Physical-Biological Coupling in Southern Lake Michigan: Influence of Episodic Sediment Resuspension on Phytoplankton

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Marine Science


The influence of episodic, sediment resuspension on phytoplankton abundance/volume and composition, the photosynthetic maximum rate (P(max)(B)) and efficiency (alpha(B)), and chlorophyll-specific growth (mu(Chl)) was evaluated during the spring isothermal period in southern Lake Michigan (Laurentian Great Lakes, USA). Resuspension altered the nutrient and light climate of nearshore waters; light attenuation (K(d)) and phosphorus concentrations corresponded (p less than or equal to 0.0001 and p less than or equal to 0.001, respectively) with concentrations of suspended particulate matter (SPM). Phytoplankton cell volume and diatom cell abundance and volume were not associated with SPM concentrations (p > 0.05). Diatom composition displayed spatial dissimilarities corresponding with resuspension (p less than or equal to 0.001); small centric diatoms exhibiting meroplanktonic life histories and pennate diatoms considered benthic in origin were most abundant within SPM-impacted, nearshore waters whereas taxa typically comprising assemblages in optically-clear, offshore waters and the basin- wide, spring bloom were not. Values of P(max)(B) and alpha(B) corresponded (p less than or equal to 0.0001) with both K(d) coefficients and SPM concentrations, potentially reflecting increased light harvesting/utilization within impacted assemblages. However, integral production was inversely associated with K(d) coefficients and SPM concentrations (p < 0.0001) and photosynthesis was light- limited (or nearly so) for most assemblages. Although mu(Chl) values corresponded with K(d) coefficients (p <= 0.05), values were quite low (<(x)over bar> +/- S. E., 0.10 +/- 0.004 d(-1)) throughout the study. Most likely, distinct rate processes between SPM- and non-impacted assemblages reflected short-term compositional (and corresponding physiological) variations due to infusion of meroplankton and/or tributary-derived phytoplankton. Overall, resuspension appears to have little, if any, long-term impact upon the structure and function of the lake's phytoplankton.

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Aquatic Ecology





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