AN OVERVIEW OF THE DISTRIBUTION AND ABUNDANCE OF FORAMINIFERA IN THE INDIAN RIVER LAGOON, FLORIDA

The Indian River Lagoon (IRL) is a narrow (2-4 km), shallow (1.2-m mean depth), 260-km long, barrier-enclosed estuarine lagoon that is situated on the east coast of the Florida peninsula. The IRL system is comprised of interconnected sub-basins (Mosquito Lagoon, Banana River, Indian River) that connect to the Atlantic Ocean by a series of natural & manmade inlets (Ponce de Leon, Sebastian, Ft. Pierce, St. Lucie, Jupiter). The IRL watershed encompasses several natural freshwater rivers & creeks, as well as a network of drainage canals & ditches that have greatly enlarged the original watershed. The IRL spans the boundary between the temperate & tropical savanna climate zones & is characterized by distinct wet (mid-Jun to Oct) & dry (mid-Oct to late May) seasons. Salinities range from 21-35 & depend on seasonality of rainfall, evaporation rates, & proximity to inlets, rivers &/or creeks. Tides are semidiurnal & microtidal close to the inlets; in the interior of the lagoon, wind-driven circulation dominates. Some northern reaches of the IRL are nontidal.

Essential foraminiferal habitats within the IRL include: sediments, muck, seagrass beds, oyster reefs, tidal wetland sediments (mangrove swamps/salt marshes) & the water column. The earliest studies on the ecology of foraminiferans in the IRL were carried out by Marty Buzas & Ken Severin, who identified 94 species in sediment samples collected from 12 transects located from the northern IRL near Haulover Canal to the St. Lucie Inlet. Species diversities & population densities were generally observed to increase in a southerly direction. Buzas also conducted numerous experiments on the effects of substrate preference & predation on foram densities. Other researchers have studied the forams living in different habitats, such as seagrass beds, mangrove sediments & muck. A total of 156 foram species are currently estimated to live in the IRL, however that number may increase as more habitats are surveyed within the lagoon.