Periphyton community dynamics in varying natural environments : a study from Northern Lake Simcoe

Abstract

Study site : near Barrie Ontario, Kempenfelt Bay - Barrie ; Concession Point - Ramara Township ; Lagoon City, Brechin. Globally, freshwater ecosystems are constantly under the threat of various biological and chemical stressors. In Canada, millions of dollars are spent on the rehabilitation process of these water bodies every year. Maintenance of healthy water systems is important for their conservation and survival of human kind. This study examines the use of periphyton as a tool for monitoring water quality by examining the dynamics (biofilm thickness, species density, species richness, species diversity, and biomass) in periphyton communities in lentic environments. Previous research validates the successful use of periphyton in lotic environments. This multi-proxy (Bacillariophyceae, Chlorophyceae, Cyanophyceae, and protozoa) study investigated the colonization pattern of periphyton on inert glass slides (10 X 3 X 0.1cm) suspended in the littoral zone of 3 sampling locations in northern Lake Simcoe, to a maximum period of 30 days (per sampling period) with intermittent sampling. The study was repeated four times in different seasons during 2011-2013. The retrieved slides were observed under a microscope for taxonomic composition of periphyton communities, species density, and biofilm thickness. The hypotheses tested were (1) periphyton community dynamics vary with season and location, (2) species diversity decreases as a result of increase in nutrient concentration, (3) diatom abundance and species composition will increase in spring and fall seasons as a result of lake turnover processes. Results indicated that there was significant variation in the periphyton colonization pattern with seasons, locations and with the duration of slide exposure. The overall periphyton growth (biofilm thickness, biomass and species density) exhibited an increase during the early phase (rmAnova p<0.05 between days of exposure); a climax during the mid phase (miAnova /7<0.05 between days of exposure); a sloughing-off period, and an increase in growth towards the late growth phase (rmAnova /7<0.05 between days of exposure). The highest species density (site LC: 7.91[subscript log10]) was observed during summer (rmAnovap<0.05 between seasons) when a decrease in diversity in Bacillariophyceae was observed. However, Bacillariophyceae abundance and diversity increased during spring and fall sampling periods as a result of lake turnover processes and the availability of nutrients. Overall species diversity did not decrease when the total phosphorus concentration increased in the water column. This is mainly because of the increased diversity in Chlorophyceae, Cyanophyceae and protozoa. The periphyton community varied with the environmental stressors such as variations in conductivity and nutrient concentrations. Thus, the mature periphyton community composition and their dynamics demonstrated that they can be used as an indicator of water quality changes in this study area.