Multi-stressor Effects of Ultraviolet Light, Temperature, and Salinity on Louisiana Sweet Crude Oil Toxicity in Larval Estuarine Organisms.

When oil is spilled into the environment its toxicity is affected by abiotic conditions. The cumulative and interactive stressors of chemical contaminants and environmental factors are especially relevant in estuaries where tidal fluctuations cause wide variability in salinity, temperature, and ultraviolet (UV) light penetration, which is an important modifying factor for polycyclic aromatic hydrocarbon (PAH) toxicity. Characterizing the interactions of multiple stressors on oil toxicity will improve prediction of environmental impacts under various spill scenarios. This study examined changes in crude oil toxicity with temperature, salinity, and UV light. Oil exposures included high-energy, water-accommodated fractions (HEWAFs) and thin oil sheens. Larval (24-48 h post hatch) estuarine species representing different trophic levels and habitats were evaluated. Mean 96 h LC50 values for oil prepared as a HEWAF and tested under standard conditions (20 ppt, 25 °C, No-UV) were 62.5 µg/L tPAH50 (mud snails), 198.5 µg/L (grass shrimp), and 774.5 µg/L (sheepshead minnows). Thin oil sheen 96 h LC50 values were 5.3 µg/L tPAH50 (mud snails), 14.7 µg/L (grass shrimp), and 22.0 µg/L (sheepshead minnows) under standard conditions. UV light significantly increased the toxicity of oil in all species tested. Oil toxicity also was greater under elevated temperature and lower salinity. Multi-stressor (oil combined with either increased temperature, decreased salinity, or both) LC50 values were reduced to 3 µg/L tPAH50 for HEWAFs and < 1.0 µg/L tPAH50 for thin oil sheens. Environmental conditions at the time of an oil spill will significantly influence oil toxicity and organismal response and should be taken into consideration in toxicity testing and oil spill damage assessments.

Surface charge controls the fate of Au nanorods in saline estuaries.

This work reports the distribution of negatively charged, gold core nanoparticles in a model marine estuary as a function of time. A single dose of purified polystyrene sulfonate (PSS)-coated gold nanorods was added to a series of three replicate estuarine mesocosms to emulate an abrupt nanoparticle release event to a tidal creek of a Spartina -dominated estuary. The mesocosms contained several phases that were monitored: seawater, natural sediments, mature cordgrass, juvenile northern quahog clam, mud snails, and grass shrimp. Aqueous nanorod concentrations rose rapidly upon initial dosing and then fell to stable levels over the course of approximately 50 h, after which they remained stable for the remainder of the experiment (41 days total). The concentration of nanorods rose in all other phases during the initial phase of the experiment; however, some organisms demonstrated depuration over extended periods of time (100+ h) before removal from the dosed tanks. Clams and biofilm samples were also removed from the contaminated tanks post-exposure to monitor their depuration in pristine seawater. The highest net uptake of gold (mass normalized) occurred in the biofilm phase during the first 24 h, after which it was stable (to the 95% level of confidence) throughout the remainder of the exposure experiment. The results are compared against a previous study of positively charged nanoparticles of the same size to parameterize the role of surface charge in determining nanoparticle fate in complex aquatic environments.

Fluoxetine effects on sheepshead minnow (Cyprinodon variegatus) locomotor activity.

Fluoxetine (FLX), a selective serotonin reuptake inhibitor, is among the top 100 drugs prescribed annually in the United States and the United Kingdom and is one of many pharmaceutical products that have been detected in global surface waters. Our study used sublethal concentrations to assess the impact of FLX exposure on sheepshead minnow (Cyprinodon variegatus) locomotor behavior. Exposures lasted for 56 hours, and fish were recorded for locomotor behavior assessment at six timepoints between 1-56 h post-dose. Behavior was recorded to quantify locomotor activity using line crossing counts. Animals treated with 300 µg L(-1) FLX exhibited reduced locomotor activity at 1, 25, 32, 49 and 56 h post-dose. An EC(25) value of 2 µg L(-1) (lower and upper 95 % confidence limits at 1.3, 43 µg L(-1), respectively) was determined for locomotor activity at 32 h of exposure. Changes in locomotor activity due to FLX exposure may have implications for the ecological response of populations to other natural and anthropogenic stressors.

Assessment of the efficacy of six field cleaning protocols for hydrocarbon quantification.

