Landscape and land use impacts on farm pond water quality in the Portage Plains of south-central Manitoba.

Abstract

Growing intensification of agriculture in southern Manitoba has raised concern over the impacts of land use such as crop and livestock production on water quality in local surface waters. In this study 59 farm ponds across south-central Manitoba were sampled in three week rotations for nutrients, ions, total chlorophyll a, total microcystins, fecal coliforms and general chemistry and correlated with surrounding land-use and landscape factors. As well, nutrient diffusing substrata (NDS) containing the four treatments of nitrogen (N), phosphorus (P), combined N and P, or neither were deployed in a subset of ponds throughout the sampling period to examine nutrient limitation and compare to ambient N to P ratios in the water. Overall intensive agricultural land-use was associated with poor water quality conditions (i.e., high nutrients and turbidity) and ambient ratios of N to P concentrations were inconsistent in predicting nutrient limitation exhibited by algal growth on NDS.