Sandy sediment and the bioavailability of 17ß-trenbolone to adult female fathead minnows.

Recent studies have detected bioavailable steroids in sediment, however, the mechanism by which these compounds become bioavailable is not completely understood. In this study, two experiments were conducted using a double aquarium system that allowed female fathead minnows to be exposed to sandy sediments without direct contact. In the first experiment, natural sediment from the Elkhorn River (Nebraska, USA) was spiked with 17ß-trenbolone. Both the fish in direct contact with the sediment as well as the fish excluded from direct contact experienced significant reductions in the hepatic expression of two estrogen-responsive genes, vitellogenin and estrogen receptor α, indicating molecular defeminization. The natural sediment contained particles ranging in size from sand to clay and it was possible that the fish in experiment 1 were being exposed to trenbolone associated with the very fine particles. The sandy sediment was sieved for experiment 2, and only the particles larger than 250 µm were used. In addition, the experiment was conducted at two different Tb concentrations (1× and 10×). Furthermore nuptial tubercles, a biomarker of exposure to a masculinizing androgen, were also evaluated in the females used in experiment 2. For tubercle number and vtg expression, significant results were obtained from a two-way ANOVA due to Tb concentration, but not tank location or interaction term (location vs. concentration). For ERα expression, results were found in response to Tb concentration and tank location, but not the interaction term. Overall the results from these studies suggest that the primary route of exposure of sediment-associated trenbolone to fish is through ventilation of free compound, rather than ingestion or direct contact with the sediments.

Methylmercury concentrations in six fish species from two Colombian rivers.

The objective of this study was to determine whether fish collected from the La Miel or Nechí Rivers (Colombia) differed in muscle methyl mercury (meHg) concentration. Two fish from six different species were collected from markets adjacent to each river. Overall, fish collected from the market adjacent to the Nechí River contained higher levels of meHg. This result however is being driven by very high meHg concentrations in four individual fish, three of which are Pimelodid, long-whiskered catfish. These catfish may represent ideal sentinel organism for the detection of meHg contamination in Colombian rivers.

Optimization of analytical methods to improve detection of erythromycin from water and sediment.

Analytical methods to improve the detection of erythromycin in water and sediment were developed to optimize for erythromycin's recovery of extractable and bound residues from the aquatic environment. The objective of this study was to determine optimal recovery of erythromycin from water and sediment to improve its detection in environmental samples through solid-phase extraction (SPE) and sediment-extraction methods. SPE methods examined included previously reported methods for macrolide and sulfonamide antibiotics with erythromycin recoveries ranging from 75.5 % to 94.7 %. Extraction of erythromycin was performed from sand employing various solvents and buffers to determine the best method for extraction from two sandy loam pond sediments. Various extraction times were also examined, and all extraction procedures were performed in duplicate. The greatest recovery of (14)C-erythromycin in the Iowa sediment was 84 % using 0.3 M ammonium acetate at pH 4.2: acetonitrile (15:85, v/v) solution. The Oklahoma sediment yielded the greatest recovery of (14)C-erythromycin at 86.7 % with 0.3 M ammonium acetate at pH 7: acetonitrile (30:70, v/v) with a 60-minute shake time. The present results demonstrate improved extraction methods for enhancing the accuracy of erythromycin detection from environmental samples.