Riparian Spiders: Sentinels of Polychlorinated Dibenzo-p-dioxin and Dibenzofuran Contaminated Sediment.

Polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/F) are persistent, toxic, and bioaccumulative. Currently, PCDD/F monitoring programs primarily use fish and birds with potentially large home ranges to monitor temporal trends over broad spatial scales; sentinel organisms that provide targeted sediment contaminant information across small geographic areas have yet to be developed. Riparian orb-weaving spiders, which typically have small home ranges and consume primarily adult aquatic insects, are potential PCDD/F sentinels. Recent studies demonstrated that spider tissue concentrations indicate the source and magnitude of dioxin-like chlorinated compounds in contaminated sediments, including polychlorinated biphenyls (PCBs). Our aim in this study was to assess the utility of riparian spiders as sentinels for PCDD/F contaminated sediments. We measured PCDD/F (total [Σ] and homologues) in surface sediments and spiders collected from 3 sites within the St. Louis River basin (Minnesota and Wisconsin, USA). We then compared (1) patterns in ΣPCDD/F concentrations between sediment and spiders, (2) the distribution of homologues within sediments and spiders when pooled across sites, and (3) the relationship between sediment and spider concentrations of PCDD/F homologues across 13 stations sampled across the three sites. ΣPCDD/F concentrations in sediment (mean ± standard error: 286,591 ± 97,614 pg/g) were significantly higher than riparian spiders (2,463 ± 977 pg/g; p < 0.001), but the relative abundance of homologues in sediment and spider were not significantly different. Spider homologue concentrations were significantly and positively correlated with sediment concentrations across a gradient of sediment PCDD/F contamination (R 2 = 0.47, p < 0.001). Our results indicate that, as has been shown for other legacy organic chemicals like PCBs, riparian spiders are suitable sentinels of PCDD/F in contaminated sediment. This article is protected by copyright. All rights reserved. Environ Toxicol Chem 2022;00:0-0. © 2022 SETAC.