The Impact of Nutrient Loading from Canada Geese (Branta canadensis) on Water Quality, a Mesocosm Approach

Abstract

We conducted a mesocosm experiment to determine the impact of Canada Goose (Branta cana.densis) feces on water quality parameters. After 30 days of fecal additions (treatments of 2.419 g, 1.209 g and 12.090 g every 3 d) we found no significant impact on soluble reactive phosphorus, total phosphorus, ammonia, nitrate, total Kjeldahl nitrogen, chlorophyll-a, phycocyanin or turbidity for any of the treatment groups versus the control (no fecal addition). Nitrogen to phosphorus ratios were not affected by the fecal additions. Although there was no significant increase in chlorophyll-a concentration or phytoplankton biovolume, there was an increase in phytoplankton counts in the high treatment group. Phytoplankton diversity (using the Shannon index of diversity) was significantly decreased by the addition of goose feces (H1'=0.575, H2'=0.433, t=l7.43, p< 0.001, where H1' is the control and H2' is the 12.090 g treatment). We performed a settling experiment which suggested that nutrients in goose feces settle to the sediment quickly, prohibiting uptake by phytoplankton which explains the apparent lack of impact of fecal additions on water quality. Since most of the nutrients in goose feces settle to the sediment, it is likely that the impact of the nutrients will not become evident until a mixing event occurs or a benthic food web passes them to the organisms of the water column.