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GLERL 2004 Milestone Reports
< GLERL 2004 Milestone main page
GOAL: Protect, Restore and Manage Use of Ocean and Coastal Resources Through Ecosystem Management Approaches
Scientist: Dr. Tom Nalepa (GLERL)
NOAA Performance Measure: Increased number and accuracy of forecasts of significant ecological events and trends.
OAR Performance Measure: Provide current assessment of the benthic community as an ongoing monitoring and assessment program. Baseline: 8 times, once every five years; Target: 1 for years 1999-2004.
Milestone: Assess changes in lake populations as a result of invasive species; assess how the quantity of invasive species impact the foodweb (e.g. population shifts, fisheries impacts).
Purpose: The purpose is to document long-term trends in the benthic macroinvertebrate community of southern Lake Michigan. Of greatest concern are changes in the abundance of invasive organisms such as zebra mussels and quagga mussels, and in the abundance of native organisms such as the amphipod Diporeia. This amphipod serves as a major food item for many fish species.
Efforts and Results (to date): The benthic monitoring program is designed such that samples are collected for two consecutive years every five years. Samples were collected in spring, summer, and fall in 1980-81, 1986-87, 1992-93, and 1998-99. Continuing with the program, sampling was successfully completed in spring 2004, and plans have been made to sample again in summer and fall 2004. An assessment of community changes between 1992-93 and 1998-99, and limited assessments s between 1999 and 2004 have indicated dramatic changes have occurred. Zebra mussel populations have continued to expand offshore, and are now most abundant at water depths of 30-50 m. Quagga mussels were first found in 1997 and are now as abundant as zebra mussels in many locations. Unlike zebra mussels, quagga mussels are found deeper than 50 m. Diporeia has continued to decline, and large areas (30 % of southern basin) are now completely devoid of this organism. There is a temporal correlation between the expansion of mussel populations and the decline of Diporeia, yet exact reasons for Diporeia’s negative response are not entirely clear. Recent studies show that the loss of Diporeia is having an impact on the condition, growth, abundance, and distribution of many fish species.
Customer(s): Fish management agencies and water resource managers.
Cause Factors (if milestone not met): N/A
Revised Completion Date (if milestone not met): N/A
Milestone main page Ecological Prediction Program main page
Last updated: 2004-07-07 js