Back

Frank J Dirrigl

Frank J Dirrigl

The University of Texas-Pan American, USA

Title: Arsenic tolerance and accumulation through a hypersaline food web

Biography

Frank Dirrigl is an Assistant Professor of Environmental Science and received his Ph.D. from the University of Connecticut

Abstract

Arsenic has been historically used as a pesticide and wood preservative, and was also produced as industrial effluent. The Laguna Madre (Texas, USA) is hyper-saline estuary impacted by arsenic and other anthropogenic compounds. The Laguna Madre has few freshwater inputs; however, one input, the Arroyo Colorado, is a man-made waterway for agricultural runoff and may contribute to arsenic influx into the Laguna Madre. We determined arsenic levels in water, sea grass, bacteria, and insects from the Arroyo Colorado and/or the Laguna Madre using Inductively-Coupled Plasma (ICP) spectroscopy and other methods. The objective was to investigate the connectivity between the aquatic and terrestrial shoreline food web. Furthermore, arsenic tolerance was tested in bacteria isolated from Laguna Madre sediments to determine the maximum concentration tolerated by microorganisms in the ecosystem. Bacteria were isolated on solid agar media containing 100 M sodium arsenate (AsV) or sodium arsenite (AsIII) then subsequently transferred to media with higher levels of arsenic. Overall, bacteria tolerated arsenate more readily than arsenite; maximum tolerated arsenic concentrations were 60 mM and 1 mM for sodium arsenate and sodium arsenite, respectively. Biotic accumulation of arsenic in sea grass, bacteria, and insects was also observed. However, arsenic values varied among trophic level, exposure pathway, and organism