |
| Key criteria: | Freshwater red algae. On streams on rocks in flowing water. Epilithic. epilithic rock |
| flattened pincer weed | Microcladia glandulosa (ceramiaceae) |
| Key criteria: | A fairly large (10 cm) species with narrow compressed axes rare in the subtidal zone of sheltered shores. It is fairly distinctive and confined to the south-west of Britain and to Ireland where it is absent from northern coasts. The record from the Outer Hebrides is erroneous and is probably based on Callophyllis cristata a northern species with a similar morphology. subtidal sheltered |
| tough laver | Porphyra umbilicalis (bangiaceae) |
| Key criteria: | Medium light- to dark-reddish brown foliose alga. Throughout the intertidal zone although mainly upper intertidal. Epilithic on bedrock boulders and other substrata e.g. concrete wood; epizoic on limpets mussels barnacles; epiphytic on other algae e.g. Fucus. On both sheltered and wave- exposed shores. Common throughout. epiphyte epilithic epizoic upper intertidal intertidal rock sheltered exposed |
| no common name | Cladophora battersii (cladophoraceae) |
| Key criteria: | Small (to 10 cm) regularly branched filamentous alga that grows loose-lying in sheltered subtidal habitats probably rare. Relatively easily identifiable. subtidal sheltered |
| no common name | Cladophora retroflexa (cladophoraceae) |
| Key criteria: | Large (to 35 cm) much-branched filamentous alga that forms free-floating balls in sheltered environments. Members of this genus are extremely difficult to separate morphologically. This species is poorly known and believed to be rare although it may be under-recorded here. sheltered |
| no common name | Heribaudiella fluviatilis (phaeostrophiaceae) |
| Key criteria: | A freshwater brown algae. ~ |
| no common name | Nitella hyalina (characeae) |
| Key criteria: | freshwater green alga ~ |
| lambs tails | Spongonema tomentosum (chordariaceae) |
| Key criteria: | A common and widely distributed epiphyte forming light brown felt-like patches on Fucus especially F. vesiculosus and F. spiralis. epiphyte |
| no common name | Vaucheria sessilis (vaucheriaceae) |
| Key criteria: | Terrestrial yellow/ green algae. ~ |
| foxtail stonewort | Lamprothamnion papulosum (characeae) |
| Key criteria: | Green algae. Whorled. Brackish low nutrient lagoons with non fluctuation levels. brackish |
| no common name | Chaetomorpha tortuosa (cladophoraceae) |
| Key criteria: | Filamentous green marine algae. ~ |
| no common name | Zygogonium ericetorum (zygnemataceae) |
| Key criteria: | Freshwater and terrestrial green algae. ~ |
| no common name | Acinetospora crinita (acinetosporaceae) |
| Key criteria: | Plants usually epiphytic forming loose entangled masses of filaments with short lateral branchlets. Only distinctive under the microscope and therefore probably very under-recorded. epiphyte |
| no common name | Acrochaete heteroclada (ulvellales) |
| Key criteria: | Minute (microscopic) irregularly branched uniseriate filaments. Mid-lower intertidal; probably subtidal. Endophytic in algae e.g. Chondrus crispus. Present all year. Only recently recognized in the flora; probably much more widespread than previously recorded. endophyte lower intertidal intertidal subtidal |
| no common name | Acrochaete operculata (ulvellales) |
| Key criteria: | Minute (microscopic) irregularly branched twisted intertwined uniseriate filaments. Mid-lower intertidal and shallow subtidal. Endophytic in Chondrus crispus to which it appears to be confined. Only recently recognized as present in the flora; much more widespread than indicated previously recorded. Requires further taxonomic investigation. endophyte lower intertidal intertidal shallow subtidal subtidal |
| no common name | Acrochaete repens (ulvellales) |
| Key criteria: | Minute (microscopic) prostrate filaments much and irregularly branched. Mid-lower intertidal to subtidal. Endophytic or epi-endophytic in tissues of various brown algae especially Chorda filum and Fucus species; endophytic in the red alga Chondrus crispus and reported on the leaves of the eel-grass Zostera marina. It is probably more widespread than the previously recorded. endophyte lower intertidal intertidal subtidal |
| no common name | Acrochaete viridis (ulvellales) |
| Key criteria: | Minute (microscopic) branched uniseriate filaments. Mid-lower intertidal and subtidal. Epi- endophytic in medullary or cortical tissues of a variety of green brown and red algae; a very common endophyte of Chondrus crispus; also in shells. Much more widespread than previously recorded. endophyte lower intertidal intertidal subtidal |
| no common name | Acrochaete wittrockii (ulvellales) |
| Key criteria: | Minute (microscopic) unbranched or sparsely branched filaments of about 10 cells in length that taper at ends. Intertidal to subtidal. Epiphytic or endophytic on or in the cells of brown algae; less commonly occurring in red algae. A number of uncertainties surround this species and there is some doubt as to the validity of records. epiphyte endophyte intertidal subtidal |
| no common name | Acrochaetium alariae (acrochaetiaceae) |
| Key criteria: | Small epiphyte of Alaria esculenta on wave-exposed shores. Generally common when present and may form extensive sheets of tufts on older plants of Alaria. Generally more common on northern and north-western shores. Common but under-recorded. epiphyte exposed |
| no common name | Acrochaetium battersianum (acrochaetiaceae) |
| Key criteria: | (Acrochaetiales Acrochaetiaceae) Microscopic epiphyte of Porphyra in the mid-intertidal. Rare. epiphyte intertidal |
| hair weed | Acrochaetium brebneri (acrochaetiaceae) |
| Key criteria: | Microscopic endophyte of Gloiosiphonia capillaris. Lower intertidal to 5 m. Rare. endophyte lower intertidal intertidal |
| no common name | Acrochaetium chylocladiae (acrochaetiaceae) |
| Key criteria: | (Acrochaetiales Acrochaetiaceae) Microscopic endophytes of Gastroclonium ovatum. Subtidal to 10 m. Rare. endophyte subtidal |
| no common name | Acrochaetium corymbiferum (acrochaetiaceae) |
| Key criteria: | Small epiphyte on a range of algae. Subtidal to 5 m. Uncommon. epiphyte subtidal |
| no common name | Acrochaetium efflorescens (acrochaetiaceae) |
| Key criteria: | Small epiphyte on a range of algae and Zostera and on a range of other substrata. Subtidal to a depth of 15 m. Northern and eastern shores. Uncommon. epiphyte subtidal depth |
| no common name | Acrochaetium endozoicum (acrochaetiaceae) |
| Key criteria: | Endozoic in the tissues of Alcyonium and other bryozoans. Widely distributed under-recorded. endophyte |
| no common name | Acrochaetium infestans (acrochaetiaceae) |
| Key criteria: | Endozoic in the perisarcs of hydroids. Lower intertidal. Widespread probably under-recorded. endophyte lower intertidal intertidal |
| no common name | Acrochaetium microscopicum (acrochaetiaceae) |
| Key criteria: | Microscopic epiphyte on a variety of algae. Lower intertidal and subtidal to 5 m. Widely distributed. Common but under-recorded. epiphyte lower intertidal intertidal subtidal |
| no common name | Acrochaetium minimum (acrochaetiaceae) |
| Key criteria: | Microscopic epiphyte in Polysiphonia in the upper subtidal. Known definitely only from Co. Galway. epiphyte subtidal |
| no common name | Acrochaetium nemalii (acrochaetiaceae) |
| Key criteria: | Microscopic epiphyte of Nemalion helminthoides. Intertidal. Rare. epiphyte intertidal |
| no common name | Acrochaetium parvulum (acrochaetiaceae) |
| Key criteria: | Microscopic epiphyte on a variety of algae. Intertidal and subtidal to 5 m. Rarely reported. epiphyte intertidal subtidal |
| no common name | Acrochaetium rosulatum (acrochaetiaceae) |
| Key criteria: | Microscopic epiphyte on Sporochnus pedunculatus and Carpomitra costata. South-western England and western Ireland. Rare. epiphyte |
| no common name | Acrochaetium sanctae-mariae (acrochaetiaceae) |
| Key criteria: | Microscopic endophyte in Himanthalia elongata. Very rare. endophyte |
| no common name | Acrochaetium savianum (acrochaetiaceae) |
| Key criteria: | Microscopic epiphyte on a range of algae in the lower intertidal and subtidal to a depth of 5 m. Rarely recorded probably of wide occurrence. epiphyte lower intertidal intertidal subtidal depth |
| no common name | Acrochaetium scapae (acrochaetiaceae) |
| Key criteria: | Microscopic epiphyte on Cladophora formerly known only from the type material from Scapa Flow in Orkney. Very rare. epiphyte |
| no common name | Acrochaetium secundatum (acrochaetiaceae) |
| Key criteria: | Microscopic epiphyte on a range of algae. Common and widely distributed. epiphyte |
| no common name | Acrochaetium seiriolanum (acrochaetiaceae) |
| Key criteria: | Small epiphyte on various algae in lower intertidal and upper subtidal. Differentiated into small disc and unbranched or sparingly branched erect axes. Rarely recorded. epiphyte lower intertidal intertidal subtidal |
| no common name | Acrochaetium sparsum (acrochaetiaceae) |
| Key criteria: | Small epiphyte on a variety of algae most often on kelps. Subtidal to 5 m. Uncommon. epiphyte subtidal |
| no common name | Acrochaetium trifila (acrochaetiaceae) |
| Key criteria: | Microscopic epiphyte on various algaein the upper subtidal. Rarely recorded. epiphyte subtidal |
| no common name | Acrochaetium virgatulum (acrochaetiaceae) |
| Key criteria: | Small epiphyte on a range of algae. Lower intertidal pools and subtidal to 10 m. Widely distributed but under-recorded. epiphyte lower intertidal intertidal subtidal pool |
| no common name | Acrothrix gracilis (chordariaceae) |
| Key criteria: | Plants epilithic rare lower intertidal and shallow subtidal with a western distribution pattern. epilithic lower intertidal intertidal shallow subtidal subtidal |
| beautiful bush weed | Aglaothamnion bipinnatum (ceramiaceae) |
| Key criteria: | Small epiphytic or epizoic filamentous species relatively easy to identify microscopically. Not uncommon subtidally in western Scotland mostly growing on sheltered kelp fronds but rarely recorded due to its small size. epiphyte epizoic subtidal sheltered |
| no common name | Aglaothamnion gallicum (ceramiaceae) |
| Key criteria: | Relatively common filamentous species epiphytic on larger algae on moderately to very exposed shores from mid-shore to shallow sublittoral growing to 8 cm or so. Easily mistaken for several more common species it is likely to be under- recorded but may be a southern species. epiphyte exposed |
| no common name | Aglaothamnion hookeri (ceramiaceae) |
| Key criteria: | Small to large filamentous species relatively conspicuous common both intertidally and subtidally in a wide range of habitats The commonest and most widely distributed member of the genus in the area its morphological variability can make identification problematic. intertidal subtidal |
| no common name | Aglaothamnion priceanum (ceramiaceae) |
| Key criteria: | Small rare and inconspicuous filamentous species confined to the sublittoral where it grows epiphytically mostly on kelp at moderately wave-exposed localities. Fairly easily distinguished microscopically. epiphyte exposed |
| no common name | Aglaothamnion pseudobyssoides (ceramiaceae) |
| Key criteria: | Small and delicate filamentous species typically epiphytic on larger red algae in the subtidal zone. Distinguishable from the common species A. tenuissimum only when bearing sexual reproductive structures it is probably under-recorded. However it is normally regarded as being confined to southern English coasts and the record from Orkney requires reassessment. epiphyte subtidal |
| no common name | Aglaothamnion roseum (ceramiaceae) |
| Key criteria: | Relatively large filamentous species 2-8 cm high found in the lower intertidal and shallow subtidal. Common in conditions of reduced salinity such as on floating pontoons in estuaries. Widely distributed in the area. lower intertidal intertidal shallow subtidal subtidal brackish |
| northern bush weed | Aglaothamnion sepositum (ceramiaceae) |
| Key criteria: | A conspicuous large and robust species confined to the intertidal zone of wave-exposed shores. It can be confused withseveral similar species such as Callithamnion granulatum. It has a northern distribution and the records here are its extreme southern limit where it is confined to extreme wave exposure. intertidal exposed |
| no common name | Aglaothamnion tenuissimum (ceramiaceae) |
