Continued disappearance of the benthic amphipod Diporeia spp. in Lake Michigan: is there evidence for food limitation?

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 63; no. 4; pp. 872 - 890
• Main Authors: Nalepa, Thomas F, Fanslow, David L, Foley III, Andrew J, Lang, Gregory A, Eadie, Brian J, Quigley, Michael A
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.04.2006; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Amphipoda; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Biological and medical sciences; Changes; Crustacea; Defense mechanisms; Demecology; Diporeia; Dreissena bugensis; Ecosystems; Environmental conditions; Fatty acids; Food availability; Freshwater; Fundamental and applied biological sciences. Psychology; Invertebrates; Lakes; Mortality; Native species; Organic carbon; Population; Population decline; Protozoa. Invertebrata; Sand & gravel; Silica; Lake Michigan; Great Lakes of America; North America; America; Canada; USA, Michigan L; Population decline; Feeding; Amphipoda; Crustacea; Freshwater environment; Aquatic environment; Population survey; Arthropoda; Limitation; Population dynamics; Invertebrata; Food supply; Population density; Benthic zone
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/f05-262

Benthic surveys were conducted in the southern basin of Lake Michigan and throughout the lake to assess trends in benthic populations, emphasizing recent changes in densities of the benthic amphipod Diporeia spp. and dreissenid mussels. In the southern basin, Diporeia populations declined 89%, 91%, and 45% between 1993 and 2002 at sites <30, 31–50, and 51–90 m, respectively. Lakewide, the population declined 65% between 1994–1995 and 2000. Over the same time period, dreissenid densities, particularly Dreissena bugensis, increased. Intensive studies at 45 m sites in the southeastern region examined changes in lipid content, age structure, and benthic food inputs relative to the hypothesis that food limitation was a factor in Diporeia's disappearance. As Diporeia densities declined to zero, length–weight remained unchanged, and lipid content generally increased. Recruitment still occurred, but the young did not survive to become adults. Based on organic carbon, biogenic silica, and chlorophyll collected in sediment traps and found in the upper sediments, pelagic inputs to the benthic region still occurred. Our field observations and laboratory experiments did not disprove the hypothesis that food limitation from dreissenid filtering activities was the cause of the decline, but direct relationships between the loss of Diporeia and indicators of food availability were difficult to establish.