We studied maternal transfer of an essential metal (copper) and a non-essential one (cadmium) in the live-bearing fishes Heterandria formosa and Gambusia affinis. The goals of this study were: (1) to determine whether metals are transferred from exposed females to their developing offspring; (2) to determine if this transfer differs between two fish species that differ in their degree of maternal provisioning during development; (3) to determine the duration of maternal metal transfer once females are no longer exposed; and (4) to determine whether copper and cadmium are transferred equivalently. We exposed gravid females to background levels (control) or 0.15 µM of metal for 10 days, and then transferred them to clean water. We allowed females to give birth to up to three broods, and then quantified metal levels in offspring born at least 3 days after the transfer. We detected maternal metal transfer for both metals and in both species. Offspring metal levels decreased as females spent more time in clean water. Similarly, metal levels were lower in later broods than in earlier ones. Maternal metal transfer was higher in H. formosa than in G. affinis. Our results constitute the first report of maternal metal transfer in live-bearing fishes, and show that developing embryos acquire both essential and non-essential metals from their mothers in both species. This shows that metal toxicity may be an issue for live-bearing fish in clean environments when the previous generation has encountered metal pollution.

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Many agricultural watersheds in the United States have impaired waterbodies due to nonpoint source pollution from agricultural activities and related processes. To understand the physical, chemical, and biological integrity of surface water in a coastal agricultural watershed, spatial and seasonal patterns of physicochemical and biological properties were investigated in Bayou Lacassine watershed (BLW) in Louisiana, United States. The relationship between the physicochemical and biological properties were also investigated. Sampling sites were located in the Bayou Chene and Lacassine Bayou subwatersheds within the BLW. Dissolved oxygen (DO), turbidity, conductivity, temperature, pH, total suspended solids (TSS), total dissolved solids (TDS), total solids (TS), five-day biological oxygen demand (BOD 5 ), nitrate and nitrite-nitrogen (NO 3 /NO 2 -N), total Kjeldahl nitrogen (TKN), soluble reactive phosphorus (SRP), total phosphorus (TP), chloride (Cl -), fluoride (F -), and sulfate (SO 4 ) were determined weekly from samples collected during 2012 to 2015. Fish and benthic invertebrate diversity and abundance in the two subwatersheds were determined in early summer and in fall of 2012 and 2013 at nine sites. Water quality was generally better at the most downstream site than at the most upstream site where agricultural intensity was highest, with significant differences in turbidity, TSS, TDS, TS, NO 3 /NO 2 -N, TKN, TP, and BOD 5 . There was also seasonal variation for the water quality parameters due to variability in agricultural activities and climatic conditions within the watershed. Results of the relationship between physicochemical properties and fish community variables showed that species richness, diversity, and abundance were negatively affected by elevated TS, NO 3 /NO 2 -N, and conductivity. For the benthic invertebrates, diversity was negatively related to BOD 5 . This study demonstrated unexpected longitudinal and seasonal patterns in physicochemical and biological properties of surface waters in a coastal agricultural watershed. This information is valuable in developing nonpoint source pollution control strategies for these subwatersheds.

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The relationship between organisms and contaminants may be a two-way interaction: contaminants affecting the biota and the biota affecting the environmental fate and distribution of the contaminants. This may be especially so for sediment-dwelling organisms, because their burrowing and feeding can drastically influence sediment characteristics. The present study looked at the influence of the suspension-feeding stout razor clam Tagelus plebeius on the distribution of crude oil and pyrene in greenhouse mesocosm experiments. Water column turbidity and sediment redox also were monitored during the 15- to 30-day exposures to provide information on the influence of hydrocarbons and the razor clams on environmental conditions. For the experiment with crude oil, sediment was taken from the mesocosms at the end of the experiment, and the hydrocarbon-degradation potential was assessed in incubations with C-naphthalene. The experiments used four treatments: hydrocarbons present/absent and razor clams present/absent. Hydrocarbon dosing levels were relatively low (1 mL of oil or 30 mg of pyrene per mesocosm with 22 L of natural sediment and 11 L of seawater). The presence of the razor clams resulted in hydrocarbon concentrations at the sediment surface being 25% lower than in mesocosms without clams. No consistent effects were noted for polycyclic aromatic hydrocarbon (PAH) concentrations in the water column or in subsurface sediment. The naphthalene-degradation potential was elevated for sediment from mesocosms dosed with oil, but the presence of the clams did not affect this potential. The presence of the razor clams resulted in a lowering of water column turbidity, but no effect on sediment redox. The hydrocarbon addition had no effect on turbidity, but sediment redox was lowered. While results show that the presence of the razor clams resulted in a loss of hydrocarbons from the surface sediment, the other results do not provide a clear picture of the underlying mechanisms and the fate of the PAHs lost from the sediment surface. We hypothesize that the loss of surface sediment PAHs was due to burial of surface sediment and possibly bioaccumulation by the clams. While additional research is needed for further insights into underlying mechanisms, the present work demonstrates that the presence of sediment-burrowing suspension feeders decreases hydrocarbon levels in surface sediment. This means that assessments of the impact of an oil spill should pay attention to effects on these organisms and to their influence on the fate and distribution of the spilled oil.