Molluscan biodiversity in the Indian River Lagoon, Florida

Using available collection and literature resources, the mollusks of the Indian River lagoonal system, central eastern Florida, were inventoried based largely on material collected during 1974-1982. 4,503 records from 1,150 stations documented 428 species-level taxa, including 243 resident species. The lagoon showed a substantially higher number of species than other well-studied western Atlantic estuaries, and showed strongest qualitative similarity to Tampa Bay, Florida. Intraregional analysis defined five faunal areas with unique molluscan components; 39 species were common throughout the lagoon. Inlet localities included 106 species not found elsewhere, including four of the five endemic species. Seagrass beds supported the highest number of species (177), and Bittiolum varium (Pfeiffer, 1840) (Gastropoda: Cerithiidae) was most frequently collected as well as quantitatively most abundant. Habitat, diet, life mode, and life history strategies were highly diverse. Analysis of species distributions supported the presence of a zoogeographic transition zone and established 14 new distributional records. The importance of endemic (yoyo clams, one opisthobranch), commercial (Mercenaria spp.), and internationally protected species (Strombus gigas Linne, 1758) to management considerations is discussed.