MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(IVE-1117-742440) Influence of water hardness and chloride on the acute toxicity of sulfate to fatmucket (Lampsilis siliquoidea) and fingernail clams (Sphaerium simile).

Ivey, C¹, Ingersoll, C¹, Soucek, D², Wang, N¹, ¹ US Geological Survey, Columbia, MO, USA² Illinois Natural History Survey, Champaign, IL, USA

ABSTRACT- Sulfate can reach concentrations in wastewater discharges that can severely impair sensitive macroinvertebrates. Previous laboratory toxicity tests with the amphipod Hyalella azteca and with the cladoceran Ceriodaphnia dubia indicate sulfate toxicity can be reduced with increased level of water hardness or increased concentration of chloride. The objective of this study was to assess the effects of water hardness and chloride on the acute toxicity of sulfate in 96-h water-only exposures to laboratory-cultured juvenile freshwater mussel, fatmucket, and field-collected fingernail clams. Sulfate toxicity tests with fatmucket juveniles were conducted at three hardness levels (100, 300, and 500 mg/L as CaCO3 with Ca:Mg ratio of 2.33) and at two chloride concentrations (5 and 33 mg/L) at one hardness (100 mg/L with Ca:Mg ratio of 1.46). Sulfate toxicity tests with fingernail clams were conducted at two hardness levels (100 or 300 mg/L as CaCO3; varying ratios of calcium to magnesium within a hardness level) and at two chloride concentrations (5 and 33 mg/L). Fatmucket juveniles tended to be less acutely sensitive to sulfate exposure compared to amphipods, cladocerans or fingernail clams. Sulfate LC50s for fatmucket ranged from 2100 to 4500 mg/L and neither water hardness nor chloride had a substantial influence on sulfate toxicity. However, sulfate was more toxic to juvenile fatmucket in water with a lower Ca:Mg ratio at the same water hardness. Fingernail clams tended to exhibit a similar sensitivity to sulfate exposure compared to amphipods and cladocerans. Sulfate LC50s for fingernail clams ranged from 2200 to 3900 mg/L and the toxicity of sulfate tended to be lower at increased water hardness levels or at decreased chloride concentrations. However, in contrast to the results of the exposures with fatmucket juveniles, sulfate toxicity to fingernail clams was higher at the highest Ca:Mg ratio tested at the same water hardness. Additional studies are needed to determine how other species of freshwater mussels respond to sulfate in acute and chronic exposures.

Key words: sulfate, mussels, chloride, water hardness