Journal Article

Sediment Records of Phosphorus-Driven Shifts to Phytoplankton Dominance in Shallow Florida Lakes

Primary producer community structure (PPCS) in shallow lakes isinfluenced by phosphorus (P) load and water column P concentration. Theoretically PPCS may shift between phytoplankton and macrophyte states with intermediate P loading, but phytoplankton dominate when P loading exceeds a critical threshold. We analyzed sediment cores from five shallow, eutrophic lakes (size range: 0.6 to 125 km2) that arephytoplankton dominated to determine whether the development of the current state was associated stratigraphically with an increase in sediment total P(TP) and a shift in PPCS. We used sponge biogenic silica(BSi-Sponges) concentrations and total carbon to total nitrogen ratios (TC:TN) as proxies for macrophyte abundance and sediment organic matter source, respectively. Three stratigraphic groups of sediments were identified with k-means cluster analysis. These samples were grouped by increasing TP concentrations and decreasing age and identified as macrophyte, transitional and phytoplankton sediments. Results show that as P loading increased in the late 19th and early 20th centuries, the lakes produced sediments with an increasing contribution from phytoplankton. Four of our lakes may represent a subset of shallow lakes because of their large size (30 to 125km2) and relatively rapid historic P enrichment. Inthese Florida lakes, PPCS shifted to phytoplankton dominance with no paleolimnological record of lake-wide alternating stable states or of lake-wide phytoplankton dominance before anthropogenic P enrichment.

Publisher - Springer

Subjects - Sediment; Chemical, Phosphorus; Water, Lake

Citation: Kenney WF, Waters MN, Schelske CL, Brenner M. 2002. Sediment Records of Phosphorus-Driven Shifts to Phytoplankton Dominance in Shallow Florida Lakes. J. Paleolimnol.; 27(3):367-377