Nitrate enrichment alters a Daphnia–microparasite interaction through multiple pathways
Article first published online: 28 DEC 2013
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Ecology and Evolution
Volume 4, Issue 3, pages 243–250, February 2014
How to Cite
Ecology and Evolution 2014; 4(3):243–250
- Issue published online: 4 FEB 2014
- Article first published online: 28 DEC 2013
- Manuscript Accepted: 19 NOV 2013
- Manuscript Revised: 16 NOV 2013
- Manuscript Received: 18 SEP 2013
- University of Georgia
- Odum School of Ecology
- Environmental change;
Nutrient pollution has the potential to alter many ecological interactions, including host–parasite relationships. One of the largest sources of nutrient pollution comes from anthropogenic alteration of the nitrogen (N) cycle, specifically the increased rate of nitrate (NO3 -N) deposition to aquatic environments, potentially altering host–parasite relationships. This study aimed to assess the mechanisms through which nitrate may impact host–pathogen relationships using a fungal pathogen (Metschnikowia bicuspidata) parasitic to crustacean zooplankton (Daphnia dentifera) as a tractable model system. First, the influence of nitrate on host population dynamics was assessed along a gradient of nitrate concentrations. Nitrate decreased host population size and increased infection prevalence. Second, the influence of nitrate on host reproduction, mortality, and infection intensity was assessed at the individual host level by examining the relationship between pathogen dose and infection prevalence at ambient (0.4 mg NO3 -N*L−1) and intermediate (12 mg NO3 -N*L−1) levels of nitrate. Host fecundity and infection intensity both decreased with increasing pathogen dose, but increased nitrate levels corresponded to greater infection intensities. Nitrate had no effect on host growth rate, suggesting that hosts do not alter feeding behavior in nitrate-treated media compared with ambient conditions. This study suggests that nutrient enrichment may enhance disease through increased transmission and infection intensity, but that high levels of nitrate may result in smaller epidemics through reduced transmission caused by smaller population sizes and increased pathogen mortality.