Hull et al. 2023 — Arsenic trophic transfer in Puget Sound lakes
Hull and colleagues investigated arsenic trophic transfer through aquatic food webs in ten arsenic-contaminated urban lakes in Washington State’s Puget Sound lowlands, a region with legacy pollution from historical copper smelting operations. Their key finding is that littoral sediment arsenic concentration is a reliable predictor of arsenic bioaccumulation across trophic levels, including in edible fish muscle tissue, providing a low-cost screening tool for human health risk from recreational fish consumption. The percent inorganic arsenic (%iAs) increased with decreasing trophic level across all lakes, confirming that iAs dilutes with trophic transfer while total arsenic biodiminishes.
Key numbers
- Sediment As: 7–213 µg As/g in littoral sediment across the 8 contaminated lakes; two deepest-lake profundal sediments reached 206–208 µg/g
- Fish (Lepomis spp.) muscle THg: not primary outcome; primary outcome was total As and iAs in muscle
- Arsenic in fish muscle: correlated significantly with littoral sediment As (r significant, p < 0.05 across species and lakes)
- Periphyton contained higher total As than other primary producers
- Snails contained higher As than zooplankton or insect macroinvertebrates at equivalent trophic position
- Percent iAs consistently increased as trophic level (measured by δ15N) decreased, across all lakes regardless of depth or mixing regime
- Modeled fish consumption from the most contaminated shallow lake resulted in incremental cancer risk > 10−5 (Washington State health threshold)
- Deeper seasonally stratified lakes showed lower bioavailability despite comparable profundal sediment concentrations; mixing regime was a significant modifying factor
Methods (brief)
Stable isotope analysis (δ13C, δ15N) for trophic position and resource use. Total As by ICP-MS; speciation by HPLC-ICP-MS. Samples from 10 lakes in UW Superfund Research Program study area. AAS not used; ICP-MS for trace metals. LOD/LOQ not individually stated in the section reviewed.
Implications
Certification: Supports the principle that sediment arsenic measurements in sourcing watersheds can serve as a screening proxy for fish tissue contamination; relevant to wild-caught freshwater fish ingredient risk.
Courses: Good illustration of iAs/tAs speciation distinction in the context of trophic transfer — iAs proportion increases near the base of the food chain.
App: Freshwater fish sourced from urban contaminated lakes in the Pacific Northwest are a specific contamination risk scenario. iAs (not just tAs) is the relevant metric for risk.
Microbiome: Not applicable.