|Title||1991 CIESIN Project: Final report on sediment warming study and water quality lake survey. I. The effect of slightly elevated temperature on the benthic algal community of Douglas Lake, Michigan. II. A water quality survey of fifteen lakes in Cheboygan an|
|Year of Publication||1991|
|Authors||DeYoe HR, Lowe RL|
|Institution||University of Michigan Biological Station|
|City||Ann Arbor, MI|
The objective of the study was to investigate the effects of a slight increase in temperature on the composition and biomass of the benthic algal community in a freshwater lake. The experimental design consisted on six ten-gallon aquaria that were continuously supplied with fresh lake water. Three of the tanks received lake water that was heated 3C while the other tanks received unheated lake water. Three baskets of lake sand were placed in each tank as algal substrates. At the end of the 28-day treatment period, the algae were separated from the sand and then enumerated and identified. There was no statistical difference in algal cell density, chlorophyll a concentration, or cell density of the dominant taxa between the treatments although there was a trend for higher algal biomass in the heated tanks. The heated and unheated tank communities were dominated by cyanobacteria and diatoms. Eight to sixteen algal taxa were unique to each community, but none were dominant. The Shannon-Weaver diversity indices were high (3.48-3.85) for both treatments and the lake community. The Horn's similarity index indicated that all the communities were similar. It was concluded that with an increase in replicates and a longer treatment period significant differences between the treatments might become apparent. The goal of this study was to collect water quality data on fifteen lakes included in the 1974 RANN study. The purpose was to provide recent water quality data for these lakes. The lakes were sampled three times during 1991: May 9-11, July 9-11 and October 5-7. Field measurements taken at the time of sample collection included depth, temperature, dissolved oxygen, pH, conductivity, Secchi disc depth, light penetration and color. Water samples collected from each lake at a depth of 2 m were analyzed for nitrate-nitrogen, ammonia-nitrogen, soluble reactive phosphate (SRP), total phosphate, dissolved silica, total alkalinity and turbidity. In addition, plankton samples were collected during each sampling trip and periphyton samples were collected from artificial substrates in July. Average pH values ranged from 7.1-8.3 except for the two bog lakes whose pH was approximately 4.5. Average total alkalinity values (2.2 to 149 mg CaCO3/L) and average conductivity values (25 to 321 uS/cm) were positively correlated. Average dissolved silica ranged from 0.10 to 6.6 mg SiO2/L and tended to increase from May to October. Mean total phosphate varied from 8.05 to 20.0 ug/L and were not highly correlated with average SRP (2.3 to 4.0 ug/L). No seasonal trend in phosphate levels was evident. Nitrate-nitrogen levels (range of means 3.8 to 43.4 ug/L) tended to be highest in May. The range of average ammonia-nitrogen concentrations was 0.08 to 1.73 mg/L and showed no seasonal trend. May phytoplankton biovolumes varied substantially and were lowest for nutrient-poor Cochran Lake and highest for mesotrophic Douglas Lake. A comparison of the cluster analyses of the 1974 and 1991 data suggested that the basic character of the lakes has not changed.