Changes in water quality after addition of sea salts to fresh water: implications during toxicity testing.

Sea salts (seven brands from six commercially-available sources) were dissolved in water to develop 30 g/l solutions, and selected water quality characteristics were then monitored for 96 h. One or more water quality characteristics changed significantly during the 96 h period in six of the reconstituted sea salts. Measured characteristics of sea water diluted to 30 g/l demonstrated no changes during the observation period. The sea salts from different sources also demonstrated differences in absolute concentrations of some characteristics measured. Application of the Biotic Ligand Model to predict copper toxicity to the bivalve Mytilus edulis in solutions of the salts tested yielded 96-h median-lethal concentrations that ranged from 2 to 13 microg/l. Since water quality affects toxicity of many environmental pollutants, the source of the sea salt and equilibration time should be considered when planning toxicity tests.

Toxicity of methyl tert-butyl ether to marine organisms: ambient water quality criteria calculation.

In response to increasing concerns over the detection of methyl tert-butyl ether (MTBE) in groundwater and surface water and its potential effects in aquatic ecosystems, industry and the United States Environmental Protection Agency (USEPA) began to collaborate in 1997 to develop aquatic toxicity databases sufficient to derive ambient water quality criteria for MTBE consistent with USEPA requirements. Acute toxicity data for seven marine species, chronic toxicity data for an invertebrate, and plant toxicity data were developed to complete the saltwater database. The species tested were Cyprinodon variegatus, Gasterosteus aculeatus, Callinectes sapidus, Mytilus galloprovincialis, Palaemonetes pugio, Rhepoxynius abronius, Americamysis bahia, and Skeletonema costatum. The toxicity tests were conducted in accordance with USEPA and American Society for Testing and Materials testing procedures and Good Laboratory Practice guidelines. Data developed from this study were consistent with existing data and showed that MTBE has low acute and chronic toxicity to the marine species tested. Based upon measured MTBE concentrations, acute effects were found to range from 166 mg MTBE/l for the grass shrimp to 1950 mg MTBE/l for marine mussel. The no-observed effect concentration for the reproduction and growth of mysids was 26 mg MTBE/l during the life cycle test. The toxicity of MTBE to saltwater organisms is comparable to its toxicity to the freshwater species tested. Reported MTBE concentrations in coastal waters are several orders of magnitude lower than concentrations observed to cause effects in marine organisms.