Benthic-pelagic coupling and Cladophora problems in large lakes

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Since the invasion of the Great Lakes by zebra mussels, many coastal areas have suffered from excessive growth of algae.  The algae wash up on and foul beaches and shorelines, which effectively prevents recreational use.  The algae also cause expensive interruptions to supplies of cooling and drinking water, and the decaying mats harbour potentially harmful bacteria.  These problems would normally be associated with excessive levels of the key nutrient phosphorus, yet phosphorus concentrations in the lakes are generally low.  We will undertake studies of how the algae manage to obtain the phosphorus they need to become a problem, and what management actions might be taken.  We will use a section of the Lake Ontario north shore to test the theory that mussels enable the growth of algae by harvesting phosphorus from the water and then releasing it again near the bottom in a form the algae can use.  Measurements of algal and mussel production will be combined with a three dimensional model that will allow us to calculate the relative importance of local phosphorus sources (e.g. storm drains and sewers) to the algal problem.  The model will allow us to predict the effectiveness of potential management actions (e.g. further reductions in lake-wide phosphorus loading) and estimate targets for remedial action.  The work will also increase our fundamental understanding of nearshore ecology in the Great Lakes as they continue to experience biological invasions and other stresses.