Submerged Aquatic Vegetation and Mussels

Primary Investigator:
Robin Churchill, M.Sc. Candidate

Supervisors:
Dr. Scott Petrie, Long Point Waterfowl Executive Director
Dr. Hugh Henry, University of Western Ontario
Dr. Michael Schummer, Long Point Waterfowl Scientist

Background

Coastal wetlands associated with the Lower Great Lakes provide important food and habitat to a variety of wetland-dependant species. There has been substantial drainage of coastal wetlands within the Lower Great Lakes region, thereby increasing the importance of remaining habitat for wetland-affiliated
organisms. However, remaining wetlands have been altered or degraded by various stressors, including the introduction of exotic plants and invertebrates (ie. Dreissenid mussels in the Lower Great Lakes). These introductions can cause changes in the species composition and reductions in the biomass of submerged aquatic vegetation, both of which can affect carrying capacity for staging waterfowl and use by fish. Therefore it is essential to periodically monitor and assess changes in submerged aquatic vegetation biomass and community composition as well as Dreissenid mussels.

Project Description

Field work for this project began in July 2009 at 321 sampling stations to determine maximum submerged aquatic vegetation and Dreissenid mussel biomass in Long Point Bay. A sub-sample (100 sites) of this was taken in December 2009 just prior to freeze up to determine waterfowl usage and senescence during fall migration. A final sample was taken in April 2010 at all 321 sample sites, immediately after ice-thaw to determine what food was available to spring-migrating waterfowl.

Preliminary results have shown a decline in total Dreissenid mussel numbers as well as a shift in submerged aquatic vegetation community structure. Wild celery is a herbaceous perennial that is probably the most important food item for diving ducks staging a Long Point Bay. This particular species experienced a decline in abundance by 1995, three years after the introduction of Dreissenid mussels in Long Point Bay. This decline was influenced by the water clarification initiated by the mussels. With a decrease in mussel population since 1995 it is likely that the water has shifted to a more eutrophic state, which is a more favourable state for this particular species resulting in a more widespread distribution.

In addition, musk grass, a perennial alga, proliferates in oligotrophic water as shown in the widespread distribution in the early 1990’s. However, it is not as widespread in distribution nor is it as abundant now as it was during the previous study, further supporting Long Point Bay’s shift to a more eutrophic state.

Project Sponsors

Ducks Unlimited Canada
Long Point Waterfowl
Ontario Federation of Anglers and Hunters
Ontario Ministry of Natural Resources

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