Michael H. Fulton

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.

Assessment of risk reduction strategies for the management of agricultural nonpoint source pesticide runoff in estuarine ecosystems.

Agricultural nonpoint source (NPS) runoff may result in significant discharges of pesticides, suspended sediments, and fertilizers into estuarine habitats adjacent to agricultural areas or downstream from agricultural watersheds. Exposure of estuarine fin fish and shellfish to toxic levels of pesticides may occur, resulting in significant declines in field populations. Integrated pest management (IPM), best management practices (BMP), and retention ponds (RP) are risk management tools that have been proposed to reduce the contaminant risk from agricultural NPS runoff into estuarine ecosystems. Field studies were conducted at three sites within coastal estuarine ecosystems of South Carolina (SC) from 1985 to 1990 that varied in terms of the amount and degree of risk reduction strategies employed. An intensively managed (IPM, BMP, and RP) agricultural treatment site (TRT) was studied for pesticide runoff impacts. From 1985 to 1987, there were minimal (some IPM and BMP) management activities at TRT, but from 1988 to 1990, TRT was managed using an intensive risk reduction strategy. A second unmanaged agricultural growing area, Kiawah (KWA), was also studied and compared with TRT in terms of pesticide runoff and the resulting impacts on grass shrimp (Palaemonetes pugio) and mummichogs (Fundulus heteroclitus). A third, non-agricultural, reference site (CTL) was used for comparing results from the managed and unmanaged agricultural sites. In situ toxicity tests and field samples of the grass shrimp populations were conducted at each site and compared in terms of survival and the effectiveness of current risk reduction strategies. Significant runoff of insecticides (azinphosmethyl, endosulfan, and fenvalerate) along with several fish kills were observed at TRT prior to the implementation of rigorous risk reduction methods. A significant reduction of in stream pesticide concentrations (up to 90%) was observed at TRT following the implementation of strict NPS runoff controls, which greatly reduced impacts on estuarine fish and shellfish. At the unmanaged KWA, continued impacts due to the runoff of these insecticides were observed, along with several fish kills. Additional monitoring indicated that gravid female grass shrimp populations from KWA had elevated levels of P-glycoprotein (P-gp), a multidrug resistance protein, which may transport various pesticides across cellular membranes. Comparison of field results with laboratory toxicity tests established that pesticide exposure was the primary cause of observed field impacts at each site. These findings clearly indicate the value of an integrated risk reduction strategy (BMP, IPM, and RP) for minimizing impacts from NPS agricultural pesticide runoff.

Characterization of cholinesterase activity in tissues of the grass shrimp (Palaemonetes pugio)

Inhibition of cholinesterases in estuarine organisms is a useful indicator of organophosphorus insecticide exposure. Recent research has indicated that more than one cholinesterase may be present in tissues of estuarine organisms and that these cholinesterases vary in their sensitivity to organophosphorus insecticides. Baseline cholinesterase activity for adult grass shrimp (Palaemonetes pugio) was determined with four substrates (acetylthiocholine iodide, acetyl-β-methylthiocholine iodide, propionylthiocholine iodide, S-butyrylthiocholine iodide) and three cholinesterase inhibitors (eserine sulfate, tetraisopropyl pyrophosphoramide, 1,5-bis(4-allyldimethyl-ammoniumphenyl) pentan-3-one dibromide). Cholinesterase activity was the highest with acetylthiocholine iodide at 57.42 nmol/mg P/min and the lowest with acetyl-β-methylthiocholine iodide at 6.17 nmol/mg P/min. The four substrates tested were not inhibited by tetraisopropyl pyrophosphoramide. Eserine sulfate significantly inhibited cholinesterase activity against all substrates except S-butyrylthiocholine iodide. The results of substrate specificity and cholinesterase inhibition in grass shrimp indicate that acetylthiocholine iodide is the most appropriate substrate for assessing cholinesterase inhibition in grass shrimp.

A Review of Grass Shrimp, Palaemonetes spp., as a Bioindicator of Anthropogenic Impacts

Coastal systems are ecologically important environments due to their diversity and productivity, but they can also serve as sinks for pollutants transported via runoff and atmospheric deposition. Grass shrimp, of the genus Palaemonetes, are a common inhabitant of East and Gulf coast estuaries of the United States and are proposed in this paper as a bioindicator of human impacts on estuarine systems. Using grass shrimp as such would involve their entire life cycle and consist of biomonitoring studies, in situ and laboratory toxicity tests, and development of biomarkers of exposure. The current interest in developing ecological indicators has put a renewed relevance on grass shrimp research. This paper reviews ecologically based studies, toxicity testing, and sublethal assessments in grass shrimp and shows how they have laid the groundwork for this genus to be an indicator species. It is concluded that correlating traditional grass shrimp assays with ecological monitoring and biomarkers of exposure is a goa...

The sensitivity of grass shrimp, Palaemonetes pugio, embryos to organophosphate pesticide induced acetylcholinesterase inhibition.

