Interactive effects of phosphorus and copper on Hyalella azteca via periphyton in aquatic ecosystems

This research examined the interaction between dissolved copper and phosphorus, with respect to their effects on the freshwater amphipod Hyalella azteca feeding on periphyton. Field-collected periphyton communities were exposed to different nutrient and metal conditions in indoor recirculating streams. H. azteca were then exposed to water and periphyton from these streams. There was rapid Cu accumulation by periphyton but the total Cu concentration of periphyton was not directly related to dissolved P. In terms of H. azteca growth, an interactive effect was found between Cu and P as growth was reduced more than expected in the low Cu-high P treatment. Our data suggest that eutrophic conditions result in greater Cu toxicity to benthic macroinvertebrates at lower metal concentrations, likely due to higher assimilation efficiency of dietary Cu from periphyton incubated under eutrophic conditions. These results imply that non-additive interactions between multiple stressors may cause ecosystem effects as detected in standard laboratory bioassays conducted under controlled conditions.

► We examine interactive effects between Cu and P on H. azteca feeding on periphyton.
► P may enhance growth of autotrophic algae and/or compensate for Cu toxicity.
► H. azteca exposed to periphyton from high Cu treatment grew slower than those in control and low Cu treatments.
► High P concentration was related to significant reduced growth of H. azteca at lower Cu level.
► H. azteca might have enhanced assimilation efficiency of dietary Cu under eutrophic conditions.