The influence of speciation on selenium uptake by a benthic euryhaline polychaete, Neanthes succinea

This study was performed to characterize the selenium (Se) content and speciation of the sediments of the Salton Sea, to distinguish and differentiate Se uptake via different routes, to determine which selenium species are bioavailable to the benthic invertebrates of this system utilizing a euryhaline polychaete worm, Neanthes succinea, and to estimate and predict Se assimilation from dietary sources through different extraction techniques. Evaluation of the Se content and speciation of the sediments involved grab samples of the upper 10 cm of sediment, collected from 11 sample locations across the Sea. Selenium concentrations ranged from 0.3--10.6 mg Se kg -1 dw, with Se tending to accumulate more in the interior portion of the Sea. Speciation of the Salton Sea sediments was determined using a sequential extraction procedure (SEP 2OH), with results showing that the primary selenium fractions of concern included two organic Se fractions (SEP III and V) and the elemental Se fraction (SEP IV).;Evaluation of dissolved Se assimilation was assessed utilizing N. succinea and various concentrations of selenite (Se (IV)) and selenate (Se (VI)). It was shown that dissolved Se (IV) was assimilated more readily than Se (VI) and that juvenile organisms demonstrated significantly greater uptake than adults. Bioavailability and assimilation of dietary Se was examined by creating a synthetic model sediment labeled with stable isotopic Se formed to mimic the Se fractions in the Salton Sea sediment. The greatest assimilated Se came from the organic Se fraction.;Examination of different extraction techniques to aid in estimating and predicting Se assimilation by N. succinea were performed by solubilizing Se using various extractants. A high positive correlation between Se assimilation by N. succinea and the extracted Se from SEP 2OH step III was found. This extraction technique may provide a very promising tool in predicting Se assimilation in benthic organisms, although the number of sediments tested needs to be increased to draw more significant conclusions.