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Keywords : macro invertebrate drift, drift sampler, fish predation on autochthonous drift . Abstractdrift . This study examined the effects of a fish community in a pool of a Kentucky woodland stream on autochthoQualitative and quantitative drift data were collected simultanenous invertebrate drift . ously above and below a pool both before and after the pool was heavily electrofished. These data revealed no significant difference between drift organism densities (#/M3 ) above or below the pool before or after fish collection . Qualitative and quantitative fish gut analyses suggest that the sunfishes Lepomis megalotis, L. macrochirus and L. cyanellus may be feeding on drifting invertebrates as these organisms comprised 58%, 37% and 35% gut volume, respectively . A design for a long-term drift net apparatus is presented .

A public/private partnership was established in 1997, under the administrative oversight of the American Petroleum Institute (API), to develop aquatic toxicity data sufficient to calculate ambient water quality criteria for methyl tertiary-butyl ether (MTBE), a gasoline oxygenate. The MTBE Water Quality Criteria Work Group consisted of representatives from private companies, trade associations, and USEPA. Funding was provided by the private entities, while aquatic biological/toxicological expertise was provided by industry and USEPA scientists. This public/private partnership constituted a nonadversarial, cost-effective, and efficient process for generating the toxicity data necessary for deriving freshwater and marine ambient water quality criteria. Existing aquatic toxicity data were evaluated for acceptability, consistent with USEPA guidance, and nineteen freshwater and marine tests were conducted by commercial laboratories as part of this effort to satisfy the federal criteria database requirements. Definitive test data were developed and reported under the oversight of industry study monitors and Good Laboratory Practice standards auditors, and with USEPA scientists participating in advisory and critical review roles. Calculated, preliminary freshwater criteria for acute (Criterion Maximum Concentration) and chronic (Criterion Continuous Concentration) exposure effect protection are 151 and 51 mg MTBE/L, respectively. Calculated, preliminary marine criteria for acute and chronic exposure effect protection are 53 and 18 mg MTBE/L, respectively. These criteria values may be used for surface water quality management purposes, and they indicate that ambient MTBE concentrations documented in U. S. surface waters to date do not constitute a risk to aquatic organisms.

The detection of methyl tertiary-butyl ether (MTBE) in groundwater and surface water in recent years has drawn attention to its potential effects in aquatic ecosystems. To address concerns regarding MTBE environmental effects and to establish safe concentrations in surface waters, a collaborative effort was initiated in 1997 to develop aquatic toxicity databases sufficient to derive ambient water quality criteria for MTBE consistent with United States Environmental Protection Agency (U.S. EPA) requirements. Acute toxicity data for six species, chronic toxicity data for a fish and an invertebrate, and plant toxicity data were developed in order to complete the freshwater database. The toxicity tests followed U.S. EPA and American Society for Testing and Materials (ASTM, Philadelphia, PA, USA) procedures and were conducted in accordance with U.S. EPA Good Laboratory Practice guidelines. Based on measured exposure concentrations, acute toxicity endpoints ranged from 472 to 1742 mg MTBE/L, while chronic endpoints (IC25) were 57 to 308 mg MTBE/L. Aquatic invertebrates were generally more sensitive than fish to MTBE in both acute and chronic exposures. Acute-to-chronic ratios for fathead minnows and Daphnia magna were 3.4 and 11.3, respectively. The measured acute and chronic toxicity were within a 10-fold factor of toxicity predicted from quantitative structure-activity relationships for baseline toxicity or nonpolar narcosis typical of ether compounds. The data developed in this study were consistent with existing data and showed that MTBE has low acute and chronic toxicity to freshwater organisms. Reported environmental concentrations of MTBE are several orders of magnitude lower than concentrations observed to cause effects in freshwater organisms.