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STATUS OF THE AMPHIPOD DIPOREIA SPP. IN LAKE SUPERIOR, 1994-2000
Citation:
Scharold, J. V. AND S J. Lozano. STATUS OF THE AMPHIPOD DIPOREIA SPP. IN LAKE SUPERIOR, 1994-2000. Presented at International Association for Great Lakes Research Conference, State-of-the Lake, Michigan Tech Univ., Houghton, MI, May 22-24, 2002.
Description:
The amphipod Diporeia spp. is the dominant component of the Great Lakes benthic macroinvertebrate fauna in terms of both numbers and biomass, and plays an important role in the ecosystem. The Great Lakes Water Quality Agreement calls for the use of Diporeia as an indicator of ecological condition, with a goal of 220-320.m-2 at depths less than 100 m and 30-160.m-2 at greater depths. Recent studies have revealed drastic declines in Diporeia populations in the lower Great Lakes, but little information is available on abundance of benthic macroinvertebrates in Lake Superior. During 1994-2000, the US EPA Mid-Continent Ecology Division conducted a series of benthic macroinvertebrate surveys in Lake Superior to support development of ecological indicators and monitoring designs. A probability based survey of 27 sites representing the U.S. nearshore waters of Lake Superior was conducted in 1994. During 1995-1998 a subset of 11 of these nearshore, non-depositional sites, plus 6 sites from major depositional basins, in the western half of the lake were revisited yearly to examine variability. The original 27 sites were sampled again in 2000. In 1994, nearshore Diporeia abundance ranged from 550 to 5500.m-2, and all sites met or exceeded the ecosystem objective. In 2000, abundance ranged from less than 10 to 2800.m-2, and 11% of sites did not meet the objective. These sites were located in the eastern half of the lake. Examination of yearly abundance data in western Lake Superior did not reveal a significant trend at nearshore or offshore sites. This abstract does not necessarily reflect US EPA policy.