Quantifying Bioavailability and Toxicity of Copper to Americamysis bahia - Mysid Shrimp

Abstract

Reliable methods are needed to measure and correlate bioavailable metals with aquatic toxicity. This research develops a method to measure bioavailable copper in estuarine waters using the cation exchange resin Chelex 100 ®. The Chelex 100 ® method performed consistently at copper concentrations from 195-495 μg/L when organic matter, pH and salinity were held constant. Varying salinity from 15-30 ppt did not affect measured bioavailable copper. As expected, an increase in pH from 4 to 8.5 and increase in NOM from 0 to 12.5 mg/L reduced measured bioavailable copper. Acute toxicity bioassays were performed with mysid shrimp (Americamysis bahia) and copper in the presence of NOM. At 20 ppt salinity, 48-hour LC50 dissolved copper concentrations were 200, 340, and 495 μg/L at 0, 12, and 24 mg/L NOM, respectively. The corresponding 48-hour LC50 values for bioavailable copper were nearly constant: 94, 98, and 105 μg/L Cu at 0, 12, and 24 mg/L NOM respectively. The consistency of the mysid shrimp LC50 values for bioavailable copper measured using the Chelex-100 ® method indicates that this method is appropriate for evaluating metal bioavailability in saline waters.