XVI International Botanical Congess

Phosphate uptake kinetics and uptake/release rates were calculated for planktonic and benthic assemblages in Lake Okeechobee, Florida. We sampled bimonthly over one year at an ecotone site and at a littoral marsh site. Based on 32P-PO4 turnover times, P-limitation was observed only during summer at the ecotone site, when P concentrations were lowest. At the marsh site, P-limitation was observed year-round. The Vm /Ks ratio in the plankton increased by over two orders of magnitude during the P-limited summer period at the ecotone site. The biomass-specific uptake rate of plankton was significantly greater than that of periphyton at both sites, suggesting that plankton were more efficient than periphyton at taking up P. DIP and DOP release rates were <10% of uptake.