Okeechobee, Lake (Fla )

The phytoplankton community of Lake Okeechobee, Florida, has been studied and algal divisions were identified. Chemotaxonomy is a process that assigns taxonomic divisions based on ratios of biomarker pigments to chlorophyll, as measured by high performance liquid chromatography (HPLC). Microscopic counts of taxonomic groups were compared to chemotaxonomic groups for lake samples for one year. Lab cultures of cyanobacteria grown at irradiance of 2 to 500 micromoles photons m-2 s-1 (muEinsteins) suggested that internal ratios of chlorophyll to both zeaxanthin and echinenone could be used to estimate abundance of cyanobacteria, as either alone missed certain populations. Lake water samples showed that both methods agreed that diatoms and cyanobacteria were the dominant groups, with moderate number of green algae and few dinoflagellates. HPLC evidence revealed cryptophytes more frequently than did microscopy. This suggested that cryptophytes may be more significant than has been previously reported.

Lake Okeechobee is one of the largest lakes in the United States, yet its formation, circulation, and geomorphology are not well known. The ridges that occur on the eastern and northern shorelines of the lake have not been studied. Sugar Ridge is the closest ridge to the lake on the central part of the eastern shoreline. It is composed of medium- to fine-grained quartz (sugar sand) sediments in a dynamic form, superimposed upon organic peat and muck layers. It contains centimeter-scale bedding that exhibits many sedimentary structures typical of an accretionary barrier beach. Wind waves are considered the most likely cause of transport of the clastic sediments to the study area. Variations in lake level and wind in the region are such that conditions were favorable for development primarily in the winter. That is when lake levels were high enough to reach the ridge and the winds were strong enough to cause waves to transport sediment. Sediment was transported from the mouth of the Kissimmee clockwise around the northern perimeter. However, today the lake is completely enclosed and its levels are constantly manipulated.