Dimethyldimethyl Hydantoin: An Alternative Fluid for Morphological and Genetic Preservation.

Modern taxonomy requires the preservation of biospecimens for both morphological and molecular applications. The utility of a previously identified preservative, dimethyldimethylhydantoin hydantoin (Dekafald®), to retain both physical diagnostic traits and the DNA integrity of biological specimens remains unknown. Using 439 eggs and 414 larvae from two North American fish species, we compared three hydantoin solutions at different concentrations (5%, 10%, and 20%) with gold standard preservatives (10% buffered formalin, 95% ethanol) to evaluate morphological trait retention up to 90 days, and DNA barcoding success up to 56 days. While the 5% hydantoin solution had the most sequencing success by 56 days, the 10% hydantoin solution was the best multipurpose preservative. Future work should assess the performance of ∼10% hydantoin solution over longer time periods, and its applicability to other taxa such as Arthropoda.

Metal Oxides in Surface Sediment Control Nickel Bioavailability to Benthic Macroinvertebrates.

In aquatic ecosystems, the cycling and toxicity of nickel (Ni) are coupled to other elemental cycles that can limit its bioavailability. Current sediment risk assessment approaches consider acid-volatile sulfide (AVS) as the major binding phase for Ni, but have not yet incorporated ligands that are present in oxic sediments. Our study aimed to assess how metal oxides play a role in Ni bioavailability in surficial sediments exposed to effluent from two mine sites. We coupled spatially explicit sediment geochemistry (i.e., separate oxic and suboxic) to the indigenous macroinvertebrate community structure. Effluent-exposed sites contained high concentrations of sediment Ni and AVS, though roughly 80% less AVS was observed in surface sediments. Iron (Fe) oxide mineral concentrations were elevated in surface sediments and bound a substantial proportion of Ni. Redundancy analysis of the invertebrate community showed surface sediment geochemistry significantly explained shifts in community abundances. Relative abundance of the dominant mayfly (Ephemeridae) was reduced in sites with greater bioavailable Ni, but accounting for Fe oxide-bound Ni greatly decreased variation in effect thresholds between the two mine sites. Our results provide field-based evidence that solid-phase ligands in oxic sediment, most notably Fe oxides, may have a critical role in controlling nickel bioavailability.

An in situ toxicity identification and evaluation water analysis system: Laboratory validation.

It is difficult to assess the toxicity of a single stressor and establish a strong stressor-causality link when multiple stressors coexist. Toxicity identification evaluation (TIE) methodology uses a series of chemical and physical manipulations to fractionate compounds within a matrix and systematically identify potential toxicants. The current US Environmental Protection Agency application of TIE can provide valuable information but often lacks ecological realism and is subject to laboratory-related artifacts. An in situ TIE device (iTIED) was designed to assess the sources of toxicity in aquatic ecosystems. For this laboratory validation, each unit was equipped with a sorbent resin chamber, an organism exposure chamber, a water collection container, and a peristaltic pump. Chemical analyses of water processed by each iTIED unit were compared with both lethal and sublethal molecular responses of the organisms. The compound removal effectiveness of different sorbent resins was also compared. In addition to successfully fractionating diverse chemical mixtures, the iTIED demonstrated a potential for early detection of molecular biomarkers, which could identify chronic toxicity that may go unnoticed in traditional TIE assays. Utilizing this novel in situ system will reduce the uncertainty associated with laboratory-based simulations and aid management efforts in targeting compounds that pose the greatest threat. Environ Toxicol Chem 2017;36:1636-1643. © 2016 SETAC.

Bioamplification as a bioaccumulation mechanism for persistent organic pollutants (POPs) in wildlife.

Persistent organic pollutant bioaccumulation models have generally been formulated to predict bioconcentration and biomagnification. A third bioaccumulation process that can mediate chemical fugacity in an organism is bioamplification.Bioamplification occurs when an organism loses body weight and the chemical partitioning capacity occurs at a rate that is faster than the chemical can be eliminated.Although bioamplification has not been widely recognized as a bioaccumulation process, the potential consequences of this process are significant. Bioamplification causes an increase in chemical fugacity in the animal's tissues and results in there distribution of contaminants from inert storage sites to more toxicologically sensitive tissues. By reviewing laboratory and field studies, we have shown in this paper that bioamplification occurs across taxonomic groups that include, invertebrates,amphibians, fishes, birds, and mammals. Two case studies are presented, and constitute multi-life stage non-steady state bioaccumulation models calibrated for yellow perch and herring gulls. These case studies were used to demonstrate that bioamplification is predicted to occur under realistic scenarios of animal growth and seasonal weight loss. Bioamplification greatly enhances POP concentrations and chemical fugacities during critical physiological and behavioral events in an animal's life history, e.g., embryo development, juvenile stages, metamorphosis, reproduction, migration, overwintering, hibernation, and disease. Consequently,understanding the dynamics of bioamplification, and how different life history scenario scan alter tissue residues, may be helpful and important in assessing wildlife hazards and risks.

Tissue distribution kinetics of 2,2',4,4',5,5'-hexachlorobiphenyl in ringdoves after oral dosing.

Ring doves were provided contaminated food spiked with [(13)C]-2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) over a period of 63 days. Animals were sacrificed after 0.33, 0.5, 1, 2, 4, 8, 18, 36 and 63 days following access to contaminated food. At each time point, chemical concentrations in blood, liver, brain, gonad, adipose and remaining whole carcass was determined. Whole body concentrations of PCB 153 increased linearly with time over the experiment indicating that the birds did not reach steady state with their food after 63 days. Tissue/plasma concentration ratios were plotted as a function of time to determine time to inter-tissue steady state for fast and slowly perfused tissues. Liver, brain and gonad achieved steady state concentrations with plasma in less than 3 days, whereas fat and carcass tissues required 9.7 and 11.5 days, respectively. The results indicate that inter-tissue distribution kinetics for PCBs in birds is relatively rapid and completed within a little over a week following exposure to a contaminated diet.