Grass shrimp, Palaemonetes pugio, are common inhabitants of salt marshes along the Atlantic and Gulf coasts of North America. Grass shrimp embryos are brooded externally on the abdomen of adult females for about 2 weeks prior to hatching. In South Carolina, the spring spawning period for grass shrimp coincides with the period of peak pesticide application on crops grown along the South Carolina coast. Thus, grass shrimp of all developmental stages are at risk of exposure to pesticides present in nonpoint source agricultural runoff. Organophosphate (OP) insecticides are commonly applied agricultural chemicals which produce toxicity by inhibiting the nervous system enzyme, acetylcholinesterase (AChE). The purpose of this study was to examine the development of AChE activity in grass shrimp embryos and to assess their sensitivity to OP-induced AChE inhibition. Embryos were exposed for 24 h to either chlorpyrifos or malathion. All exposure concentrations were nominal and ranged from 0 to 2.00 µg l(-1) for chlorpyrifos and from 0 to 120.00 µg l(-1) for malathion. Quantifiable levels of AChE activity first appeared at Stage V of development and increased as embryonic development progressed. AChE inhibition by the OPs was assessed in Stage VI and Stage VII embryos. Both stages of embryos were more sensitive to chlorpyrifos than malathion. The 24-h Effective Concentration (EC(50)) values for chlorpyrifos were 0.49 µg l(-1) (95% C.I.=0.33-0.77 µg l(-1)) and 0.36 µg l(-1) (95% C.I.=0.33-0.38 µg l(-1)) for Stage VI and Stage VII embryos, respectively. In comparison, malathion 24-h EC(50) values were 55.53 µg l(-1) (95% C.I.=22.08-80.73 µg l(-1)) for Stage VI embryos and 29.93 µg l(-1) (95% C.I.=25.22-44.22 µg l(-1)) for Stage VII embryos. For both OPs, there were no significant differences in the EC(50) values calculated for Stage VI and Stage VII embryos; however, AChE inhibition was significantly (P</=0.05) greater in Stage VII embryos at the two highest exposure concentrations for each insecticide. A comparison of the results of these embryo tests with those found for adult and larval toxicity tests indicated that embryos were at least as sensitive to both the OPs as larval and adult grass shrimp. Embryo bioassays provide a number of important advantages over traditional laboratory toxicity tests including reduced laboratory space requirements, large numbers of embryos from a few ovigerous females, and small volumes of waste.

Toxicity and physiological effects of brominated flame retardant PBDE-47 on two life stages of grass shrimp, Palaemonetes pugio.

This study examined the effects of a polybrominated diphenyl ether (PBDE) compound, PBDE-47, on adult and larval stages of the estuarine grass shrimp (Palaemonetes pugio). The 96-h LC50 test resulted in an estimate of 23.60 microg/L (95% confidence interval=14.51-38.37 microg/L) for larval shrimp. Adult shrimp had a higher 96-h LC50 of 78.07 microg/L (95% CI=65.1-93.63 microg/L). Four physiological biomarkers glutathione (GSH), lipid peroxidation (LPx), cholesterol (CHL) and acetylcholinesterase (AChE) were then assessed to study the sublethal effects of PBDE-47 exposure. GSH, LPx and AChE levels in both adults and larvae were not affected by PBDE-47 at concentrations up to 50 microg/L for 96 h. CHL levels were elevated in adults and larvae at the lowest exposure concentrations tested, but significant differences were found only in adult exposures. Effects associated with PBDE-47 aqueous exposures were observed at levels well above those reported in the environment.

Long Term Monitoring of Grass Shrimp Palaemonetes spp. Population Metrics at Sites with Agricultural Runoff Influences

Abstract Rising concern over pesticide usage near estuarine systems and evidence of physical and physiological impacts on estuarine organisms have strengthened the need to better identify the ecological effects of nonpoint source runoff. Grass shrimp, Palaemonetes spp., are ecologically important and abundant marsh inhabitants that may be impacted by anthropogenic contamination. Populations of grass shrimp were sampled monthly, over a period of ten years, at four sites in South Carolina with varying upland land use characteristics. Spatial and temporal trends in grass shrimp densities were noted over time and between sites. Agricultural and golf course land usage corresponded with decreased grass shrimp population levels, overall shrimp size, and percentage of gravid females. Conservation methods, such as the use of best management practices (BMPs) and integrated pesticide management (IPM) at agricultural fields, corresponded with increased grass shrimp population density.

Physiological factors contributing to the species-specific sensitivity of four estuarine microalgal species exposed to the herbicide atrazine

Algal species vary considerably in sensitivity to the commonly used herbicide atrazine, and it is hypothesized that several factors may contribute to species-specific sensitivity. In this study four estuarine microalgal species, a planktonic chlorophyte (Dunaliella tertiolecta), a benthic chlorophyte (Ankistrodesmus sp.), a cryptophyte (Storeatula major) and a dinoflagellate (Amphidinium operculatum), were exposed to atrazine to determine toxicity and identify factors that might influence species sensitivity. Atrazine effects were examined at the population (cell density, primary productivity and biomass), cellular (biovolume), and subcellular (pigment composition, protein concentration and lipid concentration) levels. Atrazine significantly decreased cell density, productivity rate, biomass and biovolume in all the algal populations tested at atrazine concentrations ≥ 12.5 μ g l−1. Toxicity values (96 h EC50 values) for the four species ranged from 11.87 to 146.71 μ g l−1. Species sensitivity rankings varied with endpoint measured. Overall, Ankistrodesmus sp. was the most sensitive species followed by Storeatula, Dunaliella and Amphidinium. Cellular biovolume was a significantly more sensitive test endpoint for Amphidinium, chlorophyll a was a significantly more sensitive test endpoint for Ankistrodesmus sp., and phototrophic carbon assimilation was a significantly more sensitive test endpoint for both Storeatula and Amphidinium. Algal subcellular responses to atrazine were also species dependent. Chlorophyll a concentration per cell decreased in the green algae, increased in Amphidinium and did not change in Storeatula. Total lipids per cell increased in Storeatula, decreased in Amphidinium and did not change in the green algae. Ankistrodesmus sp. pigments were not significantly altered after atrazine exposure; however selected Amphidinium pigments increased per cell, and selected Dunaliella and Storeatula pigments decreased per cell in the atrazine treatments. Atrazine significantly reduced cellular biovolume in all test species. Species with smaller biovolumes and less chlorophyll a per cell tended to be more sensitive to atrazine exposure based on population growth rate.

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.

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.