RESPONSE OF AGGLUTINATED FORAMINIFERA TO A REVERSE-OSMOSIS BRINY DISCHARGE: ALBEMARLE SOUND, NORTH CAROLINA

Reverse osmosis water treatment plants are becoming the preferred means of producing potable water for many coastal communities in the southeastern United States. At these facilities reject brine solutions -- sometimes containing up to 10 times the initial concentration of dissolved solids -- are created and often discharged into estuarine waters. State and federal agencies have expressed concern over the potential ecological impacts this wastewater could have on these sensitive environments. Monitoring of a brine discharge site in Currituck County, North Carolina, revealed significantly higher conductivity values within ~50 m of the point source.

To assess the impact of this discharge on lower trophic levels within the estuarine community we collected foraminifers from increasing distances from the discharge site. These microfossils have been demonstrated to be excellent bioindicators of ecological disturbance from anthropogenic pollution in marginal-marine environments and buried assemblages provide insights into pre-impact diversity and density. Species abundance data was collected from surface and sub-surface samples taken in the area surrounding the brine discharge site. Two taxa (Ammobaculites spp. and Ammotium sp.) accounted for 98.5% of all normalized specimens. Abundance is significantly less in the sub-surface samples (Student’s t-test, p<0.0001), likely resulting from taphonomic degradation of the agglutinated tests. Foraminifer population does not appear correlated with discharge of the wastewater; instead, natural parameters (e.g. depth, substrate, dissolved oxygen) appear to influence abundance in an assemblage to a greater degree. Species distribution is similar in surface and sub-surface samples and preliminary findings indicate foraminiferal diversity is significantly less near the discharge point source.