Consumers play an important role in nutrient cycling in many aquatic ecosystems by releasing nitrogen, phosphorus, and carbon. In some cases animal-mediated element cycling makes a significant contribution to whole ecosystem flux of these elements. Temperature and body size are known to impact nutrients excretion rates. However, little is known about how parasites impact excretion; yet some models suggest that parasites will increase due to climate change. Therefore, understanding the synergistic influence of climate warming and parasites on animal excretion remains an open question. In lakes of the southern boreal forest, where temperatures are rising, pumpkinseed sunfish (Lepomis gibbosus) are common and abundant fish, and in some lakes, are infected by trematodes (Uvulifer ambloplitis), (Clinostomum marginatum) and cestodes (Proecocephalus embloplites).Working at Station de Biologie des Laurentides, we exposed pumpkinseed to one of three temperatures(20°, 25, or  30°C) and variable parasite infections and measured their nutrient excretion rates. Phosphorus (P) excretion was negatively correlated with parasite load and positively correlated with temperature, while nitrogen (N) excretion was not correlated with either parasite load or temperature. Thus, the N:P ratio excreted also increased significantly with parasite load and decreased with temperature. Parasites may sequester some P ingested by fish, leading to lower P excretion. Analysis of fish body nutrient contents will be used to address how parasites (and warming temperatures) alter stoichiometric flux through fish.

Primary Presenter: Carrie Sharitt, Miami University, OH (sharitca@miamioh.edu)

Authors:

Sandra Binning, Université de Montréal  (sandra.ann.binning@umontreal.ca)

Roxane Maranger, Université de Montréal  (r.maranger@umontreal.ca)

Michael Vanni, Miami University (Ohio)  (vannimj@miamioh.edu)