The effect of food provisioning on persistent organic pollutant bioamplification in Chinook salmon larvae.

Fall spawning pacific salmon provision large amounts of yolk to their eggs to allow survival of larvae during under the ice winter conditions. This yolk provisioning leads to maternal offloading of persistent organic pollutants (POPs) to eggs and larvae. Previous research has shown that Chinook salmon larvae exhibit limited capacity to eliminate POPs during the cold water period resulting in bioamplification of POP residues. This study compared POPs bioamplification in Chinook salmon larvae under a high food provisioning treatment and a non-fed treatment to test whether or not food availability attenuates POPs bioamplification via growth dilution. Results demonstrate that larvae in the food provisioning treatment did not gain weight until after day 129. Between hatching and day 129, fed and non-fed treatments exhibited similar decreases in whole body lipid content, negligible POPs elimination and POPs bioamplification factors approaching 1.6. By day 184 of the study, POPs bioamplification factors in the non-fed treatment were as high as 5.3 across chemicals but ranged from non-detectable to approaching 1 in the fed group. This study demonstrates that POPs bioamplification occurs in Chinook salmon larvae even under ideal rearing conditions but peaks after day 129, following which growth dilution can attenuate bioamplification relative to starved individuals.

Bioamplification and the selective depletion of persistent organic pollutants in Chinook salmon larvae.

The maternal provisioning of yolk to eggs transfers significant quantities of persistent organic pollutants (POPs). As yolk utilization progresses via metabolic activity, there is a potential to realize further increases in POP concentrations if yolk lipids are depleted at a faster rate than POPs, a condition referred to as bioamplification. This study investigated the bioamplification of POPs in Chinook salmon ( Oncorhynchus tshawytscha ) eggs and larvae. Chinook eggs were sampled from the Credit River, ON, Canada, and brought to an aquaculture facility where they were fertilized, incubated, and maintained posthatch until maternally derived lipid reserves became depleted (approximately 168 days). The loss of chemicals having an octanol-water partition coefficient (log K(OW)) greater than 5.8 was slow to negligible from days 0-135. However, during the increase in water temperatures in early spring, K(OW)-dependent elimination of POPs was observed. Bioamplification was maximized for the highest log K(OW) POPs, with an approximate 5-fold increase in lipid equivalents concentrations in 168 day old larvae as compared to newly fertilized eggs. This study demonstrates that later yolk-sac Chinook larvae (before exogenous feeding) are exposed to higher lipid equivalents POP concentrations than predicted by maternal deposition, which could lead to underestimates in the toxicity of critical life stages.

Aquatic to terrestrial transfer of sediment associated persistent organic pollutants is enhanced by bioamplification processes.

Ephemeral emergent insects, such as mayflies (Hexagenia spp.), are commonly used as biomonitors of persistent organic pollutants (POPs) and provide a vector for aquatic-terrestrial contaminant transfer. Mayflies bioaccumulate sediment-associated contaminants by bioconcentration and biomagnification during the aquatic stage and concentrate POP residues postemergence due to bioamplification, which occurs as a result of weight and lipid loss without contaminant loss. The present study quantified polychlorinated biphenyl (PCB) bioamplification in male and female emergent mayflies at three sites. Male mayflies used 36 to 68% of their lipids during emergence, with the exception of caged males that were prevented from flight. Females did not lose lipid content between pre-emergent nymph and emerged life stages. Mass balance indicated no PCB elimination between life stages. The mean PCB bioamplification factor, expressed as the ratio of lipid-equivalent PCB concentrations across life stages, was 2.05 ± 0.38 for male imagos/nymphs and 1.91 ± 0.18 for male imago/subimago life stages. For females, bioamplification factors were close to unity. Wildlife consumers of imago stages of emergent mayflies can potentially increase their total daily intake of PCBs by 36% depending on the sex-ratio composition of their diet relative to animals that feed predominantly on nymph or subimago stages during mass emergence events.

Evidence for bioamplification of nine polychlorinated biphenyl (PCB) congeners in yellow perch (Perca flavascens) eggs during incubation.

This study investigated bioamplification of polychlorinated biphenyls (PCBs) in yellow perch (Perca flavescens) eggs resulting from nutrient utilization by developing embryos during incubation. Newly fertilized eggs containing trace levels of PCBs via maternal deposition were collected from an aquaculture pond in which adult broodstock had been reared over their natural lives. The eggs were incubated using a flow through system that received the same pond water at in-situ temperatures from which they were spawned. Replicate samples of eggs were collected at six time points throughout incubation, ranging from day 0 (newly fertilized eggs) to post-hatch larvae (2-d old). Congener specific PCB fugacities in pooled egg samples showed increases over the incubation period. Just prior to hatching, incubated eggs averaged 2.7-fold higher PCB fugacities compared to fresh eggs. The increase in PCB fugacity with egg incubation time was independent of chemical K(OW). After hatching, PCB residues were lost from the larvae, attenuating the maximum chemical fugacity achieved in late-incubated eggs. However, the rate of PCB elimination in the early larvae stages was K(OW) dependent such that a significant larvae/egg fugacity ratio was still evident for intermediate and highly hydrophobic compounds 2 d post-hatching. This study provides the first evidence of in-ovo PCB bioamplification in eggs of an aquatic species and suggests that incubating fish embryos are exposed to higher chemical fugacities in-ovo than would be predicted by maternal deposition alone.