Effects of the endocrine disrupter chemicals chlordane and lindane on the male green neon shrimp (Neocaridina denticulata)

The purpose of this study was to investigate the effect of chlordane and lindane on morphological changes and endocrine disruption in male Green neon shrimp (Neocaridina denticulata). In this experiment, individuals of N. denticulata, a common inhabitant of freshwater systems in Taiwan, were exposed to chlordane (1 and 10 ng/l and lindane (0.1 and 1 microg/l morphological changes and reproductive hormone levels were observed following four weeks exposure. According to our findings, an increase in estrogen, a reduction in testosterone, and morphological alternations of the masculine appendage were observed in both chlordane- and lindane-treated shrimp, while induction of a vitellogenin-like protein appeared only in shrimp treated with 10 ng/l chlordane. An endocrine disruption effect on N. denticulata was demonstrated, and may apply to other organochlorine pesticides or endocrine disruption chemicals.

Ecological roles of natural products of the Brazilian red seaweed Laurencia obtusa

Laboratory and field experiments were performed to assess the ecological roles of natural products produced by the Brazilian red seaweed Laurencia obtusa. Laboratory assays revealed that the natural concentration of the crude organic extract of L. obtusa significantly inhibited feeding by two herbivores: the crab Pachygrapsus transversus and the sea urchin Lytechinus variegatus. It was verified that this chemically defensive action was due to halogenated sesquiterpenoid elatol, found to be the major natural product of this red seaweed. In addition, it was verified that the antifouling property of the chemicals produced by L. obtusa could make this red alga less attractive for fish grazing. Direct protection against two herbivore species and indirect protection against herbivory by fouling inibition constitute evidence that the major natural product from Brazilian L. obtusa plays multiple environmental roles, thereby increasing the adaptive value of these metabolites. On the other hand, the evidence reinforces the idea that marine natural products may have different functions in the sea.

Ecological risk assessment of neem-based pesticides

A tiered process was used to evaluate the risks of pure azadirachtin (AZA) and two neem-based insecticides (Neemix and Bioneem) on six aquatic animals [crayfish (Procambarus clarkii), white shrimp (Penaeus setiferus), grass shrimp (Palaemonetes pugio), blue crabs (Callinectes sapidus), water fleas (Daphnia pulex), and mosquito larvae (Culex quinquefasciatus)] through short term acute toxicity tests. The risk was calculated using the level of concern endpoints (Q values) and relative hazard index (RHI) for acute and chronic exposure scenarios. The Q values of Neemix, Bioneem, and pure AZA derived from acute exposure tests indicated that D. pulex is the only sensitive species to the test pesticides. Furthermore, the RHI values of Neemix and Bioneem for D. pulex were above the critical limit of 10 indicating that these pesticides may pose a moderate hazard to this species and related crustaceans in acute exposure scenarios. The RHI values of the two pesticides and pure AZA were all below the critical limit of 10 for P. clarkii, P. setiferus, P. pugio, C. sapidus, and C. quinquefasciatus. The aquatic risk assessment process showed that the risk values of tested pesticides did not exceed the criteria, and therefore, no ecological hazard is likely to result from their use.

A phage-displayed peptide can inhibit infection by white spot syndrome virus of shrimp

White spot disease, caused by white spot syndrome virus (WSSV), results in devastating losses to the shrimp farming industry around the world, and no effective treatments have been found. Control focuses on exclusion of the virus from culture ponds but, once introduced, spread is often rapid and uncontrollable. The purpose of this study was to select a phage-displayed peptide that might be able to prevent WSSV infection. A 10-mer phage display peptide library (titre 7.2 x 10(7)) was constructed and screened against immobilized WSSV. Selected peptides were assessed for specificity and efficiency of inhibition of virus infection. Of four peptides that specifically bound to WSSV one, designated 2E6, had a high specificity and blocked virus infection, with the possible critical motif for virus inhibition being VAVNNSY. The results suggest that peptide 2E6 has potential for exploitation as an antiviral peptide drug.

Toxic effects of microcystins in the hepatopancreas of the estuarine crab Chasmagnathus granulatus (Decapoda, Grapsidae)

Microcystins are toxins produced by cyanobacteria, being toxic to aquatic fauna. It was evaluated alternative mechanisms of microcystins toxicity, including oxidative stress and histopathology in the hepatopancreas of the estuarine crab Chasmagnathus granulatus (Decapoda, Grapsidae). Microcystins was administered to crabs (MIC group) over 1 week, whereas the control (CTR group) received the saline from cyanobacteria culture medium. At day 7, catalase activity was higher in the MIC than in the CTR group, although a decrease of activity was verified in both groups with respect to time 0. Glutathione-S-transferase activity augmented in MIC with respect to CTR, suggesting a higher conjugation rate of the toxins with glutathione. No differences were detected in the superoxide dismutase activity. Lipid peroxidation remained stable in both groups. Histopathological analyses showed that the number of B cells decreased significantly in the CTR as a possible effect of starvation, while no significant change was observed in the MIC group. The hepatopancreas from the MIC group exhibited some necrotic tubules and melanin-like deposits. Overall, results showed that some enzymes of the antioxidant defense system were activated after microcystins exposure, this response being able to maintain lipid peroxidation levels, but insufficient to completely prevent histological damage.

Oscillapeptin J, a new grazer toxin of the freshwater cyanobacterium Planktothrix rubescens

Oscillapeptin J (1), a new and highly potent crustacean grazer toxin, was isolated from the axenic cyanobacterium Planktothrix rubescens, which frequently forms blooms in freshwater lakes. Chemical and spectroscopic analyses, including high resolving MS and two-dimensional NMR, were used to elucidate the compound's structure as a depsiheptapeptide of the oscillapeptin type. Strict application of a bioassay-guided isolation procedure proved this compound to be one of the major causative agents (besides [d-Asp(3),(E)-Dhb(7)]microcystin-RR) of the acute grazer toxicity of P. rubescens from Lake Zürich. The LC(50) value of oscillapeptin J as determined for the freshwater crustacean Thamnocephalus platyurus was 15.6 microM.

