Ecological stoichiometry in benthic food webs: Effect of light and nutrients on periphyton food quantity and quality in lakes

To quantify the effect of light and nutrients on periphyton food quantity and quality, a series of experiments, consisting of full light and shade treatments, was conducted in 2003 in 11 lakes differing in nutrient status and turbidity. Periphyton chlorophyll a, C:P, and benthic macroinvertebrate biomass were measured on rocks or artificial substrates (glass slides) or both. Periphyton biomass increased and periphyton C:P decreased as total phosphorus increased. Periphyton biomass and C:P were higher in light than in shade. Benthic macroinvertebrate biomass was higher with high periphyton biomass and low periphyton C:P. Both turbidity and nutrient concentrations in natural water bodies are altered by human-driven and natural processes; therefore we expect periphyton biomass and C:P to increase in lakes as clarity increases and nutrient content decreases, resulting in high-quantity but low-quality benthic food.