| Key criteria: | Known until recently as A. byssoides this delicate filamentous species is largely confined to the subtidal but occurs in damp places in the intertidal. It is difficult to distinguish from A. pseudobyssoides unless it has sexual reproductive structures. It is widely distributed in sheltered subtidal habitats and is probably more widespread than indicated previously recorded. intertidal subtidal sheltered |
| no common name | Aglaothamnion tripinnatum (ceramiaceae) |
| Key criteria: | A large and relatively robust filamentous species growing in sheltered subtidal habitats. It is probably under-recorded due largely to problems of distinguishing it from the similar species A. hookeri. subtidal sheltered |
| shrublets | Antithamnion cruciatum (ceramiaceae) |
| Key criteria: | Small and delicate filamentous species that is largely confined to the subtidal and extreme low water mark growing both epiphytically and on stones. It is readily identifiable microscopically. It is widely distributed in the area but generally uncommon and the previous recording seems to over-represent it perhaps because it is recorded when found because relatively unusual. epiphyte subtidal |
| shrublets | Antithamnion densum (ceramiaceae) |
| Key criteria: | Small inconspicuous filamentous species epiphytic and epilithic in the subtidal at extremely wave-exposed sites. Very rare. epiphyte epilithic subtidal exposed |
| shrublets | Antithamnion villosum (ceramiaceae) |
| Key criteria: | Relatively common filamentous species occasionally up to 10 cm probably often overlooked or confused with A. cruciatum. Grows epiphytically at moderately sheltered to wave-exposed sites from extreme low water to about 10 m. Readily identifiable microscopically. epiphyte sheltered exposed |
| shrublets | Antithamnionella floccosa (ceramiaceae) |
| Key criteria: | Delicate filamentous species which is now very rare in the area but apparently more common in the nineteenth century. It has a distinctly northern distribution. This species is now relatively easy to identify but earlier taxonomic confusion apparently led to the records shown here from Galway and Lundy both of which may be erroneous. ~ |
| no common name | Antithamnionella spirographidis (ceramiaceae) |
| Key criteria: | Delicate filamentous species which was formerly confused with A. ternifolia. Most of the records shown here probably represent A. ternifolia which is much more common than A. spirographidis. Both species are believed to be introduced from different sources. The lack of records from the east coasts indicate that it is rare if not absent there. ~ |
| no common name | Antithamnionella ternifolia (ceramiaceae) |
| Key criteria: | Delicate filamentous species which was formerly confused with A. spirographidis and hence is much under-recorded here. It is generally common on southern and south-western coasts epiphytic on large algae in the lower intertidal and subtidal. epiphyte lower intertidal intertidal subtidal |
| no common name | Apoglossocolax pusilla (delesseriaceae) |
| Key criteria: | Minute parasite of Apoglossum ruscifolium extremely rare in the shallow subtidal. shallow subtidal subtidal |
| no common name | Asperococcus scaber (chordariaceae) |
| Key criteria: | An extremely rare lithophyte occurring in intertidal pools and the subtidal. Due to its tiny size (< 2 cm in height) it is probably under-recorded. Presently recorded only from the Isle of Scilly. intertidal subtidal pool |
| no common name | Asterocolax erythroglossi (delesseriaceae) |
| Key criteria: | Relatively common but inconspicuous tiny parasite of Erythroglossum laciniatum probably widely distributed on southern and western coasts but frequently overlooked. parasite |
| no common name | Blastophysa rhizopus (chaetosiphonaceae) |
| Key criteria: | Minute endophytic cells growing in other green and red algae. Very poorly known requiring taxonomic investigation. endophyte |
| no common name | Bolbocoleon piliferum (chaetophoraceae) |
| Key criteria: | A microscopic filamentous form found endophytically inside a wide range of intertidal and subtidal brown and red seaweeds. Widespread throughout the area and likely to be much more common than the previous records suggests. endophyte intertidal subtidal |
| no common name | Bonnemaisonia asparagoides (bonnemaisoniaceae ) |
| Key criteria: | Gametophytes medium-sized without modified branches. More or less confined to the subtidal with a largely western distribution except for an outlier population in north-eastern England. Sporophytes a submicroscopic disc found in other algae or animals and recorded very rarely. The closely related B. clavata has dioecious sexual plants in contrast to this monoecious entity. subtidal |
| no common name | Bornetia secundiflora (ceramiaceae) |
| Key criteria: | Large and robust filamentous species that is confined to the shallow subtidal and to extreme low water mark on wave-exposed coast. It is rare and frequently confused with Griffithsia and Halurus species. It reaches its extreme northern limit in the area at the sites shown. shallow subtidal subtidal exposed |
| no common name | Botrytella micromora (chordariaceae) |
| Key criteria: | Plants epiphytic rare forming small filamentous tufts characterised by secund branching and grape-like clusters of plurilocular sporangia. epiphyte |
| evenly branched mossy feather weed | Bryopsis plumosa (bryopsidaceae) |
| Key criteria: | Large (to 15 cm) feathery species growing in deep lower shore pools and subtidally; epilithic in sheltered and wave-exposed habitats. Relatively easy to identify; very common and widespread in the area as indicated.Mid to lower intertidal and pools. epilithic lower intertidal intertidal subtidal sheltered exposed pool |
| no common name | Buffhamia speciosa (chordariaceae) |
| Key criteria: | Plants rare epiphytic forming small branched filiform gelatinous thalli on Sauvageaugloia griffithsiana. epiphyte |
| bush weed | Callithamnion corymbosum (ceramiaceae) |
| Key criteria: | A fairly delicate filamentous species that can grow up to 5 cm mostly subtidally but rarely in lower intertidal pools both epilithic and epiphytic. It is widely distributed in sheltered subtidal habitats and its records on the previous records reflect the distribution of these habitats. epiphyte epilithic lower intertidal intertidal subtidal sheltered pool |
| bush weed | Callithamnion granulatum (ceramiaceae) |
| Key criteria: | A large (to 15 cm) and robust filamentous species growing primarily in rock pools on exposed coasts. It can be confused with Aglaothamnion sepositum. It is common on suitable wave-exposed shores particularly in the south and west and is under-recorded here probably due to identification problems. rock exposed pool |
| bush weed | Callithamnion tetragonum (ceramiaceae) |
| Key criteria: | A large (to 11 cm) and robust filamentous species growing both intertidally and subtidally on moderately to strongly wave- exposed shores. Its most characteristic habitat is kelp fronds but it is also common on marina pontoons. Its absence from the previous records along much of the east coast of Scotland and England is presumably due to a lack of suitable substrata. intertidal subtidal exposed |
| bush weed | Callithamnion tetricum (ceramiaceae) |
| Key criteria: | A large and robust filamentous species growing intertidally on moderately wave-exposed shores especially on damp shaded vertical faces. It is not readily confused with any other species. It is confined to the south-west of Britain and to Ireland where it is commonest on southern and western coasts. The record from south-west Scotland requires re-examination but its distribution probably varies somewhat from year to year. intertidal exposed |
| no common name | Callocolax neglectus (kallymeniaceae) |
| Key criteria: | Tiny cushion-like or irregular whitish pinkish or buff parasite on Callophyllis laciniata generally on older plants. Subtidal to about 30 m. Not uncommon and widely distributed. subtidal |
| northern crested spermwell | Callophyllis cristata (kallymeniaceae) |
| Key criteria: | Medium-sized flattened to compressed regularly and repeatedly branched fronds. Variable in the degree of dissection. Epiphytic on the holdfasts of Laminaria hyperborea or occasionally on the stipes; found in shallow subtidal to 30 m. Northern distribution unknown in Ireland. epiphyte shallow subtidal subtidal |
| no common name | Calosiphonia vermicularis (calosiphoniaceae) |
| Key criteria: | Gametophytes are small gelatinous fronds with cylindrical to slightly compressed branches. Known only from the subtidal to a depth of about 15 m on small stones and shells in relatively wave-sheltered situations. South western distribution. Rare. subtidal sheltered depth |
| no common name | Capsosiphon fulvescens (capsosiphonaceae) |
| Key criteria: | Thallus tubular superficially resembling Ulva with which it may be confused. On microscopic examination the cell arrangement is unmistakable. Probably widespread and under-recorded because of confusion with Ulva but also because some populations seem very short-lived. Sporadic populations flourish only briefly in a wide range of habitats including both severely polluted and very clean estuarine sites. ~ |
| banded pincer weed | Ceramium botryocarpum (ceramiaceae) |
| Key criteria: | Large and robust filamentous species that seems to be confined to the intertidal zone growing particularly on damp vertical faces. It is very difficult to discriminate from other members of the genus and could be regarded as a sibling species with C. virgatum. Undoubtedly under-recorded here owing to difficulties of identification. intertidal |
| banded pincer weed | Ceramium ciliatum (ceramiaceae) |
| Key criteria: | Small but fairly robust filamentous species growing both intertidally and subtidally on moderately to strongly wave-exposed shores generally on bedrock. It is easy to identify because of its multicellular spines and its wide distribution seems to be accurately indicated here. intertidal subtidal rock exposed |
| banded pincer weed | Ceramium cimbricum (ceramiaceae) |
| Key criteria: | Small but fairly robust filamentous species complex still requiring further nomenclatural and taxonomic work. Confined to the subtidal generally in sheltered habitats. This species is relatively uncommon but the sparse records also reflect taxonomic uncertainties. subtidal sheltered |
| banded pincer weed | Ceramium circinatum (ceramiaceae) |
| Key criteria: | Large robust filamentous species which is very poorly known in the area but seems to be confined to the shallow subtidal zone. Easy to identify microscopically but can be confused with C. virgatum otherwise. All records shown here may be misidentifications because this primarily Mediterranean species is known with certainty only from the south coast of England. shallow subtidal subtidal |
| banded pincer weed | Ceramium deslongchampsii (ceramiaceae) |
| Key criteria: | Small but fairly robust filamentous species growing exclusively intertidally on sheltered shores generally on bedrock rarely epiphytically. It is relatively easy to identify by the ecorticate internodes and protruding sporangia. Its distribution reflects its abundance in low salinity or polluted areas such as the Thames and Severn estuaries. epiphyte intertidal rock sheltered brackish |
| banded pincer weed | Ceramium diaphanum (ceramiaceae) |
| Key criteria: | Small filamentous species that is easy to identify microscopically but can be confused with other ecorticate species otherwise. The name was widely used for all ecorticate species until recently and the previous records indicate this history. C. diaphanum sensu stricto is uncommon confined to the subtidal zone of sheltered embayments. It is probably a southern species. subtidal sheltered |
| banded pincer weed | Ceramium echionotum (ceramiaceae) |
| Key criteria: | Large (to 15 cm) filamentous species growing both intertidally and subtidally on sheltered to strongly wave-exposed shores generally on bedrock. It is easy to identify because of its unicellular spines. Its absence from the south-east coast may be due to lack of suitable hard substrata. intertidal subtidal rock sheltered exposed |
| banded pincer weed | Ceramium flaccidum (ceramiaceae) |
| Key criteria: | Delicate small filamentous species growing in the subtidal fringe of on sheltered to strongly wave-exposed shores mostly epiphytically. It is easy to identify because of its unicellular rhizoids. It is under-recorded. epiphyte subtidal sheltered exposed |
| banded pincer weed | Ceramium gaditanum (ceramiaceae) |
