Photosynthetically-mediated calcite and phosphorus precipitation by submersed aquatic vascular plants in Lake Pleasant, Pennsylvania

Abstract

Photosynthetically-mediated calcite precipitation by phytoplankton and charophytes has been shown to be a significant pathway for the removal of epilimnetic Ca and P in hardwater lakes, but the role of submersed aquatic vascular plants has not been examined. We measured calcite precipitation on 5 species of submersed aquatic vascular plants in moderately hardwater Lake Pleasant semi-monthly during the growing season. Maximum mass-specific accumulation ranged from 22.9 mg Ca g(-1) leaf dry weight in Megalodonta Beckii to 176.3 mg Ca g(-1) leaf dry weight in Potamogeton Richardsonii. Analysis of the crude deposits gave mean Ca concentration of 318 mg g(-1) dry wt., and mean total P concentration of 169.8 mu g g(-1) dry wt, however, only 38% of this total phosphorus was composed of chemical species specifically associated with Ca co-precipitation. We used whole lake estimates of submersed aquatic vascular plant mass to calculate the mass of P co-precipitated with Ca. Results suggest that in spite of conspicuous precipitate on plants during midsummer in this lake, there is a negligible effect on epilimnetic P concentrations.