Spiders Can Transfer Mercury Contamination from Water to Land, Study Finds

A new study conducted by the U.S. Geological Survey Upper Midwest Water Science Center reveals that spiders living near the shoreline can transfer mercury contamination from riverbeds to land animals. The researchers found that spiders that feed on insects like dragonflies, which inhabit mercury-contaminated waters, can accumulate the hazardous metal in their bodies and pass it up the food chain.

Aquatic insects play a crucial role in supporting terrestrial ecosystems by providing food for birds, bats, amphibians, and spiders. However, when these insects accumulate contaminants such as mercury from their aquatic environment, they can transfer these pollutants to land animals that consume them. This contaminant transfer is often overlooked but poses serious health risks to wildlife.

Mercury contamination is a significant environmental concern caused by industrial waste and human activities. When mercury enters aquatic environments, microorganisms transform it into methylmercury, a highly toxic form that bioaccumulates in animals up the food chain. Spiders living near water bodies, like lakeshores and riverbeds, have been increasingly recognized as potential conduits for contaminant transfer from aquatic to terrestrial creatures.

To better understand this process, the researchers collected long-jawed spiders near Lake Superior and examined their tissue for mercury. They also analyzed sediments, dragonfly larvae, and yellow perch fish from the same locations. The study revealed that the level of mercury in sediments was consistent with the mercury concentration in dragonfly larvae, spiders, and yellow perch tissues. This suggests that long-jawed spiders could serve as indicators of mercury pollution moving from water to land-based wildlife.

The researchers also found that different species of spiders had varying sources of mercury contamination. Fishing spiders, which primarily hunt on land near water, and orb-weaver spiders, which consume both aquatic and terrestrial insects, exhibited different sources of mercury. This suggests that not all spider species living near shorelines can effectively indicate mercury pollution.

Mercury contamination poses significant health risks to humans and wildlife, affecting the nervous, digestive, and immune systems. Efforts to reduce mercury contamination involve stricter regulations on emissions and responsible disposal of mercury-containing products.

Overall, this study highlights the importance of monitoring the transfer of contaminants from aquatic to terrestrial ecosystems and the role of spiders in indicating mercury pollution. By understanding how mercury moves through the food chain, researchers and policymakers can make informed decisions to mitigate and remediate mercury contamination.

Source: Environmental Sciences & Technology Letters