Differences in Prey Capture in Grass Shrimp, <Emphasis Type="Italic">Palaemonetes pugio,</Emphasis> Collected Along an Environmental Impact Gradient

The waterways and associated salt marshes along the western border of Staten Island, New York (Arthur Kill) have long been under environmental duress. Environmental threats include industrial and municipal discharges, oil spills, and possible leachate from landfills. These impacts are compounded due to the low flushing of this body of water. Grass shrimp, Palaemonetes pugio, inhabiting the Arthur Kill are, therefore, potentially at risk of exposure to metal and organic pollutants. Successful prey capture (of live brine shrimp, Artemia franciscana) was used to compare the relative health of shrimp collected from three sites along an environmental impact gradient. Study sites included a relatively unimpacted harbor (Great Kills Harbor, GK) and two creeks adjoining the Arthur Kill (Nassau Creek, NC, and Richmond Creek, RC). Shrimp originating from GK exhibited a rate of prey capture (6.3 prey h^–1) that was about two times greater (p < 0.05) than that of shrimp originating from a creek behind a series of landfills (RC, 3.2 prey h^–1). The rate of prey capture for shrimp collected from a creek impacted by historic smelting activities (NC) was intermediate (5.4 prey h^–1). Laboratory studies with shrimp from a pristine site (Tuckerton, NJ) exposed to RC conditions (i.e., sediment and water) for eight weeks indicate that reduced prey capture can be induced in healthy shrimp. Finally, video analysis suggests that reduced prey capture in RC shrimp may not be the result of less effort, but rather the combination of (1) 80% fewer (p < 0.05) prey being captured with a lunge type of attack and (2) a greater reliance (p < 0.05) on a less efficient grab type of foraging behavior (64% success rate for RC versus 87% success rate for GK; p = 0.058). These results indicate that sublethal toxicity in environmentally impacted populations can occur and that prey capture may be used to assay the relative health of field specimens. Additionally, impaired prey capture may have important implications for the energy flow within impacted environments.     

Wood preservative leachates from docks in an estuarine environment

Environmental concentrations and biological effects of certain metals and organic compounds found in wood preservatives were examined. The study focused on leachates from private residential docks in South Carolina tidal creeks. Copper, chromium, arsenic, and polynuclear aromatic hydrocarbons (PAHs) were measured in composite samples of surficial sediments and naturally occurring oyster populations (Crassostrea virginica) from creeks with high densities of docks, and from nearby reference creeks with no docks. In some cases, metal concentrations in sediments and oysters were higher immediately adjacent to dock pilings than they were elsewhere in the same creek. Sediments from most sites had concentrations of metals and total PAHs which were below levels reported to cause biological effects, however. Solid-phase Microtox^® bioassays using whole sediments and rotifer bioassays using sediment pore water showed no significant differences in acute toxicity between creeks with and without docks. Oysters growing directly on dock pilings had significantly higher concentrations of copper than oysters growing at least 10 m away; however, there was no significant difference in the physiological condition of these oysters. Four-day field bioassays measuring percent survival of mummichogs (Fundulus heteroclitus), mud snails (Ilyanassa obsoleta), juvenile red drum (Sciaenops ocellatus), and juvenile white shrimp (Penaeus setiferus) showed no significant differences between sites near to and distant from newly constructed docks. Hatchery-reared oysters showed no significant differences between dock and reference sites in percent survival, growth, or bioaccumulation of metals after six weeks of exposure. The results suggest that, in estuarine environments with a moderate tidal range (1.5–2.0 m), wood preservative leachates from dock pilings have no acutely toxic effects on four common estuarine species, nor do they affect the short-term survival or growth of juvenile oysters.     

