Food Webs

Decline of the amphipod Diporeia

Decline of the amphipod Diporeia in Lake Huron

Diporeia density (thousands per m2), 2000 to 2007
Three graphs: decline of the amphipod Diporeia in Lake Huron. Click for graphic description (new window).
Source: Environment Canada and U.S. Environmental Protection Agency, 20092
Photo: adult diporeia © Tomas Hook
Adult Diporeia (size of a rice grain)
Photo: Lake Huron © iStock.com/janeff

Small invertebrates are important in Great Lakes food webs as they provide a link between the base of the web (algae, bacteria, and bits of dead organic matter) which they eat, and fish, which eat them. Since 1995, populations of Diporeia amphipods, historically abundant, widespread, and dominant in deep-water food webs, have declined drastically in all lakes except Lake Superior.2 These declines coincide with the introduction of invasive zebra and quagga mussels, but the continuing downward trend is more complex, likely with several interacting causes.

Declines in Diporeia have had major impacts on Great Lakes food webs, with both forage fish and commercial species negatively affected. For example, when Diporeia declined, growth and body condition of lake whitefish declined significantly in areas of lakes Huron, Ontario, and Michigan.2