Deposition signatures in Onondaga Lake, New York: Observations from a 28‐year sediment‐trap study

Abstract

We tested paradigms and models that relate deposition of phytoplankton constituents to lake metabolism based on analyses of long-term sediment-trap collections (28 yr of the 1980-2010 period) from a dimictic urban lake, Onondaga Lake, New York. There were major changes in a number of important drivers of deposition, including decreases in the concentration of a divalent cation (Ca 2+ ), nutrient loading and primary production, and variations in food-web effects. The summertime downward fluxes of particulate organic carbon (DF POC ), particulate nitrogen, particulate phosphorus (P), and chlorophyll were greater than values reported in the literature at the start of the program and decreased . 70% in response to decreases in Ca 2+ and P loading. Results include (1) the positive dependence of DF POC on primary production, (2) the positive dependence of the rate of hypolimnetic oxygen depletion on DF POC , (3) the negative effect of Daphnia grazing on DF POC under eutrophic and hypereutrophic conditions, and (4) the dependence of the stoichiometry of depositing material on particle origins and nutrient status of the phytoplankton community. The relationship between the export ratio, the fraction of gross primary production lost to deposition, and primary production reported in the literature was extended based on inclusion of Onondaga Lake data, and described by a nonlinear (polynomial function) relationship.

Resolution and Analysis of Spatial Variations and Patterns in an Urban Lake with Rapid Profiling Instrumentation

“…The turbidity is composed primarily of clay mineral particles (Effler and Peng, ). Depositional losses of these particles, and thereby the attenuation of the T n signatures, is promoted by the high calcium concentrations of the lake that enhances particle aggregation (Weilenmann et al ., ; Effler et al ., ).…”