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GLERL 2005 Milestone Reports
< GLERL 2005 Milestone main page
GOAL: Ecosystem
Scientist: Tom Nalepa (GLERL)
NOAA Performance Objective: Increase number of regional coastal and marine ecosystems delineated with approved indicators of ecological health and socio-economic benefits that are monitored and understood
NOAA Corporate Measure: TBD
Ecosystem Research Program Performance Measure: PM5: Number of integrated ecological forecast models developed, and the technology transferred to the appropriate agency.
OAR Performance Measure: Increased number and accuracy of forecasts of significant ecological events and trends (e.g., harmful algal blooms, coral bleaching and population shifts), that provide necessary information for NOAA’s stewardship responsibilities.
NOAA Program: Ecosystem Research
Milestone: Complete assessments of trends in the benthic macro invertebrate community of Lake Huron. (Baseline 0, Target 1 Lake Huron Assessment) (Thomas Nalepa, GLERL).
Purpose: This milestone reports on the results of a project to determine relative changes in abundances of the major benthic macroinvertebrate groups in Lake Huron. The benthic macroinvertebrate community of this lake has been the least studied of all the Great Lakes--prior to this project the last benthic survey in the main basin of the lake was in 1972.
Efforts and Results (to date): As part of this project, surveys of the macroinvertebrate community of Lake Huron were conducted in 2000 and 2003. A total of 65 sites were sampled in 2002 and 77 sites were sampled in 2003. All samples have been processed and data entered into spreadsheets. Of the five major taxonomic groups (Diporeia, Oligochaeta, Chironomidae, Sphaeriidae, and Dreissena), greatest changes were observed in the benthic amphipod Diporeia. At sites less than 90 m in water depth, this organism declined 77% between 1972 and 2000, and 57% between 2000 and 2003. Diporeia is now completely gone from large areas of the lake. Since Diporeia is an important diet item for many fish species, including the commercially important lake whitefish, the loss of Diporeia will have strong implications to upper trophic levels. While Diporeia has declined, Dreissena (zebra and quagga mussel) have increased. For instance, the quagga mussel has increased from 2 to 357 per m2 at sites < 30 m, and from 2 to 1586 per m2 at sites 31-50 m. The exact reason for the negative relationship between Diporeia and Dreissena has not been clearly defined, but we expect the Diporeia population will continue to disappear as the Dreissena population continues to expand.
Customer(s): Trends in macroinvertebrate populations have long been used to assess the general ecological health of the Great Lakes. These organisms integrate changes in both the water column and sediments, and the ratio of pollution-sensitive vs pollution-tolerant forms provides a good index of lake status. Trends in populations are therefore of interest to the general scientific community as well as to resource managers. In addition, macroinvertebrates are fed upon by many fish species, and shifts in community composition can have consequences to fish management practices. For instance, the loss of Diporeia has been strongly implicated in an observed decline in the growth and condition of lake whitefish (http://www.glfc.org/pubs/TechReports/Tr66.pdf ). Thus, fish management agencies are keenly interested in declines in Diporeia populations and trends in other benthic populations that may serve as alternate fish food.
Cause Factors (if milestone not met):
N/A
Revised Completion Date (if milestone not met):
N/A
Last updated: 2005-09-27 mbl