Product Citations and Abstracts

Flow-through toxicity tests using marine organisms can generate large volumes of contaminated seawater effluent which should be treated to remove the contaminants before discharge into the environment. We have developed a sand filtration/carbon treatment system that removes from these effluents a diversity of organophosphate, organochlorine and pyrethroid pesticide residues down to their detection limit. The sand filter removed an average of 72% (range 4-99%) of the chemicals by continuously filtering suspended particulates and chemicals associated with the particulate. Following sand filtration, effluent water slowly percolates through granular carbon. Overall, organic removal efficiencies average 91% (range 24-99%). Initial construction cost was less than $20,000.

Moore, James C., E.M. Lores, James R. Clark, P. Moody, J. Knight and J. Forester. 1985. Effects of Ground ULV Applications of Fenthion on Estuarine Biota: II. Analytical Methods and Results. EPA/600/J-85/461. J. Fla. Anti-Mosquito Assoc. 56(2):62-68. (ERL,GB 523b). (Avail. from NTIS, Springfield, VA: PB87-152773)

Methods of analyses were validated for quantitating fenthion residues in samples from two salt marsh sites subjected to ground ultra-low volume sprays. Concentrations of these residues were followed from the water's surface, through the water column and onto the sediment. For all sprays, the highest concentration, detected in the upper portion of the water column, was 0.48 µg/l and occurred within the first hour after spraying. Detectable concentrations (>0.010 µg/l) of fenthion persisted in the water for up to 24 h. Fenthion did not accumulate to a detectable level (0.010 µg/g) in tissues of caged shrimp or fish.

Moore, James C., James C. Dukes, James R. Clark, Janice Malone, Charles F. Hallmon and Phillip G. Hester. 1993. Downwind Drift and Deposition of Malathion on Human Targets from Ground Ultra-Low Volume Mosquito Sprays. EPA/600/J-94/015. J. Am. Mosq. Control Assoc. 9(2):138-142. (ERL,GB 775). (Also avail. from NTIS, Springfield, VA: PB94-140654)

Malathion (S-[1,2-bis(etyhoxycarbonyl)ethyl] phosphoro-dithioate, Cythion® , American Cyanamid Company) is applied by aircraft and trucks in Florida to control mosquitoes. Spray effectiveness has been determined by mortality of caged mosquitos, field measures of mosquito abundance or activity and analysis of droplets collected on slides. Undesirable ecological effects of malathion used for mosquito control purposes are commonly associated with misapplication or are limited to short-term effects on sensitive crustaceans and insects (Mulla et al. 1979). Since malathion is acutely toxic to mammals in doses generally ranging from 200 to 1,000 mg/kg (US DHHS 1991), human exposures during mosquito control operations are considered inconsequential. Increasing public awareness and concern over personal and environmental exposures to mosquito control pesticides requires that malathion deposition be quantified. The objectives of this research were: 1) to determine the amount of malathion deposited on human subjects located at various distances from the path of a spray vehicle during typical spray conditions, 2) to determine the amount of malathion deposited at ground level at various distances from the spray vehicle, and 3) to compare the deposition of malathion onto body surfaces with published dermal LD50 values for mammalian toxicity.

Moore, James C. and E.M. Lores. Unpublished. Chemical Analyses of Sediment from Two Sites Near the Pensacola, Florida, Naval Air Station and Tissues of Marine Organisms Exposed to Sediment. Pp. 11p+tables. (ERL,GB X1077).

Chemical analyses were performed on sediment collected from two sites near the Pensacola, Florida, Naval Air Station and on three types of marine organisms exposed to these sediment samples during a 10-day bioaccumulation test conducted by the Dredged Materials Research Team of the Gulf Breeze Laboratory. Five replicates of each sediment and type of organism were analyzed for residues of selected chlorinated hydrocarbon pesticides, PCB8, chiorpyrifos (Dursban), petroleum hydrocarbons, and nine heavy metals. The purpose of these chemical analyses was to determine if residues were detectable in the sediments and if chemicals accumulated in tissues of organisms exposed to the sediments. Two samples of each type of organism and sediment were analyzed before use in the bioaccumu­lation test. Residues of selected pesticides or PCBs were not detected in sediments or animal tissues before or after exposure but several metals were detected in sediments and in tissues of organisms before and after exposure. Concentrations of cadmium in oysters (Crassostrea virainica) exposed to sediment from Site 2 were statistically greater than concentrations of cadmium in animals exposed to the reference sediment. Concentrations of arsenic, copper, and zinc were statistically greater in oysters exposed to sediment from Site 1 and in oysters exposed to sediment from Site 2 than those exposed to the reference sediment. Concentrations of lead in shrimp (Penaeus duorarum) exposed to sediment from Site 1 and in shrimp exposed to sediment from Site 2 were greater than concentrations of lead in shrimp exposed to the reference sediment. Certain metals were detected in lugworms (Arenicola cristata) exposed to sediment from Site 1 and from Site 2 but concentrations were not significantly greater than in lugworms exposed to the reference sediment. Aliphatic and aromatic petroleum hydrocarbon residues were found in oysters, shrimp and lugworms after the 10-day exposure study; however, no statistically significant differences were determined.

The objectives of this survey were to determine the genotoxic potential of sediment pore waters above and below 10 wastewater outfalls and to compare the results to sediment chemical quality guidelines, acute toxicity, and macrobenthic community composition. The focus of the study was on genotoxicity since its occurrence in environmental media below wastewater discharges in the Gulf of Mexico region has not been reported in the scientific literature. Pore waters from 43 sediment samples were assayed using a microbial mutagenicity assay before and after activation with a rat liver microsome mix (S-9). A combination of either direct or activated responses was observed for 40% of the pore waters. Direct, activated, and both direct and activated responses were observed in 5, 26, and 9% of the total samples, respectively. Mutagenic effects were observed below 7 of the 10 outfall areas and in 4 of 6 control areas associated with 6 outfalls. The lowest pore water concentrations causing an activated mutagenic response were statistically similar above and below the outfalls. Mutagenicity occurred more frequently than acute toxicity to estuarine and freshwater invertebrates and there was no consistent relationship between its occurrence and the exceedance of sediment chemical quality guidelines. In contrast, there was some indication that mutagenic activity paralleled low benthic community diversity.

