Benthic oxygen demand in Lake Apopka, Florida

Abstract

The benthic oxygen demand of Lake Apopka, Florida was determined using laboratory core uptake and flow through system techniques. The core-uptake for 5 stations in Lake Apopka averaged 67 mg O 2 m −2-h and partitioning experiments indicated that the oxygen uptake was primarily biological, with bacterial respiration dominating. No significant statistical correlations were found between core oxygen uptake rates and TKN levels ( r = 0.33), percent volatile solids ( r = 0.49), or macroinvertebrate densities ( r = 0.59). Sediment oxygen uptake rates ( D B ) were logarithmically related to flow rate in the following form D B = − A + B In flow. Flow-through system sediment oxygen uptake at each station approached similar maximum uptake rates of 130 mg O 2 m −2-h at high (> 200 l h −1) flow rates. Lake Apopka is an extremely shallow, wind mixed system and sediment uptake rates are expected to approximate this value during periods of intense wind mixing. The relatively low sediment uptake rates obtained for Lake Apopka, a hypereutrophic lake, supports the view that during eutrophication sediment respiration is progressively replaced by respiration in the water column.