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GLERL 2001 Milestone Reports
GOAL: SUSTAIN HEALTHY COASTS
OBJECTIVE 2: Promote Clean Coastal Waters to Sustain Living Marine Resources and Ensure Safe Recreation, Healthy Seafood, and Economic Vitality
PM: Number of coastal and Great Lakes states provided with improved predictive capabilities and understanding of coastal processes.
Milestone: Describe the seasonal mesoscale patterns of plankton along onshore-offshore transects in southern Lake Michigan and evaluate the importance of these patterns to developing a monitoring program of the lake.
Scientist: H. Vanderploeg
Purpose: A number of monitoring programs and experimental studies have had limited seasonal coverage for plankton distribution and abundance and were limited to either nearshore or more often to offshore regions of Lake Michigan. Therefore, it has been difficult to get a multi-year picture of seasonal and spatial changes of plankton in Lake Michigan.
Efforts: An intense seasonal study along onshore-offshore transects at Muskegon and St. Joseph Michigan was undertaken using traditional and advanced sensor technologies at monthly intervals as well as onshore-offshore transects with less seasonal coverage to examine spatial and temporal variability of plankton distribution and abundance (Fig. 1) during 1998-2000. The purpose was to obtain insights into the appropriate design for a comprehensive monitoring program and to find sites that would be representative of southern Lake Michigan. Nutrients and plankton were very similar at offshore sites regardless of transect, and transects at St. Joseph and Muskegon showed similar seasonal patterns suggesting either transect is suitable for sampling the eastern side of the southern basin. There were considerable differences in plankton and nutrients going from inshore to offshore; therefore, nearshore sampling in addition to offshore sampling is required to get a picture of seasonal changes in Lake Michigan. Surprisingly, total abundance of zooplankton per unit volume did not generally decrease going from inshore to offshore. Also, the thermal front associated with spring warming usually had relatively little effect on zooplankton abundance. However, there were great differences between plankton concentration in nearshore areas between transects for eastern (St. Joseph, Fig. 2) and southern shores (Chicago, Fig. 3) of Lake Michigan. Low concentrations of chlorophyll and zooplankton were often found in the southern part of the lake; therefore, any monitoring program will have to consider these great differences.
Figure 1. Location of sampling stations and transects in southern Lake Michigan. Location of the Evans et al. (1980) study site is represented by symbol ME. Stations for the offshore EPA sites are represented by circles.
Figure 3. Physical and biological variables as seen along the Chicago transect (Fig.1) on April 3, 1999, by the plankton survey system (PSS). The white sinusoidal tracings on the panels show the path taken by the PSS along the transect.
Customers: US Environmental Protection Agency, NOAA , fisheries interests, academics and state DNRs
Significance: This is the first time both nearshore and offshore regions have been covered simultaneously on a seasonal basis.
Success: The project has given us great insights into design of monitoring programs for nutrients and plankton in southern Lake Michigan.
Next Steps: Publish findings in the open literature and exploit use of both traditional and advanced sensor technologies in our research and monitoring programs.
Last updated: June 10, 2002 mbl