Marine bioinvasions of New England
More than 100 species---ranging from protists and sea squirts to seaweeds---have probably been introduced between the Gulf of Maine and Long Island Sound, but the histories and distributions of many of these species are poorly known. Very important invasions, in terms of predominance and probable impacts on marine communities, include the European periwinkle Littorina littorea, which is now the predominant omnivorous snail of rocky shores, marsh fringes, and other habitats and has significantly changed the abundance and distribution of many species in these habitats. Other invasions include the European shore crab, Carcinus maenas and the Asian shore crab, Hemigrapsus sanguineus, which are two of the most abundant roving omnivores of lower energy rocky shores. Also included is the green seaweed Codium fragile tomentosoides which can form extensive beds in shallow harbors and bays, and a plethora of fouling seasquirts from Europe and Asia that cover boat bottoms, floats, piers, traps, buoys, and virtually all other hard structures in shallow waters with a colorful and massive array of leathery and gelatinous masses. In addition, a variety of oyster parasites have arrived in the last quarter of the twentieth century in the Gulf of Maine and southern New England waters, apparently derived from more southern oyster populations.
---James Carlton