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Benthic and Pelagic Contributions to Mysis Nutrition across Lake Superior
Citation:
SIERSZEN, M. E., J. R. KELLY, T. D. CORRY, J. V. SCHAROLD, AND P. M. YURISTA. Benthic and Pelagic Contributions to Mysis Nutrition across Lake Superior. CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES. NRC Research Press, Ottawa, Canada, 68(6):1051-106, (2011).
Impact/Purpose:
The high importance of benthos to Mysis’ nutrition is highly significant to estimates of benthic-pelagic coupling and to the ultimate ability of Mysis to support fisheries in systems that have lost Diporeia.
Description:
Quantification of the sources of nutrition to Mysis diluviana is needed to better understand the basis for production in Mysis lakes and to improve models of migration-driven nutrient and contaminant transport. We collected Mysis, plankton, and benthos across Lake Superior using a stratified-random sampling design that provided a statistically valid representation of the lake. Depth-specific abundance of Mysis, and abundance and biomass of plankton and benthos were determined. Mysis, zooplankton, Diporeia spp., and oligochaetes were analyzed for carbon and nitrogen stable isotope ratios. Contributions to Mysis were calculated using a multiple-source, dual-isotope mixing model. Published isotope values for the benthic nepheloid layer were used to represent recently-sedimented detritus. Lakewide, small (< 1.0 cm) mysids relied almost exclusively upon plankton at all depths. Small-fraction (63 - 160 µm) plankton were responsible for approximately two-thirds of small Mysis’ nutrition, which supports earlier reports of an herbivorous role. Accordingly, small mysids were most abundant in deep water, where total plankton biomass was highest. Large (> 1.0 cm) mysids occupied a higher trophic position than small mysids and obtained nutrition from across food sources. Benthic contributions to large Mysis were on the order of 50%. Declines in the biomass of benthos with depth were predicted to result in decreased importance of benthos to Mysis in deep zones. Model results indicate that if Diporeia were the only benthic food eaten by Mysis, benthic contributions would decline with depth but still constitute 40% of nutrition. If, however, Mysis feeds upon detritus at all depths, the importance of benthos to Mysis did not decline with depth. The high importance of benthos to Mysis’ nutrition is highly significant to estimates of benthic-pelagic coupling and to the ultimate ability of Mysis to support fisheries in systems that have lost Diporeia.