| Key criteria: | Small but fairly robust filamentous species confined to the intertidal where it is most common epiphytic on damp shaded rock faces. It is relatively easy to identify by its spines. It is widely distributed in the area and the apparent absence from northern Scotland could usefully be investigated further. The large number of records from Northern Ireland represent one detailed survey. epiphyte intertidal rock |
| banded pincer weed | Ceramium pallidum (ceramiaceae) |
| Key criteria: | Variable in size and morphology but can be large (15 cm) and robust. Very common in intertidal rock pools rarely in the shallow subtidal. This species is relatively easy to identify. The previous records indicate that this species has been very much under-recorded particularly in Ireland presumably due to earlier identification problems that have now been resolved. intertidal shallow subtidal subtidal rock pool |
| banded pincer weed | Ceramium secundatum (ceramiaceae) |
| Key criteria: | Very large (to 50 cm) and robust filamentous species. Abundant in the shallow subtidal growing on other algae such as kelp fronds and in deep lower-shore lagoons. This species is sometimes difficult to discriminate from C. virgatum. The previous records indicate that this species has been very much under-recorded particularly in Ireland presumably due to earlier identification problems that have now largely been resolved. shallow subtidal subtidal |
| banded pincer weed | Ceramium shuttleworthianum (ceramiaceae) |
| Key criteria: | Small turf-forming filamentous species confined to the intertidal where it is very common on mid- to upper-shore rock faces especially on wave-exposed shores. It is relatively easy to identify by its multicellular spines. The records accurately depicts its widespread distribution in the area. intertidal rock exposed |
| banded pincer weed | Ceramium siliquosum (ceramiaceae) |
| Key criteria: | Large (to 18 cm) filamentous species found at extreme low water and in the subtidal zone at wave-exposed sites epiphytic on larger algae. Easy to identify this species is clearly under-recorded although not particularly common. epiphyte subtidal exposed |
| no common name | Ceratocolax hartzii (phyllophoraceae) |
| Key criteria: | Minute parasite with an irregular outline occurring on Coccotylus truncatus. Only bknown definitely from Shetland and Ireland. Report from Co. Mayo Ireland in the early part of the last century has not been rediscovered. Very rare. parasite |
| brick weed | Chaetomorpha aerea (cladophoraceae) |
| Key criteria: | Chaetomorpha aerea and C. linum are very similar plants; indeed some believe them to be conspecific. This species is the attached form and C. linum is unattached. It is likely that some records of C. aerea have been recorded as C. linum which shows a very widespread distribution. The recent re-emergence of C. aerea as a separate entity may result in more records. ~ |
| brick weed | Chaetomorpha crassa (cladophoraceae) |
| Key criteria: | The separation of species of Chaetomorpha is problematical. Most collectors would have identified this entity as C. linum. Whether or not some of the many recordings of C. linum are really C. crassa is not clear. It may also be that this species is not common. ~ |
| brick weed | Chaetomorpha litorea (cladophoraceae) |
| Key criteria: | This is one of the less well-known species of Chaetomorpha. Its characteristics overlap with those of the more well- known C. linum. It is likely that some records of the latter include some that could be C. litorea giving it a more widespread distribution than indicated. However the species distinction in Chaetomorpha needs reassessment. ~ |
| brick weed | Chaetomorpha melagonium (cladophoraceae) |
| Key criteria: | This is a highly characteristic plant occurring as single attached filaments in rock pools with cells so large they can be seen with the naked eye. Although it needs to be searched for when found it is so obvious that this probably accounts for the frequent records. It is rarely abundant but is widespread occurring on most shores with suitable rock pools. rock pool |
| no common name | Characium marinum (characiaceae) |
| Key criteria: | A microscopic unicell epiphytic on other intertidal algae. Probably under-recorded because of its inconspicuous nature but not thought to be common. epiphyte intertidal |
| no common name | Chilionema hispanicum (chordariaceae) |
| Key criteria: | A rarely recorded epiphyte forming small spots on Saccorhiza polyschides and Laminaria saccharina although probably occurring on other hosts. epiphyte |
| no common name | Chilionema ocellatum (chordariaceae) |
| Key criteria: | Plants epiphytic forming small spots on Palmaria palmata in the intertidal and subtidal. Recorded for a few localities but probably more widely distributed. A summer annual. epiphyte intertidal subtidal |
| no common name | Chlorochytrium cohnii (chlorococcaceae) |
| Key criteria: | Probably widespread in the area but its obscure nature as a unicellular endophyte in the mucilaginous tubes of filamentous colonial diatoms mean that it is probably under-recorded. endophyte |
| no common name | Chlorochytrium dermatocolax (endosphaeraceae) |
| Key criteria: | A unicellular endophyte found within various intertidal filamentous red and brown seaweeds. Likely to be more widespread than this single record suggests though not common. According to the literature it is likely to be restricted to northern Britain. endophyte intertidal |
| no common name | Chlorochytrium facciolae (endosphaeraceae) |
| Key criteria: | A unicellular endophyte within mat- forming green seaweeds and in Cyanobacteria in intertidal pools and salt marshes. Likely to be more widespread than the single record shown but may not be common. endophyte intertidal marsh pool |
| no common name | Choreocolax polysiphoniae (choreocolacaceae) |
| Key criteria: | Minute whitish parasite of Polysiphonia lanosa an obligate epiphyte of fucoid algae. Not visible to the unaided eye. Probably commoner than records indicate. Seemingly absent from most of eastern England. epiphyte |
| no common name | Choristocarpus tenellus (choristocarpaceae) |
| Key criteria: | A rare south-western species reported for the subtidal. subtidal |
| no common name | Chroodactylon ornatum (goniotrichaceae) |
| Key criteria: | Minute (microscopic) blue-green uniseriate mucilaginous filaments pseudodichotomously branched arising from a single basal cell. Lower intertidal to shallow subtidal. Epiphytic on small algae and on Zostera. May also occur in freshwater habitats. More widely distributed around the western half of Britain and Ireland than indicated by previous records but probably not common. epiphyte lower intertidal intertidal shallow subtidal subtidal |
| no common name | Cladosiphon contortus (chordariaceae) |
| Key criteria: | A rare summer annual inhabiting lower intertidal pools and apparently confined to south-western coasts. lower intertidal intertidal pool |
| no common name | Cladosiphon zosterae (chordariaceae) |
| Key criteria: | Plants rare. A summer annual forming gelatinous filiform thalli on Zostera in the shallow subtidal and with a western distribution pattern. shallow subtidal subtidal |
| no common name | Coccotylus truncatus (phyllophoraceae) |
| Key criteria: | Small to medium fronds with flattened wedge-fronds borne on narrow cylindrical or slightly flattened stipes. Often associated with extreme lower intertidal pools affected by sand and on wave-washed ledges to a depth of 15 m. Northern distribution. Relatively common in appropriate habitats. lower intertidal intertidal sand depth pool |
| no common name | Codium adhaerens (codiaceae) |
| Key criteria: | Forming adherent felty covering on rock in the lower intertidal; relatively easy to identify except for discrimination from basal holdfasts of erect Codium species. Rare in the area as indicated here. lower intertidal intertidal rock |
| no common name | Colacodictyon reticulatum (goniotrichaceae) |
| Key criteria: | Microscopic (minute) rose-red irregular net-like patches of round to elongate cells. Subtidal. Occurring in the cell walls of Desmarestia dresnayi and Desmarestia ligulata. Not common as indicated by the records but may be more widespread in the west and north. subtidal |
| no common name | Colaconema asparagopsis (colaconemataceae) |
| Key criteria: | Microscopic endophyte in Asparagopsis armata gametophytes. Generally common when mature male and female plants of the basiphyte are examined. Very under-recorded. endophyte |
| no common name | Colaconema bonnemaisoniae (colaconemataceae) |
| Key criteria: | Microscopic endophyte in Bonnemaisonia hamifera gametophytes. Generally common when mature male and female plants of the basiphyte are examined. Under-recorded. endophyte |
| no common name | Colaconema caespitosum (colaconemataceae) |
| Key criteria: | Small tufted epiphyte and zoophyte on a wide range of organisms most commonly on limpets on exposed shores. Widely distributed on south-western and western shores but under-recorded. epiphyte exposed |
| no common name | Colaconema daviesii (colaconemataceae) |
| Key criteria: | Tiny filamentous epiphyte on a range of basiphytes particularly fringing Palmaria palmata. Common and widely distributed. epiphyte |
| no common name | Colaconema endophyticum (colaconemataceae) |
| Key criteria: | Microscopic endophyte in Heterosiphonia plumosa generally found in older plants. Common and widespread but under-recorded. endophyte |
| no common name | Compsonema microspongium (scytosiphonaceae) |
| Key criteria: | A rare epiphytic species only recorded in the south west it forms small hemispherical cushions on Ralfsia verrucosa in the upper intertidal. epiphyte upper intertidal intertidal |
| no common name | Compsonema minutum (scytosiphonaceae) |
| Key criteria: | Plants epilithic forming microscopic confluent tufts on bedrock in the upper intertidal. Only known from the south coast of England but probably more widespread. epilithic upper intertidal intertidal rock |
| no common name | Compsonema saxicolum (scytosiphonaceae) |
| Key criteria: | A rare but probably under-recorded plant it forms microscopic tufts on rocks or limpets in the intertidal. Probably a summer annual. intertidal rock |
| no common name | Compsothamnion decompositum (ceramiaceae) |
| Key criteria: | Small delicate filamentous species confined to the subtidal zone of wave-exposed coasts. It is relatively easy to identify microscopically but the two records shown here require confirmation as it was previously known only from western Ireland and France. subtidal exposed |
| no common name | Compsothamnion gracillimum (ceramiaceae) |
| Key criteria: | Large but delicate filamentous species found in the sublittoral fringe and shallow subtidal zone of wave-exposed coasts growing epilithically. It is difficult to distinguish from C. thuyoides and is relatively rare as indicated here. epilithic shallow subtidal subtidal exposed |
| no common name | Cryptonemia hibernica (halymeniaceae) |
| Key criteria: | Introduced species difficult to separate from an eastern Pacific species complex. Plants large and foliose with thin but tough fronds. Confined to an area in the vicinity of Cork Harbour and west Cork. The record from Northern Ireland requires confirmation. I have also seen genuine material from the shallow subtidal of Plymouth Sound. Confined to the shallow subtidal on small stones. shallow subtidal subtidal |
| no common name | Cryptonemia seminervis (halymeniaceae) |
| Key criteria: | A medium-sized species with flattened fronds and a distinctive evanescent midrib. Found only in Scilly Isles in deep water. ~ |
| no common name | Cylindrocarpus microscopicus (chordariaceae) |
| Key criteria: | Plants endophytic rare forming minute brown patches on Gracilaria bursa- pastoris. Apparently confined to the south coast of England but this requires further investigation. endophyte |
| tree weed | Dasya corymbifera (dasyaceae) |
| Key criteria: | Large (to 10 cm) robust polysiphonous species confined to the subtidal zone and deep rock pools. It is difficult to discriminate from other members of the genus unless fertile but is also very rare so the sparse records here all from south and west coasts may give a true picture. subtidal rock pool |
| hairy tree weed | Dasya hutchinsiae (dasyaceae) |
| Key criteria: | Large (to 10 cm) robust polysiphonous species confined to the subtidal zone and deep rock pools. It is difficult to discriminate from other members of the genus unless fertile. It is relatively common subtidally in sheltered habitats in south-west Britain. As shown here it is confined to western Britain and Ireland with its northern limit at the Western Isles subtidal rock sheltered pool |