Goodman, Larry R., Michael A. Lewis, John M. Macauley, Ralph Smith, Jr. and James C. Moore. 1999. Preliminary Survey of Chemical Contaminants in Water, Sediment, and Aquatic Biota at Selected Sites in Northeastern Florida Bay and Canal C-111. Gulf Mex. Sci. 17(1):1-16. (ERL,GB 1049).

Several actions are under way to alter water management capabilities and practices in south Florida in order to restore a more natural hydroperiod for the Everglades. Because relatively little research has been conducted on contaminants entering Florida Bay, we undertook a preliminary study in June 1995 to determine contaminant concentrations in surface water, sediment, and biota prior to major changes in water management. The areas studied were the C-111 canal (five sites) beginning just above water control structure S-197 and extending to Manatee Bay (part of the Biscayne Bay system), Shell Creek (three sites), the mouth of Taylor River, Trout Creek (two sites), and a site near the Key Largo Ranger Station. Hydrographic observations were made at each site, and samples of water and sediment were collected at each of the five areas except the Key Largo site. Bioresidues were determined for indigenous oysters collected from the C-111 canal and Shell Creek and for transplanted oysters exposed at the Key Largo site, the C-111 canal, Shell Creek, Taylor River, and Trout Creek for 5-29 days. Water samples were analyzed for selected organochlorine pesticides and metals; sediments were analyzed for the same compounds and for polycyclic aromatic hydrocarbons (PAHs). Fish filets and shucked oysters were analyzed for selected organochlorine pesticides, polychlorinated biphenyl (PCB) congeners, and metals. Other than low dissolved oxygen at some C-111 canal sites, water quality was generally good. Most contaminants were below water and sediment quality guidelines designed to protect aquatic life, and contaminant concentrations in oysters were low. Threshold effect levels were exceeded for some organochlorine pesticides and PAHs in some sediment samples, but all values measured were below probable effect levels. Low concentrations of organochlorine pesticides were detected in sediments from the C-111 canal, Shell Creek, Taylor River, and Trout Creek; except for Taylor River, low concentrations of PCB congeners and PAHs were detected from the same areas. The only organochlorine pesticide detected in filets from seven fish was 3.2 µg DDE/kg (wet weight) in a sea catfish. Total mercury concentrations in filets of four species of fishes ranged from 0.53 to 1.3 µg/g, wet weight, which falls within a limited consumption advisory by the State of Florida.

Lewis, Michael A., James C. Moore, Larry R. Goodman, James M. Patrick, Roman S. Stanley, Thomas H. Roush and Robert L. Quarles. 2001. Effects of Urbanization on the Chemical Quality of Three Tidal Bayous in the Gulf of Mexico. Water Air Soil Pollut. 127(1/4):65-91. (ERL,GB 1056).

Water and sediment quality in three tidal bayous located near Pensacola, Florida, were assessed during 1993-1995. The primary objective was to determine the environmental condition of the relatively small urban bayous by comparing the chemical quality of the sediments and surface water with published guidelines and criteria developed to protect marine life. Surface water concentrations of most potential toxicants such as heavy metals, organochloride pesticides, PAHs and PCBs were usually below method detection limits. The major exception to this trend was for copper which consistently exceeded Florida and National chronic water quality criteria. Nickel, cadmium and chromium intermittently exceeded these criteria. Sediment contamination was site-specific and chemically diverse. The concentrations of as many as 17 compounds exceeded proposed Florida sediment quality assessment guidelines indicating the potential for adverse biological effects. Nutrient concentrations, with one exception, were below average levels found in other Florida estuaries. Seasonal variation in contaminant concentrations for sediment collected from the same sampling station was less than an order of magnitude. The differences in the concentrations of the same analytes as measured for the multiple sampling stations located within the same bayou varied 1 to 2 orders of magnitude and over 2 orders of magnitude for the 20 sampling stations located in the three bayous. A within-bayou sediment contaminant gradient was evident; sediment quality generally improved seaward.

Schimmel, Steven C., Richard L. Garnas, James M. Patrick, Jr. and James C. Moore. 1983. Acute Toxicity, Bioconcentration, and Persistence of AC 222,705, Benthiocarb, Chlorpyrifos, Fenvalerate, Methyl Parathion, and Permethrin in the Estuarine Environment. EPA-600/J-82-030. J. Agric. Food Chem. 31(1):104-113. (ERL,GB 186). (Also avail. from NTIS, Springfield, VA: PB83-191239)

Six pesticides were evaluated in laboratory studies to determine acute (96-h) toxicity, octanol-water partition coefficients (log P), solubility, and persistence in seawater. In addition, three of the six pesticides (synthetic pyrethroids) were tested using the eastern oyster (Crassostrea virginica) in long-term (28-day) tests to determine their respective bioconcentration factors (BCF). Acute toxicity tests provided the following decreasing order of toxicity to estuarine crustaceans and fishes: AC 222,705, fenvalerate, permethrin, chlorpyrifos, methyl parathion, and benthiocarb. The estuarine mysid (Mysidopsis bahia) was consistently the most sensitive species, with LC50 values as low as 0.008 µg/L. The sheepshead minnow (Cyprinodon variegatus) was generally the least sensitive (range of LC50 values = 1.1-1370 µg/L). log P values were inversely related to solubility in seawater. The following are the increasing order of log P values (range, 1.8-6.5) and decreasing order of solubility (range >1000-24 µg/L): methyl parathion, benthiocarb, chlorpyrifos, AC 222,705, fenvalerate, and permethrin. Pesticide half-lives in sediment-water studies ranged from 1.2 to 34 days and were in the following order of increasing persistence: methyl parathion, permethrin, benthiocarb, AC 222,705, chlorpyrifos, and fenvalerate. The steady-state BCF's of the three synthetic pyrethroids were 1900 for permethrin, 2300 for AC 222,705 and 4700 for fenvalerate. After termination of the exposure, each insecticide was depurated by oysters to nondetectable concentrations within one week.

Lewis, Michael A., Steven S. Foss, Peggy S. Harris, Roman S. Stanley and James C. Moore. 2001. Sediment Chemical Contamination and Toxicity Associated with a Coastal Golf Course Complex. Environ. Toxicol. Chem. 20(7):1390-1398. (ERL,GB 1099).

