Meta-analysis of freshwater aquaculture provincial water quality monitoring data
Increases in finfish production in Ontario, Saskatchewan, and British Columbia have prompted regulators to look at strategies for managing freshwater aquaculture. particularly considering ecosystem carrying capacity (the number of living organisms that a region can support without environmental degradation). Carry capacity is tightly linked with the phosphorus released from finfish aquaculture waste (CSAS 2014). Since 2000 in Ontario, a water quality monitoring program is a condition of aquaculture licenses to ensure that the release of phosphorus from finfish farms does not exceed regulatory thresholds. Phosphorus can cause environmental concerns as it contributes to algae and phytoplankton blooms that, if excessive amounts of phosphorus are released, can pose a risk of eutrophication causing reductions in deep-water oxygen concentrations that can bring about changes in benthic habitats and community structure.
The goal of this project was to conduct a meta-analysis of the water monitoring data collected since 2000 through the Ontario Water Quality Monitoring program. It sought to determine whether there is evidence that the cage aquaculture industry in Ontario contributes to increased total phosphorus concentrations in receiving waters, and if there has been an increase in total phosphorus over time that would suggest cumulative effects. Given the link between the assimilation of phosphorus (from aquaculture waste) and carrying capacity, the results of this project may provide further insight on the relationship between freshwater ecosystem carrying capacity and sustainable growth of freshwater aquaculture, and help to inform the sustainable management of the freshwater cage aquaculture industry.
Results showed no difference between phosphorus levels for the three different seasons; spring turnover, summer, and autumn turnover. While there was also no difference in the phosphorous levels among the cage, upstream and downstream locations. There was a difference in phosphorus levels between farms. This difference was expected since farms are in different locations.
Although there were many instances where individual samples exceeded the regulatory threshold, the median values did not. In general, the samples collected 30 m away from cages had higher total phosphorus concentration and the median concentration downstream of the cages was frequently the lowest. Total phosphorus concentration did not increase over time.
2014 - 2015
Research Scientist, Environmental Sciences Division, Freshwater Institute, Ontario and Prairies Region
Joise Kshymensky, Biologist, Environmental Sciences Division, Freshwater Institute, Ontario and Prairies Region
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