ECTOPROCT DIVERSITY OF THE INDIAN-RIVER COASTAL LAGOON

Thirty-six species of ectoprocts are known so far from the Indian Rive r Lagoon. The highest diversity occurs where salinities are above 30 p arts per thousand. Only 12 species have been found in the less saline portions of the lagoon. Ectoproct habitats include seagrass meadows, d rift algal communities, oyster ''rock,'' docks, pilings, breakwaters, and man-made debris. Ectoproct diversity within the IRL is about one t hird that of area coastal and offshore habitats, but is probably fairl y diverse relative to the available species pool. No ectoprocts are en demic to the IRL. About a third of the species recorded have western A tlantic or western Atlantic/Caribbean distributions. The rest are cosm opolitan fouling or eurytopic species. Species composition of the faun a has remained stable over the last 20 years, but large population flu ctuations occur for some species on both a seasonal and year-to-year b asis. IRL ectoprocts are somewhat protected from natural disturbance b y their physiological tolerance and/or the presence of spatial refuges , but the fact that over a 20-year period many species were observed o nly at one site indicates that degradation of critical habitats would quickly reduce ectoproct diversity. Most important from a management p oint of view is the role of these animals in maintaining water quality . Like other suspension feeders, ectoproct colonies act as seawater pu rifiers-living water treatment plants. For example, colonies of Zoobot ryon verticillatum found in 1 m(2) of a seagrass bed could clear and r ecirculate about 48,000 gallons of water per day. Priorities for futur e work include evaluation and quantification of the role of bryozoans and other suspension feeders in maintaining lagoon water quality, as w ell a more through taxonomic survey, particularly of the much less wel l-known northern- and southernmost portions of the