PCB concentrations in riparian spiders (Tetragnathidae) consistently reflect concentrations in water and aquatic macroinvertebrates, but not sediment: Analysis of a seven-year field study

Abstract

Tetragnathid spiders have been used as sentinels to study the biotransport of contaminants between aquatic and terrestrial environments because a significant proportion of their diet consists of adult aquatic insects. A key knowledge gap in assessing tetragnathid spiders as sentinels is understanding the consistency of the year-to-year relationship between contaminant concentrations in spiders and sediment, water, and macroinvertebrates. We collected five years of data over a seven-year investigation at a PCB contaminated-sediment site to investigate if concentrations in spiders were consistently correlated with concentrations in sediment, water, and aquatic macroinvertebrates. Despite significant year-to-year variability in spider PCB concentrations, they were not correlated with sediment concentrations (p = 0.186). However, spider PCB concentrations were significantly, positively correlated with PCB concentrations in water (p < 0.0001, annual r2 = 0.35–0.84) and macroinvertebrates (p < 0.0001; annual r2 = 0.59–0.71). Analysis of covariance (ANCOVA) showed that spider PCB concentrations varied consistently with water (β = 0.63) and macroinvertebrate PCB concentrations (β = 1.023) among years. Overall, this study filled a critical knowledge gap in the utilization of tetragnathid spiders as sentinels of aquatic pollution by showing that despite year-to-year changes in PCB concentrations across environmental compartments, consistent relationships existed between spiders and water and aquatic macroinvertebrates.