Trophic Transfer of Lead Through a Model Marine Four-Level Food Chain: <Emphasis Type="Italic">Tetraselmis suecica</Emphasis>, <Emphasis Type="Italic">Artemia franciscana,Litopenaeus vannamei</Emphasis>, and <Emphasis Type="Italic">Haemulon scudderi</Emphasis>

The objective of this investigation was to assess the transfer of lead (Pb) along an experimental, four-level food chain: Tetraselmis suecica (phytoplankton) → Artemia franciscana (crustacean, brine shrimp) → Litopenaeus vannamei (crustacean, white shrimp) → Haemulon scudderi (fish, grunt). T. suecica was exposed to a sublethal dose of Pb in solution and then used as the base of a marine food chain. Significant differences in Pb concentrations were found between exposed organisms of the different trophic levels and the control. Particularly, Pb concentrations in fish of the simulated trophic chain were two-to three times higher in the exposed specimens than in the control. Levels of Pb in phytoplankton showed a substantial increase with respect to the solution (level I), with bioconcentration factors averaging from 930 to 3630. In contrast, a strong decrease in Pb concentration from phytoplankton to zooplankton (level II) and from zooplankton to shrimp tissues (level III) was evidenced by bioaccumulation factors <1. Despite the decrease in the assimilation efficiency of metal transfer observed in these two predators, Pb concentration in the grunt fish (level IV) was higher than in the shrimp (level III) (bioaccumulation factor >1.0). Some of the added Pb is transferred from the phytoplankton along the food chain, thus producing a net accumulation of Pb mainly in fish and, to a lesser extent, in shrimp tissues. Because Pb is one of the most pervasive contaminants in coastal ecosystems, its transference by way of diet and potential net accumulation in higher predators is of ecologic importance for marine life. In addition, because shrimp and adult Haemulon scudderi are commercially important resources, this issue is of particular relevance to the safety of marine products.     

Acute Effects of <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> from the Patos Lagoon Estuary,Southern Brazil,on the Microcrustacean <Emphasis Type="Italic">Kalliapseudes schubartii</Emphasis> (Crustacea: Tanaidacea)

Toxic blooms of the cyanobacterium Microcystis aeruginosa, a microcystin producer, have been observed in the past two decades in the Patos Lagoon estuary (southern Brazil). This cyanobacterium reaches the estuary from northern waters and accumulates as toxic blooms in the shallow margins of the environment. Microcystins are phosphatase (PP1 and PP2A) inhibitors and cause animal death via alteration of the liver cell cytoskeletons and intrahepatic hemorrhage. The massive accumulation of toxic material affects the survival of several benthonic estuarine local organisms. The tanaidacea Kalliapseudes schubartii is a benthonic estuarine species which occurs at high densities throughout the year in mixohaline areas of the Patos Lagoon. This microcrustacean is of high ecological relevance and plays an important role in the estuarine food web, as it is consumed on a large scale by estuarine fish. This work verifies the acute toxicity of aqueous extracts of M. aeruginosa RST9501 and of sediments spiked with lyophilized material of the same strain on K. schubartii; it also evaluates the sublethal effects on tanaidacean oxygen consumption rates and glycogen levels under acute exposure to M. aeruginosa aqueous extracts. The strain M. aeruginosa RST9501 was cultured in BGN/2 medium. The aqueous extracts were prepared using the lyophilized material from the strain cultures. Acute tests were performed over 96 h at a salinity of 15, at six toxic concentrations, and resulted in an average 96-h LC50 of 1.44 mg ml^–1. The spiked sediment tests were performed with a 10-day duration, using the lyophilized material in three proportions of powder/sediment and showed an average LC50 of 1.79 mg ml^–1. Oxygen consumption was determined after 24 and 48 h of incubation in adult organisms exposed to sublethal aqueous extract concentrations and showed a significant increase at the highest concentrations. This suggests alterations in the organisms metabolism by exposure to the cyanobacterium extract. The glycogen levels were determined with a commercial kit (Glicox 500; DOLES Ltd.); after 24 and 48 h the dosages were administered in the same organisms utilized in the oxygen consumption test and did not demonstrate significant differences. The results demonstrate the possible risks of intoxication to which the natural populations of K. schubartii were exposed in the environment and emphasize the importance of studies involving sublethal concentrations of M. aeruginosa to other organisms of the trophic web in this aquatic system.     

Toxicity and bioconcentration of BHC and lindane in selected estuarine animals.