The defensibility of field sampling data collected in support of natural resource damage assessments and other environmental investigations depends on rigorous quality assurance and control both in the field and laboratory. One important step in field procedures is the cleaning of sampling equipment between samples to minimize the carryover of contaminants. Large-scale sampling efforts during the Deepwater Horizon oil spill event have highlighted the importance of understanding how multiple equipment cleaning protocols affect interstation cross-contamination and the resulting chemical data quality. In this study, six field cleaning techniques were tested on metal sampling equipment using two different sediment types spiked with crude oil in order to understand their relative and absolute effectiveness in reducing chemical carryover. The complexity of the cleaning protocols ranged from a simple water and scrub brush application to protocols that included soap and/or solvent. In this study, percent residual hydrocarbon transfer, relative to total loading in sediments, never exceeded 0.032%. The least labor-intensive protocol, water and scrub brush application, had the highest potential for hydrocarbon transfer (0.011-0.032%). Statistical differences were observed among treatments, and it was found that protocols containing a solvent step were more effective than protocols without solvents. Depending on the data quality objectives, the differences may not be meaningful, and choosing a cleaning technique should be governed by health, safety, and environmental factors. The residual hydrocarbons measured after equipment cleanings for all techniques in this study were negligible when compared with other variables that occur during routine sampling and laboratory activities.

Developmental and reproductive effects in grass shrimp (Palaemon pugio) following acute larval exposure to a thin oil sheen and ultraviolet light.

Many early stages of estuarine species congregate at the surface or in the upper mixing layer making them prone to UV light exposure and oil sheens. Laboratory testing was used to assess UV-oil sheen interactions with grass shrimp (Palaemon pugio). Newly hatched grass shrimp larvae were exposed to a 1-µm thick oil sheen for 24 h with or without an 8-h pulse of UV light. Grass shrimp were then transferred to clean seawater and non-UV conditions to measure development, growth, and reproductive fitness. Minimal toxicity was observed after the initial exposure but larval development was significantly delayed in shrimp exposed to the UV enhanced sheen. After reaching sexual maturity, shrimp were paired to evaluate effects on reproduction. Shrimp initially exposed to the UV enhanced sheen as larvae had a significant reduction in fecundity compared to controls. This demonstrates the importance of examining interactions between UV light and oil since negative effects to aquatic organisms may be underestimated if based on standard laboratory fluorescent lighting. Acute exposures of early life stages to thin oil sheens and UV light may lead to long-term impacts to individuals and ultimately to grass shrimp populations.

Toxicity of synthetic pyrethroid insecticides to the grass shrimp, Palaemonetes pugio, parasitized with the bopyrid isopod, Probopyrus pandalicola.

The grass shrimp, Palaemonetes pugio, plays a large role in the marine ecosystem, serving as a vital link in the food web between many other species. Marine parasites such as the bopyrid isopod, Probopyrus pandalicola, reduce shrimp growth and reproductive output and may also cause P. pugio to be more vulnerable to the lethal effects of contaminants. The purpose of this study was to determine the toxicity of resmethrin and bifenthrin on the grass shrimp, P. pugio, infected with the bopyrid isopod, Probopyrus pandalicola. A 96-h static renewal test was conducted to determine the toxicity of the pyrethroid insecticides resmethrin and bifenthrin to grass shrimp, Palaemonetes pugio, parasitized with the bopyrid isopod, Probopyrus pandalicola. The results were then compared to similar tests utilizing unparasitized P. pugio. Parasitized P. pugio had lower 24-h LC(50) (1.08 microg/L) and 96-h LC(50) (0.43 microg/L) values for resmethrin than unparasitized P. pugio. However, LC(50) ratio tests found that there was no significant difference between parasitized and unparasitized shrimp when affected by resmethrin (p = 0.1751 and 0.1108, respectively). In contrast, an LC(10) ratio test indicated that there was a significant difference between parasitized and unparasitized P. pugio after 96 h (p < 0.0001). When subjected to bifenthrin, parasitized P. pugio had a higher 24-h LC(50) (0.049 microg/L6) than unparasitized P. pugio. The LC(50) ratio test established that the effects of bifenthrin on parasitized P. pugio when compared to unparasitized P. pugio were significantly different at 24 h (p = 0.0065). However, there were no significant differences between parasitized and unparasitized after 96 h (p = 0.4229). In conclusion, both resmethrin and bifenthrin are toxic to the grass shrimp, P. pugio, regardless of parasite presence, and parasitized shrimp may be more susceptible to lower doses of resmethrin (when exposed in the field).

