Please join the Great Lakes Center for a seminar presented by Dr. Thomas Nalepa, from the Graham Institute at the University of Michigan, and NOAA's Great Lakes Environmental Research Laboratory (emeritus). The seminar will be held on Thursday, April 30th from 12:15 to 1:30 p.m. in Classroom Building B118.
Trends in the major groups of benthic macroinvertebrates were examined in the Lake Huron system based on surveys in Saginaw Bay (2007-2010), and in Lake Huron, North Channel, and Georgian Bay (in 2007 and 2012). These recent data were compared to similar data collected at the same sites in the mid-1990s and early 2000s.
Perhaps the most dramatic change was the decline of the dreissenid populations in inner Saginaw Bay. Dreissenid abundances and biomass declined by 80% on hard substrates between the mid-1990s and 2007-2010. On the other hand, the dreissenid population continued to expand at all depths in the main basin of Lake Huron in 2012. The amphipod Diporeia was not present at sites <50 m in Lake Huron, and continued to decline at sites >50 m. The only region where Diporeia remained relatively abundant in 2012 was in North Channel where few dreissenids were found.
Of the other groups, changes in abundances and distributions of oligochaetes were noteworthy. While oligochaete abundances remained lower and stable in inner Saginaw Bay compared to the pre-dreissenid period, abundances in nearshore areas of Lake Huron (<30 m) have increased 2-3 fold. For all these changes, temporal trends and quantitative estimates will be compared to the other Great Lakes, and driving forces will be discussed relative to current theory.
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