Water Resources Research Act Program

Details for Project ID 2016AR387B

Biological and ecological consequences of sub-lethal ion concentrations on microbial and macroinvertebrate detritivores.

Institute: Arkansas
Year Established: 2016 Start Date: 2016-03-01 End Date: 2017-02-28
Total Federal Funds: $12,093 Total Non-Federal Funds: $30,000

Principal Investigators: Sally Entrekin, Michelle Evans-White, Natalie Clay

Abstract: Road deicers, water softeners, sewage, resource extraction effluent and weathering of rock formations exposed by mining and drilling contribute excess sodium and chloride to streams. Many studies have measured toxic levels on aquatic invertebrates that typically exceeded 2 or 3 orders of magnitude. However, gradual and low-level increases in ion concentrations are common in regions with urban, agriculture, and resource extraction. Despite the widespread low-level increase, few have studied the biological and ecological consequences. In Arkansas Valley streams and rivers, ion concentrations are among the lowest natural concentrations in the U.S. Ion concentrations have been increasing where sodium (Na: 0.7-7.0 mg/L) and chloride (Cl: 0.8-21.2 mg/L) has increased in 20 wadeable streams that drain agriculture and resource extraction. Additionally, Arkansas Department of Environmental Quality (ADEQ) has measured a range in Cl concentrations from 0.4 to over 150 mg/L in Arkansas Valley streams (ADEQ database accessed 27Oct15) that suggest rising levels with human modifications in the watershed. Ion increases in Arkansas Valley streams are likely from a combination of agriculture, wastewater from septic systems and development associated with resource extraction. Aquatic organisms adapted to naturally low ion concentrations could be more physiologically sensitive and prone to experience osmoregulatory stress and a subsequent growth decline that could lead to population decline and eventual species loss. Also, many aquatic organisms sensitive to altered water quality are detritivores that consume leaf litter in forested streams. Leaf litter decomposition rates could decline directly from lower micro- and macro- detritivore litter consumption and indirectly from reduced litter palatability and subsequent decline in macro-detritivore consumption. Most Arkansas Valley streams are detrital-based and could be at-risk for changes in leaf litter processing due to small rises in stream ion concentrations. We will investigate how detrital organisms and their associated processes change in response to sub-lethal increases in ions; specifically Na and Cl.