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Friday's Findings October 15 2021

October 8, 2021

Ecological Pathways of Contaminant Transfer and Effects: Aquatic Insects and Insectivores

Date: October 15, 2021 from 2-2:30 p.m. eastern time

Speaker: Johanna M. Kraus, USGS Columbia Environmental Research Center

Click here to join the meeting

Call in (audio only): 202-640-1187

ID: 728518794#  


A fishing spider eats a freshly emerged damselfly.
A fishing spider eats a freshly emerged damselfly (Zygoptera) while floating on a maple leaf in a pond in the Appalachian Mountains of Virginia. The recently shed nymph exoskeleton is visible on the surface of the leaf, suggesting that this damselfly did not take a single wing beat before entering the ‘terrestrial’ food web. (Credit: Johanna Kraus, USGS. Public domain.)

Summary: Environmental contaminant exposure can disrupt natural food webs by reducing the quantity and quality of resources available to consumers. Insects, especially aquatic insects that metamorphose into terrestrial adults, are an abundant and nutritious food source for aquatic and terrestrial wildlife including some with declining populations such as aerial insectivorous birds, amphibians, and bats.  

Using field studies, laboratory experiments, meta-analysis and conceptual modelling, USGS scientists have discovered that various classes of contaminants, including trace metals and insecticides, can reduce the availability of insect prey (reduce food sources for predators), while other contaminants like mercury and persistent organic contaminants can accumulate in the insects (transfer contaminants to predators).  These effects of contaminants can have large consequences for insects such as reducing adult aquatic insect biomass by 97 percent from mining-impacted streams and increasing insect-mediated pesticide fluxes by 50 percent from agriculturally influenced wetlands. As a result, insectivores shift their diets to terrestrial insects, show reduced biomass, and suffer from increased exposure to toxins.

In this webinar, Dr. Kraus will discuss the effects of contaminant exposure on aquatic insects and their aquatic and terrestrial predators in watersheds with sources of contaminants originating from mining, and industrial and agricultural land use. She will highlight interdisciplinary, interagency, and international collaborations forged to 1) predict the impact of contaminants on aquatic insects and their linkages with terrestrial consumers and 2) operationalize this science into a decision tool to aid managers in designing resource assessment studies.

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