First Non-native North American Marine/Estuarine Record: 1987
First Non-native East/Gulf Coast Marine/Estuarine Record: 1987
The encrusting bryozoan Membranipora membranacea was described from the Baltic Sea in Sweden by Linnaeus in 1767. In its native European waters, it occurs from the Barents Sea to the Atlantic coast of Spain, usually growing on macroalgae (Kluge 1975; Schwaninger 1999). It had been previously considered to have a global anti-tropical distribution, in the Northern and Southern Hemispheres, but North Pacific populations have been regarded as separate species by some taxonomists (Dick et al. 2005), while some or all Southern Hemisphere occurrences have been attributed to introductions by shipping (Keough and Ross 1999; Gappa 2000; Griffiths et al. 2009). However, mitochondrial DNA studies indicate that this 'species' consists of three long-separated clades in the North Pacific, and monophyletic clades in the North Atlantic, Southeast Pacific (Chile), Southwest Pacific (Australia, New Zealand), and Southeast Atlantic (South Africa) (Schwaninger 1999; Schwaninger 2008). The South African population has been described as a new species, M. rustica (Florence et al. 2007, cited by Mead et al. 2011b). This species complex may have originated in the North Pacific and colonized the Southern Ocean (Chile, South Africa, Australia, New Zealand) 10-20 million years ago, before reaching the Northeast Atlantic (Schwaninger 2008). The only verified invasion is its introduction from the Northeast Atlantic to the Northwest Atlantic. It was first reported from the Isles of Shoals, New Hampshire in 1987, and now occurs from Long Island Sound to southern Labrador (Berman et al. 1992; Wantanabe et al. 2010; Fisheries and Oceans Canada 2011; USGS Nonindigenous Species Program 2011).
Membranipora membranacea was first reported from kelp beds around the Isles of Shoals (New-Hampshire-Maine), and from Cape Neddick, Maine, in 1987 (Berman et al. 1992; Lambert et al. 1992). It was first reported south of Cape Cod at Mohegan Bluffs, Block Island, Rhode Island (1990, USGS Nonindigenous Aquatic Species Program 2011). Its southern limit appears to be Long Island Sound (1993, USGS Nonindigenous Aquatic Species Program 2011). Its northward spread has been more extensive. It has colonized Great Bay, Casco Bay, and Penobscot Bay in the Gulf of Maine (Whitlatch and Osman 2000; Pratt and Grason 2007; USGS Nonindigenous Aquatic Species Program 2011), and in 1992 was found on the Atlantic Coast of Nova Scotia, in Mahone and St. Margarets Bay (Saunders and Metaxas 2007). By 2002, it reached the western coast of Newfoundland, on the Gulf of St. Lawrence, and by 2009 was reported from several bays on the south and north coasts of the island. Its current northernmost record is Red Bay, Labrador, on the Straits of Belle Isle (Fisheries and Oceans 2011).