DIATOM SUCCESSION IN THE RECENT SEDIMENTS OF LAKE OKEECHOBEE, FLORIDA, U.S.A.

Abstract

Diatoms and other siliceous microfossils were extracted from 1 cm samples of a 49 cm, ²¹⁰Pb-dated core taken in 1988 from Lake Okeechobee, a large, shallow lake located in southern Florida (27° N Lat), U.S.A. Microfossil assemblages consisted mainly of sponge spicules and diatoms. Cysts or other chrysophyte remains were exceedingly rare. Although diatoms were present in low numbers and preservation was poor, trends in assemblage composition suggest that Lake Okeechobee has undergone substantial changes in hydrologic budget and trophic status during the period studied. The ratio of planktonic to benthic species was highest just prior to western settlement of the region and has been low and stable thereafter, probably indicating reduction in lake level. Taxa, particularly Actinocyclus, which are tolerant of eutrophication and salinization, increased after ca. 1940, indicating further modification of inputs to the lake.