Flow-through, 96-hr bioassays were conducted to determine the acute toxicity of technical BHC and lindane to several estuarine animals. Test animals and their respective 96-hr lindane LC50 values were: mysid (Mysidopsis bahia), 6.3 microgram/L; pink shrimp (Penaeus duorarum), 0.17 microgram/L; grass shrimp (Palaemonetes pugio), 4.4 microgram/L; sheepshead minnow (Cyprinodon variegatus), 104 microgram/L; and pinfish (Lagodon rhomboides), 30.6 microgram/L. The 96-hr LC50 values for pink shrimp and pinfish exposed to BHC were 0.34 and 86.4 microgram/L, respectively. Two BHC bioconcentration studies were conducted with the oyster, Crassostrea virginica, and pinfish. After 28 days exposure, oysters bioconcentrated an average of 218 X the BHC measured in exposure water, while pinfish bioconcentrated 130 X in their edible tissues and 617 X in offal. After one week in BHC-free sea water, no detectable residues were measured in oysters or pinfish.     

Toxicity of Chiral Pesticide <Emphasis Type="Italic">Rac-</Emphasis>Metalaxyl and <Emphasis Type="Italic">R-</Emphasis>Metalaxyl to <Emphasis Type="Italic">Daphnia magna</Emphasis>

Chirality in pesticides has become a challenge because of enantiomers’ different toxicities to non-target organisms. Acute and chronic toxicities of Rac-metalaxyl and R-metalaxyl to Daphnia magna were determined and compared. The 48-h LC50 for Rac- and R-metalaxyl to Daphnia magna were 51.5 and 41.9 mg/L. In a 14-day chronic test, the lowest-observed-effective concentration (LOEC) and no-observed-effective concentration (NOEC) of Rac-metalaxyl were 2 and 1 mg/L, respectively, whereas those of R-metalaxyl were 1 and 0.1 mg/L. Body length, days-to-first-brood and number of broods per female were significantly (p < 0.05) affected by R-metalaxyl at >1.0 mg/L, but affected by Rac-metalaxyl at ≥2.0 mg/L.     

Toxicopathic Branchial Lesions in Grass Carp (<Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis>) Exposed to Chlorpyrifos

Present investigation aimed to assess the alterations in branchial architecture of Ctenopharyngodon idellus exposed to chlorpyrifos. 96 h LC50 of chlorpyrifos to C. idellus was found to be 7.24 µg/L. Fish were exposed chronically to 2.41 and 1.44 µg/L sublethal concentrations (ecologically relevant concentrations) of chlorpyrifos for 15, 30 and 60 days. The gills of the CPF exposed fish showed partially affected secondary lamellae with shortening and curling, increased inter-lamellar space, sloughed off epithelium, hyperplasia and necrosis of pavement cells. On 60 days exposure, more pronounced degenerative changes, including severe necrosis, hyperplasia and hypertrophy of pavement cells, eroded and uplifted lamellar epithelium were noticed. Ultrastructural alterations include distorted nucleus and mitochondria in pavement cells, marked contraction in cisternae of golgi complex. Particularly in chloride cells, abundant mitochondria with distorted shape and size, dilation in between their cristae and tubular network were observed. The severity of damage was more profound at 60 days exposure. Thus, the observed cytopathological lesions of fish gills can be used as sensitive biomarkers for pesticide contamination.     

Water-Quality Parameters and Total Aerobic Bacterial and <Emphasis Type="Italic">Vibrionaceae</Emphasis> Loads in Eastern Oysters (<Emphasis Type="Italic">Crassostrea virginica</Emphasis>) From Oyster-Gardening Sites

Oyster gardening is a practice designed to restore habitat for marine life and to improve water quality. This study determined physical and chemical water-quality parameters at two oyster gardening sites in the Delaware Inland Bays and compared them with total aerobic bacteria and Vibrionaceae concentrations in Eastern oysters (Crassostrea virginica). One site was located at the end of a man-made canal, whereas the other was located in an open bay. Measured water parameters included temperature, dissolved oxygen (DO), salinity, pH, total nitrogen, nitrate, nitrite, total phosphorus, and total suspended solids. The highest Vibrionaceae levels, as determined by the colony overlay procedure for peptidases, were at the canal site in September (3.5 × 10⁵ g⁻¹) and at the bay site in August (1.9 × 10⁵ g⁻¹). Vibrionaceae levels were significantly greater during the duration of the study at the canal site (P = 0.01). This study provides the first baseline levels for total Vibrionaceae in the Delaware Inland Bays. Minimum DO readings at the bay and canal sites were 3.0 and 2.3 mg l⁻¹, respectively, far less than the state-targeted minimum threshold of 5.0 mg l⁻¹. Total phosphorus levels exceeded recommendations of ≤0.1 mg l⁻¹ at the bay and canal sites for all monthly samplings, with mean monthly highs at both sites ≥0.68 mg l⁻¹ in August. Nitrogen occasionally exceeded the recommended level of 1.0 mg l⁻¹ at both sites. Overall, waters were highly degraded from high phosphates, nitrogen, and total suspended solids as well as low DO.     