| tree weed | Dasya ocellata (dasyaceae) |
| Key criteria: | Small (to 3 cm) robust polysiphonous species confined to the subtidal zone and deep exposed-shore rock pools. It is relatively easy to discriminate from other members of the genus but is also very rare so the sparse records here all from south and west coasts may give a true picture. subtidal rock exposed pool |
| tree weed | Dasya punicea (dasyaceae) |
| Key criteria: | Large (to 10 cm) robust polysiphonous species confined to the subtidal zone. It is difficult to distinguish from other members of the genus but is also very rare and confined to southern England. subtidal |
| no common name | Derbesia tenuissima (derbesiaceae) |
| Key criteria: | This species is very similar to the more frequently recorded Derbesia marina. It is likely that many collectors have not distinguished them so some records of D. tenuissima may be recorded for D. marina. However there is a serious question whether D. tenuissima occurs widely in the area. ~ |
| no common name | Dermocorynus montagnei (halymeniaceae) |
| Key criteria: | Crustose species found exclusively on 5-10 mm wide pebbles or maerl fragments forming tiny erect reproductive papillae. Exclusively subtidal and very rare. Largely western in distribution. subtidal |
| no common name | Dichosporangium chordariae (chordariaceae) |
| Key criteria: | Plants endophytic rare with a northern distribution pattern forming minute spots on various algae particularly Chordaria flagelliformis. endophyte |
| no common name | Dictyosiphon chordarius (chordariaceae) |
| Key criteria: | Plants not uncommon mainly with a northern distribution pattern. ~ |
| no common name | Drachiella minuta (delesseriaceae) |
| Key criteria: | Small foliose species which is rare and confined to the subtidal zone and deep lower-shore pools of wave-exposed coasts. In addition to the Irish distribution shown here it probably occurs in SW England. subtidal exposed pool |
| filamentous browns | Ectocarpus siliculosus (eetocarpaceae) |
| Key criteria: | Plants abundant and widespread epilithic epizoic or epiphytic forming much-branched filamentous tufts which can reach 30 cm or more in length. Microscopic examination required to distinguish it from E. fasciculatus and other morphologically similar ectocarpoids. epiphyte epilithic epizoic |
| no common name | Epicladia flustrae (ulvellaceae) |
| Key criteria: | A microscopic filamentous form which occurs endozoically in the skeletons of both living and dead hydroids and bryozoans both intertidal and subtidal. Much more common than the records suggests. Likely to occur on most shores in the area where the hosts can be found but probably under-recorded because of the obscure habitat. endophyte intertidal subtidal |
| no common name | Epicladia perforans (ulvellaceae) |
| Key criteria: | Microscopic filaments penetrating Zostera chalk cliffs and periwinkle shells. Possibly more widespread but difficult to identify and the range of habitat quoted suggests that two entities might be confused here. Many microscopic green endophytic filaments belong to a variety of species which few workers can identify with confidence. endophyte |
| no common name | Erythrocladia irregularis (erythrotrichiaceae) |
| Key criteria: | Minute (microscopic) irregular single- layered irregular red patches to c. 150 micro m in diameter. Lower intertidal and subtidal. Epiphytic and epizoic e.g. on bryozoans and hydroids. Much more widespread than indicated by the records. epiphyte epizoic lower intertidal intertidal subtidal |
| no common name | Erythropeltis discigera var. flustrae (erythrotrichiaceae) |
| Key criteria: | The type variety has not been recorded for the area and its taxonomic status is uncertain. In the var. flustrae Batters the thallus is minute (microscopic) rose-red horizontally expanded orbicular to irregular lobed disc-like colonies to c. 270 micro m in diameter. Subtidal. Epizoic on the bryozoan Flustra foliacea. This species has a southern distribution; the northern records require reinvestigation. epizoic subtidal |
| no common name | Erythrotrichia bertholdii (erythrotrichiaceae) |
| Key criteria: | Tiny erect purple-red filaments to 10 mm long arising from one slightly expanded or a few clustered basal cells; filaments uniseriate below becoming multiseriate above; cells radially arranged in cross section. Lower mid-intertidal to the shallow subtidal. Epiphytic on algae especially Ceramium and on the eelgrass Zostera marina. More widespread than previously recorded, but apparently uncommon. epiphyte intertidal shallow subtidal subtidal |
| no common name | Erythrotrichia carnea (erythrotrichiaceae) |
| Key criteria: | Minute (microscopic) to very small rose- red erect uniseriate filaments to 30 mm long arising from a single basal cell which is swollen or lobed and/or with a slight thickening of the wall. Mid- intertidal to shallow subtidal in sheltered habitats; solitary plants occurring in the mid-intertidal to deep subtidal. Epiphytic on a wide range of algae and on the eelgrass Zostera marina. Common throughout and more widespread than indicated by the previous records. epiphyte intertidal shallow subtidal subtidal sheltered |
| no common name | Erythrotrichia investiens (erythrotrichiaceae) |
| Key criteria: | Minute (microscopic) to very small bright red-purple erect filaments uniseriate below biseriate above to 40 mm long arising from one to a few basal cells. Epiphytic on other algae including Fucus. This species requires further taxonomic investigation. epiphyte |
| no common name | Erythrotrichia reflexa (erythrotrichiaceae) |
| Key criteria: | Minute (microscopic) to very small purple-red erect filaments uniseriate reflexed sometimes branched at base. Epiphytic on algae. Apparently uncommon. Distribution southerly. epiphyte |
| no common name | Erythrotrichia welwitschii (erythrotrichiaceae) |
| Key criteria: | Minute (microscopic) to very small rose- pink to pale violet erect filaments to c. 0.5 mm long arising from a single elongate basal cell. Lower filaments embedded between filaments of the brown alga Ralfsia verrucosa; branches present where filaments emerge from host. Species appearing as a red-purple felt when nearly dry. Mid- to lower- intertidal. On R. verrucosa on molluscs. More widespread particularly in the south-west than records suggest. intertidal |
| brown jelly weed | Eudesme virescens (chordariaceae) |
| Key criteria: | Plants common and widely distributed except for on the south-east and east coasts of England. A soft branched gelatinous summer annual found in intertidal pools. intertidal pool |
| no common name | Eugomontia sacculata (ulotrichaceae) |
| Key criteria: | This is a shell-boring filamentous species predominantly found in dead drift cells in the subtidal in estuaries and on intertidal mud flats. It is very widespread in the area and definitely under-recorded. intertidal subtidal mud |
| no common name | Feldmannia irregularis (acinetosporaceae) |
| Key criteria: | A rarely recorded but widely distributed epiphyte forming small filamentous tufts on various hosts. epiphyte |
| no common name | Feldmannia lebelii (acinetosporaceae) |
| Key criteria: | A rare epiphyte forming small branched filamentous tufts on various hosts. epiphyte |
| no common name | Feldmannia padinae (acinetosporaceae) |
| Key criteria: | A rare epiphyte forming small filamentous tufts on Padina. Only known for the Channel Islands. epiphyte |
| no common name | Feldmannia paradoxa (acinetosporaceae) |
| Key criteria: | A rarely recorded epiphyte forming small filamentous tufts on various hosts. epiphyte |
| creeping maerl weed | Gelidiella calcicola (gelidiaceae) |
| Key criteria: | Small creeping epiphyte of maerl (detached coralline algae forming extensive beds in clean-water areas at depths of 0-35 m.). Infrequently recorded but probably common in all maerl beds. epiphyte depth |
| no common name | Gelidium corneum (gelidiaceae) |
| Key criteria: | Largest species of the genus in Britain and Ireland often reaching 40 cm. Confined to south-western England where it occurs in large pools and on rocks in the lower intertidal. Generally rare but may be common on certain shores. lower intertidal intertidal rock pool |
| no common name | Gelidium crinale (gelidiaceae) |
| Key criteria: | Small species found generally in lower- shore sandy pools. Long confused with Gelidium pusillum and G. pulchellum and probably under-recorded. Uncommon probably with a south-western distribution. sand pool |
| no common name | Gelidium maggsiae (gelidiaceae) |
| Key criteria: | Medium species found only growing prolifically on rhodoliths and maerl. Not tobe confused with Gelidiella calcicola. Monoecious. Known only from the type locality (Flannery Bridge Co. Galway) where bridge engineering works may have damaged the site permanently. epiphyte |
| no common name | Gelidium pulchellum (gelidiaceae) |
| Key criteria: | Medium species found commonly fringing pools in the mid-and lower-intertidal on shores with medium to strong wave- exposure. Form strongly seasonal. Common probably with a predominantly western distribution. Records from Britain are probably included under G. pusillum. intertidal pool |
| creeping straggle weed | Gelidium pusillum (gelidiaceae) |
| Key criteria: | Small creeping plant with flattened branches. Common on upper intertidal rocks forming a mat often occurring in damp cracks or under larger seaweeds. Confused with Gelidium crinale and G. pulchellum. Widely distributed but many of the records represented here are probably of other species of the genus. upper intertidal intertidal rock |
| no common name | Giraudia sphacelarioides (chordariaceae) |
| Key criteria: | A distinctive rare southern species forming small tufts epiphytic on various algae in the lower intertidal and shallow subtidal. epiphyte lower intertidal intertidal shallow subtidal subtidal |
| no common name | Gomontia polyrhiza (endosphaeraceae) |
| Key criteria: | A shell-boring form in calcareous parts of mollusc shells calcareous tube-worms and barnacles. Very commonly found as the unicellular sporophyte generation on almost every shore. Likely to occur throughout the area and to be grossly under-recorded owing to its obscure habitat. epizoic |
| no common name | Gonimophyllum buffhamii (delesseriaceae) |
| Key criteria: | Tiny (to 4 mm) species hemiparasitic on Cryptopleura ramosa. Its small size and inconspicuous habit mean that it is probably under-recorded here. hemiparasitic |
| cleaved wart weed | Gracilaria multipartita (gracilariaceae) |
| Key criteria: | Medium-sized species with thick fleshy quite brittle fronds. Virtually confined to the south-western coast of England in the lower intertidal and shallow subtidal where it is found growing epilithically. The two Irish sites may represent ephemeral introductions. epilithic lower intertidal intertidal shallow subtidal subtidal |
| no common name | Grateloupia filicina var. luxurians (halymeniaceae) |
| Key criteria: | Large (to 70 cm) once or twice regularly pinnately branched mucilaginous but firm distinctly flattened long elegant fronds. Probably introduced from Australia to the Solent area. Presently known only from Dorset Hampshire (including the Isle of Wight) and Sussex in Britain. ~ |
| Norwegian fan weed | Gymnogongrus griffithsiae (phyllophoraceae) |
| Key criteria: | Small cylindrical fronds with regularly dichotomous branching cartilaginous and wiry. Shallow pools and small stones in sandy or silty areas. Lower intertidal and shallow subtidal. Widely distributed occasional. lower intertidal intertidal shallow subtidal subtidal sand pool |
| encrusting red | Haemescharia hennedyi (haemeschariaceae) |
| Key criteria: | Crustose species very similar to the tetrasporophyte of Mastocarpus stellatus. Found on stones shells and Laminaria hyperborea holdfasts in the lower intertidal and upper intertidal. Rare. Epiphyte epilithic and epizoic. epiphyte epilithic epizoic lower intertidal upper intertidal intertidal |
| no common name | Halochlorococcum moorei (chlorocystidaceae) |
| Key criteria: | This is a large single-celled plant which lives partially endophytically within Blidingia spp. When found it is very characteristic but few collectors would seek it. It is likely to occur on all coasts widespread but not necessarily common. endophyte |
| no common name | Halosacciocolax kjellmanii (rhodophysemataceae) |
