Spatial and temporal patterns of planktonic and community metabolism along the riverine-lacustrine gradient in Texas reservoirs.

In this study I quantified planktonic and community metabolism of the upper mixed zone along the riverine-lacustrine gradient in four Texas reservoirs from May 2005 to March 2006. Planktonic metabolism was estimated using the laboratory incubation methodology. The diel change of subsurface dissolved oxygen in-situ was used to determine community metabolism. In direct contrast to the predictions of the traditional reservoir zonation model, planktonic P:R ratio in the lacustrine zone was significantly less than one, while planktonic P:R ratios exceeded one in both the riverine and transition zones. Community P:R ratios were less than one in all three zones during the study, indicating net community heterotrophy at all locations. On average the plankton was responsible for 82% of total community production but only 33% of total community respiration. The factors controlling planktonic and community P and R were consistent with previous studies.