Acute and Chronic Toxicity of Imidacloprid to the Aquatic Invertebrates <Emphasis Type="Italic">Chironomus tentans</Emphasis> and <Emphasis Type="Italic">Hyalella azteca</Emphasis> under Constant- and Pulse-Exposure Conditions

The toxicity of imidacloprid, a nicotinic mimic insecticide, to the aquatic invertebrates Chironomus tentans and Hyalella azteca, was first evaluated in static 96-hour tests using both technical material (99.2% pure) and Admire, a commercially available formulated product (240 g a.i. L(-1)). The 96-h lethal concentration (LC)50 values for technical imidacloprid and Admire were 65.43 and 17.44 microg/L, respectively, for H. azteca, and 5.75 and 5.40 microg/L, respectively, for C. tentans. Admire was subsequently used in 28-day chronic tests with both species. Exposure scenarios consisted of a constant- and a pulse-exposure regime. The pulse exposure lasted for four days, after which time the animals were transferred to clean water for the remaining 24 days of the study. Assessments were made on both day 10 and day 28. In the C. tentans under constant exposure, larval growth on day 10 was significantly reduced at 3.57 microg/L imidacloprid, the lowest-observed-effect concentration (LOEC). The no-observed-effect concentration (NOEC) and LOEC for the 28-day exposure duration (adult survival and emergence) were 1.14 and greater than 1.14 mug/L, respectively; the associated LC50 and LC25 were 0.91 and 0.59 microg/L, respectively. The LOEC for the pulse treatment was greater than 3.47 microg/L, but the day 10 LC25 was 3.03 microg/L. In the H. azteca tests, the day 10 and 28 constant exposure, as well as the day 28 pulse exposure, LOEC (survival) values were similar at 11.95, 11.46, and 11.93 microg/L, respectively. The day 10 and 28 constant exposure effective concentration (EC)25s (dry weight) were also similar, at 6.22 and 8.72 microg/L, respectively, but were higher than the pulse-exposure day 10 LOEC and EC25 (dry weight) values of 3.53 and 2.22 microg/L, respectively. Overall, C. tentans was more sensitive to acute and chronic imidacloprid exposure, but less sensitive to a single pulse, than H. azteca. Chronic, low-level exposure to imidacloprid may therefore reduce invertebrate survival and growth, but organisms are able to recover from short-term pulse exposure to similar imidacloprid concentrations if the stressor is removed after four days.     

Comparative Embryonic and Larval Developmental Responses of Estuarine Shrimp (<Emphasis Type="Italic">Palaemonetes pugio</Emphasis>) to the Juvenile Hormone Agonist Fenoxycarb

Grass shrimp (Palaemonetes pugio) were reared separately through both embryonic and total larval development during exposure to fenoxycarb at measured concentrations of <2.2 to 888 g L^–1. A fenoxycarb concentration of 888 g L^–1 significantly (p < 0.05) inhibited embryonic development to larval hatching and extended the embryonic developmental period from 11.9 to 12.7 days. Exposure to fenoxycarb concentrations 502 g L^–1 had no significant (p > 0.05) effect on complete embryonic development. Significantly fewer shrimp successfully metamorphosed to postlarvae when exposed through complete larval development to fenoxycarb concentrations 4 g L^–1. Larval development of grass shrimp was therefore >2 orders of magnitude more sensitive to this juvenile hormone agonist than was embryonic development. Viability of larvae developing in fenoxycarb was concentration dependent. Development beyond third zoeal stage was significantly inhibited at fenoxycarb concentrations 190 g L^–1, whereas development beyond fourth zoeal stage was inhibited by a concentration of 45 g L^–1. Fenoxycarb exposure of developing larvae did not alter either the duration of total larval development or the total number of larval stages before metamorphosis. Rearing of fenoxycarb-exposed embryos through larval development without further exposure had no significant effect on number of larval stages, larval development rate, or metamorphic success of larvae. Similarities in the sensitivity of grass shrimp larvae and mosquito larvae to fenoxycarb suggests that the use of a bioassay protocol measuring the metamorphic success of crustacean larvae would be a valuable adjunct to the hazard assessment of newly developed pesticides that target endocrine control of metamorphosis in insects and possibly other endocrine-disrupting xenobiotics as well.     

