Field-based selenium partitioning coefficients, trophic transfer factors, and otolith time-series analyses for a walleye community from an ecotonal plains reservoir, Colorado. III.

Little is known about partitioning coefficients, tissue bioaccumulation, trophic transfer, and otolith time-series analyses of selenium (Se) in a fishery dominated by walleye (Sander vitreus) that consume multiple prey species and occur in a Se-rich reservoir. Concentrations of dissolved total Se in Pueblo Reservoir water consistently exceeded the current EPA criterion benchmark for lentic aquatic ecosystems. The major objectives of this study were to analyze Se in diet-borne consumables of a walleye fishery and perform time-series trend tests of 21 walleye sagittae. In contrast to previous reports, we proposed investigating Se partitioning from water to subsequent trophic levels in a meso-eutrophic ecotonal reservoir using concentrations in water, sediment, periphyton, filamentous algae, diatom mats, chironomids, whole crayfish, muscle of stocked rainbow trout (Oncorhynchus mykiss), whole gizzard shad (Dorosoma cepedianum), and tissues of walleye analyzed by ICP-MS. The indicator values for the level-1 (water to particulate) partitioning coefficients (K_d values) or enrichment factors were as high as 2325 L/kg dw and as low as 588 L/kg dw. Of 36 trophic transfer factors (TTFs) for invertebrates, 33 were >1, while for walleye tissues, 57 of 90 TTFs were <1. For gizzard shad, 8 of 8 TTFs were >1.8. We proposed nonlinear food-web exposure scenarios for walleye and gizzard shad in the Pueblo Reservoir ecosystem. Temporal series analyses of walleye sagittal otoliths showed significantly increasing annular Se concentrations over time for 19 of 21 walleye. Concentrations of Se in whole-body gizzard shad were greater than Se levels in the 3 highest walleye tissues (liver, gill, and kidney). This is the first comprehensive Se study that addresses nearly all components of a walleye ecosystem.