John Wiley & Sons, Ltd.

A critical body residue approach for predicting persistent bioaccumulative toxicant effects on reproduction and population dynamics of meiobenthic copepods

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Critical body residues (CBRs) are the measured tissue toxicant concentrations yielding a median dose–response on a dry‐weight or lipid‐normalized basis. They facilitate management decisions for species protection using tissue analysis. Population CBR is the mean dose yielding 50% population suppression and was predicted here in Amphiascus tenuiremis for fipronil sulfide (FS) using lifetables and the Leslie matrix. Microplate bioassays (ASTM E‐2317‐14) produced biomass sufficient for dry mass and lipid‐normalized CBR estimates of reproduction (fertility) and population growth suppression. Significant FS toxic effects were delayed naupliar development (at ≥0.10 µg L−1), delayed copepodite development (at 0.85 µg L−1), decreased reproductive success (at ≥ 0.39 µg L−1), and decreased offspring production (at 0.85 µg L−1). A reproductive median effective concentration (EC50) of 0.16 µg L−1 (95% CI: 0.12–0.21 µg L−1) corresponded to an adult all‐sex CBR and lipid‐normalized CBR of 0.38 pg FS · µg−1 dry weight (95% CI: 0.27–0.52 pg FS · µg−1) or 2.8 pg FS · µg−1 lipid (95% CI: 2.2–3.6 pg FS · µg−1), respectively. Copepod log bioconcentration factor (BCF) = 4.11 ± 0.2. Leslie matrix projections regressed against internal dose predicted fewer than five gravid females in a population by the third generation at 0.39 and 0.85 µg FS · L−1 (i.e., 9.6–10.2 µg FS · µg−1 lipid), and 50% population suppression at a CBR of 1.6 pg FS · µg−1 lipid. This more integrative population CBR as a management tool would fall 1.75 times below the CBR for the single most sensitive endpoint—fertility rate. Environ. Toxicol. Chem. 2012; 31: 1076–1082. © 2012 SETAC

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