| Key criteria: | A minute hemispherical parasite of Palmaria palmata. Generally rare and usually present on older plants in spring. May be confused with copepod galls that frequently occur on the host. ~ |
| no common name | Halothrix lumbricalis (chordariaceae) |
| Key criteria: | A rarely recorded epiphyte forming minute tufts on Zostera blades. A summer annual. epiphyte |
| no common name | Halymenia latifolia (halymeniaceae) |
| Key criteria: | Large ligulate delicate species rarely found in drift. Generally occurring on maerl for a short period during the late summer and frequently decimated by autumnal gales. ~ |
| no common name | Haplospora globosa (tilopteridaceae) |
| Key criteria: | A northern shallow subtidal species plant recorded from lower intertidal pools and the shallow subtidal. lower intertidal intertidal shallow subtidal subtidal pool |
| no common name | Harveyella mirabilis (choreocolacaceae) |
| Key criteria: | Minute white to buff cushion-like parasite of Rhodomela confervoides. Not visible generally to the unaided eyes. Relatively uncommon but widespread. parasite |
| no common name | Hecatonema terminale (chordariaceae) |
| Key criteria: | A widely distributed but undoubtedly under-recorded intertidal species which forms minute usually epiphytic tufts only discernible by microscopic examination. epiphyte intertidal |
| no common name | Herponema solitarium (chordariaceae) |
| Key criteria: | Plants endophytic/epiphytic rare forming minute tufts on various hosts. Only recorded for a few localities in Ireland. epiphyte endophyte |
| no common name | Herponema valiantei (chordariaceae) |
| Key criteria: | Plants endophytic/epiphytic forming minute tufts on Cystoseira. epiphyte endophyte |
| no common name | Herponema velutinum (chordariaceae) |
| Key criteria: | Plants endophytic/epiphytic forming brown colorations on the thongs of Himanthalia elongata during the summer months. Fairly widespread but probably under-recorded. epiphyte endophyte |
| no common name | Hildenbrandia crouaniorum (hilenbrandiaceae) |
| Key criteria: | Crustose species forming thin incrustations on rocks stones and small pebbles mainly in the upper intertidal extensive growths are often apparent sometimes covering many square metres. Probably more widespread than records indicate. upper intertidal intertidal rock |
| no common name | Hildenbrandia rubra (hilenbrandiaceae) |
| Key criteria: | Similar to H. crouaniorum in appearance and habitat. Widespread and common. ~ |
| no common name | Hincksia fenestrata (acinetosporaceae) |
| Key criteria: | A rarely recorded much branched filamentous plant only reported for Scotland. ~ |
| no common name | Hincksia granulosa (acinetosporaceae) |
| Key criteria: | A common and widespread small much branched filamentous species occurring both as a lithophyte and an epiphyte in intertidal pools and the shallow subtidal. epiphyte intertidal shallow subtidal subtidal pool |
| no common name | Hincksia hincksiae (acinetosporaceae) |
| Key criteria: | Plants epiphytic forming small much branched filamentous tufts on various hosts particularly kelps. Not uncommon and widely distributed although unaccountably not recorded from muchof south-eastern and eastern England. epiphyte |
| no common name | Hincksia ovata (acinetosporaceae) |
| Key criteria: | Plants uncommon reported on various substrata forming small branched filamentous tufts only distinctive under a microscope. ~ |
| no common name | Hincksia sandriana (acinetosporaceae) |
| Key criteria: | Plants usually epiphytic forming small delicate much-branched filamentous tufts. Not uncommon and widely distributed. epiphyte |
| no common name | Hincksia secunda (acinetosporaceae) |
| Key criteria: | Not uncommon and widely distributed epiphyte on various hosts much branched filamentous tufts closely resembling H. granulosa. epiphyte |
| no common name | Hinksia mitchelliae (acinetosporaceae) |
| Key criteria: | A small much branched filamentous epiphyte found on various hosts characterised by its cigar-shaped plurilocular sporangia. Probably much more common and widespread than shown on the previously recorded. epiphyte |
| no common name | Holmsella pachyderma (pterocladiophilaceae) |
| Key criteria: | Tiny white or pinkish cushions barely visible to the unaided eye parasitic on Gracilaria gracilis. South-western in distribution; relatively uncommon. parasite |
| no common name | Isthmoplea sphaerophora (chordariaceae) |
| Key criteria: | Plants not uncommon and widely distributed forming small usually epiphytic tufts on various algae in lower intertidal pools. epiphyte lower intertidal intertidal pool |
| margined oar weed | Itonoa marginifera (nemastomataceae) |
| Key criteria: | Gametophytes medium somewhat delicate gelatinous fronds with variable branching. Subtidal in situations with clear oceanic water. Rare. Sporophytes unknown in the area. subtidal |
| no common name | Kuetzingiella battersii (chordariaceae) |
| Key criteria: | Plants epiphytic and extremely rare forming small little-branched filamentous tufts only distinctive under a microscope. epiphyte |
| no common name | Kuetzingiella holmesii (chordariaceae) |
| Key criteria: | Plants rare forming small filamentous branched tufts only distinctive under a microscope. ~ |
| no common name | Laminariocolax aecidioides (chordariaceae) |
| Key criteria: | A minute endophyte erupting as small pustules on Laminaria blades. Probably much more common and widespread than previously thought. endophyte |
| no common name | Laminariocolax tomentosoides (chordariaceae) |
| Key criteria: | A minute epiphyte forming small spots on Laminaria blades. Probably much more common and widespread than previously thought. epiphyte |
| no common name | Leblondiella densa (chordariaceae) |
| Key criteria: | A rarely recorded summer annual forming tiny erect filamentous shoots on Zostera blades. epiphyte |
| no common name | Leptonematella fasciculata (chordariaceae) |
| Key criteria: | A rare but widely distributed spring and summer annual forming small erect tufts of unbranched filaments on various algae and shells. epiphyte epizoic |
| no common name | Liebmannia leveillei (chordariaceae) |
| Key criteria: | A rare summer annual inhabiting lower intertidal pools and only known from the south-west coast of Ireland. lower intertidal intertidal pool |
| no common name | Litosiphon laminariae (chordariaceae) |
| Key criteria: | A common summer and autumn annual forming small quite dense brush-like tufts on various algae especially Chorda filum and Alaria esculenta in intertidal pools and the shallow subtidal. Its apparent absence from south-eastern and eastern England requires further investigation. intertidal shallow subtidal subtidal pool |
| creeping siphon weed | Lophosiphonia reptabunda (rhodomelaceae) |
| Key criteria: | Small (to 2 cm) species with branched polysiphonous axes. Intertidal on sandy or muddy shores. It is extremely rare in Britain and believed to be restricted to south and south-west coasts of England and Ireland; the record from Scotland requires re-examination. intertidal mud sand |
| no common name | Meiodiscus spetsbergensis (rhodophysemataceae) |
| Key criteria: | Discoid plants with sparse sparingly branched erect filaments. Found exclusively on hydroids in the subtidal. Rare and may be confined to colder more northern waters. subtidal |
| brown jelly weed | Mesogloia lanosa (chordariaceae) |
| Key criteria: | A quite rare summer annual forming branched gelatinous thalli in lower intertidal pools and with a predominantly western and northern algae. A summer annual. lower intertidal intertidal pool |
| brown jelly weed | Mesogloia vermiculata (chordariaceae) |
| Key criteria: | A not uncommon and fairly widespread summer annual forming branched gelatinous thalli in mid to lower intertidal pools. lower intertidal intertidal pool |
| no common name | Microcoryne ocellata (chordariaceae) |
| Key criteria: | Plants rare forming small variously shaped erect gelatinous thalli on various distribution pattern. ~ |
| no common name | Microspongium gelatinosum (chordariaceae) |
| Key criteria: | Plants widespread and common epilithic or epizoic forming small slightly spongy crusts in the intertidal. It is probably present on all coasts but has been misidentified due to its close resemblance to Stragularia clavata. Culture studies have indicated that it is the alternate phase of Scytosiphon lomentaria. epilithic epizoic intertidal |
| no common name | Microspongium globosum (chordariaceae) |
| Key criteria: | Plants epiphytic forming small spots on various hosts. A quite rare summer annual with a western and northern distribution pattern. epiphyte |
| no common name | Microspongium immersum (chordariaceae) |
| Key criteria: | Minute profusely branched endophyte found on Harveyella mirabilis a parasite on Rhodomela confervoides. Known positively only from the Isle of Man. endophyte |
| no common name | Microspora ficulinae (microsporaceae) |
| Key criteria: | A microscopic filament endozoic within sponges. This obscure habit may have led to under-recording. Unidentified green filaments in sponges are found occasionally throughout Britain so it may be widespread though not thought to be common. A microscopic filament endozoic within sponges. This obscure habit may have led to under-recording. Unidentified green filaments in sponges are found occasionally throughout Britain so it may be widespread though not thought to be common. endophyte |
| no common name | Mikrosyphar polysiphoniae (chordariaceae) |
| Key criteria: | Plants endophytic forming small circular spots on Polysiphonia. Probably more widespread than the records suggest. endophyte |
| no common name | Mikrosyphar porphyrae (chordariaceae) |
| Key criteria: | Plants endophytic forming small circular spots on Porphyra. Probably under-recorded. endophyte |
| matchstick weed | Monosporus pedicellatus (delesseriaceae) |
| Key criteria: | Large fairly robust filamentous species found in the sublittoral and sublittoral fringe growing epilithically. It is readily identifiable by the monosporangia when fertile. The lack of records from the east coasts of Scotland and England probably indicates its relative rarity there rather than absence. epilithic |
| no common name | Monostroma grevillei (monostromataceae) |
| Key criteria: | A monostromatic foliose plant which could be superficially confused with Ulva. Very common and likely to occur frequently throughout the area but only found in late winter and spring spending the rest of the year as the microscopic unicellular sporophyte which can bore into shells. The foliose form is commonest in mid and upper intertidal rock pools. upper intertidal intertidal rock pool |
| no common name | Monostroma obscurum (monostromataceae) |
| Key criteria: | A monostromatic foliose plant which occurs most commonly attached to other algae and to shells and stones most frequently in mid to upper intertidal pools. Easily confused with other Monostroma species and superficially with Ulva. Probably occurs on all coasts though not necessarily common. Likely to be under-recorded because the species is not well-known and easily confused. upper intertidal intertidal pool |
| no common name | Monostroma oxyspermum (monostromataceae) |
| Key criteria: | A monostromatic foliose form which is much more common and widespread than the previous records suggest. Exists in several forms on the open coast at sporadic locations but is really common in the mid-reaches of estuaries. Likely to be under-recorded since its habitat is rarely visited by collectors. ~ |
| no common name | Myriactula areschougii (chordariaceae) |
| Key criteria: | Plants endophytic forming small gelatinous pustules emergent from the cryptostomata of Fucus especially F. serratus. Recorded throughout the year and probably more widely distributed than the records suggest. endophyte |
| no common name | Myriactula areschougii (chordariaceae) |
| Key criteria: | Plants epiphytic forming small gelatinous pustules emergent from the conceptacles on the thongs of Himanthalia elongata. A summer annual which is probably much more widely distributed thanthe records suggest. epiphyte |
| no common name | Myriactula chordae (chordariaceae) |
| Key criteria: | Plants forming small gelatinous cushions on hosts. Rare. A summer annual which is probably under-recorded. ~ |
| no common name | Myriactula haydenii (chordariaceae) |
| Key criteria: | Plants epiphytic forming minute tufts on Scytosiphon lomentaria. A summer annual which is probably under-recorded. epiphyte |
| no common name | Myriactula rivulariae (chordariaceae) |
