Effects of nitrogenous wastes on survival of the Barton Springs salamander (Eurycea sosorum).

The objective of our study was to determine the acute toxicity of 3 common aquatic nitrogenous toxicants to the federally endangered Barton Springs salamander (Eurycea sosorum). Based on our findings, the 96-h median lethal concentrations (96-h LC50) for un-ionized ammonia-N, nitrite-N, and nitrate-N to E. sosorum are 2.

Aquaculture genomics, genetics and breeding in the United States: current status, challenges, and priorities for future research.

Advancing the production efficiency and profitability of aquaculture is dependent upon the ability to utilize a diverse array of genetic resources. The ultimate goals of aquaculture genomics, genetics and breeding research are to enhance aquaculture production efficiency, sustainability, product quality, and profitability in support of the commercial sector and for the benefit of consumers. In order to achieve these goals, it is important to understand the genomic structure and organization of aquaculture species, and their genomic and phenomic variations, as well as the genetic basis of traits and their interrelationships.

Effects of roof and rainwater characteristics on copper concentrations in roof runoff.

Copper sheeting is a common roofing material used in many parts of the world. However, copper dissolved from roof sheeting represents a source of copper ions to watersheds. Researchers have studied and recently developed a simple and efficient model to predict copper runoff rates.

Influence of pH, hardness, dissolved organic carbon concentration, and dissolved organic matter source on the acute toxicity of copper to Daphnia magna in soft waters: implications for the biotic ligand model.

The influence of pH, dissolved organic carbon (DOC) concentration, water hardness, and dissolved organic matter (DOM) source on the acute toxicity of copper were investigated with standardized 48-h Daphnia magna toxicity tests. Toxicity tests were conducted according to a four-factor complete factorial design. Nominal factor levels were as follows: pH 6 and 8; DOC, 2.

Influence of copper exposure on whole-body sodium levels in larval fathead minnows (Pimephales promelas).

Because metals such as Cu inhibit ionoregulation, the increased energy requirement to counter passive diffusive losses in soft water may translate into increased sensitivity to metal exposure. We developed a method to determine whole-body Na concentrations of larval fathead minnows (Pimephales promelas) as a physiological indicator of health. This method was used to characterize net rates of Na flux from fish exposed to Cu in the presence of varying levels of hardness and alkalinity.

Toxicity of two pulsed metal exposures to Daphnia magna: relative effects of pulsed duration-concentration and influence of interpulse period.

Aquatic organisms living in surface waters experience fluctuating contaminant exposures that vary in concentration, duration, and frequency. This study characterized the role of pulsed concentration, pulsed duration, and the interval between pulses on the toxicity of four metals (Cu, Zn, Se, and As) to Daphnia magna. During 21-d toxicity tests, neonatal D.

An integrated model describing the toxic responses of Daphnia magna to pulsed exposures of three metals.

Some toxicology research in which toxicant exposures are continual (pulsed) rather than continuous have been reported. A number of toxicity models have been developed for pulsed and continuous exposures. Most of these models were developed based on one- or two-compartment, first-order toxicokinetics and were calibrated with organic compounds.

Whole-body sodium concentration in larval fathead minnows (Pimephales promelas) during and following copper exposure.

This research used whole-body sodium concentration to characterize exposure and recovery of larval fathead minnows (Pimephales promelas) from acute pulsed copper exposures. Whole-body sodium was chosen because the acute mechanism of copper toxicity to fishes is putative disruption of ion regulation, resulting in a loss of sodium and eventually leading to mortality. Whole-body sodium response in larval fathead minnows exposed to copper was both concentration and duration dependent.

Responses of hybrid striped bass to waterborne and dietary copper in freshwater and saltwater.

Mechanisms of copper toxicity and consequences of exposure vary due to uptake route and ionoregulatory status. The goal of this research was to develop a model fish system to assess the influence of different Cu exposure routes (waterborne or dietary) on bioavailability, uptake, and effects in hybrid striped bass (Morone chrysops x Morone saxatilis) acclimated to fresh- or saltwater. Initially, hybrid striped bass were exposed to dietary Cu concentrations of 571, 785, and 1013 mug Cu/g, along with a control (approximately 5 microg Cu/g), for 14 days in saltwater.

