Stream mesocosm phosphorus dose-response validation study
Citation:
Nietch, C., P. Weaver, Jim Lazorchak, AND N. Smucker. Stream mesocosm phosphorus dose-response validation study. Society of Freshwater Science Annual Meeting, Detroit, Michigan, May 20 - 24, 2018.
Impact/Purpose:
Validate stream phosphorus target for water quality management with a mesocosm experiment that demonstrates causal effects on biota and lends confidence to the users and stakeholders of such target.
Description:
Validating stream nutrient targets for water quality management with experiments that can demonstrate causal effects on biota lends confidence to the users and stakeholders of such targets. Numeric nutrient thresholds are based on correlation-type analyses using data from multiple field sites and linkage variables like dissolved oxygen to indicate the mechanism causing biological impairment. To help validate thresholds determined from field data, we conducted a replicated mesocosm dose-response study with nominal dissolved phosphate treatments of <15, 40, 100, 300, 600, and 1200 ppb using an ecotoxicology framework. Dose effects on the periphytic and macroinvertebrate components of the stream mesocosms were assessed within a community context and with more traditional, single-species toxicity assays run in parallel. Results suggest that there were differences in the periphyton community occurring between the 100 and 300 ppb phosphate treatments that coincided with a significant effect on insect emergence. Specifically, the emergence of adult Tanytarsini chironomids decayed exponentially with dose producing a 20% effective total phosphorus concentration (ppb) response (i.e., EC20) of 148 ± 60 ppb.