Pesticides are likely impacting invertebrate life essential to our nation’s streams

A new nationwide study by USGS scientists provides additional scientific evidence that pesticides are likely negatively impacting aquatic invertebrate community health and therefore the health of our stream and river ecosystems.

The USGS used multiple research strategies from statistical modeling to laboratory experiments to sampling in more than 400 streams across the United States. Scientists determined that four pesticides – bifenthrin, chlordane, fipronil and imidacloprid – were each likely impacting the health of aquatic invertebrates at the regional scale in at least one of the five regions studied.

Pesticides are used in agricultural and urban environments to control a variety of pests including invertebrates such as insects, mammals such as rodents, fungi, algae, and plants. They act through a variety of modes on the target organism; however, non-target organisms are often affected either through direct toxicity or secondary or indirect impacts to prey species or habitat. Overspray, drift, and runoff may carry a pesticide far from its application site. 

Aquatic ecosystems are critical to our economy and communities, providing sources of drinking water, buffering communities against storms through wetland and marsh areas, driving vast sportfishing and recreational industries, and filling a host of other functions. Invertebrates are keystone species in those river and stream ecosystems. They are also already impacted by other environmental stressors in their environment, such as habitat degradation and changing temperatures, therefore they may be particularly sensitive to pesticide effects.

As part of the study, scientists sampled water, bed sediment and invertebrates to assess their exposure to pesticides. Knowing that pesticides are present in their environment and that aquatic invertebrate communities are struggling does not alone mean that pesticides are the cause. Therefore, scientists needed to investigate a variety of forms of evidence to determine the likelihood that pesticides were negatively impacting aquatic invertebrates in U.S. streams.

The research in this study used multiple lines of investigation to gather evidence. This included:

• Toxicity predictions based on measured pesticide concentrations in streams.
• Statistical analyses that tested the relationship between pesticides and invertebrate communities in streams.
• Multivariate models that identified which pesticides best explained the invertebrate community structure and health.
• Experiments using “mesocosms,” which are aquatic invertebrates brought into the laboratory and dosed with pesticides under controlled conditions to demonstrate the impacts these pesticides have.

“Stream invertebrates are impacted by many environmental stressors, including pesticides, habitat disruption, and changing temperatures, especially in streams that […]

Full article: www.usgs.gov