P.A.Gainey & P.E.Tompsett

The very long Cornish coastline with its numerous inlets provides a wide diversity of habitats which has ensured that the region is well represented with regards to the marine algae. Many of the algal species which are found here have a distinctly southern and western distribution in the British Isles. The problems associated with recording marine algae, especially those in the subtidal zone, are obvious. This, in conjunction with the fact that many of the algae are small and difficult to identify, may mean that many of them are somewhat more common than it would at first appear. Many of these rarer algae are difficult to identify positively, and have been recorded by only a few experts such that the distribution merely reflects where these algologists have been looking. Given these constraints, the following lists indicate those species thought to be very rare or scarce around the coastline of Cornwall and the Isles of Scilly at the present time.

There is currently no official Red Data Book (RDB) for the great majority of algal species, however, Brodie et al. (2007) list important sites for marine algae in the United Kingdom and also attempt a “rarity assessment” of many of the least common species. They identify the Falmouth Bay and Estuary, the Helford Estuary, the Isles of Scilly, the Tamar and Plymouth Sound as Important UK Plant Areas for marine algae and also potentially in a European context, exhibiting a particularly diverse algal flora with numerous interesting and rare species many of which have the type locality here. Hardy & Guiry (2003) published a phycological checklist and atlas of the seaweeds of Britain and Ireland which has provided a good overview of the various algal species and their standardised nomenclature has been followed here.

The marine algae listed here are designated as provisional RDB for Cornwall species in order to indicate that they would possibly be considered for inclusion in a Red Data Book of Marine Algae, should such a book ever be produced. In addition to these potential RDB species, the relatively warm, clear and unpolluted water of the Cornish coastline also acts as host to other algal species. Many of these would be considered as Nationally Scarce if the same criteria used for other groups of organism, were applied to them. These species are listed separately.

A wide range of sources was used when preparing this account, including Brodie & Irvine (2003), Brodie et al. (2007), Brodie, Maggs & John (2007), Dixon (1959), Farnham & Bishop (1985), Gainey (2003), Gill & Mercer (1989), Guiry & Guiry (2009), Hiscock, K. (1984), Hiscock, S. (1979; 1985), James (1983), Maggs & Hiscock, (1979), Price et al. (1980, 1981), Rostron & Hiscock (1987), Russell (1968) and Scruby et al. (1989). The authors are very grateful to Dr Juliet Brodie (British Natural History Museum) for her helpful involvement in the preparation of this account. Species are listed here alphabetically.

