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Monday, January 25 • 3:20pm - 3:40pm
Spatiotemporal Differences In The Condition of Bythotrephes Longimanus In Lake Michigan

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AUTHORS: Margaret Hutton*, Purdue University; Paris Collingsworth, Purdue University and Illinois-Indiana Sea Grant; Samuel Guffey, Purdue University; Ed Rutherford, NOAA-Great Lakes Research Laboratory; Mitchell Zischke, Purdue University; Tomas Höök, Purdue University

ABSTRACT: Over the past two decades, Lake Michigan’s ecosystem has undergone numerous changes related to nutrient abatement, climatic effects, and influences of various invasive species. For example, chlorophyll a concentrations have decreased offshore but increased in some nearshore regions, and some secondary and tertiary consumers (e.g., planktivorous fishes) have come to rely more on nearshore production than offshore. However, these spatial shifts do not appear to be ubiquitous throughout the lake. With the increase in relative nearshore productivity and emerging spatial patterns, we hypothesize that the condition and growth (as indexed via RNA:DNA ratios, relative fecundity, and length-at-age) of the invasive predatory zooplankton Bythotrephes longimanus will also reflect these patterns. If Bythotrephes are able to devote more energy to growth (more RNA in the organism) due to increased food availability in nearshore areas, we would expect to see a decreasing RNA:DNA ratio from nearshore to offshore locations. To examine spatiotemporal trends in RNA: DNA, Bythotrephes were sampled from nine transects throughout Lake Michigan in both the northern and southern basins along a nearshore (~15m) to offshore (~105m) gradient. With different production pathways dominating different regions causing heterogeneous shifts in production, we expect the condition of Bythotrephes to mirror these patterns. For example, the increase in production in the last two decades in the northwestern region may allow Bythotrephes to devote more energy to growing and thus have a higher RNA:DNA ratio compared to regions with less nutrient input. Ultimately, we will relate resulting spatial patterns of Bythotrephes condition to both abiotic and biotic variables collected concomitantly.

Monday January 25, 2016 3:20pm - 3:40pm EST
Emerald B