Lethal and sublethal effects of simvastatin, irgarol, and PBDE-47 on the estuarine fish, Fundulus heteroclitus.

This study investigated the effects of simvastatin, a lipid-regulating drug; irgarol, an antifouling biocide; and PBDE-47, a brominated flame retardant, on the estuarine fish, Fundulus heteroclitus. Sublethal effects (changes in glutathione (GSH), lipid peroxidation (LPx), acetylcholinesterase (AChE), and cholesterol (CHL) levels) and lethal effects (survival) were determined after individual exposure to the three compounds. There were no significant differences in GSH or CHL levels in fish exposed to any of the test compounds. LPx levels significantly decreased with increasing irgarol concentrations. AChE levels were significantly lower in fish exposed to simvastatin at the 1.25 mg/L concentration and significantly higher at the PBDE-47 concentration of 0.0125 mg/L. The LC50 values were 2.68, 3.22, and > 0.1 mg/L for simvastatin, irgarol and PBDE-47, respectively.

Lethal and sublethal effects of the pyrethroid, bifenthrin, on grass shrimp (Palaemonetes pugio) and sheepshead minnow (Cyprinodon variegatus).

This study investigated the lethal and sublethal effects of the pyrethroid insecticide bifenthrin on adult and larval grass shrimp, Palaemonetes pugio, and adult sheepshead minnows, Cyprinodon variegatus. The effects were determined by conducting 96-h aqueous static renewal tests and 24-h static tests with sediment. Oxidative stress biomarkers, lipid peroxidation, glutathione, and catalase were also assessed. The 96-h aqueous LC50 value for adult shrimp was 0.020 microg/L (95% CI: 0.015-0.025 microg/L) and for larval shrimp was 0.013 microg/L (95% CI: 0.011-0.016 microg/L). The 96-h aqueous LC50 for adult sheepshead minnow was 19.806 microg/L (95% CI: 11.886-47.250 microg/L). The 24-h sediment LC50 for adult shrimp was 0.339 microg/L (95% CI: 0.291-0.381 microg/L) and for larval shrimp was 0.210 microg/L (95% CI: 0.096-0.393 microg/L). The oxidative stress assays showed some increasing trends toward physiological stress with increased bifenthrin concentrations but they were largely inconclusive. Given the sensitivity of grass shrimp to this compound in laboratory bioassays, additional work will be needed to determine if these exposure levels are environmentally relevant.

Atrazine effects on meiobenthic assemblages of a modular estuarine mesocosm.

Atrazine is a widely used herbicide in the US found at levels ranging from <10 ng/L to 62.5 microg/L in estuaries throughout the southeast. Effects of atrazine on estuarine meiobenthic assemblages chronically exposed to environmentally relevant concentrations are unknown. The purpose of our research was to assess effects of atrazine on meiobenthos at concentrations near the proposed USEPA SWQC (26 microg/L) using modular estuarine salt marsh mesocosms as a field surrogate. Indigenous copepod and nematode densities were assessed after 28 days of exposure in transplanted colonization chambers. Cluster analysis showed a group characterized by low copepod densities, mostly atrazine exposed chambers, and a group containing all but one control chamber. The later group included chambers with high densities of the copepods Paronychocamptus wilsoni and Enhydrosoma baruchi. Compared to controls, copepod densities was approximately 70% lower in atrazine chambers, with three of the most common copepod species (E. baruchi, Onychocamptus sp. and P. wilsoni) showing an average of 50-70% reduction in population densities (p<0.05). Although nematode density did not differ between atrazine and control chambers, the nematode-to-copepod ratio was significantly higher in atrazine (9.95+/-7.61; p=0.011) than in control chambers (0.61+/-0.35). Our findings suggest that chronic exposures over multiple generations to atrazine at concentrations near the proposed USEPA SWQC could have significant effects on the abundance and composition of estuarine meiobenthic copepod assemblages.

A survey of trace element distribution in tissues of the dwarf sperm whale (Kogia sima) stranded along the South Carolina coast from 1990-2011.