1. Provisional Red Data Book species

1.1. Green algae ( Chlorophyta)

Cladophora coelothrix

Cladophora pygmaea

Codium adhaerens

Codium bursa

Codium vermilara

1.2. Brown algae (Phaeophyta)

Acrothrix gracilis

Asperococcus scaber

Choristocarpus tenellus

Cladosiphon contortus

Compsonema microspongium

Cystoseira humilis var. myriophylloides

Desmarestia dresnayi

Leblondiella densa

Mesogloia lanosa

Myrionema papillosum

Phaeostroma pustulosum

Punctaria crispata

Sphacelaria tribuloides

Streblonema fasciculatum

Streblonema stilophorae

1.3. Red algae (Rhodophyta)

Acrochaetium battersianum

Acrochaetium lorraine-smithiae

Acrochaetium rosulatum

Aglaothamnion pseudobyssoides

Anotrichium furcellatum

Atractophora hypnoides

Bornetia secundiflora

Calosiphonia vermicularis

Ceramium cimbricum

Chondria coerulescens

Cruoria cruoriaeformis

Cryptonemia lomation

Cryptonemia seminervis

Dasya corymbifera

Drachiella minuta

Gelidiella calcicola

Gelidiella corneum

Gigartina pistillata

Grateloupia dichotoma

Grateloupia montagnei

Halymenia latifolia

Helminthocladia calvadosii

Itonea marginifera

Laurencia pyramidalis

Lithophyllum duckerae

Lophosiphonia reptabunda

Microcladia glandulosa

Osmundea truncata

Peyssonnelia armorica

Polysiphonia devoniensis

Polysiphonia foetidissima

Polysiphonia furcellata

Porphyra drachii

Pterosiphonia ardreana

Pterosiphonia pennata

Ptilothamnion sphaericum

Rhodophysema georgii

Rhodymenia delicatula

Schmitzia hiscockiana

Schmitzia neopolitana

Spermothamnion strictum

Titanoderma laminariae

2. Species occurring in Cornwall and the Isles of Scilly that could be considered as provisionally Nationally Scarce.

2.1. Green algae (Chlorophyta)

Aegagropila linnaei

Blastophysa rhizopus

Chlorochytrium cohnii

Chlorochytrium facciolaae

Cladophora vagabunda

Epicladia perforans

Pringsheimiella scutata

Pseudendoclonium fucicola

Ulvella lens

Umbraulva olivascens

2.2. Brown algae (Phaeophyta)

Asperococcus compressus

Bifurcaria bifurcata

Carpomitra costata

Chilionema ocellatum

Cladosiphon zosterae

Cystoseira baccata

Cystoseira foeniculacea

Cystoseira nodicaulis

Dictyota spiralis

Feldmannia simplex

Herponema valiantei

Herponema velutinum

Hincksia sandriana

Hincksia secunda

Laminaria ochroleuca

Microsyphar polysiphoniae

Microsyphar porphyrae

Myriactula clandestina

Myriactula rivulariae

Myrionema orbiculare

Padina pavonica Peacock’s Tail

Petalonia zosterifolia

Petroderma maculiforme

Petrospongium berkeleyi

Phycocelis foecunda

Pogotrichum filiforme

Protectocarpus speciosus

Pseudolithoderma roscoffense

Punctaria tenuissima

Tilopteris mertensii

Zanardinia typus

2.3. Red algae (Rhodophyta)

Acrochaetium efflorescens

Acrochaetium endozoicum

Acrochaetium infestans

Acrochaetium microscopicum

Acrochaetium parvulum

Acrochaetium trifilum

Aglaothamnion diaphanum

Aglaothamnion feldmanniae

Aglaothamnion priceanum

Ahnfeltiopsis devoniensis

Antithamnion cruciatum

Antithamnionella ternifolia

Callithamnion tetricum

Ceramium botryocarpum

Champia parvula

Chondracanthus acicularis

Chondracanthus teedei

Chondria capillaris

Choreocolax polysiphoniae

Choreonema thuretii

Colaconema asparagopsis

Colaconema bonnemaisoniae

Colaconema caespitosum

Colaconema endophyticum

Crouania attenuata

Dasya hutchinsiae

Dasya ocellata

Drachiella heterocarpa

Drachiella spectabilis

Dudresnaya verticillata

Erythropeltis discigera var. flustrae

Erythrotrichia bertholdii

Erythrotrichia welwitschii

Gastroclonium reflexum

Gloiosiphonia capillaris

Gonimophyllum buffhamii

Gracilaria bursa-pastoris

Gracilaria multipartita

Griffithsia devoniensis

Gymnogongrus crenulatus

Gymnogongrus griffithsiae

Haemescharia hennedyi

Haliptilon squamatum

Halopithys incurva

Helminthora divaricata

Hildenbrandia crouaniorum

Holmsella pachyderma

Hydrolithon boreale

Jania rubens var. corniculata

Lithophyllum nitorum

Lithothamnion corallioides Common maërl

Naccaria wiggii

Peyssonnelia atropurpurea

Peyssonnelia harveyana

Peyssonnelia immersa

Phyllophora sicula

Phymatolithon calcareum Common maërl

Pikea californica

Pneophyllum confervicola

Pneophyllum coronatum

Pneophyllum limitata

Pneophyllum myriocarpum

Polysiphonia atlantica

Polysiphonia denudata

Polysiphonia devoniensis

Polysiphonia elongella

Polysiphonia harveyi

Polysiphonia simulans

Porphyrostromium boryanum

Porphyrostromium ciliare

Pterosiphonia complanata

Pterothamnion crispum

Radicilingua thysanorhizans

Rhodymenia ardissonei

Schizymenia dubyi

Scinaia interrupta

Solieria chordalis

Sphaerococcus coronopifolius

Spyridia filamentosa

Stenogramme interrupta

2.4. Tribophyta

Vaucheria piloboloides