Development of a Methodology for Successful Multigeneration Life-Cycle Testing of the Estuarine Sheepshead Minnow, <Emphasis Type="Italic">Cyprinodon variegatus</Emphasis>

Evaluation of effects on fish reproduction and development during chemical exposures lasting for multiple generations is sometimes limited by variable reproductive responses and the time required for the exposure. Established testing methods and the short life cycle of the sheepshead minnow, Cyprinodon variegatus, make this species particularly suitable for use in identifying potential impacts of contaminants in estuarine and marine environments. This study describes the refinement of life-cycle exposure methods that increased the reliability of reproduction in sheepshead minnows and reduced the time to maturation for larvae and juvenile fishes. A test of three spawning chamber designs, three sex ratios, and two photoperiods identified conditions that reduced the coefficient of variation in egg production from >100% to as little as 32%. The most reliable results were produced with groups of three female and two male fishes (all of similar size) when they were placed in a rectangular chamber and acclimated for 12 days. A test water temperature of 26.5 ± 2°C and a 14L:10D photoperiod resulted in fish producing a mean of 74 embryos per female per day, with a coefficient of variation of 31.8%. Egg fertility exceeded 90%, with a hatch rate of 95% for normal embryos (≥80% yolk) and a hatch rate of ≤45% for embryos containing ≤77% yolk. The length of time to grow larvae to spawning adult fish was reduced to ~60 days posthatch by feeding them flake food twice daily to satiation for 15 min, and it was observed that size (≥2.7 cm standard length) was critical for spawning readiness. Adult fish were prepared for the spawning assessment by adding frozen brine shrimp to their diet. Results of these experiments provide methods that are of particular interest in assessment of endocrine-disrupting chemicals that are known to affect reproduction.     

Contrasting Sensitivities to Fluoride Toxicity between Juveniles and Adults of the Aquatic Snail <Emphasis Type="Italic">Potamopyrgus antipodarum</Emphasis> (Hydrobiidae,Mollusca)

In contrast to aquatic vertebrates, there is scarce available information on the contrasting tolerance to fluoride of different life stages and/or sizes of aquatic invertebrates. The purpose of this study was to assess the likely differences in sensitivity between juveniles and adults of the aquatic snail Potamopyrgus antipodarum (Hydrobiidae, Mollusca) to short-term (4 days) toxicity of fluoride ion (F⁻). LC50 and EC50 values for juveniles were significantly lower than those for adults at 24, 48, 72 and 96 h. Based on our results, the use of fluoride data of bioassays with juveniles should provide more protective water quality criteria than data from adult stage.     

Fate and toxicity of temephos applied to an intertidal mangrove community

The distribution, persistence, and toxicity of the mosquito larvicide temephos was monitored following aerial applications to an intertidal mangrove community in Lee County, Florida. The amount of temephos penetrating to the mangrove floor ranged from 15 to 70% of the amount entering the upper leaf canopy, with 50-60% of that applied remaining on the mangrove leaves. Rainfall caused an additional influx of temephos from the leaves to the mangrove floor. Residues were detected in intertidal water at 2 h, but not 4 h after application. However, temephos was observed to persist in simulated tidal pools and on mangrove leaves for up to 72 h and in oysters for up to 48 h after application. Marine organisms placed in cages at 3 test sites and a control site were monitored for toxic effects. Mortality among natural mosquito larvae was simultaneously monitored. Mysids (Mysidopsis bahia) exhibited a significant mortality at one site during 1 of 3 applications monitored; however, no correlation was observed between mortality and temephos concentration in water. No significant mortality was observed for the other organisms, which included: brown shrimp (Panaeus aztecus), grass shrimp (Palaemonetes pugio), juvenile snook (Centropomis undecimalis) and sheepshead minnow (Cyprinodon variegatus).     