The increasing density of golf courses represents a potential source of sediment contamination to nearby coastal areas, the chemical and biological magnitude of which is almost unknown. The objective of this study was to determine the concentrations of contaminants and toxicities of sediments impacted by a coastal golf course complex. Sediment contaminant concentrations were determined at least twice during the two-year study period at 14 sampling stations. In addition, a combination of acute and chronic bioassays were conducted exposing four invertebrate test species to whole sediments and associated pore waters. Overall, the Florida, USA, golf course complex had a measurable impact on sediment chemical quality, particularly in near-field areas. Higher concentrations of several trace metals and organochlorine pesticides were detected in many golf course-associated sediments compared to reference areas; however, concentrations decreased seaward and only a few, primarily chlorinated pesticides, exceeded proposed sediment quality guidelines. Chromium, zinc and mercury were detected more frequently than other trace metals. The DDT and associated metabolites, dieldrin and chlordane were the more commonly detected organic contaminants. Acute toxicity was uncommon and occurred consistently for sediment collected from one coastal location. In contrast, chronic toxicity occurred at several study sites based on the response of Mysidopsis bahia. It was concluded that the impact of golf course runoff on sediment quality may be subtle and sensitive biological assessment methods, such as chronic toxicity tests, will be needed to determine adverse effects.

Lewis, Michael A., David L. Weber and James C. Moore. 2002. Trace Metal Availability to Periphyton Colonized Below Near-Coastal Wastewater Discharges in the Gulf of Mexico. Dimensions of Pollution. 1:86-103. (ERL,GB 1111).

The primary objective of this baseline survey was to determine the concentrations of eight trace metals in periphyton colonized above and below eight municipal, industrial and forest product wastewater outfalls in northwest Florida. Trace metal residues and bioconcentration factors (BCF) for periphyton colonized below or adjacent to each of the eight outfalls were typically greater than those for periphyton colonized in the corresponding control or reference areas. The average increase in the eight metal residues for periphyton colonized in wastewater-impacted areas was 35 (± 1 standard deviation = 31)% and ranged from 0 to 89% for the specific metals. The increases were more significant for zinc and mercury. The trace metal residues had no significant relationship to ash free dry wt and chlorophyll a content of periphyton colonized on substrates adjacent to those used for the residue analyses. The mean percentage increase in the bioconcentration factors for the eight metals was 31 (± 39, range = 0-106). The average BCF values ranged from 231 (mercury) to 25194 (zinc) in control areas and 260 (cadmium) to 27527 (zinc) in wastewater-impacted areas. The increase in the mean BCF value for mercury was the most statistically significant.

Lewis, Michael A., Ronald G. Boustany, Darrin D. Dantin, Robert L. Quarles, James C. Moore and Roman S. Stanley. 2002. Effects of a Coastal Golf Complex on Water Quality, Periphyton, and Seagrass. EPA/600/J-00/418. Ecotoxicol. Environ. Saf. 53(1):154-162. (ERL,GB 1127).

The objective of this study was to provide baseline information on the effects of a golf course complex on water quality, colonized periphyton, and seagrass meadows in adjacent freshwater, near-coastal, and wetland areas. The chemical and biological impacts of the recreational facility, which uses reclaimed municipal wastewater for irrigation, were limited usually to near-field areas and decreased seaward during the 2-year study. Concentrations of chromium, copper, and organochlorine pesticides were below detection in surface water, whereas mercury, lead, arsenic, and atrazine commonly occurred at all locations. Only mercury and lead exceeded water quality criteria. Concentrations of nutrients and chlorophyll a were greater in fairway ponds and some adjacent coastal areas relative to reference locations and Florida estuaries. Periphyton ash free dry weight and pigment concentrations statistically differed but not between reference and nonreference coastal areas. Biomass of Thallassia testudinum (turtle grass) was approximately 43% less in a meadow located adjacent to the golf complex (P < 0.05). The results of the study suggest that the effects of coastal golf courses on water quality may be primarily localized and limited to peripheral near-coastal areas. However, this preliminary conclusion needs additional supporting data.

Lewis, Michael A., Larry R. Goodman, John M. Macauley and James C. Moore. 2004. Sediment Toxicity and Community Composition of Benthos and Colonized Periphyton in the Everglades-Florida Bay Transitional Zone. EPA/600/J-04/164. Ecotoxicology. 13(3):231-244. (ERL,GB 1164).

This survey provides information on sediment toxicity and structural characteristics of the macrobenthic and periphytic algal communities at 10 locations in northeast Florida Bay. Whole sediments were not acutely toxic to Mysidopsis bahia (marine invertebrate) and Hyallea azteca (freshwater invertebrate) relative to reference sediment. Survival was between 80% and 100%. Community structure of the macrobenthos and algal-periphyton varied spatially. A total of 116 benthic species were identified at the 10 locations; mean density was greater in Shell Creek (10,017 organisms/m2) and least in Canal C-103 (441 organisms/m2). Tubificids and the crustacean Halmyrapseudes bahamensis (Family: Apseudidae) dominated the benthos at 4 of 10 locations. One hundred and six species of periphytic algae representing 52 genera were identified on substrates colonized for 21 days. Mean algal density was greater in Florida Bay (19,440 cells/cm2) and least in Long Sound (10 cells/cm2). Diatoms and blue green algae dominated the algal-periphyton. Major diatom genera were Navicula, Brachysira and Nitzschia. The more abundant and widely occurring blue-green taxa were species of Oscillatoria, Polycystis and Lyngbya. Ash free dry weight and chlorophyll a were significantly greater for periphyton colonized in Canal C-111 and Florida Bay and the least in Long Sound. Spatial variation and the availability of reference areas are important issues that need consideration in future biomonitoring efforts conducted in this region to ensure relevancy of results.

Goodman, Larry G., John M. Macauley, Thomas H. Roush, Geoff I. Scott, Daniel W. Bearden, James C. Moore, Scott K. Sivertsen, Aaron R. Dias and Erich D. Strozier. Unpublished. Chemical Contaminants in Sediment, Water, and Fish From the Lower C-111 Canal System and Selected Tributaries to Northeastern Florida Bay During 1997. Arch. Environ. Toxicol. Chem. 26p. (ERL,GB 1174).