Evaluation of acute copper toxicity to larval fathead minnows (Pimephales promelas) in soft surface waters.

The hardness-based regulatory approach for Cu prescribes an extrapolation of the toxicity-versus-hardness relationship to low hardness (< or =50 mg/L as CaCO3). Hence, the objective of the present research was to evaluate the influences of water quality on acute Cu toxicity to larval fathead minnow (Pimephales promelas) in low-hardness surface waters. Seasonal water sampling was conducted at 24 sites throughout South Carolina, USA, to determine the site-specific influences of soft surface-water conditions on acute Cu toxicity.

Physiological basis for large differences in resistance to nitrite among freshwater and freshwater-acclimated euryhaline fishes.

Uptake of environmental NO2- by most freshwater fishes occurs at the gills where NO2- is actively transported into the blood by the Cl- uptake pathway. Some freshwater fishes do not concentrate NO2- in their plasma, regardless of environmental NO2- exposure and exhibit a high degree of resistance to NO2-. Recent studies indicate that freshwater-adapted killifish (Fundulidae: Fundulus heteroclitus) and European eel (Anguillidae: Anguilla anguilla) have no or minimal Cl- uptake activity at the gills relative to most freshwater fishes; rather, Cl- requirements are met in other ways (probably dietary).

Influence of multiple water-quality characteristics on copper toxicity to fathead minnows (Pimephales promelas).

Water quality influences the bioavailability and toxicity of copper to aquatic organisms. Understanding the relationships between water-quality parameters and copper toxicity may facilitate the development of site-specific criteria for water quality and result in better protection of aquatic biota. Many studies have examined the influence of a single water-quality parameter on copper toxicity, but the interactions of several characteristics have not been well studied in low-hardness water.

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.

Influence of natural organic matter source on copper toxicity to larval fathead minnows (Pimephales promelas): implications for the biotic ligand model.

The influence of dissolved natural organic matter (NOM) source on copper toxicity was investigated with larval fathead minnows (Pimephales promelas) in reconstituted moderately hard water. Ninety-six-hour static renewal toxicity tests were conducted to investigate an assumption of the biotic ligand model (BLM) that NOM source does not need to be considered to adequately predict copper toxicity. The nine different NOM isolates used in these toxicity tests were chemically well-characterized substances that were obtained by reverse osmosis as part of an NOM typing project based in southern Norway.

Influence of water quality and age on nickel toxicity to fathead minnows (Pimephales promelas).

This research characterized the effects of water quality and organism age on the toxicity of nickel (Ni) to fathead minnows (Pimephales promelas) to facilitate the accurate development of site-specific water-quality criteria. Nickel sulfate hexahydrate (NiSO4 x 6H2O) was used as the Ni source for performing acute toxicity tests (median lethal concentration after 96-h exposure [96-h LC50]) with < 1-d-old and 28-d-old P. promelas under varying regimes of hardness, pH, alkalinity, and natural organic matter (NOM).

Influence of dissolved organic matter source on silver toxicity to Pimephales promelas.

In the environment, the formation of organic and inorganic silver complexes can decrease Ag bioavailability (toxicity) to aquatic organisms. However, current water quality regulations do not consider the protective effects of water quality parameters such as dissolved organic carbon (DOC) concentration. To determine the effect of DOC concentration and source on silver toxicity, nine different natural organic matter isolates were used in 96-h static-renewal toxicity tests with fathead minnow (Pimephales promelas).

Brain Monoamine Concentrations as Predictors of Growth Inhibition in Channel Catfish Exposed to Ammonia.

Fingerlings of channel catfish Ictalurus punctatus exhibited a significant exposure-dependent decrease in growth (measured by weight gain and increase in total length) and condition factor after 9 weeks of exposure to environmental ammonia. Concentrations of 5-hydroxytryptamine (5-HT) and dopamine in the brain decreased significantly whereas the ratio of 5-hydroxyindoleacetic acid (5-HIAA) to 5-HT increased significantly in exposure-dependent manners. The brain dopamine concentrations and the 5-HIAA : 5-HT ratio collectively explained 88% of the variation in growth due to ammonia exposure.