posted on 2020-07-30, 21:29authored byBrittany G. Perrotta, Marie Simonin, Jeffrey A. Back, Steven M. Anderson, Astrid Avellan, Christina M. Bergemann, Benjamin T. Castellon, Benjamin P. Colman, Gregory V. Lowry, Cole W. Matson, Emily S. Bernhardt, Ryan S. King
Freshwater ecosystems are exposed
to engineered nanoparticles through
municipal and industrial wastewater-effluent discharges and agricultural
nonpoint source runoff. Because previous work has shown that engineered
nanoparticles from these sources can accumulate in freshwater algal
assemblages, we hypothesized that nanoparticles may affect the biology
of primary consumers by altering the processing of two critical nutrients
associated with growth and survivorship, nitrogen and phosphorus.
We tested this hypothesis by measuring the excretion rates of nitrogen
and phosphorus of Physella acuta, a
ubiquitous pulmonate snail that grazes heavily on periphyton, exposed
to either copper or gold engineered nanoparticles for 6 months in
an outdoor wetland mesocosm experiment. Chronic nanoparticle exposure
doubled nutrient excretion when compared to the control. Gold nanoparticles
increased nitrogen and phosphorus excretion rates more than copper
nanoparticles, but overall, both nanoparticles led to higher consumer
excretion, despite contrasting particle stability and physiochemical
properties. Snails in mesocosms enriched with nitrogen and phosphorus
had overall higher excretion rates than ones in ambient (no nutrients
added) mesocosms. Stimulation patterns were different between nitrogen
and phosphorus excretion, which could have implications for the resulting
nutrient ratio in the water column. These results suggest that low
concentrations of engineered nanoparticles could alter the metabolism
of consumers and increase consumer-mediated nutrient recycling rates,
potentially intensifying eutrophication in aquatic systems, for example,
the increased persistence of algal blooms as observed in our mesocosm
experiment.