Newswise — Spiders that live along lake shorelines are good predictors of mercury pollution in and around bodies of water, according to a recent study by researchers at Texas Christian University in Fort Worth.
In a survey of 10 experimental ponds with different levels of mercury contamination, investigators found the average mercury concentration in a common shoreline spider, the long-jawed orb weaver, was correlated with mercury levels in aquatic insects (midges) that emerged from the ponds.
Mercury contamination in lakes is frequently monitored by sampling fish. However, this approach is time consuming and expensive, and fish in lakes or ponds on private land are rarely sampled. In addition, many lakes are small water bodies that do not contain fish, but these water bodies could still pose a risk wildlife that consume the aquatic insects.
Mercury is one of the most toxic pollutants found in the environment. It can impact the health of fish, wildlife and humans. Mercury from the atmosphere is deposited in the lakes, converted to methyl mercury by bacteria, and moves into the food chain. Some aquatic insects, like midges, spend part of their lifecycle in the water but emerge as adults to reproduce. Shoreline spiders consume these “emergent” insects and are in turn consumed by birds. In fact, spiders can be an important food source to nesting songbirds.
“The levels of mercury in spiders and midges were strongly correlated in our study ponds,” said Matt Chumchal, Assistant Professor of Biology at Texas Christian University. “This is an important finding because it means that scientists and environmental managers can use spiders to efficiently collect data on mercury levels in water bodies with and without fish.”
This study was published in the February 2013 edition of Environmental Science & Technology.