A survey was conducted in the spring and fall of 1997 to determine concentrations of selected contaminants in sediment, water, and fish from the C-111 canal system and northeastern Florida Bay. Twenty eight sites were sampled during the spring period of low water flow and agricultural pesticide application. These were contrasted with samples collected during the fall period of high rainfall. Concentrations of endosulfan I from 10. to 76. ng/l were measured in water samples from four canal sites during March. The endosulfan concentration of 95. ng/l (sum of endosulfan I and endosulfan II) at site C111E-1, above structure S-178, exceeds the freshwater criteria chronic value (56. ng/l) and is approximately 1/3 of the freshwater criteria acute value of 220. ng/l. Nine organochlorine compounds were detected at low concentrations in sediment samples. Endosulfan was the most frequently detected pesticide in freshwater sediments. Endosulfan I concentrations at 8 sites ranged from 0.93 to 5.6 ng/g. Fillets of fish from the freshwater canals frequently contained low concentrations of a number of organochlorine comounds. Mercury was detected (0.046 to 3.6 ug/g, dry weight) in most of the tissue samples analyzed; three largemouth bass samples contained concentrations >0.50 ug/g, wet weight, which is within a limited consumption advisory by the State of Florida. During at least one of the sampling periods, dissolved oxygen (D.O.) concentrations in bottom waters at all of the freshwater canal sites were less than the minimum value of 5.0 mg/l allowed under FDEP criteria for Class III waters. Surface D.O. concentrations at 10 of the 13 freshwater sites were <4.0 mg/l during September sampling.

Lewis, Michael A., Robert L. Quarles, Darrin D. Dantin and James C. Moore. 2004. Evaluation of a Florida Coastal Golf Complex as a Local and Watershed Source of Bioavailable Contaminants. EPA/600/J-04/043. Mar. Pollut. Bull. 48(3-4):254-262. (ERL,GB 1183).

Contaminant fate in coastal areas impacted by golf course runoff is not well understood. This report summarizes trace metal, pesticide and PCB residues for periphyton, Ruppia maritima (widgeongrass), Callinectes sapidus Rathbun (blue crabs) and Crassostrea virginica Gemlin (Eastern oyster) collected from areas adjacent to a Florida golf course complex which receive runoff containing reclaimed municipal wastewater. Concentrations of 19 chlorinated pesticides and 18 PCB congeners were usually below detection in the biota. In contrast, trace metals were commonly detected although concentrations were not usually significantly different for biota collected from reference and non-reference coastal areas. Residue concentrations in decreasing order were typically: zinc, arsenic, copper, chromium, lead, nickel, cadmium and mercury. Mean BCF values for the eight trace metals ranged between 160-57000 (periphyton), 79-11033 (R. maritima), 87-162625 (C. virginica) and 12-9800 (C. sapidus). Most trace metal residues in periphyton colonized adjacent to the golf complex, were either similar to or significantly less than those reported for periphyton colonized in nearby coastal areas impacted by urban stormwater runoff and treated municipal and industrial wastewater discharges. Consequently, the recreational complex does not appear to be a major source of bioavailable contaminants locally nor in the immediate watershed based on results for the selected biota.

Cook, Gary H. and James C. Moore. 1976. Determination of Malathion, Malaoxon, and Mono- and Dicarboxylic Acids of Malathion in Fish, Oyster, and Shrimp Tissue. J. Agric. Food Chem. 24(3):631-634. (ERL,GB 273).

A method is described for monitoring the presence of malathion and its metabolites in the aquatic environment. Malathion, malaoxon, malathion monoacid, and malathion diacid were determined in fish, oyster, and shrimp tissues by gas-liquid chromatography (GLC) using phenthoate and phenthoate acid as internal standards. GLC analyses were performed without cleanup, using a flame photometric detector operating in the phosphorus mode. Acid compounds were methylated with deaxomethane. Pinfish exposed to 75 µg/l. of malathion in flowing seawater for 24 h contained no residues of malathion or malaoxon, although the concentration of the malathion monoacid in the gut was 31.4 µg/g. The data illustrate that pinfish rapidly convert malathion to the mono- and dicarboxylic acids of malathion.

Cook, Gary H., James C. Moore and David L. Coppage. 1976. Relationship of Malathion and Its Metabolites to Fish Poisoning. Bull. Environ. Contam. Toxicol. 16(3):283-290. (ERL,GB 275).

We conclude that periodic environmental monitoring by chemical analyses of sensitive fishes or water for malathion or malaoxon would not show poisoning caused by enzyme-bound metabolites because malathion and malaoxon are rapidly absorbed and metabolically altered in fish. Parent pesticide remaining in water is probably dispersed or altered. Our data indicate analysis for malathion monoacid in gut and measurement of brain acetylcholinesterase acitivity in fish from the natural environment are a practical measure of poisoning caused by malathion in sensitive fish. Measurable concentrations of parent compound need not be present, but acetylcholinesterase inhibition in brain must occur for fish to be poisoned.

Tagatz, Marlin E., Joel M. Ivey, James C. Moore and Michael Tobia. 1977. Effects of Pentachlorophenol on the Development of Estuarine Communities. EPA-600/J-77-069. J. Toxicol. Environ. Health. 3(3):501-506. (ERL,GB 310). (Avail. from NTIS, Springfield, VA: PB-277 154)

Pentachlorophenol affected the composition of communities of estuarine organisms developed in sand from planktonic larvae in estuarine water that flowed through ten control aquaria and ten aquaria per exposure concentration averaging 7, 76, or 622 µg/liter. Annelids, arthropods, and mollusks were the numerically dominant phyla when animals were collected in a 1-mm-mesh sieve after 9 wk of exposure. Mollusks were markedly fewer at 7 µg/liter; annelids and arthropods at 76 µg/liter. Almost no animals occurred at 622 µg/liter. The total numbers of individuals and species were significantly less (a=0.01) In aquaria exposed to 76 µg/liter. than in those unexposed or exposed to 7 µg/ liter.

Faas, Linda F. and James C. Moore. 1979. Determination of Pentachlorophenol in Marine Biota and Sea Water by Gas-Liquid Chromatography and High-Pressure Liquid Chromatography. EPA-600/J-79-053. J. Agric. Food Chem. 27(3):554-557. (ERL,GB 350). (Avail. from NTIS, Springfield, VA: PB80-163678)

A method is described for measuring pantachlorophenol (PCP) in samples from the estuarine environment. Gas-liquid chromatography (GLC) is used to determine PCP residues in tissues as low as 0.01 ppm by formation of the ethyl diazohydorcarbon derivative, followed by Florisil cleanup. Application of the method to exposed organisms indicates that PCP accumulates in mullet (Mugil cephalus), grass shrimp (Palaemonetes pugio), and eastern oysters (Crassostrea virginica). Sea water concentrations as low as 0.002 ppb may be detected by formation of the amyl diazohydrocarbon derivative. Formation of the amyl derivatives of PCP and several related compounds gives GLC separation not possible with the methyl or ethyl derivatives. Parameters are outlined for high-pressure liquid chromatography (LC) determination of the free phenol without cleanup. Ultraviolet detection limits for PCP by LC are 5.0 ppm in tissues and 2.0 ppb in seawater.

