|Introduced marine and estuarine mollusks of North America: an end-of-the-20th-century perspective|
Carlton, J.T. (1992). Introduced marine and estuarine mollusks of North America: an end-of-the-20th-century perspective. J. Shellfish Res. 11(2): 489-505
In: Journal of Shellfish Research. National Shellfisheries Association: Duxbury. ISSN 0730-8000, more
A review of the introduced marine and estuarine (brackish water) bivalves and prosobranch and pulmonate gastropods of the Atlantic, Gulf and Pacific coasts of North America reveals an established fauna of 36 non-indigenous species. Sixteen species are native to temperate or tropical coasts of North America, and have been transported to regions of the continent where they did not occur in historical time; the remaining 20 species are from Europe, the Mediterranean, South America, the Indo-Pacific, and the northwestern Pacific. The movement of Pacific (Japanese) and Atlantic commercial oysters to the Pacific coast, and ship fouling, boring, and ballast water releases, have been the primary human-mediated dispersal mechanisms. Regional patterns are striking: 30 species are established on the Pacific coast, 8 on the Atlantic coast, and 1 on the Gulf coast (three species occur on both coasts); 19 (63%) of the Pacific species occur in San Francisco Bay alone. These patterns may be linked to a combination of human-mediated dispersal mechanisms and regional geological-biological Pleistocene history: at least 27 species of Japanese and Atlantic coast mollusks were introduced to the American Pacific coast by the oyster industry, in large part into geologically young regions with low native molluscan diversity. With the exception of a few species, there is little experimental elucidation of the ecological impact of the introduced marine mollusks in North America. Negative effects by introduced gastropods on native gastropods have been demonstrated on both the Atlantic and Pacific coasts; for one species, the Atlantic pulmonate marsh snail Ovatella on the Pacific coast, experimental evidence suggests that its establishment did not arise at the expense of native species. No introduced marine mollusk in North America has had a greater ecological impact than the periwinkle Littorina littorea, which colonized the Atlantic coast from Nova Scotia to New Jersey in the 30 year period between 1860 and 1890, and subsequently altered the diversity, abundance, and distribution, of many animal and plant species on rocky as well as soft bottom shores. Future marine invasions, through ballast water release and perhaps through aquaculture activities, can be expected with confidence.