PHYTOPLANKTON AND PERIPHYTON RESPONSES TO IN-SITU EXPERIMENTAL NUTRIENT ENRICHMENT IN A SHALLOW SUBTROPICAL LAKE

Experiments were performed in situ in shallow, subtropical Lake Okeech obee (Florida, USA) to quantify and compare the responses of phytoplan kton (in 201 clear polycarbonate carboys) and periphyton (on nutrient- diffusing clay substrates) to additions of nitrogen and/or phosphorus. During early and late summer, 1994, both assemblages were nitrogen li mited or co-limited by nitrogen-and phosphorus, indicating the potenti al for competition between benthic and planktonic communities. During late summer, there was evidence that high phytoplankton biomass reduce d light penetration through the water column and may have suppressed p eriphyton growth. The similar phytoplankton and periphyton taxonomic s tructures, both dominated by Lyngbya sp. and pennate diatoms, suggeste d that in shallow regions of this lake, resuspended meroplankton might account for a large portion of phytoplankton biomass. This phenomenon has been observed in other shallow, wind-driven Florida lakes.