The effect of nutrient loading on algal growth and subsequent snail grazing by two Michigan snail species (Pysella acuta, Planorbella campanulata)

Abstract

Excessive nutrient loading can have detrimental effects on ecosystems, though nutrient addition in relatively low or appropriate amounts can have beneficial effects instead. We examined the effect of varied nutrient loading on two Michigan snail species (Physella acuta, Planorbella campanulata) to determine the effect nutrient loading had on grazing behavior. We also examined the effect on algal cell richness and nutrient capture in each of the three nutrient loading treatments: high-nutrient-added, low-nutrient-added, and control. Snails overall consumed more algal from high-nutrient-added tiles as compared to low-nutrient-added and control tiles, with significant differences existing between consumption of Physella acuta alone and Physella acuta with Planorbella campanulata for both the high-nutrient-added and lownutrient added treatments (ANOV A p < 0.05). Algal communities on the high-nutrient-added tended to have higher cell counts and equivalent but low assimilation of both nitrogen and phosphorus. Communities on control tiles consisted on a much larger proportion of diatoms as compared to blue-green and green algae. The results of this study did not prove significant in most cases, though did point to trends that support the hypotheses that both snail species grazed more on algae grown in a high-nutrient environment.