Animal-mediated nutrient cycling across lakes

Animals are increasingly recognized as important mediators of nutrient cycling in aquatic ecosystems. They can release nutrients through excretion and egestion, transport nutrients across habitat boundaries as they move through their environment, or sequester nutrients within their body. While animals likely play a role in ecosystem-level nutrient dynamics in many lakes, variation in the importance of animals as regulators of nutrient dynamics across lakes is poorly characterized. This project seeks to understand how the recycling (excretion) of nutrients by animals compares across a large diversity of lakes and identify which lake characteristics (e.g. size, depth, trophic state) predict the size of this contribution. We will combine a recently published global model that effectively predicts nitrogen and phosphorus excretion rates of individual aquatic animals as a function of body size and temperature (Vanni & McIntyre 2016, Ecology), with in situ observations of animal densities and body size to estimate ecosystem level excretion rates across a broad diversity of lakes to address our research questions.