Sentinel Riparian Spiders Predict Mercury Contamination of Riverine Fish

Abstract

Mercury (Hg) is a widespread and toxic environmental contaminant. It is challenging to determine the level of Hg contamination of food chains and fish within the millions of water bodies in the United States. Mercury contamination can vary 10-fold between ecosystems, even those in the same region. Therefore, aquatic ecosystems need to be individually monitored for Hg contamination to determine which ecosystems are most contaminated and pose the greatest risk to human and wildlife health. One approach to monitoring Hg is to use sentinel species, defined as biological monitors that accumulate a contaminant in their tissues without significant adverse effects. Riparian spiders such as long-jawed orb weavers (Tetragnathidae) have been proposed as sentinels of persistent bioavailable contaminants, like Hg, in aquatic systems. Long-jawed orb weavers feed on emergent aquatic insects and have concentrations of Hg that reflect levels of Hg contamination in the aquatic food web. Previous studies have documented elevated contaminant concentrations in long-jawed orb weavers from shorelines of aquatic ecosystems, suggesting that they could be used as sentinels of chemical contaminants in aquatic ecosystems. We demonstrate for the first time that long-jawed orb weavers can be used as sentinels to identify aquatic systems that contain fish with elevated concentrations of Hg.