Diporeia sediment preference along a Lake Superior transect

Session: Mud, Macrofauna and Microbes: Benthic Organism-Abiotic Interactions at Varying Scales (1)

Kirsten Rhude, University of Minnesota - Duluth Large Lakes Observatory, [email protected]
Robert Sterner, University of Minnesota Duluth, [email protected]

Abstract

The benthic amphipod Diporeia is an important part of the Lake Superior food web. Previous studies have found that Diporeia are most abundant at a depth of approximately 30-125m in Lake Superior. This pattern is hypothesized to be due to higher food availability and sediment deposition at these depths. We surveyed a transect from 15m to 150m depth throughout the summer of 2018, collecting Diporeia and surface sediment. In the laboratory, 150-hour preference/avoidance assays showed that Diporeia preferred sediment from 30m and 60m sites compared to those at shallower and deeper depths. Carbon, nitrogen, and phosphorus content do not appear to correlate with these depths, as shallower sites (15m and 30m) have lower carbon and nutrient content than deeper sites (60m and deeper). This suggests that carbon and nutrient content alone do not explain Diporeia preference. Subsequent sediment analysis including grain size analysis and possibly penetration resistance may help further explain the causes of the spatial distribution of Diporeia in Lake Superior.