A Catalogue of Irish Seaweeds

An updated systematic catalogue of the seaweeds of the island of Ireland is presented with sources, habitats, distributions, and notes on nomenclature, taxonomy and distribution. Included are 570 303 species of Rhodophyta, 93 species of Chlorophyta, 13 species of Vaucheria, and 161 species of Phaeophyceae. Three phyla (Rhodophyta, Chlorophyta, and Ochrophyta), 11 classes (5 Rhodophyta; 4 Chlorophyta; 2 Ochrophyta), 35 orders (19 Rhodophyta; 5 Chlorophyta; 11 Ochrophyta), 91 families (50 Rhodophyta; 16 Chlorophyta; 25 Ochrophyta) are represented. English and Irish vernacular names, and sources for these are given, together with a glossary of Irish names. A list of seaweeds found in Britain but not reported from Ireland to date is given together with distributional, taxonomic, nomenclatural, and other details. A preliminary comparative conservation assessment of 334 species of rare or potentially rare species in Britain and Ireland is given (Gigartinales, Rhodophyta), and Schmitziellaceae, M.D.Guiry, D.J.Garbary & G.W.Saunders fam. nov. (Gigartinales, Rhodophyta). Ninety-six species are known from Britain (including two varieties of species not otherwise known to occur in Britain), but not from 53 reds, 14 greens, a single Vaucheria, and 28 browns. Twenty of these (18 reds and two browns) are considered to be adventive or potentially adventive, leaving only 76 native species that are found in Britain but not in Ireland, which results in an Irish seaweed flora that is currently about 88% of the native British seaweed flora, contrasting very favourably with a native flowering-plant flora in Ireland of about 50% of that of Britain (approximately 850 vs 1700 species).