Cyanobacteria Dominance in the Lake Simcoe Georgian Bay Area: an Oxygen, Sulfate and Iron Approach.

English Abstract:

Cyanobacteria blooms are an increasing concern for cottage owners and tourists in the Lake Simcoe and Georgian Bay area. These blooms ruin the aesthetics of lakes and can result in the production of toxins that have led to the illness of children and, in some cases, the death of animals. The near annual appearance of these blooms on some lakes has reduced property values to the point where land is unsellable. Current knowledge suggests that an excess of nutrients, such as phosphorous (P) and nitrate (NO₃), are the leading cause for algal blooms. However, it is proposed that the availability of ferrous iron (Fe²⁺) in the water column is the key to cyanobacteria dominance due to the inability of cyanobacteria to transfer Fe³⁺ across the cell membrane. This research is focused on predicting the potential of a lake to support cyanobacteria by observing the biogeochemical interactions of P, O₂, Fe²⁺ and sulfate (SO₄) in several lakes in the Georgian Bay and Lake Simcoe area. Excess P promotes anoxia of the hypolimnion which allows for the dissolution of Fe²⁺ _­making it available to cyanobacteria which can migrate into the hypolimnion. Once O₂ becomes scarce, SO₄^2- reducers which produce sulfide (HS^-) can dominate. HS^- binds with Fe²⁺ forming insoluble iron sulfides FeS. Three sites: Sturgeon Bay, Deep Bay and North Bay were sampled throughout the summer season for SO₄^2-, TP, TN, O₂, Fe, NH₄⁺ and NO₃^- in 2012 when blooms where present and in 2014 when blooms where absent. It is hypothesized that in 2014 these sites had less P loading, higher SO₄² concentrations and lower Fe²⁺ concentrations than were present in 2012. If this is the case then it may be possible to predict which lakes are likely to become dominated by cyanobacteria based solely on their chemistry and implement preventive measures accordingly.