Factors Affecting Diporeia Growth Rates in Lake Superior

The freshwater amphipod Diporeia is a dominant macroinvertebrate speciesin Lake Superior’s benthic community and an important prey item for many fish. Acapacity to predict growth and production rates of Diporeia using a bioenergeticsmodel requires information on physiological processes of the species. The objectiveof this study is to quantify oxygen consumption of Lake Superior Diporeia and todetermine if respiration rate changes by size class. Diporeia were collected from Lake Superior and kept in natural sediment maintained at 4°C. Dissolved oxygen levels for groups of Diporeia immatures, juveniles, and adults in 20 mL microcosmswere measured using a polarographic microelectrode. Mass-specific respiration rates for Lake Superior Diporeia ranged from 32.0 to 44.7mgO2·gDW·d. Asignificant relationship between body length and mass-specific respiration rate(p>0.1) was not found. The estimate of Diporeia respiration presented here is significantly higher (p<0.05) than previous findings from populations in Lake Michigan and Lake Ontario. This study provides new data on respiration rates of Diporeia in Lake Superior and compares findings to studies for other Great Lakes.