An investigation of land-use impacts on water quality and phytoplankton communities of the Vermilion River and major tributaries, Sudbury, Ontario, Canada
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The Vermilion River and major tributaries (VRMT) receive numerous inputs from point and non-point sources along their continuum. In addition to these inputs from the surrounding landscape, a hydroelectric impoundment and control dams/weirs have modified the natural flow regime. Further development in the Vermilion watershed has been proposed and there are concerns that it will push the system beyond a tipping point, leading to a state of permanent impairment. In order to understand how ecosystem health may be impacted by future stressors baseline water quality and phytoplankton data were collected monthly (6 months per year) over a period of two years (2013-2014) for twenty-eight sites. Landscape-scale data were also extracted for these sites using the geographical information software QGIS. A broad range of quaternary geology types, land-cover types, and road densities were found to exist in the VRMT study area. Impervious land-cover types (i.e. barren and developed land-cover) and road density were positively correlated with many water quality parameters, whereas, forest land-cover was negatively correlated with many water quality parameters. Principal component analyses revealed that sites on the main-stem of the Junction tributary exhibited above average values for the majority of water quality parameters. Notably, sites located downstream of the Sudbury WWTP had above average values for chlorophyll-a, total phosphorus, nitrate, and nitrite, whereas the site upstream had above average values pH and total kjeldahl nitrogen. Further correspondence analyses and canonical correspondence analyses demonstrated that the abundance and composition of major phytoplankton groups and genera were different between sites and likely influenced by the surrounding landscape (i.e. point and non-point sources) and water quality differences. For all CCAs general biological/chemical parameters and nutrients were slightly better predictors at explaining the variation in phytoplankton biomass compared to metals. Of these general biological/chemical parameters and nutrients, many of parameters were important or moderately important (e.g. Chl-a, CaCO3, DOC, Cond, Cl, TP, TN, TKN, NO3, and NO2). The major phytoplankton group Chlorophyta (i.e. green algae) was abundant at many sites located in Junction tributary in 2013 and in 2014, however, CC-12 which was also located in the Junction tributary was primarily dominated by the major phytoplankton group Bacillariophyta (i.e. diatoms) and had extremely low biomass for all sampling dates. In addition, the major phytoplankton group Cyanophyta (i.e. blue-green algae) was regularly abundant later in the sampling season at ELA-25 for both years and this major phytoplankton group was mainly comprised of Microcystis.