| Key criteria: | Plants epiphytic forming small hemispherical cushions on various algae particularly Cystoseira and Sargassum muticum and with a southern and western distribution pattern. epiphyte |
| no common name | Myriactula stellulata (chordariaceae) |
| Key criteria: | Plants epiphytic forming minute tufts on Dictyota dichotoma. A rarely recorded summer annual. epiphyte |
| brown jelly weed | Myriocladia lovenii (chordariaceae) |
| Key criteria: | Plants rare epiphytic forming sparsely branched gelatinous thalli on Laminaria blades. epiphyte |
| brown jelly weed | Myriocladia tomentosa (chordariaceae) |
| Key criteria: | Plants rare but widely distributed forming sparsely branched gelatinous thalli. Probably widely under-recorded. ~ |
| no common name | Myrionema corunnae (chordariaceae) |
| Key criteria: | Plants epiphytic forming small discs on Laminaria blades. Probably widely under-recorded. epiphyte |
| no common name | Myrionema liechtensternii (chordariaceae) |
| Key criteria: | Plants epiphytic rare forming small brown spots on bedrock in the upper intertidal. epiphyte upper intertidal intertidal rock |
| no common name | Myrionema orbiculare (chordariaceae) |
| Key criteria: | Plants epiphytic forming minute discs on Zostera blades. A summer annual probably under-recorded. epiphyte |
| no common name | Myrionema papillosum (chordariaceae) |
| Key criteria: | Plants epiphytic forming small discs on Laminaria saccharina blades. A rarely recorded summer annual requiring microscopic examination to distinguish it from the closely related M. strangulans. epiphyte |
| no common name | Myrionema strangulans (chordariaceae) |
| Key criteria: | Plants epiphytic forming small discs on various hosts especially Ulva and Ulva. A common and widespread summer annual rarely recorded throughout the year. epiphyte |
| no common name | Myriotrichia clavaeformis (chordariaceae) |
| Key criteria: | Plants epiphytic forming small tufts on various algae and Zostera in intertidal pools and the shallow subtidal. A quite widely distributed summer annual. epiphyte intertidal shallow subtidal subtidal pool |
| no common name | Neevea repens (phragmonemataceae) |
| Key criteria: | Minute (microscopic) colonies of red or violet to rosy-purple multiseriate filaments sometimes pseudobranched. Subtidal. Endozoic in bryozoans especially Flustra foliacea annelid worm tubes and ascidians. Southern distribution in Britain and probably more widespread along the south coast of England than the records indicate. endophyte subtidal |
| no common name | Nemastoma canariense (nemastomataceae) |
| Key criteria: | Tough tubular or slightly flattened gelatinous alga with a few dichotomies. Known only from the subtidal of Lough Hyne Co. Cork. Very rare. subtidal |
| no common name | Ochlochaete hystrix (ulvellaceae) |
| Key criteria: | A microscopic disc reported to occur on a variety of algae and other plants both subtidal and intertidal coastal and estuarine. The few recordings shown do not reflect this and are likely to be an underestimate of its distribution. It probably occurs on all coasts but may not be common. intertidal subtidal |
| no common name | Ostreobium quekettii (ulvellaceae) |
| Key criteria: | This obscure plant bores through subtidal dead mollusc shells. When found it is highly characteristic but it lives in a particularly obscure situation which is rarely sampled. It is likely to occur on all coasts but has simply not been sought. It is one of the deepest-growing species in the subtidal. subtidal |
| no common name | Percursaria percursa (ulvellaceae) |
| Key criteria: | Small (to 10 cm) unbranched filamentous species that grows entangled in tufts in sheltered habitats in the intertidal zone penetrating high into estuaries. Relatively inconspicuous this species has probably been under-recorded in the area. intertidal sheltered |
| broad leaf weed | Petalonia fascia (scytosiphonaceae) |
| Key criteria: | A common and widely distributed spring annual. The dorsiventrally flattened blades of this mainly epilithic species are found predominantly in shallow pools and runnels throughout the intertidal. epilithic intertidal pool |
| no common name | Petalonia filiformis (scytosiphonaceae) |
| Key criteria: | Forming fine ribbon-like spirally twisted gregarious blades this widely but infrequently recorded spring annual can be found locally common on vertical cliff faces large boulders etc in the upper intertidal. upper intertidal intertidal |
| no common name | Petalonia zosterifolia (scytosiphonaceae) |
| Key criteria: | This widely distributed but infrequently recorded spring annual is similar to P. fascia but forms narrower more linear blades and occurs in the upper intertidal in moderately to very exposed areas. upper intertidal intertidal exposed |
| no common name | Petroderma maculiforme (ralfsiaceae) |
| Key criteria: | A fairly widespread crust probably under-recorded forming thin confluent patches on stones and shells in intertidal pools and channels. Appears to show a preference for hard substrata such as flint stones. intertidal pool |
| no common name | Petrospongium berkeleyi (chordariaceae) |
| Key criteria: | Plants epilithic more rarely epiphytic on Ralfsia verrucosa in the lower intertidal forming small gelatinous hemispherical cushions. A summer annual which has a south-western and western distribution pattern. epiphyte epilithic lower intertidal intertidal |
| encrusting red | Peyssonnelia armorica (peyssonneliaceae) |
| Key criteria: | Crustose plants found on small stones. Rare known from only a few localities. ~ |
| encrusting red | Peyssonnelia atropurpurea (peyssonneliaceae) |
| Key criteria: | Crustose plants found mainly on crustose corallines generally in shady places. Upper subtidal to 13 m. Apparently with a south- western distribution. Occasional. subtidal |
| encrusting red | Peyssonnelia dubyi (peyssonneliaceae) |
| Key criteria: | Crustose plants found mainly on rocks stones and on crustose corallines Laminaria holdfasts and shells in shallow pools in lower intertidal and in subtidal to 16 m. Widespread except eastern England. Occasional. lower intertidal intertidal subtidal rock pool |
| encrusting red | Peyssonnelia harveyana (peyssonneliaceae) |
| Key criteria: | Crustose plants adherent except at margins generally growing epilithically or on coralline algae or kelp holdfasts in the upper subtidal to 12 m usually in places with some current flow. Widely distributed but rarely recorded. epilithic subtidal |
| encrusting red | Peyssonnelia immersa (peyssonneliaceae) |
| Key criteria: | Crustose plants adherent throughout generally growing epilithically on shells or on maerl in pools in the lower intertidal and subtidal to 19 m usually in moderately sheltered locations. Widely distributed mainly on western coasts. Rare. epilithic lower intertidal intertidal subtidal sheltered pool |
| no common name | Phaeophila dendroides (ostreobiaceae) |
| Key criteria: | Minute (microscopic) irregularly branched filaments. Cells often bearing long undulate and twisted hairs without a basal swelling. Intertidal and subtidal. Endophytic in larger algae such as brown (e.g. Laminaria digitata) and red species (e.g. Polysiphonia elongata); endozoic in shells of polychaetes barnacles and bivalves. Possibly more widespread than indicated by the records but this species requires taxonomic investigation. endophyte intertidal subtidal |
| no common name | Phaeostroma pustulosum (chordariaceae) |
| Key criteria: | Plants minute epiphytic forming small spots on various hosts. Microscopic examination reveals a prostrate system of short branched filaments. Probably under-recorded. epiphyte |
| no common name | Phycocelis crouaniorum (chordariaceae) |
| Key criteria: | Plants epiphytic forming small spots on various hosts especially Fucus serratus in the lower intertidal and shallow subtidal. Probably much under-recorded. epiphyte lower intertidal intertidal shallow subtidal subtidal |
| no common name | Phycocelis foecunda (chordariaceae) |
| Key criteria: | Plants epiphytic forming small spots on Palmaria palmata and Laminaria saccharina blades in the lower intertidal and shallow subtidal. A summer annual probably much under-recorded. epiphyte lower intertidal intertidal shallow subtidal subtidal |
| no common name | Pikea californica (dumontiaceae) |
| Key criteria: | An introduced species. Medium cartilaginous compressed fronds with fairly regular branching. Easily confused with Gelidium corneum found on wave-exposed shores in the lower intertidal. Extreme south-west Britain. Rare. lower intertidal intertidal exposed |
| no common name | Pilinia rimosa (not known) |
| Key criteria: | A rare but widely distributed species forming short confluent turf-like patches in caves or exposed on rock in shaded conditions in the upper intertidal. upper intertidal intertidal rock exposed |
| encrusting red | Plagiospora gracilis (gloiosiphoniaceae) |
| Key criteria: | Small mucilaginous crusts found on stones and pottery in the subtidal. Rare. May be the tetrasporophyte of Gloiosiphonia capillaris. subtidal |
| Borrer's seed weed | Pleonosporium borreri (ceramiaceae) |
| Key criteria: | Small (to 5 cm) filamentous species generally confined to the subtidal zone where it occurs in wave-exposed kelp forests. It is relatively easy to identify when examined microscopically and the lack of records here probably indicates a lack of diving surveys rather than its rarity. subtidal exposed |
| no common name | Pogotrichum filiforme (acinetosporaceae) |
| Key criteria: | Plants epiphytic forming small tufts on various algae especially kelps in intertidal pools and the shallow subtidal. A spring and summer annual probably more widely distributed than the records suggests. epiphyte intertidal shallow subtidal subtidal pool |
| no common name | Porphyridium purpureum (porphyridiaceae) |
| Key criteria: | Minute (microscopic) bright red spherical unicellular alga. The unicells tend to aggregate to form loose masses. Intertidal. The species occurs on wood walls and bare earth in estuarine and damp terrestrial conditions on vertical walls. Possibly more widespread in brackish and saline conditions than records suggest. Also reported from freshwater and terrestrial environments. intertidal brackish |
| no common name | Porphyrostromium boryanum (erythrotrichiaceae) |
| Key criteria: | Microscopic purple-rose single-layered variable prostrate system from which arise several very small unbranched uniseriate erect filaments becoming multiseriate above sometimes expanded into a one cell thick ribbon-like blade. Lower intertidal and shallow subtidal. Epiphytic various algae and Zostera. Scattered localities from around Britain and Ireland. Uncommon probably overlooked but more widespread than recorded. epiphyte lower intertidal intertidal shallow subtidal subtidal |
| no common name | Porphyrostromium ciliare (erythrotrichiaceae) |
| Key criteria: | Microscopic dark purple single-layered prostrate system to c. 200 micro m in diameter from which arise several very small multiseriate terete filaments. Subtidal. Epiphytic on subtidal algae and mixed with other algae; also on the eel grass Zostera marina. Recorded from scattered localities throughout Britain and Ireland. Uncommon probably overlooked but more widespread than has been recorded. epiphyte subtidal |
| no common name | Prasiola calophylla (prasiolaceae) |
| Key criteria: | Occurs on upper intertidal rocks on the open coast and in estuaries. More widespread than the records suggests. Often misidentified as Prasiola stipitata resulting in under-recording. upper intertidal intertidal rock |
| no common name | Prasiola crispa (prasiolaceae) |
| Key criteria: | A small thallose green alga found both in terrestrial and maritime habitats. Relatively uncommon and occurring in enhanced-nitrogenous compound conditions. Under-recorded but likely to be more common in western situations. ~ |
| no common name | Prasiola furfuracea (prasiolaceae) |
| Key criteria: | A very small foliose plant with a highly characteristic cell arrangement but which can be confused with the more common Prasiola stipitata. May be rather more widespread than the records show but not thought to be common. Likely to be restricted to northern Britain. ~ |
| no common name | Prasiola stipitata (prasiolaceae) |
| Key criteria: | A very common species found on high intertidal rocks throughout the area. The commonest of the Prasiola species although records of it may include other Prasiola species with which it has been confused. intertidal rock |
