Gracilaria vermiculophylla Ohmi

Also known as Agarophyton vermiculophyllum (Ohmi) Gurgel, J.N.Norris & Fredericq and Gracilaria asiatica Zhang & B.M.Xia.

Common names: Worm Wart Weed
Description: Cartilaginous, dark red or red-brown to almost black (lighter in colour if sun-bleached). Branched fronds are elongated and slender, growing to around 2 m in length but most common 10-30 cm. Branches irregular, terete to slightly compressed in cross-section, often wrinkled with longitudinal grooves, lower parts may be hollow. Holdfast is a small disc.
Habitat: Found in sheltered, shallow habitats. Favours soft-bottomed, muddy, sheltered bays, inlets, harbours, lagoons and estuaries rich with nutrients. Tolerant of many stresses. Most commonly found loose-lying or attached to small stones or shells. Biomass peaks during early to mid-summer. In Ireland, found in estuarine muddy bays (Clonakilty, Roscarbary, and probably Blackwater estuary, Dungarvan Bay), often in conditions of varying salinity.
Distribution: Orignally described from Japan. Native to east Asia (China, Japan, Korea, Russia) and and SE Astia (Vietnam). Introduced to NE (Scandinavia south to Spain, including Britain and Ireland) and W Atlantic, W Mediterranean.
Simiar species: Gracilaria gracilis, which tends to be less branched, and not compressed and most commonly found on sandy rocks on wave-exposed shores. Expert help is required for certain identification.
Links: Invasion history in North America. Global Invasive Species Database.
Identification guide for selected marine non-native species (National Museum Wales). (Download free PDF, about 3.5 Mb).

Images: © David Fenwick