The production, nitrogen, and phosphorus dynamics of Elodea sp., Potamogeton sp., and Nitella sp. in Sam Rayburn reservoir, Texas

Abstract

The 1977 annual maximum biomass of Elodea sp., Fota- — 2 mogeton sp., and Nitella sp. was found to be 1013.6 g m~ , 168.4 g m **, and 32?.6 g m~'', respectively. Combined, these plants produce 80,528.16 kg dry wt lake”* year”*. However, this value is only 0.289?5 of phytoplankton production. Production of the macrophytes may have been greater had a a severe draw-down not occurred. The seasonal changes in ash weight and nutrient concentrations did not conform to the typical curves» nor did the seasonal change in biomass conform to the expected sigmoid curve (Westlake, 1965b)* The atypical patterns were due to the effects suffered from the water level change. Nitrogen and phosphorus concentrations in the plant tissues were not found to be indicative of environmental concentrations of nitrogen and phosphorus. This occurrence may have been due to neither nitrogen nor phosphorus of waters or sediments being limiting. Evidence for secretion of phosphorus by Elodea sp. was found. Diffusion gradients of phosphorus were found between the interior and exterior of the Elodea sp. stands.