| no common name | Pringsheimiella scutata (chaetophoraceae) |
| Key criteria: | A microscopic discoid epiphyte on a wide range of intertidal and subtidal seaweeds and on the eelgrass Zostera. Likely to occur throughout the area and be more widespread than the records suggest but likely to be under-recorded because of its inconspicuous form. epiphyte intertidal subtidal |
| no common name | Protectocarpus speciosus (chordariaceae) |
| Key criteria: | Plants epiphytic more rarely epilithic and epizoic forming minute tufts. A spring and summer annual which is probably under-recorded because of its microscopic size. epiphyte epilithic epizoic |
| no common name | Pseudendoclonium fucicola (chaetophoraceae) |
| Key criteria: | A gelatinous microscopic cushion- shaped epiphyte on Fucus. Probably occurs more widely in the area but may be under-recorded because of difficulty of identification and possible confusion with other green epiphytes. epiphyte |
| no common name | Pseudendoclonium submarinum (chaetophoraceae) |
| Key criteria: | Forms a green pseudoparenchymatous crust on a wide range of substrata in theupper intertidal. Probably more widespread in Britain but often overlooked. In superficial surveys without microscopic examination may sometimes be confused with intertidal lichens. upper intertidal intertidal |
| no common name | Pseudolithoderma extensum (ralfsiaceae) |
| Key criteria: | Plants crustose firm and coriaceous forming extensive strongly adherent patches on stones and bedrock in the subtidal. A perennial species it is probably much more common and widely distributed than the records suggest. subtidal rock |
| no common name | Pseudolithoderma roscoffense (ralfsiaceae) |
| Key criteria: | Plants crustose forming confluent loosely adherent patches on stones and pebbles in pools and exposed in the lower intertidal. A perennial species restricted to the south and southwest coasts it is only distinguished from P. extensum by its different shaped plurilocular sporangia. lower intertidal intertidal exposed pool |
| no common name | Pseudopringsheimia confluens (chaetophoraceae) |
| Key criteria: | A cushion-forming epiphyte on Laminaria stipes. May also occur on other species but is difficult to identify and could be under-recorded. Not thought to be common or widespread in the area. epiphyte |
| no common name | Pterosiphonia ardreana (rhodomelaceae) |
| Key criteria: | Small (to 10 cm) polysiphonous species with regular tooth-like laterals. Rare on wave-exposed coasts of southern England Ireland on the lower shore and sublittoral. exposed |
| no common name | Pterosiphonia pennata (rhodomelaceae) |
| Key criteria: | Small (to 8 cm) compressed polysiphonous species with regular laterals. Rare on coasts of southern England SW Ireland occurs mostly in the subtidal zone of moderately sheltered shores. subtidal sheltered |
| no common name | Pterosiphonia pinnulata (rhodomelaceae) |
| Key criteria: | Probable introduction to Britain where it has been found in the vicinity of an oyster farm near Milford Haven Wales. Small (to 5 cm) turf-forming in the shallow subtidal. shallow subtidal subtidal |
| no common name | Pterothamnion crispum (ceramiaceae) |
| Key criteria: | A small delicate filamentous species that is difficult to identify owing to its similarity to some forms of P. plumula. It probably has a south-western distribution as shown here. ~ |
| bushy feather weed | Pterothamnion plumula (ceramiaceae) |
| Key criteria: | Delicate but large (15 cm) filamentous species It grows both intertidally and subtidally in a wide range of habitats including rock pools. This species is common and relatively easy to identify as indicated by the large number of records shown here. intertidal subtidal rock pool |
| no common name | Pterothamnion polyacanthum (ceramiaceae) |
| Key criteria: | Small filamentous alga (to 3 cm) found growing epiphytically on other algae or on rocks to 20 m. Type locality is Kilkee Co. Clare Ireland. Reported from Milford Haven and Plymouth. Seemingly very rare. epiphyte rock |
| feather bush weed | Ptilothamnion pluma (ceramiaceae) |
| Key criteria: | Tiny (< 10 mm) filamentous species that forms a turf mostly on kelp stipes and in shady places such as caves It can easily be confused with Spermothamnion spp. Much under-recorded here probably because it is so inconspicuous but appears to be generally distributed in the area as shown here. ~ |
| no common name | Ptilothamnion sphaericum (ceramiaceae) |
| Key criteria: | Turf-forming small filamentous alga that lives both epiphytically and epilithically at moderately to extremely wave-exposed sites; often growing on maerl. epiphyte epilithic exposed |
| no common name | Punctaria crispata (chordariaceae) |
| Key criteria: | Plants rare epiphytic forming dorsiventrally flattened peripherally ruffled blades which might be mistaken for Laminaria saccharina. A rarely recorded summer annual in lower intertidal pools. epiphyte lower intertidal intertidal pool |
| no common name | Punctaria latifolia (chordariaceae) |
| Key criteria: | A fairly widespread species forming dorsiventrally flattened blades usually found epiphytic on a wide variety of algae in intertidal pools and the subtidal. A spring and summer annual. epiphyte intertidal subtidal pool |
| no common name | Punctaria plantaginea (chordariaceae) |
| Key criteria: | A fairly widely distributed not uncommon species found in intertidal pools and the subtidal. A spring and summer annual not easily distinguishable from P. latifolia. intertidal subtidal pool |
| no common name | Punctaria tenuissima (chordariaceae) |
| Key criteria: | A widely distributed and probably under-recorded species epiphytic on various algae in intertidal pools and the subtidal. A spring and summer annual characterized by more ribbon-shaped and thinner blades than P. latifolia. epiphyte intertidal subtidal pool |
| filamentous browns | Pylaiella littoralis (acinetosporaceae) |
| Key criteria: | A widespread and commonly recorded much branched filamentous species superficially similar to Ectocarpus but distinguishable by microscopic examination. Often found epiphytic on Fucus serratus. epiphyte |
| no common name | Rhizoclonium tortuosum (cladophoraceae) |
| Key criteria: | Forming fleecy mats of much-branched fine filaments in the upper intertidal zone. Relatively easy to identify except for discrimination from its congener R. riparium; abundant and widespread in the area as indicated. upper intertidal intertidal |
| no common name | Rhodella maculata (porphyridiaceae) |
| Key criteria: | Microscopic unicellular alga found in sand. Known only from Southend in England. sand |
| no common name | Rhodochorton concrescens (acrochaetiaceae) |
| Key criteria: | Tiny discoid growths on hydroids generally in subtidal habitats. Widespread but uncommon. Under-recorded. subtidal |
| no common name | Rhodochorton membranaceum (acrochaetiaceae) |
| Key criteria: | Endophyte in hydroids generally in subtidal or lower-shore habitats. Widespread and common. endophyte subtidal |
| no common name | Rhodochorton purpureum (acrochaetiaceae) |
| Key criteria: | Tuft-forming on rocks in the upper intertidal particularly in crevices and under other seaweeds. Very common and widespread. upper intertidal intertidal rock |
| straggly tail weed | Rhodomela lycopodioides (rhodomelaceae) |
| Key criteria: | Large (to 30 cm) cylindrical much-branched species with regular laterals. Found rarely but mostly commonly on kelp stipes in moderately wave-exposed locations. Confined to the north and NE coasts. exposed |
| encrusting red | Rhodophysema elegans (rhodophysemataceae) |
| Key criteria: | Extensive crustose growths in the lower intertidal on subtidal rocks to about 10 m. small stones and pebbles glass crustaceans and molluscs and on maerl. Common and widespread. lower intertidal intertidal subtidal rock |
| encrusting red | Rhodophysema feldmanii (rhodophysemataceae) |
| Key criteria: | Microscopic monostromatic crust to 1 mm in diameter. Epizoic on the hydroid Amphisbetia. Known only from Kilkieran Bay Co. Galway. Very rare. epizoic |
| encrusting red | Rhodophysema georgei (rhodophysemataceae) |
| Key criteria: | Minute globose growths fringing subtidal sea-grasses (mainly Zostera marina). Uncommon and generally western in distribution. subtidal |
| no common name | Rosenvingiella polyrhiza (prasiolaceae) |
| Key criteria: | A filamentous plant which occurs mixed with Prasiola species and independently on high intertidal rocks and in green mats in estuaries. Likely to be more common in northern Britain. It is often overlooked by collectors and is much more widespread than the records suggests. Apparent concentration in Northern Ireland and north-east England is a reflection of intensive surveys there by collectors familiar with this obscure plant. intertidal rock |
| no common name | Sahlingia subintegra (erythrotrichiaceae) |
| Key criteria: | Microscopic bright red single layered compact regular disc up to c. 200 micro m in diameter. Marginal cells of discs elongate bifid. Branching pseudodichotomous at apices. Subtidal. Epiphytic on various algae and on hydroids. Widespread in the southern half of Britain. epiphyte subtidal |
| no common name | Sarcodiotheca gaudichaudii (areschougiaceae) |
| Key criteria: | Probably introduced. Medium to large species with cylindrical rather brittle fronds laterals tapering both basally and apically. Colour varies from straw yellow in summer when bleached to pale pink to deep red or reddish brown. Morphologically similar to Gracilaria bursa-pastoris but differing anatomically (filimentous medulla) and with zonate tetrasporangia and less obvious cystocarps. Lower intertidal pools to upper subtidal mainly on small stones and shells; also marina pontoons. Rare. lower intertidal intertidal subtidal pool |
| no common name | Sauvageaugloia griffithsiana (chordariaceae) |
| Key criteria: | Plants widely distributed and not uncommon forming branched gelatinous thalli in lower intertidal pools. lower intertidal intertidal pool |
| feather shrublet | Scagelothamnion pusillum (ceramiaceae) |
| Key criteria: | Delicate small filamentous species confined to the subtidal and to the extreme northern part of the area which is the southern edge of its range. It is difficult to identify and apparently very rare. subtidal |
| no common name | Schmitzia neapolitana (calosiphoniaceae) |
| Key criteria: | Gametophytes are small gelatinous plants with cylindrical fronds. Known only from the subtidal to depths of 15 m. on cobble in strong current-affected areas south western to western distribution. Rare. Tetrasporophytes unknown in area. subtidal depth |
| Sciana's weed | Scinaia interrupta (galaxauraceae) |
| Key criteria: | Fairly large soft dichotomously branched cylindrical alga found in the lower shore and in the subtidal to 30 m. See the legend for S. furcellata regarding the confused state of identification of the two entities. Scinaia interrupta is not common but widely distributed on western shores north to Shetland. subtidal |
| no common name | Scytosiphon dotyi (scytosiphonaceae) |
| Key criteria: | A rare probably under-recorded species occupying the sides of vertical cliff faces large boulders etc. in the upper intertidal during the spring. upper intertidal intertidal |
| chain seed bush weed | Seirospora interrupta (ceramiaceae) |
| Key criteria: | A fairly delicate filamentous species that is largely confined to the subtidal and extreme low water mark on sheltered shores where it grows both epiphytically and on stones. It is readily identifiable when bearing the unique seirospores but very similar to Aglaothamnion when vegetative. The records suggest it to be commoner in Scotland but this may represent sampling bias or the distribution of sheltered subtidal habitats. epiphyte subtidal sheltered |
| no common name | Sorapion kjellmanii (scytosiphonaceae) |
| Key criteria: | An extremely rare thin crustose species only distinguishable from S. simulans by microscopic examination. ~ |
| no common name | Sorapion simulans (scytosiphonaceae) |
| Key criteria: | A rarely recorded crustose species forming thin closely adherent patches on stones in the subtidal. subtidal |
| creeping bush weed | Spermothamnion repens (ceramiaceae) |
| Key criteria: | Small (to 3 cm) filamentous species that forms a turf on hard substrata and large algae in the subtidal and lower intertidal in a wide range of habitats. It appears to be generally distributed in the area as shown here but is probably under-recorded because it is inconspicuous. lower intertidal intertidal subtidal |
