IDEQ Phytoplankton Community Assessment
Coeur d’Alene Lake is fed by two primary river systems, the Coeur d’Alene River which enters the lake in the east, and the Saint Joe River which enters the lake in the south. The outflow of the lake is the Spokane river in the north which ultimately feeds into the Columbia River. The Coeur d’Alene River flows out of the Silver Valley which has a long history of mineral mining while the Saint Joe River mainly flows through wilderness or agricultural use areas. Idaho Department of Environmental Quality (IDEQ) has been monitoring water quality in Coeur d’Alene Lake for many years. IDEQ, in collaboration with the Coeur d’Alene Tribe, developed the Lake Management Plan (LMP) in 2009 to address concerns regarding increasing nutrients in the lake. This LMP included sampling the water column for phytoplankton communities and other environmental factors (e.g. dissolved metals, nutrients, chlorophyll, etc.). IDEQ was interested in exploring correlations between the measured environmental factors and changes to the phytoplankton communities.
EcoAnalysts taxonomists harmonized the entire dataset which included updating any name changes and ensuring that each taxon was identified to a similar level across the dataset. Following the taxonomic harmonization step, 10 years’ worth of the data from two of the long-term monitoring stations were investigated for both spatial and temporal trends. The investigation included defining the phytoplankton communities during specific season using multivariate techniques and then overlaying results from environmental factors (nutrients, metals, etc.) to investigate correlations between changes to these phytoplankton communities. All analyses were reported to the agency and a presentation of the results was given to the management group.