Goodman, Larry R., David J. Hansen, David L. Coppage, James C. Moore and Edward Matthews. 1979. Diazinon: Chronic Toxicity to, and Brain Acetylcholinesterase Inhibition in, the Sheepshead Minnow, Cyprinodon Variegatus. EPA-600/J-79-071. Trans. Am. Fish. Soc. 108(5):479-488. (ERL,GB 374).

We investigated the toxicity of Diazinon to sheepshead minnows continuously exposed in flow-through toxicity tests. In the 96-hour acute test, a measured concentration of 1,400 µg/liter was lethal to 50% of the juvenile test animals. In the partial life-cycle test, we also investigated uptake of Diazinon by sheepshead minnows and effect of Diazinon on brain acetylcholinesterase (AChE) activity. Average measured concentrations in the partial life-cycle test were nondetectable (control), 0.47, 0.98, 1.8, 3.5, and 6.5 µg of Diazinon per liter of seawater. Although the number of eggs spawned by continuously exposed fish was significantly reduced (a=0.05) in all concentrations, no concentration tested significantly affected parental survival or fertility of eggs, nor were survival and growth of progeny affected in a subsequent 28-day test. Fish exposed to 0.47 µg/liter spawned 22.6 eggs/female-day, or 69% of control production (32.8 eggs/female-day). The number of eggs spawned by fish exposed to 6.5, 3.5, 1.8, and 0.98 µg/liter Diazinon was similar (14.9-17.9 eggs/female-day), averaging 45-55% of production by control fish. Egg production by fish that had been previously exposed to 3.5 µg/liter did not change significantly following depuration for 23 to 31 days. AChE activity varied inversely with exposure concentration, fish in the highest concentration (6.5 µg/liter) averaging 71% inhibition. The concentration of Diazinon measured in adult fish exposed to 1.8, 3.5, and 6.5 µg/liter averaged 169 times the concentration measured in the water. Diazinon was not consistently detected (< 0.05 mg/kg) in fish exposed to 0.98 and 0.47 µg/liter. The maximum acceptable toxicant concentration (MATC) for sheepshead minnows continuously exposed to Diazinon, based on reduced fecundity, is < 0.47 µg/liter; the application factor (MATC divided by 96-hour median lethal concentration) is <0.0003.

Hansen, David J., Larry R. Goodman, James C. Moore and Peggy K. Higdon. 1983. Effects of the Synthetic Pyrethroids AC 222, 705, Permethrin, and Fenvalerate on Sheepshead Minnows in Early Life-Stage Toxicity Tests. EPA-600/J-83-106. Environ. Toxicol. Chem. 2(2):251-258. (ERL,GB 462). (Avail. from NTIS, Springfield, VA: PB84-117415)

Sheepshead minnows (Cyprinodon variegatus) were exposed to the synthetic pyrethroid insecticides AC 222,705, fenvalerate and permethrin for 28 days in early life stage toxicity tests. AC 222,705 was 370 times more toxic than permethrin and 30 times more toxic than fenvalerate with survival and size of newly hatched fish being the most sensitive measures of effect. AC 222,705 reduced survival of hatched fish 0.61 µg/L and their average weight at 0.06 µg/ L; no effects were detected at 0.03 µg/L. Two of the AC 222,705 concentrations that diminished weights, 0.06 and 0.12 µg/L, were below our limit of chemical detection, 0.15 µg/L. Permethrin reduced survival of hatched fish at 22 µg/L; no effects were detected at 10 µg/L. Fenvalerate reduced survival of hatched fish are 3.9 µg/L and both weight and length at 2.2 µg/L; no effects were detected at 0.56 µg/L. Permethrin reduced survival of hatched fish at 22 µg/L and no effects were detected at 10 µg/L. The quotient of the 96-hr LC50 divided by the no-effect concentration was 0.8 for permethrin, 9 for fenvalerate and 37 for AC 222,705. The mean bioconcentration factors, concentrations measured in whole fish divided by concentrations measured in exposure water, were 480 for permethrin and 570 for fenvalerate; AC 222,705 was not detected in fish that survived the exposure.

Lores, Emile M., James C. Moore, Paul Moody, James Clark, Jerrold Forester and J. Knight. 1985. Temephos Residues in Stagnant Ponds After Mosquito Larvicide Applications by Helicopter. EPA/600/J-85/185. Bull. Environ. Contam. Toxicol. 35(3):308-313. (ERL,GB 524). (Avail. from NTIS, Springfield, VA: PB86-120516, A02)

This paper has shown that temephos, in actual field applications as a mosquito larvicide, behaves in much the same way as was predicted by Henry et al. (1971) and Sanders et al. (1981). The results indicate that the pesticide remains intact in water up to 48 hours, and residues as high as 62 µg/l were found. A problem of stabilization in this study was overcome by using mineral oil as an extracting solvent until the samples could be returned to the laboratory. The two new methods presented for analysis, although similar to methods already published, incorporate some newer technology.

Clark, James R., James M. Patrick, Jr., James C. Moore and Jerrold Forester. 1986. Accumulation of Sediment-Bound PCBs by Fiddler Crabs. EPA/600/J-86/087. Bull. Environ. Contam. Toxicol. 36:571-578. (ERL,GB 533).

Polychlorinated biphenyls (PCBs) have been, and continue to be, an ecological problem because of their environmental persistence. In aquatic systems, PCBs sorb to organic matter, accumulate in sediments, and contaminate food chains. Because of the potential for causing reproductive impairment, PCBs in aquatic food chains pose a threat to human and other predators that consume fish and shellfish. Fiddler crabs accumulate PCBs from contaminated sediments and detritus and can transfer them to aquatic, avian, and terrestrial food webs when preyed upon by fishes, birds, and small mammals. The primary objective of our research was to characterize rates of PCB uptake and depuration by fiddler crabs in a simulated spoil bank habitat that contained PCBs in weathered sediment. Also, we examined whether the concentration of PCBs in substrates affected bioaccumulation by mixing PCB-laden sediments with clean sand. In a pilot study, we tested Uca pugilator, an inhabitant of relatively dry and sandy areas, and U. minax, which inhabits wetter and muddier substrates, to determine if species differ in PCB uptake and depuration rates.

