Date of this Version
Published in NOAA Technical Memorandum GLERL-144 (2008) 25 pages.
This technical report provides basic results of benthic surveys conducted in Lake Michigan in 1994-1995, 2000, and 2005. The focus of these surveys was to assess lakewide trends in abundances of the amphipod Diporeia spp., the zebra mussel (Dreissena polymorpha), and the quagga mussel (Dreissena rostriformis bugensis). These lakewide surveys were an expansion of a monitoring program in the southern basin that has examined trends in the abundance and composition of the macroinvertebrate community since 1980 (Nalepa 1987, Nalepa et al. 1998). The original purpose of the monitoring program was to assess the response of the benthic community to phosphorus abatement efforts in the mid-1970s (Nalepa 1987). However, after D. polymorpha became established in the southwestern portion of the lake in 1989 (Marsden et al. 1993), the monitoring program detected several dramatic changes in the benthic community in the early 1990s. For one, the Diporeia population began to systematically disappear (Nalepa et al. 1998). Also, D. polymorpha rapidly expanded and soon became dominant in the nearshore region. To determine if the same dramatic changes in the southern basin were occurring over a broader lake area, the monitoring program was expanded in 1994-1995 to include the entire lake. Sampling in these two years was conducted jointly with several other Lake Michigan programs -- Environmental Monitoring and Assessment (EMAP) and Lake Michigan Mass Balance (LMMB). After 1994-1995, lakewide monitoring of Diporeia and Dreissena populations continued at 5-year intervals (i.e., in 2000 and 2005) as part of a regular monitoring program.
The purpose of this report is to provide all abundance data collected in 1994-1995, 2000, and 2005, and to provide basic details of the lakewide sampling program, including station locations, sampling methods, and laboratory procedures. Data are presented with little attempt at interpretation; detailed analysis and discussions of relevance will be provided in other publications (see Nalepa et al. in press).