| creeping bush weed | Spermothamnion strictum (ceramiaceae) |
| Key criteria: | Small (to 3 cm) filamentous species that forms a turf on hard substrata and large algae in the subtidal in sheltered habitats. It is difficult to discriminate from the commoner S. repens but is probably rare rather than just under-recorded here because of its inconspicuousness. subtidal sheltered |
| no common name | Sphaerotrichia divaricata (chordariaceae) |
| Key criteria: | Plants rare. A summer annual forming slimy cartilaginous branched thalli in lower intertidal pools. lower intertidal intertidal pool |
| no common name | Stictyosiphon griffithsianus (chordariaceae) |
| Key criteria: | A branched filiform species usually found as an epiphyte on Palmaria palmata. A summer annual mainly with a western distribution. epiphyte |
| no common name | Stictyosiphon soriferus (chordariaceae) |
| Key criteria: | A fairly rare branched filiform species occurring epiphytically on various hosts. A summer annual with a northern distribution pattern. epiphyte |
| no common name | Stictyosiphon tortilis (chordariaceae) |
| Key criteria: | Plants not uncommon on western and northern shores occurring in mid to lower intertidal pools during the spring and summer. lower intertidal intertidal pool |
| no common name | Stilopsis lejolisii (chordariaceae) |
| Key criteria: | Plants rare forming branched filiform thalli on rocks in the lower intertidal. lower intertidal intertidal rock |
| no common name | Stragularia clavata (scytosiphonaceae) |
| Key criteria: | Plants crustose usually epilithic especially on _soft̨ bedrock forming discrete or confluent dark-brown patches in pools or runnels or under fucoids. Common and widely distributed. epilithic rock pool |
| no common name | Stragularia spongiocarpa (scytosiphonaceae) |
| Key criteria: | Plants crustose epilithic forming discrete or confluent light yellow-brown crusts on the sides and bottoms of sandy pools in the lower intertidal. An extremely rare perennial crust distinguishable only when fertile during the winter. epilithic lower intertidal intertidal sand pool |
| no common name | Streblonema breve (chordariaceae) |
| Key criteria: | Plants endophytic/epiphytic forming minute tufts on Ascophyllum. epiphyte endophyte |
| no common name | Streblonema fasciculatum (chordariaceae) |
| Key criteria: | Plants rare widely distributed and endophytic in Eudesme virescens. endophyte |
| no common name | Streblonema infestans (chordariaceae) |
| Key criteria: | Minute profusely branched filaments endozoic in Alcyonidium. Probably under-recorded. endophyte |
| no common name | Streblonema parasiticum (chordariaceae) |
| Key criteria: | Plants endophytic forming minute spots on various hosts. endophyte |
| no common name | Streblonema stilophorae (chordariaceae) |
| Key criteria: | Plants endophytic forming minute spots on Stilophora tenella. endophyte |
| no common name | Streblonema tenuissimum (chordariaceae) |
| Key criteria: | Plants endophytic forming minute spots in Sauvageaugloia griffithsiana. endophyte |
| no common name | Streblonema zanardinii (chordariaceae) |
| Key criteria: | Plants endophytic forming small spots in the cortical tissues of Chylocladia verticillata. endophyte |
| no common name | Stylonema alsidii (goniotrichaceae) |
| Key criteria: | Minute (microscopic) to very small brownish-red to purple usually uniseriate filamentous alga to c. 2 mm in length. Cells rectangular and mostly wider than long. Lower intertidal and subtidal in sheltered areas. Epilithic epiphytic and epizoic. Much more widespread around British and Irish coasts than indicated by the records. epiphyte epilithic epizoic lower intertidal intertidal subtidal sheltered |
| no common name | Sykidion dyeri (chlorococcaceae) |
| Key criteria: | A microscopic unicell found epiphytic on intertidal mat-forming algae. There is a possibility of confusion with similar unicells belonging to the genus Chlorochytrium. It may or may not therefore be under-recorded and requires re-investigation. epiphyte intertidal |
| no common name | Symphyocarpus strangulans (scytosiphonaceae) |
| Key criteria: | A small very rare closely adherent epiphytic and epizoic crustose species reported for the intertidal and subtidal down to 20 m. epiphyte epizoic intertidal subtidal |
| no common name | Tellamia contorta (chaetophoraceae) |
| Key criteria: | A microscopic endozoic branched filament which lives between the periostracum and the calcareous parts of shells of Littorina littoralis. Very rarely occurs in other gastropods with a thick periostracum. A very characteristic plant which is definitely under-recorded presumably because of its obscure habitat. Likely to be on most or all shores in the area where its usual host species is present. endophyte |
| no common name | Tsengia bairdii (nemastomataceae) |
| Key criteria: | Very rare small and gelatinous Northern species only collected once in the last 100 years outside the mouth of Loch Resort Lewis and Harris growing on mobile substrata in the subtidal. subtidal |
| no common name | Ulonema rhizophorum (chordariaceae) |
| Key criteria: | Plants epiphytic forming minute spots on Dumontia contorta. A spring and summer annual. Not uncommon and widely distributed. epiphyte |
| no common name | Ulothrix flacca (ulotrichaceae) |
| Key criteria: | Separation of the species of Ulothrix is difficult. They occur all around Britain in estuaries in the upper intertidal on rocks and on other algae. U. flacca is the best known name and it is likely that some records of this entity represent misidentifications of other species. upper intertidal intertidal rock |
| no common name | Ulothrix implexa (ulotrichaceae) |
| Key criteria: | This species occurs on all coasts in the area on upper intertidal rocks in estuaries and as an epiphyte on salt- marsh plants. The apparently restricted distribution is an artifact due to severe under- recording in much of Britain and detailed recording in Northern Ireland by a specialist on this genus. epiphyte upper intertidal intertidal marsh rock |
| no common name | Ulothrix speciosa (ulotrichaceae) |
| Key criteria: | This species occurs in a wide range of situations on upper intertidal rocks on mud in estuaries on fucoids and on salt- marsh plants. It is likely to be seriously under-recorded because of the difficulty of distinction from other Ulothrix species. upper intertidal intertidal mud marsh rock |
| no common name | Ulothrix subflaccida (ulotrichaceae) |
| Key criteria: | This is the smallest and the least obvious of the easily confused microscopic filamentous Ulothrix species. It occurs frequently in estuaries but may well be overlooked. Furthermore some regard it as conspecific with other Ulothrix species. The likelihood is that it is much more widespread around the whole of Britain than the records suggest. ~ |
| no common name | Ulvaria fusca (monostromataceae) |
| Key criteria: | The taxonomy of foliose monostromatic green seaweeds is very confused. This is one of the less well known and less clearly defined species. It is unlikely that it is as common as the related common and more easily identified Monostroma grevillei and M. oxyspermum. Nonetheless it may be more widespread than the records indicate but is not recorded because collectors cannot distinguish it from the common ones. ~ |
| no common name | Urospora penicilliformis (ulotrichaceae) |
| Key criteria: | This species most commonly occurs in the winter and is found on all coasts in the area mainly as an epilithic form in the upper intertidal. It may be confused with Ulothrix and is likely to occur in the stretches of coastline where it has not previously been recorded. epilithic upper intertidal intertidal |
| no common name | Urospora wormskioldii (ulotrichaceae) |
| Key criteria: | This is a highly characteristic species which owing to its large cell size would be difficult to confuse with other Ulothrix and Urospora species. The sparse clumped distribution shown is a reflection of specific surveys by those particularly interested in this plant. It is not common but is likely to be more widespread than shown. ~ |
| no common name | Vaucheria arcassonensis (vaucheriaceae) |
| Key criteria: | Small to large green mats of microscopic siphons. Salt marshes. Widespread but not common. Under-recorded. marsh |
| no common name | Vaucheria compacta (vaucheriaceae) |
| Key criteria: | Small to large green mats or even carpets of microscopic siphons. Salt marshes exposed mud or permanently under water in estuaries. Widespread common under- recorded. The north-east coast of England has seen little recording but there are few rivers or streams that enter the sea so this species will be uncommon there. mud marsh exposed |
| no common name | Vaucheria coronata (vaucheriaceae) |
| Key criteria: | Small to large green mats of microscopic siphons. Salt marshes and upper estuaries. Widespread and common. Under-recorded. marsh |
| no common name | Vaucheria dichotoma (vaucheriaceae) |
| Key criteria: | The colonies may form bearskin-like masses in calm water and grow at considerable depth on muddy substrata. Lakes and ditches. Uncommon brackish-water species. mud depth brackish |
| no common name | Vaucheria erythrospora (vaucheriaceae) |
| Key criteria: | Small mats of green microscopic siphons. In streams and ditches in the upper parts of estuaries. Originally thought to be a south-east England species but is common on the north- west coast of England where brackish water meets freshwater. Its northern limit is probably to be found in south-west Scotland. Under-recorded. brackish |
| no common name | Vaucheria intermedia (vaucheriaceae) |
| Key criteria: | Small to large green mats of microscopic siphons. Salt marshes of diverse salinity. Widespread common. Under-recorded. marsh brackish |
| no common name | Vaucheria litorea (vaucheriaceae) |
| Key criteria: | Dark green mats of microscopic siphons. Sheltered parts of salt marshes. Widespread and generally uncommon but frequent in Morecambe Bay. Under-recorded. marsh sheltered |
| no common name | Vaucheria longicaulis (vaucheriaceae) |
| Key criteria: | Green mats of microscopic siphons. At or below low tide level. Rare. Recently recorded and reported by the late T. Christensen. Under-recorded. ~ |
| no common name | Vaucheria medusa (vaucheriaceae) |
| Key criteria: | Small to large green mats of microscopic siphons. The upper parts of estuaries on mud near freshwater within reach of brackish water. Uncommon. Under-recorded. mud brackish |
| no common name | Vaucheria minuta (vaucheriaceae) |
| Key criteria: | Small to large green mats of microscopic siphons. Salt marshes and the sides of ditches. Rare. Under-recorded. Most finds by P.J.G. Polderman. Easy to miss in crude culture as it grows so much shorter and is hidden by the other Vaucheria species amongst which it grows. marsh |
| no common name | Vaucheria piloboloides (vaucheriaceae) |
| Key criteria: | Small green mats of microscopic siphons. Sheltered parts of salt marshes above or below water. Uncommon. Under-recorded. marsh sheltered |
| no common name | Vaucheria sescuplicaria (vaucheriaceae) |
| Key criteria: | Small to large green mats of microscopic siphons. Sheltered parts of salt marshes above or below water. Uncommon. Under-recorded marsh sheltered |
| no common name | Vaucheria subsimplex (vaucheriaceae) |
| Key criteria: | Small to large green mats or carpets of microscopic siphons. Bare soil or mud in salt marshes. Widespread common under-recorded. mud marsh |
| no common name | Vaucheria synandra (vaucheriaceae) |
| Key criteria: | Small to large green mats and cushions of microscopic siphons. Uppermost parts of salt marshes and estuaries. Widespread common under-recorded. marsh |
| no common name | Vaucheria velutina (vaucheriaceae) |
| Key criteria: | Small to large green mats of microscopic siphons. Salt marshes down to low shore. Widespread common under-recorded. marsh |
| no common name | Vaucheria vipera (vaucheriaceae) |
| Key criteria: | Small to large green mats of microscopic siphons. Salt marshes. Rare. The find by N. Carter in 1933 has not been rediscovered by the late T. Christensen or R. Merritt on Canvey Island. The environment there has been much changed by building and sea walls. marsh |
A Check-list and Atlas of the Seaweeds of Britain and Ireland. F. G. Hardy and M. D. Guiry. The British Phycological Society, 2003. ISBN 0 9527115 16 Seaweeds of Britain and Ireland. Bunker, Brodie, Maggs and Bunker. Seasearch 2012.