Few studies report trace elements in dwarf sperm whale (Kogia sima). As high trophic level predators, marine mammals are exposed through diet to environmental contaminants including metals from anthropogenic sources. Inputs of Hg, Pb, and Cd are of particular concern due to toxicity and potential for atmospheric dispersion and subsequent biomagnification. Liver and kidney tissues of stranded K. sima from coastal South Carolina, USA, were analyzed for 22 trace elements. Age-related correlations with tissue concentrations were found for some metals. Mean molar ratio of Hg:Se varied with age with higher ratios found in adult males. Maximum concentrations of Cd and Hg in both tissues exceeded historical FDA levels of concern, but none exceeded the minimum 100µg/g Hg threshold for hepatic damage. Tissue concentrations of some metals associated with contamination were low, suggesting that anthropogenic input may not be a significant source of some metals for these pelagic marine mammals.

Environmental effects and fate of the insecticide bifenthrin in a salt-marsh mesocosm.

Bifenthrin is a widely used synthetic pyrethroid insecticide that is often applied to crops, turf, and residential structures for the control of insects. Like other insecticides, bifenthrin has the potential to contaminate bodies of water that are adjacent to the application site via spray drift and runoff during storm events. The objective of this study was to examine the lethal and sublethal effects of bifenthrin on grass shrimp, Palaemonetes pugio, and sheepshead minnow, Cyprinodon variegatus in a 28 d mesocosm experiment under estuarine conditions. Endpoints included mortality and growth and the oxidative stress biomarkers of lipid peroxidation, glutathione, and catalase. In the mesocosm experiment, 24 h and 96 h caged shrimp LC50s were 0.061 and 0.051 µg L(-1), respectively. The uncaged grass shrimp 28 d LC50 was 0.062 µg L(-1). Fifty percent mortality was not reached in the uncaged sheepshead minnow. Bifenthrin did not have a significant effect on the growth of the shrimp, but there was an increasing impact on fish growth. However, it is uncertain as to whether this pattern is a direct effect of the chemical or if it is due to increased food availability resulting from mortality in prey species. The oxidative stress assays were largely inconclusive. Bifenthrin was eliminated rapidly from the water column and readily partitioned to sediments. The LC50s for adult and larval P. pugio were below published Estimated Environmental Concentration (EEC) values and were within the range of bifenthrin concentrations that have been measured in rivers, channels, and creeks.

Domoic acid induced status epilepticus promotes aggressive behavior in rats.

Domoic acid (DA), a naturally occurring environmental toxin, has been observed to induce status epilepticus in humans, sea lions and pelicans. In a recent Sprague Dawley rat model, domoic acid dosing induced a state of status epilepticus which, after a symptom-free latent period without further dosing, progressed to recurrent spontaneous seizures, a hallmark of epilepsy. Certain individuals in this study also developed unusual behavioral changes, in particular an atypical aggression towards conspecifics. In this report we characterized the progression of aggressive behaviors after DA-induced status epilepticus and explored the relationship between aggressive behavior and recurrent spontaneous seizures. Experimental studies in this laboratory rat model are particularly relevant to California sea lions (Zapholus californianus), which show a spectrum of both epileptic and unusual behaviors, including aggression towards conspecifics in rehabilitation facilities, weeks to months after suspected exposure to domoic acid in the wild.

Pilot estuarine mesocosm study on the environmental fate of Silver nanomaterials leached from consumer products.

Although nanosilver consumer products (CPs) enjoy widespread availability, the environmental fate, leaching, and bioaccumulation behaviors of silver nanoparticles (AgNPs) from these products are not well understood. In this work, three nanosilver CPs, two AgNP standards, and an ionic silver (Ag(+)) standard were studied in estuarine mesocosms. The CPs exhibited long-term release of significant amounts of silver over a 60d residence time in the mesocosms, and ultimately released 82 - 99% of their total silver loads. Measurements of total silver as a function of time, by inductively coupled plasma mass spectrometry (ICP-MS), indicated that the silver was transferred from the water column and accumulated in the estuarine biota, including hard clams, grass shrimp, mud snails, cordgrass stalks and leaves, biofilms, intertidal sediment, and sand. The ICP-MS results and calculations of bioconcentration and trophic transfer factors indicated that significant amounts of silver were taken up by the organisms through trophic transfer. Silver was also adsorbed from the seawater into the biofilms, sediment, and sand, and from the sand into the clams.

