Codium fragile ssp. tomentosoides (Chlorophyta) invades the Gulf of St Lawrence, Atlantic Canada

Codium fragile (Suhr) Harlot ssp. tomentosoides (van Goer) Silva is reported for the first time from the Gulf of St Lawrence in Nova Scotia based on collections made in August 1996. Three drift thalli were collected initially from the southeast corner of Doctor Island, Caribou Harbour. Later an extensive subtidal population extending over 0.5 km(2) was located in the adjacent subtidal zone (1 m) associated with a former oyster lease. The habitat was a soft bottom embayment dominated by Zostera marina, and the Codium fragile was found as scattered individuals in scours in the Z. marina bed. The potential ecological impact of C. fragile on community structure and human activities in the southern Gulf of St Lawrence is discussed.