Clark, James R., James M. Patrick, Jr., Douglas P. Middaugh and James C. Moore. 1985. Relative Sensitivity of Six Estuarine Fishes to Carbophenothion, Chlorpyrifos, and Fenvalerate. EPA/600/J-85/336. Ecotoxicol. Environ. Saf. 10(3):382-390. (ERL,GB 541). (Avail. from NTIS, Springfield, VA: PB86-171634)

The acute toxicity (96-hr LC50) of carbophenothion, chlorpyrifos, and fenvalerate to six estuarine fishes was determined in flow-through laboratory tests. The atherinid fishes (Menidia menidia, M. peninsulae, M. beryllina, and Leuresthes tenuis) consistently were among the most sensitive species tested and were similar to each other in their sensitivity to pesticides. The sensitivity of sheepshead minnows (Cyprinodon variegatus) to carbophenothion was the same as that of the atherinids. For fenvalerate, the sheepshead minnow LC50 was an order of magnitude greater than that of the most sensitive atherinid, whereas the LC50 for chlorpyrifos and sheepshead minnows was two orders of magnitude greater. Gulf toadfish (Opsanus beta) were the least sensitive fish tested with carbophenothion and chlorpyrifos and their 96-hr LC50 for fenvalerate ranked between the LC50 for sheepshead minnows and atherinids. Test results were compared to acute toxicity data for other estuarine fishes and invertebrates.

Clark, James R., Patrick W. Borthwick, Larry R. Goodman, James M. Patrick, Jr., Emile M. Lores and James C. Moore. 1987. Comparison of Laboratory Toxicity Test Results with Responses of Caged Estuarine Animals Exposed to Fenthion in the Field. EPA/600/J-87/063. Environ. Toxicol. Chem. 6:151-160. (ERL,GB 545). (Avail. from NTIS, Springfield, VA: PB87-213237)

Acute, lethal effects of fenthion (an organophosphate insecticide) on mysids (Mysidopsis bahia), grass shrimp (Palaemonetes pugio), pink shrimp (Penaeus duorarum), and sheepshead minnows (Cyprinodon variegatus) were determined in laboratory tests and after field applications. Exposure at four field sites ranged from short-term exposures (12 h or less) of rapidly decreasing fenthion concentrations to extended intervals (more than 72 h) with slowly increasing or decreasing fenthion concentrations. Laboratory-derived LC50s provided a reliable benchmark for predicting acute, lethal effects of fenthion on caged animals in the field when exposures persisted for 24 h or more but overestimated the toxicity for exposures less than 24 h. Laboratory pulse-exposure tests with rapidly changing concentrations for 12 h were predictive of nonlethal and lethal effects observed for short-term field exposures.

Lores, Emile M., James C. Moore and Paul Moody. 1987. Improved Silica Gel Cleanup Method for Organophosphorous Pesticides. EPA/600/J-87/144. Chemosphere. 16(5):1065-1069. (ERL,GB 571). (Avail. from NTIS, Springfield, VA: PB88-149018)

Quantitative recovery of some organophosphorous pesticide residues has not been possible with existing silica gel-cleanup procedures. We have developed a modification that permits quantitative recovery of all organophosphorous pesticides tested, except those with a carbamate functional group. The method uses a 3.5 g silica gel column with a 1% acetic acid wash to condition the column prior to the addition of the sample. Percentage recovery and standard deviation of compounds such as phorate and disulfoton are 96 (5.6) and 98 (1.0), respectively. Recoveries range from 92 to 101% for the 11 compounds tested.

Clark, James R., James M. Patrick, Jr., James C. Moore and Emile M. Lores. 1987. Waterborne and Sediment-Source Toxicities of Six Organic Chemicals to Grass Shrimp (Palaemonetes pugio) and Amphioxus (Branchiostoma caribaeum). EPA/600/J-87/141. Arch. Environ. Contam. Toxicol. 16:401-407. (ERL,GB 575). (Avail. from NTIS, Springfield, VA: PB88-149034)

Grass shrimp (Palaemonetes pugio) were exposed to either waterborne or sediment-source concentrations of fenvalerate, cypermethrin, 1,2,4-trichlorobenzene (TCB), tributyltin oxide (TBTO), triphenyltin oxide, and di-n-butylphthalate in static or flow-through test systems. Similarly, amphioxus (Branchiostoma caribaeum) were tested with fenvalerate, TCB, and TBTO. The LC50 and no-effect and 100% mortality concentrations are reported from 96-hr and 10-day tests. The toxicity of contaminated sediments could be explained by chemical partitioning into overlying or interstitial water. Amphioxus is not recommended as a routine test species because of (1) difficulty in distinguishing severely affected from dead animals, (2) inability to determine the status of burrowed animals without disrupting sediment, (3) their relative lack of sensitivity in acute exposures to toxic chemicals, and (4) difficulty in routine collection of sufficient numbers of animals. Grass shrimp, however, are useful as an epibenthic test species for waterborne and sediment-source toxicants.

Clark, James R., Larry R. Goodman, Patrick W. Borthwick, James M. Patrick, Jr., Geraldine M. Cripe, Paul H. Moody, James C. Moore and Emile M. Lores. 1989. Toxicity of Pyrethroids to Marine Invertebrates and Fish: A Literature Review and Test Results with Sediment-Sorbed Chemicals. EPA/600/J-89/040. Environ. Toxicol. Chem. 8(5):393-401. (ERL,GB 618). (Avail. from NTIS, Springfield, VA: PB90-103599)

Data on the acute and chronic toxicities of permethrin, cypermethrin and flucythrinate to marine invertebrates and fish are reviewed. Generally, crustaceans are more sensitive than fish; oysters are comparatively insensitive. The mysid Mysidopsis bahia consistently is among the most sensitive crustaceans tested, with 96-h LC50s of less than 0.02 µg/L for permethrin and of less than 0.01 µg/L for fenvalerate, cypermethrin and flucythrinate. The potential for chronic toxicity to fish is minimal for permethrin, moderate for fenvalerate and relatively great for flucythrinate. Laboratory toxicity tests were conducted with sediment-source fenvalerate and cypermethrin under static and flow-through conditions to determine the degree of contamination necessary to achieve acute lethal effects on mysids, grass shrimp (Palaemonetes pugio) and pink shrimp (Penaeus duorarum). Mortality was observed in test animals only in systems where the concentrations of sediment-source pyrethroids were sufficient to establish lethal concentrations in the overlying water through sediment/water partitioning. For fenvalerate, lethal effects occurred at nominal sediment concentrations of 0.1 mg/kg (static and flow-through) for mysids and grass shrimp and at 10 mg/kg for pink shrimp. Nominal sediment concentrations of cypermethrin of 0.1 mg/kg (static) or 0.1 mg/kg (flow-through) resulted in mortality in mysids and grass shrimp, whereas 1.0 mg/kg was the only test concentration that caused mortality in pink shrimp in the static and flow-through test systems. The correspondence between aqueous concentrations and LC50s for test animals demonstrated the importance of quantitating the bioavailable portion of pyrethroids in field samples to characterize accurately the environmental risk associated with pyrethroid runoff after agricultural applications.

