Some shoreline spiders, such as the long-jawed spider shown here, move mercury contamination from riverbeds up the food chain to land animals. Credit: Ryan Otter, Grand Valley State University
Key points:
- Long-jawed shoreline spiders living along Lake Superior’s shoreline move mercury contamination from riverbeds up the food chain to land animals.
- Spiders’ feeding strategies determine how well their tissues reflect mercury sources and contamination.
- Using spiders to track aquatic contamination has the potential to inform management decisions and monitor remediation activities.
A new study, published in ACS’ Environmental Science & Technology Letters, demonstrates how certain shoreline spiders can move mercury contamination from riverbeds up the food chain to land animals, such as birds, bats, and amphibians.
Mercury can enter waterways from natural sources, industrial pollution and other human activities. In the water, microbes transform the mercury into methylmercury, which is a toxic form that biomagnifies and increases in organisms up the food chain. Insects living in mercury-contaminated waterway can pass mercury along to the spiders that feed on them.
Researchers collected long-jaw spiders along two tributaries to Lake Superior and sampled sediments, dragonfly larvae, and yellow perch fish from the waterways. They also measured mercury and identified its sources including direct industrial contamination, precipitation, and soil runoff.
The long-jawed spiders showed how mercury pollution moved from the aquatic environment to terrestrial wildlife, suggesting that spiders can provide clues to sources of mercury contamination in the environment.
However, not all spiders provide accurate contamination information. For example, the team collected and analyzed tissues from fishing spiders and orb-weaver spiders and found that mercury sources varied among the three species likely due to their different feeding strategies as fish spiders hunt primarily on land, orb-weavers eat aquatic and terrestrial insects, and long-jawed spiders feed heavily on aquatic insects.
Tracking aquatic contamination with specific spiders such as long-jawed spiders has the potential to inform management decisions and monitor remediation activities.