New RBC Publication: Nutrient Enrichment Increases Energy Flow to Predators

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New RBC Publication: Nutrient Enrichment Increases Energy Flow to Predators

The blackbelly salamander, Desmognathus quadramaculatus, shifted its prey consumption in response to stream nutrient additions.
Copyright Todd Pierson / Discover Life

A paper co-authored by RBC staff has been published in the October 2017 issue of the scientific journal Freshwater Biology.  This study investigates how nutrient enrichment of stream ecosystems affects energy pathways to predator species.  In order to accomplish this, the researchers experimentally increased nitrogen and phosphorus in a stream system and studied the diets and growth of two predatory salamander species, Desmognathus quadramaculatus and Eurycea wilderae, over a two-year period.  

The researchers saw an increase in prey size, number, and biomass for D. quadramaculatus and determined that these changes were mostly driven by the increase in phosphorus.  However, little evidence was found for increases in E. Wilderae diets; the researchers hypothesize that differences in body size between the two species may explain this.  Surprisingly, the observed growth occurred mostly through autotrophic pathways even though the system is largely heterotrophic.

This study helps to illustrate how enriching basal nutrients can have cascading effects through a food web by altering food availability for predators and also highlights that even closely related predators can be affected by this in different ways.  Human activity, especially agriculture, increases nutrient availability in streams and this study begins to investigate the mechanisms behind how this can alter a stream ecosystem.

This paper is authored by RBC staff Phillip Bumpers and Amy Rosemond, as well as John Maerz (Warnell, UGA) and Jonathan Benstead (Dept. of Biological Sciences, Univ. of Alabama).  This paper is published in the October 2017 issue of Freshwater Biology and is available to view via the Wiley Online Library.