A New Developmental Toxicity Test for Pelagic Fish Using Anchoveta (<Emphasis Type="Italic">Engraulis ringens</Emphasis> J.)

A series of six 96-h static bioassays were performed to validate the use of anchoveta (Engraulis ringens) embryos as test organisms for ecotoxicological studies. The standardization protocol utilized potassium dichromate (K₂Cr₂O₇) as a reference toxicant and egg mortality as the endpoint. The results indicated that the mean sensitivity of anchoveta embryos to potassium dichromate was 156.1 mg L⁻¹ (range: 131–185 mg L⁻¹). The statistical data analysis showed high homogeneity in LC50 values among bioassays (variation coefficient = 11.02%). These results demonstrated that the protocol and handling procedures implemented for the anchoveta embryo bioassays comply with international standards for intra-laboratory precision. After secondary treatment, an effluent from a modern Kraft pulp mill was tested for E. ringens embryo toxicity, finding no significant differences from the controls.     

Oxidative Stress Responses and Recovery Patterns in the Liver of <Emphasis Type="Italic">Oreochromis niloticus</Emphasis> Exposed to Chlorpyrifos-Ethyl

Chlorpyrifos is the most common insecticide in freshwater ecosystems, and detected in agricultural and fishery product. In this study, Oreochromis niloticus were exposed to 5, 10 and 15 ppb sublethal concentrations of chlorpyrifos in order to determine the oxidative stress response in liver. Acetylcholinesterase (AChE) activity was significantly inhibited. Superoxide dismutase activity (SOD) increased after 15 days of chlorpyrifos treatments at all concentrations (146.95%, 53.04%, 208.70%, respectively). Malondialdehyde levels were higher than that of the control level after 15 days of 5 ppb (95.65%), 10 ppb (69.56%) and 15 ppb (252.17%) chlorpyrifos treatments. Malondialdehyde levels were also increased ranging from 59.09%, 113.63% to 195.46% after 30 days of 5, 10 and 15 ppb chlorpyrifos exposures. Glutathione S-transferase activity decreased except for 15 days low concentration exposure. Catalase (CAT) activity decreased while there is no significant alteration in glutathione peroxidase activity. After recovery period, the low concentration group of chlorpyrifos provided a protection in AChE activity during recovery, but fish were observed to be unable to overcome the inhibition of AChE activity at high concentration groups. CAT activity remained reduced, SOD activity increased whereas the other biochemical parameters recovered to control levels. Results of this study suggest that chlorpyrifos induces oxidative stress in the liver of O. niloticus and this effect is not related with anti-acetylcholinesterase activity of pesticide.     

Acute Toxicity of Sodium Metabisulphite in Larvae and Post-Larvae of the Land Crab, <Emphasis Type="Italic">Cardisoma guanhumi</Emphasis>

Sodium metabisulphite (SMB) is used in marine shrimp aquaculture to prevent the occurrence of black spot. The release SMB into the estuarine environment from shrimp farm pond effluents has been reported. This study evaluated the susceptibility of larvae and post-larvae of land crab, Cardisoma guanhumi to this salt. A decrease in dissolved oxygen and pH occurred with increasing concentration of SMB and exposure time. LC₅₀ values after 48 h of exposure were 34 ± 1.1 mg/L, 31.1 ± 1.9 mg/L, and 30.6 ± 0.5 mg/L for I zoea larvae, megalopa larvae and stage I juveniles, respectively.     

Toxicity of Sediment-Associated Pesticides to <Emphasis Type="Italic">Chironomus dilutus</Emphasis> and <Emphasis Type="Italic">Hyalella azteca</Emphasis>

