PHYTOPLANKTON OF SUDBURY AREA LAKES (ONTARIO) AND RELATIONSHIPS WITH ACIDIFICATION STATUS

Phytoplankton data from samples collected in July 1981 from 111 lakes in the Sudbury area were analyzed by canonical community ordination analysis and other techniques to reveal associations of taxa which were related to environmental gradients among the lakes. Phytoplankton data from a group of seven lakes sampled in the mid-1970's or early 1980's and in the mid-1980's were analyzed for evidence of temporal change. In both data sets, factors related to trophic status and acidification status were inferred to be important controlling variables. For example, desmid genera fell into two general groupings, one typical of clear-water, nutrient-poor, low-alkalinity lakes (e.g. species of Micrasterias, Bambusina, Euastrum, Spondylosium) and the other representing lakes higher in nutrients and alkalinity (e.g. species of Teilingia, Closterium, Xanthidium, Staurastrum). This latter group also included several chlorophytes (Ulothrix, Schroederia, Scenedesmus) and euglenoids (Euglena, Phacus). Well-defined relationships existed between lake alkalinity, pH, and total numbers of phytoplankton taxa. The smaller data set included lakes subjected to recent decreases in acid deposition and corresponding increases in pH over a 10-yr interval, and the increased numbers of phytoplankton taxa were indicative of recovery from earlier acidification.