A survey of trace element distribution in tissues of stone crabs (Menippe mercenaria) from South Carolina coastal waters.

The stone crab (Menippe mercenaria) is an important component of the estuarine food web as both predator and prey. Stone crabs live in sediment, primarily consume oysters, and as a result, have the potential to accumulate significant quantities of pollutants including metals. In South Carolina, the stone crab is becoming a targeted fishery as an ecologically sustainable seafood choice. To date, no studies have reported metals in stone crab tissues. This study examined the distribution of major and minor trace elements in chelae and body muscle, gill, and hepatopancreas. Crabs were collected from three tidal areas within Charleston County, South Carolina, with differing upland use. Results were compared by collection location and by tissue type. Concentrations of some metals associated with anthropogenic activities were up to three times higher in crabs from sites adjacent to more urbanized areas. Concentrations in edible tissues were below historical FDA levels of concern.

Transfer of gold nanoparticles from the water column to the estuarine food web.

Within the next five years the manufacture of large quantities of nanomaterials may lead to unintended contamination of terrestrial and aquatic ecosystems. The unique physical, chemical and electronic properties of nanomaterials allow new modes of interaction with environmental systems that can have unexpected impacts. Here, we show that gold nanorods can readily pass from the water column to the marine food web in three laboratory-constructed estuarine mesocosms containing sea water, sediment, sea grass, microbes, biofilms, snails, clams, shrimp and fish. A single dose of gold nanorods (65 nm length x 15 nm diameter) was added to each mesocosm and their distribution in the aqueous and sediment phases monitored over 12 days. Nanorods partitioned between biofilms, sediments, plants, animals and sea water with a recovery of 84.4%. Clams and biofilms accumulated the most nanoparticles on a per mass basis, suggesting that gold nanorods can readily pass from the water column to the marine food web.

Toxicity of atrazine to the juvenile hard clam, Mercenaria mercenaria.

The herbicide atrazine is one of the most heavily used pesticides in the United States. The effects of atrazine on the clam Mercenaria mercenaria were evaluated in aqueous and sediment laboratory assays. Juvenile clams of approximately 1mm in size were used for all experiments. An acute aqueous bio-assay was used to determine the 96-h LC(50) for the juvenile clams. A chronic aqueous bioassay was conducted at lower atrazine concentrations over a 10-day exposure period to examine both lethal and sublethal (dry mass, shell size, and condition index) endpoints. A chronic sediment bioassay examined mortality and sublethal endpoints in a 10-day exposure. The acute 96-h LC(50) was 5608 microg/L with 95% confidence intervals ranging from 5003 to 6287 microg/L. Results of the chronic aqueous assay indicated both lethal and sublethal (reduced shell size) effects at high atrazine concentrations. In the 10-day chronic aqueous assay, the no observable effect concentration was 500 microg/L, the lowest observable effect concentration was 1000 microg/L, and the maximum allowable toxicant concentration (MATC) was 707 microg/L. There were no significant effects of atrazine in the chronic sediment exposure. Safe concentrations for the aqueous experiments were estimated by applying an uncertainty factor of 10 to the calculated MATC values. While there were adverse effects of atrazine at high concentrations, these results suggest that atrazine is not directly toxic to M. mercenaria at environmentally relevant concentrations.

The fate of fipronil in modular estuarine mesocosms.

The degradation and corresponding product manifold for the pesticide fipronil was determined in three replicate estuarine mesocosms. Aqueous fipronil concentrations rapidly decreased over the 672 h timescale of the experiment (95% removal). Loss was apparently first-order in fipronil, although there appeared to be a change in the removal mechanism after 96 h that corresponded to a dramatic slowdown in its disappearance. The reduction product of fipronil, fipronil sulfide, was not detected in the water column; however, it formed rapidly in sediments and was identified as the major product of fipronil degradation in the system (20% yield at 672 h, with respect to initial fipronil concentration). Fipronil sulfone is thought to form primarily via biological oxidation; and, although it was generated rapidly in the water column (10% yield), only trace amounts were detected in the sediment (1% yield). The direct photolysis product of fipronil, fipronil desulfinyl, was present in all samples; it formed rapidly in the water column (4% yield) and partitioned into the sediment phase (7% yield) over the course of the experiment. The mass balance on fipronil and associated products was 42% at 672 h.