Two hundred sediment samples were collected and their toxicity evaluated to aquatic species in a previous study in the agriculturally dominated Central Valley of California, United States. Pyrethroid insecticides were the main contributors to the observed toxicity. However, mortality in approximately one third of the toxic samples could not be explained solely by the presence of pyrethroids in the matrices. Hundreds of pesticides are currently used in the Central Valley of California, but only a few dozen are analyzed in standard environmental monitoring. A significant amount of unexplained sediment toxicity may be due to pesticides that are in widespread use that but have not been routinely monitored in the environment, and even if some of them were, the concentrations harmful to aquatic organisms are unknown. In this study, toxicity thresholds for nine sediment-associated pesticides including abamectin, diazinon, dicofol, fenpropathrin, indoxacarb, methyl parathion, oxyfluorfen, propargite, and pyraclostrobin were established for two aquatic species, the midge Chironomus dilutus and the amphipod Hyalella azteca. For midges, the median lethal concentration (LC₅₀) of the pesticides ranged from 0.18 to 964 μg/g organic carbon (OC), with abamectin being the most toxic and propargite being the least toxic pesticide. A sublethal growth endpoint using average individual ash-free dry mass was also measured for the midges. The no–observable effect concentration values for growth ranged from 0.10 to 633 μg/g OC for the nine pesticides. For the amphipods, fenpropathrin was the most toxic, with an LC₅₀ of 1–2 μg/g OC. Abamectin, diazinon, and methyl parathion were all moderately toxic (LC₅₀s 2.8–26 μg/g OC). Dicofol, indoxacarb, oxyfluorfen, propargite, and pyraclostrobin were all relatively nontoxic, with LC₅₀s greater than the highest concentrations tested. The toxicity information collected in the present study will be helpful in decreasing the frequency of unexplained sediment toxicity in agricultural waterways.     

Acute Toxicity of Antimony Chloride and its Effects on Oxygen Consumption of Common Carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>)

The purposes of this study were to investigate the acute toxicity and effects of sublethal antimony (sb) concertrations on respiratory activity changes in the common carp (Cyprinus carpio). Median lethal concentrations were determined in acute tests. The 96-h LC50 value was 14.05 (11.09~17.80) mg L⁻¹. Common carp were exposed to 4 different sublethal levels of antimony (1.0, 2.0, 4.0, and 8.0 mg L⁻¹) over a 28-day test period and a 14-day recovery period. On days 14 and 28, decreases in oxygen consumption were significant (p < 0.05) for the higher-exposure level groups (4.0 and 8.0 mg L⁻¹). An increase in oxygen consumption was observed in the recovery period (on day 42) compared to the respective groups at the same level on day 28 at the higher exposure levles.     

Toxicity and bioconcentration of BHC and lindane in selected estuarine animals

Flow-through, 96-hr bioassays were conducted to determine the acute toxicity of technical BHC and lindane to several estuarine animals. Test animals and their respective 96-hr lindane LC50 values were: mysid(Mysidopsis bahia), 6.3 µg/L; pink shrimp(Penaeus duorarum), 0.17 µg/L; grass shrimp(Palaemonetes pugio), 4.4 µg/L; sheepshead minnow(Cyprinodon variegatus), 104 µg/L; and pinfish(Lagodon rhomboides), 30.6 µg/L. The 96-hr LC50 values for pink shrimp and pinfish exposed to BHC were 0.34 and 86.4 µg/L, respectively.Two BHC bioconcentration studies were conducted with the oyster,Crassostrea virginica, and pinfish. After 28 days exposure, oysters bioconcentrated an average of 218 X the BHC measured in exposure water, while pinfish bioconcentrated 130 X in their edible tissues and 617 X in offal. After one week in BHC-free sea water, no detectable residues were measured in oysters or pinfish.Gulf Breeze Contribution No. 288.     

Effects of the insecticide permethrin on three life stages of the grass shrimp, Palaemonetes pugio

Toxicity of the pyrethroid insecticide permethrin was assessed using three life stages of the estuarine grass shrimp, Palaemonetes pugio. Adult and larval shrimp were tested with and without sediment. An aqueous embryo test was also conducted. Cellular stress biomarkers, glutathione, and lipid peroxidation, were assessed. Larval shrimp were the most sensitive life stage with a 96-h lethal concentration (LC(50)) value of 0.05 microg/L, compared to 0.25 microg/L for adults, and 6.4 microg/L for embryos. The presence of sediment significantly decreased toxicity of permethrin to both adult and larval shrimp. Permethrin exposure increased time to hatch in embryos and decreased swimming behavior of larvae. Lipid peroxidation levels were significantly decreased in the adult shrimp, but increased in larval shrimp exposed to permethrin. Low levels of permethrin may negatively affect grass shrimp health and survival. Permethrin use in the coastal zone should be carefully managed to avoid adverse impacts on nontarget estuarine organisms.