Hemmer, Michael J., Douglas P. Middaugh and James C. Moore. 1990. Effects of Temperature and Salinity on Menidia beryllina Embryos Exposed to Terbufos. EPA/600/J-90/375. Dis. Aquat. Org. 8:127-136. (ERL,GB 667). (Avail. from NTIS, Springfield, VA: PB91-163881)

Embryos of the inland silverside, Menidia beryllina, were exposed to the organophosphorus pesticide terbufos at nine combinations of temperature (20°, 25° and 30° C) and salinity (5, 12.5 and 20 o/oo). Nominal exposure concentrations were 12.5, 25, 50 and 100 µg terbufos l-1 with an acetone and seawater control for each temperature/salinity combination. Test durations were temperature dependent and ranged from 5 to 14 days. Endpoints were embryo survival, hatching and percentage of larvae with normal vertebrae. Embryo survival was significantly (a= 0.05) lower in tests conducted at 20° C for all salinities. Salinity affected survival only at combinations of 20 o/oo and 100 µg terbufos l-1. Both temperature and salinity affected the percentage hatch, with the lowest hatching occuring in 20° C tests, and in tests conducted at 20 o/oo. The percentage of larvae with normal vertebrae was significantly (a=0.05) reduced from controls at terbufos concentrations of 25 (7 to 32 %), 50 (44 to 62 %) and 100 µg l-1 (58 to 73 %) for the 3 temperatures tested, whereas salinity showed no significant effect. Anomalies in the development occurred across all temperature and salinity combinations, and were observed at concentrations as low as 12.5 µg terbufos l-1.

Walsh, Gerald E., David E. Weber, Tasha L. Simon, Linda K. Brashers and James C. Moore. 1991. Use of Marsh Plants for Toxicity Testing of Water and Sediment. In: Plants for Toxicity Assessment: Second Volume. ASTM STP 1115. EPA/600/A-92/121. J.W. Gorsuch, W.R. Lower, W. Wang, and M.A. Lewis, Editors. American Society for Testing and Materials, Philadelphia, PA. Pp. 341-354. (ERL,GB 694). (Avail. from NTIS, Springfield, VA: PB92-195882)

The freshwater wetland plants, Echinochloa crusgalli crusgalli and Echinochloa crusgalli zelayensis, and the saltmarsh plant, Spartina alterniflora, were exposed to the herbicides, metolachlor and norflurazon, in two types of toxicity tests: seed germination and early seedling growth in water, and seedling survival and growth in natural and synthetic sediments. The synthetic sediments were formulated to be similar to the natural sediments with regard to particle size distribution and organic content. The herbicides did not affect rate of germination, but significantly inhibited rate of early growth, and survival and rate of growth of older seedlings in sediments. Echinochloa was more sensitive than Spartina to both herbicides. Inhibition of the growth rates of the two varieties of E. crusgalli was similar in natural and synthetic sediments, but inhibition of growth of S. alterniflora was greater in synthetic than in natural sediment. It is concluded that the species tested may be used for estimation of potential effects of toxicants on wetland plants and that synthetic sediments of know composition may be used in sediment toxicity tests.

Collins, Gary, David A. Bengtson and James C. Moore. 1991. Characterization of Reference Artemia III for Marine Toxicological Studies. In: Aquatic Toxicology and Risk Assessment: 14th Volume, ASTM STP 1124. M.A. Hayes and M.G. Barron, Editors. American Society for Testing and Materials, Philadelphia, PA. Pp. 315-323. (ERL,GB 696).

ASTM Practice for Using Brine Shrimp Nauplii as Food for Test Animals in Aquatic Toxicology Tests (E1203) suggests use of Reference Artemia as a reference standard for evaluating other batches of brine shrimp as food for organisms used in toxicology. In 1988 the U.S. EPA was able to procure a 200-kg quantity of presumed high-quality, small-sized Artemia cysts that had been homogeneously mixed and packaged for long-term storage. These cysts and hatched nauplii have now been characterized in terms of fatty acid profile, toxicaznt residues, biometrics, and ability to support good survival and growth of saltwater fish and survival and reproduction of saltwater mysids. These cysts have been approved for use as reference cysts and have been designated RAC III. The fatty acid profile of the RAC III includes a 20:5w3 level greater than 7%, which is in excess of the 5% minimum level recommended for marine fish and crustacean larvae. The size of newly hatched nauplii is <430 µm, which is in the low end of the normal size range (420 to 520 µm) for Artemia nauplii from various strains. Thus they should be relatively easily ingested by marine fish larvae. Analyses of RAC III for metals, organophosphorus pesticides, chlorinated pesticides, and PCBs indicate no problems with toxicant residues. RAC III nauplii were evaluated as a food for marine fish and crustaceans in comparison to RAC II nauplii and a known poor-quality Artemia. There were not statistical differences in survival and growth of sheepshead minnows (Cyprinodon variegatus) and inland silversides (Menidia beryllina) raised on RAC II and RAC III. Survival and reproduction of mysids (Mysidopsis bahia) raised for 25 days on RAC III were comparable to RAC II-raised mysids. The availability of RAC III to U.S. marine toxicologists will make it easier for them to comply with ASTM E 1203 and therefore help to assure the quality of the toxicological data that they generate.

