Zebra and quagga mussels responsible for Cladophora fouling
Ann Arbor, MI — Cladophora, a filamentous benthic alga, has a long and storied history in the Great Lakes. Prior to the implementation of phosphorus control under the Great Lakes Water Quality Agreement, large mats of decaying Cladophora frequently washed up on shorelines in the summer, producing unpleasant odours and an unsightly mess. Phosphorus management was thought to have been largely successful at reducing, if not eliminating, this problem and research efforts were shifted elsewhere in the mid 1980s. Starting in the mid 1990s, fouling of shorelines in Lakes Erie, Ontario and Michigan again become an issue, and has been postulated to be a result of changes to near shore nutrient retention facilitated by dreissenid (zebra and quagga) mussels.
A study conducted during 2005 investigated spatial patterns of Cladophora standing crop at selected locations in Lakes Erie, Ontario and Huron across a gradient of land use, water quality and mussel abundance. Researchers used high frequency acoustics to map the spatial distribution and estimate the quantity of Cladophora at each site. Nuisance quantities of Cladophora were found in Lakes Erie and Ontario at both near shore and off shore shoal sites, but not in Lake Huron. Mussel abundances better explained the site specific variation in Cladophora crops than the more traditionally cited causes (water quality, land use).
While this research does not conclusively identify mussels as the causative factor in the apparent resurgence of Cladophora fouling in the lower lakes, phosphorus controls designed to control offshore nutrient content may no longer be as effective for near shore areas where mussels exist in sufficient abundance. Future research to further clarify mussel – benthic algae interactions will be crucial for nutrient management policy.
Original Publication Information
Results of this study, "Distribution of nuisance Cladophora in the lower Great Lakes: Patterns with land use, near shore water quality and dreissenid abundance," are reported by David C. Depew, Adam J. Houben, Stephanie J. Guildford and Robert E. Hecky in Volume 37, No. 4, of the Journal of Great Lakes Research, published by Elsevier, 2011.
Contacts
For more information about the study, contact David Depew, School of Environmental Studies, Queen’s University, Kingston, Ontario K7L 3N6; david.depew@queensu.ca.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, Environment Canada, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; jglr@ec.gc.ca; (306) 975-5310.
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