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United States Department of Agriculture

Agricultural Research Service

Research Project: Developing Sustainable Cropping Systems to Improve Water Productivity and Protect Water and Soil Quality in Irrigated Agriculture

Location: Water Management Research

Title: Biotransformation and accumulation of selenium inside organisms in an engineered aquatic ecosystem designed for bioremediation of Se from agriculture drainage water and brine shrimp production

Authors
item Schmidt, R -
item Banuelos, Gary
item Tantoyotai, P -
item Fakra, S -
item Marcus, M -
item Yang, S -
item Pickering, I -
item Hristova, K -
item Freeman, J -

Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 28, 2012
Publication Date: May 1, 2013
Citation: Schmidt, R., Banuelos, G.S., Tantoyotai, P., Fakra, S., Marcus, M., Yang, S.I., Pickering, I., Hristova, K., Freeman, J. 2013. Biotransformation and accumulation of selenium inside organisms in an engineered aquatic ecosystem designed for bioremediation of Se from agriculture drainage water and brine shrimp production. Environmental Science and Technology. 47:(10)5057-5065.

Interpretive Summary: Selenium (Se) is a naturally-occurring trace element found in soils derived from Cretaceous shale deposits in the western United States. Water-soluble Se, as selenate, is often leached from naturally enriched soils by irrigation water and rains into surface runoff or drainage effluent. Much of the drainage water was collected and stored in large evaporation ponds. Ecotoxicity concerns were expressed regarding the potential excessive accumulation of Se within the stored water and its conversion to organic Se forms. If there is a biomagnification of Se throughout the aquatic food chain, an ecological disaster leading to biological toxicities could be an unexpected result. As part of a larger study to investigate the biological impact of Se concentrated in evaporation ponds, we analyzed the internal Se content of the bacteria, diatoms, microalgae, brine shrimp and brine fly contained within the Se-laden aquatic ecosystem. Our results showed the pathway and transformations of Se throughout the aquatic food chain. In addition, we fully characterized the biochemistry of Se and developed a new way to monitor for Se toxicity in wetland ecosystems. Furthermore our results provide insight for developing an aquatic bioremediation strategy for Se and the novel production of Se-enriched brine shrimp, a nutritious Se-enriched animal feed supplement that unexpectantly can be produced in such poor quality saline waters.

Technical Abstract: Excessive selenium (Se) in soils and waters present in the westside of central California was determined to be responsible for ecotoxicities observed in water fowl frequenting large bodies of water, i.e., evaporation ponds. In order to monitor the fate and potentially design an aquatic Se remediation program to reduce this risk, an engineered aquatic ecosystem was specifically developed to evaluate the biomagnification of Se in aquatic organisms and determine if this biological process could bioremediate inorganic Se from hypersalinized agricultural drainage water. Inorganic selenate present in drainage water was first differentially concentrated in microalgae, bacteria and diatoms, where it was reduced into various inorganic Se forms (selenite, selenide, or elemental Se) or partially incorporated into organic Se as selenomethionine. Brine shrimp and brine fly larva then accumulated and bio-concentrated Se from ingesting aquatic microorganisms and then further metabolized Se into predominately organic Se. Nets were then used to harvest the Se-enriched brine shrimp. The molecular results provide an in-depth understanding of how selenate is bioaccumulated from water, metabolized into organic Se, and how it moves up the food chain after being biotransformed by various aquatic organisms. Furthermore, our findings demonstrate that our engineered aquatic ecosystem can remove Se from agricultural drainage water, while producing potentially value-added products.

Last Modified: 8/31/2014
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