Goodman, Larry R., Michael J. Hemmer, Douglas P. Middaugh and James C. Moore. 1992. Effects of Fenvalerate on the Early Life Stages of Topsmelt (Atherinops affinis). EPA/600/J-92/217. Environ. Toxicol. Chem. 11(3):409-414. (ERL,GB 719). (Also available from NTIS, Springfield, VA: PB92-195742)

Flow-through acute and early life-stage (ELS) toxicity tests were conducted with topsmelt (Atherinops affinis), a Pacific Coast saltwater fish, and fenvalerate, a synthetic pyrethroid insecticide. The 96-h LC50 for juvenile fish was 0.66 µg/L. In the 30-d ELS test with laboratory-spawned embryos, average measured fenvalerate concentrations were nondetectable (< 0.075 µg/L) in two control treatments, 0.14, 0.34, 0.82, 1.5, and 3.2 µg/L. Survival of embryos to hatching ranged from 94% to 100%, with no statistically significant difference among treatments. No fry survived exposure to fenvalerate concentrations > 0.82 µg/L; overall survival in lower concentrations and control treatments ranged from 86% to 97%. There were no consistent concentration-dependent differences in weight between fish in the carrier-control treatment and fish exposed to fenvalerate. Mean wet weights of surviving fish ranged from 16.9 mg in 0.34 µg/L to 20.3 mg in 0.14 µg/L. The average bioconcentration factor for fish exposed to 0.14 and 0.34 µg fenvalerate/L was 315.

Flemer, David A., Roman S. Stanley, Barbara F. Ruth, Charles M. Bundrick, Paul H. Moody and James C. Moore. 1995. Recolonization of Estuarine Organisms: Effects of Microcosm Size and Pesticides. EPA/600/J-95/375. Hydrobiologia. 304:85-101. (ERL,GB 857).

Two six-week laboratory experiments were conducted to evaluate effects of pesticides and microcosm size on benthic estuarine macroinvertebrate recolonization. Sediments fortified with the pesticides (fenvalerate: controls, 5 (low) and 50 mg-1 wet sediment (high); endosulfan: controls, 1 (low) and 10 mg g-1 wet sediment (high) were fined-grained, organically rich (approximately 3.5% organic carbon and 22% dry weight) material. Relative dominance of the four most abundant taxa in both experiments was consistent amongtreatments with few exceptions. The amphipod, Corophium acherusicum, dominated abundance in both experiments. In the fenvalerate experiment, large trays (400 cm2) contained significantly (p<0.05) more total number of taxa (TNT) than small microcosms (144 cm2) but tray size was not significantly related to total number of organisms (TNO). When size was adjusted to a common unit area, small trays was 2.5 times that of large containers; a ratio close to that of microcosm sizes (i.e., 2.8). This result suggests that larval supply may have been inadequate to 'saturate' the available sediment in large containers. Fenvalerate significantly reduced abundance in the high treatment compared to both controls and low treatment but low treatment was not significantly different from controls. The amphipod; Corophium acherusicum, accounted for most of the decrease in abundance in response to fenvalerate. The holothruroid, Leptosynpta sp. and the polychaete, Mediomastus ambiseta, increased in abundance significantly with increased concentration of fenvalerate. Combined effects of actual microcosm size and concentration of endosulfan were not significant for TNO or TNT. As in the fenvalerate experiment, adjusted abundance of small microcosms was 2.6 times that of large trays which approximated the ratio of unit area between microcosm sizes. Abundance of a few taxa responded significantly to adjusted and unadjusted area. Abundance of the tunicate, Molgula manhattensis, increased significantly with increased concentration of endosulfan. Abundance was affected by sample location (e.g., interior vs exterior cores) within microcosms. Abundance adjusted to unit area resulted in significantly greater TNO in external vs internal cores. This has improtance for sequential sub-sampling of microcosms to determine temporal dynamics. Statistically significant effects were measured in benthic community structure associated with microcosm size; however, the magnitude was relatively small. There appears to be no major biological reason to select one microcosm size over the other for screening for contaminant effects. Where feasible, the small trays provide savings in sample preparation and analysis, allow more replicates where laboratory space is limiting and generate less chemical waste. These benefits may be off-set by less 'artifacts' associated with edge effects of larger microcosms and the need for a larger mass of sediment to accommodate additional analytical requirements (e.g., thin vertical surficial samples to refine contaminant exposure at the sediment/water interface.

Flemer, David A., Barbara F. Ruth, Charles M. Bundrick and James C. Moore. 1997. Laboratory Effects of Microcosm Size and the Pesticide Chlorpyrifos on Benthic Macroinvertebrate Recolonization of Soft Estuarine Sediments. Mar. Environ. Res. 43(4):243-263. (ERL,GB 951).

A 42-d flow-through experiment was conducted to evaluate the effects of the organophosphate pesticide, chlorpyrifos, and microcosm size (small: 144 cm2; large: 400 cm2) on benthic estuarine macroinvertebrate colonization. Nested central and perimeter (outside margin) cores were used to assess animal distribution within microcosms. Fine-grained, organically-rich (approximately 4.0% organic carbon and 20% dry wt) sediments were nominally fortified with chlorpyrifos controls, low (1.0) and high treatments (10.0 µg-1 wet sediment). Large microcosms contained a significantly (p<0.05) higher average taxa richness (10.9) than small microcosms (8.6) but small microcosms contained a significantly greater average animal density (295.8; numerical abundance adjusted to unit area) than large microcosms (120.5). Density of the polychaete, Neanthes succinea, the amphipod, Corophium acherusicum, and the barnacle, Balanus sp., was signficantly greater in small microcosms but density of Ensis minor was significantly greater in large microcosms. In small and large microcosms, respectively, densities averaged significantly greater numbers in perimeter cores (e.g. 203.1 and 75.1) vs central cores (71.9 and 45.4). Average density decreased significantly with increasing chlorpyrifos concentration from controls (326.8), to low (123.8) and high (78.8) treatments. The density decrease was significantly related only to C. acherusicum whose densities decreased from controls (258.8) to low (88.5) and high (43.9) dosed microcosms. Application of an equilibrium partitioning model indicated that density of C. acherusicum was sensitive to an estimated interstitial water concentration of approximately 0.48 µg liter-1. Non-metric multidimensional scaling ordination analyses provided important insights into response patterns not available through ANOVA procedures. A permutation procedure (ANOSIM) detected a significant size effect (p<0.0001) and a significant effect between controls and low (p<0.042) and high doses (p<0.013) but not between low and high chlorpyrifos treatments (p<0.465). A single species, C. ascherusicum, as in the ANOVA analyses, dominated contributions to community average percent dissimilarity in most combinations of microcosm size and chlorpyrifos treatment effects (range:8.4-21.9%). Community structure differed significantly in several combinations of microcosm size, core position and chlorphyifos treatment. Results confirm earlier work that intrinsic design factors influence benthic macroinvertebrate community structure and determine taxa available to pesticide exposure in microcosms.