Effects of widespread trace chemicals on aquatic and riparian communities in the Portage River watershed
Water, the essence of life, can also be a vector for toxins. This study compares macroinvertebrate diversity with the distribution of six trace chemicals in the upper tributaries of the Portage River watershed, the second largest tributary to the Western Basin of Lake Erie. The Portage is surrounded by agricultural fields and urban areas that discharge a variety of chemicals into the river and its tributaries. Some of these chemicals have been linked to developmental, reproductive, and survival changes in certain organisms. This study aims to estimate the distribution of trace chemicals that may impact arthropod populations.
Concentrations of atrazine, glyphosate, caffeine, bisphenol A (BPA), triclosan and estradiol were tested at fifteen sites throughout the upper tributaries of the Portage in August and September 2014. Concentrations were estimated using ELISA (an immunoassay method). The biodiversity of the waterways was also sampled via macroinvertebrate surveys upstream and downstream of three wastewater treatment plants.
Most of the chemicals we tested ranged from 0.41 to 0.98 parts-per-billion with mean concentrations from 0.68 to 0.76 parts-per-billion. Atrazine, triclosan, and estradiol concentrations were at levels that may affect crustacean, frog, and minnow development, respectively. When compared to a US Geological Survey (USGS) study examining chemical contamination in United States waterways, the Portage watershed had higher mean concentrations than United States medians of caffeine, BPA, and triclosan in the early 2000’s. Estradiol concentrations were lower than those medians and atrazine and glyphosate were not included in the USGS study.
The sites near the smallest town had the highest mean richness of arthropod orders, but had chemical concentrations that were slightly higher than the mean across all sites for atrazine (6%), triclosan (7%), caffeine (3%), and glyphosate (2%). Mean arthropod abundance was highest furthest downstream, but had concentrations of atrazine that were 2% lower than the mean across all sites. Sites near Fostoria, a medium city, had the lowest richness of arthropod orders, and had slightly higher concentrations of triclosan (3%) and caffeine (2%) than the mean across all sites. Differences in geomorphology, a small sample size, and low variability in trace chemical concentrations may have masked much of the possible effect of trace chemicals on arthropods. Future investigations should include sampling high runoff periods, low-chemical reference sites, and further examination of the food web.