Stelzer, R. S. University of Notre Dame,
Lamberti, G. S. University of Notre Dame,

The chemical composition and growth rates of periphyton in streams are known to track changes in dissolved nutrients such as phosphorus and nitrogen. We tested how periphyton quality (e.g. C:P ratios) and quantity (e.g. total carbon) affected the growth rates of Elimia livescens, a herbivorous freshwater snail. We manipulated the chemical composition of periphyton on clay tiles in artificial streams by adding phosphorus (low or high) and nitrogen (low or high) in 4 different combinations to 32 once-through flumes. Periphyton was offered to snails at low and high quantities for each chemical composition treatment every 2 days for 5 weeks. For a given periphyton quantity (low or high), periphyton total carbon, as estimated from ash-free dry mass, was kept the same among chemical composition treatments. At low food quantity, snail growth rates were 40% higher on periphyton grown under high phosphorus. When food quantity was high (ad libitum), snail growth rates were not affected by periphyton quality. Measurements of periphyton removal suggest that snails consumed food in proportion to its availability regardless of chemical treatment. Our results suggest that snails were limited by the chemical composition of their food when periphyton abundance was low, but not when periphyton abundance was high. Limitation of herbivores by periphyton quality may be widespread in nutrient-poor streams, where both periphyton quality and production is expected to be low.
Day: Tuesday, Feb. 2
Time: 04:45 - 05:00pm
Location: Sweeney Center
Code: SS49TU0445S