Superoxide dismutase as modulator of immune function in American white shrimp (Litopenaeus vannamei)

The immunomodulatory action of superoxide dismutase (SOD) and its possible use as an indicator of immune responses in American white shrimp (Litopenaeus vannamei) were studied. Juvenile shrimp were immersed in aerated beta-glucan and sulfated polysaccharide solutions for 6 h. SOD activity in haemocytes and muscle was quantified to evaluate whether beta-glucan and sulfated polysaccharide induce immunostimulatory activity. Haemocytes and muscle showed similar increased levels of SOD activity (1.5- and 1.4-fold that of control, respectively). Total haemocyte count decreased within the first 24 h after challenge with immunostimulants, but total haemocyte count and total soluble haemocyte protein increased over normal values after 48-120 h. Single immunostimulation with beta-glucan and sulfated polysaccharide is sufficient to generate an increase in the antioxidant activity of L. vannamei SOD.

Dietary amino acid profiles and growth performance in juvenile kuruma prawn Marsupenaeus japonicus

To assess the reference dietary amino acid profiles for juvenile kuruma prawn Marsupenaeus japonicus a feeding trial was conducted using six semi-purified diets containing casein-gelatin and pre-coated supplemental crystalline amino acids (CAA) and a control diet containing intact protein (casein-gelatin). Pre-coated CAA were supplemented to the diets to simulate dietary amino acid profiles to those of the prawn egg protein (PEP), prawn larvae whole body protein (PLP), prawn juvenile whole body protein (PJP), squid meal protein (SMP), short-necked clam protein (SNP) and brown fish meal protein (BFP). The result showed that kuruma prawn juveniles are capable of utilizing the pre-coated CAA and higher growth performances were observed in the groups fed the PJP, SMP and the control diets than those fed the PLP, SNP, BFP and PEP diets. The essential amino acid proportions (A/E ratios) of the whole body of kuruma prawn differ slightly when compared with the other penaeids or freshwater prawn. The results suggest that PJP and SMP would be suitable as a reference dietary amino acid profile for juvenile prawn.

Effects of extracts from the cyanobacterium Microcystis aeruginosa on ion regulation and gill Na+,K+-ATPase and K+-dependent phosphatase activities of the estuarine crab Chasmagnathus granulata (Decapoda, Grapsidae)

Recent discoveries indicate that microcystins affect enzymes, such as Na(+),K(+)-ATPase, involved in ion regulation of aquatic animals, through K(+)-dependent phosphatase inhibition. In vitro studies showed the inhibitory effect of Microcystis aeruginosa extracts on Na(+),K(+)-ATPase and K(+)-dependent phosphatase activities in gills of Chasmagnathus granulata (Decapoda, Grapsidae). Extracts of M. aeruginosa were prepared from lyophilized or cultures cells of the cyanobacterium. For lyophilized cells, IC(50) values were estimated as 0.46 microg/L (95% confidence interval [CI]=0.40-0.52 microg/L) and 1.31 microg/L (95% CI=1.14-1.51 microg/L) for Na(+),K(+)-ATPase and K(+)-dependent phosphatase, respectively. However, extracts prepared from cultured cells presented a much lower inhibitory potency against both enzymes. Gas chromatography revealed long-chain fatty acids in the lyophilized cell extracts, indicating that they are in part responsible for the enzyme inhibition. In vivo studies showed that the toxin inhibited Na(+),K(+)-ATPase activity in anterior gills, whereas an increased augmented activity of glutathione-S-transferase was observed in both kind of gills, indicating that the crab has increased its ability to conjugate the toxin. No significant differences in hemolymph sodium or chloride concentration were detected. This result is in agreement with the lack of effects of microcystin on Na(+),K(+)-ATPase activity of posterior (osmoregulating) gills.

In situ tests for water quality assessment: a case study in Pampean rivers

Two invertebrate species (Hyalella curvispina and Palaemonetes argentinus) and one macrophyte (Egeria densa) from a naturally high nutrient content system (Pampean rivers of La Plata, Argentina) were evaluated for their potential use in situ assays aiming to assess changes in water quality. Invertebrates were individually placed in cylindrical chambers in polluted sections of rivers and in reference upstream sites. Mortality after 48 h was high in polluted and reduced in control sites. Mortality was also higher in situ assays than in laboratory static tests. Standard sections of the macrophyte were also deployed at the reference and control sites. Growth (7 days) in terms of mass increment (but not in length) was consistently reduced in polluted sites. Results of benthic invertebrate and periphitic algae surveys were consistent with the in situ tests: pollution resulted in a decrease in the number of taxa, taxa replacement and in changes in the value of the biotic indices Indice Biótico PAMPeano and Indice de Diatomeas Pampeano, indicating deterioration of water quality. In situ assays have a high potential as environmental tools in integrated approaches of bioassessment programs.

[Effect of different environmental factors on the activities of digestive enzymes and alkaline phosphatase of Macrobrochium nipponense]

The activities of digestive enzymes and alkaline phosphatase from the hepatopancreas of Macrobrochium nipponense were determined under different environmental factors (calcium concentrations 20 mg.L-1, 35 mg.L-1, 60 mg.L-1, 80 mg.L-1, 150 mg.L-1; salinity 7@1000, 14@1000, pH 7.6, 8.8, 9.8). The results showed that higher Ca2+ concentration could enhance the pepsin activity, but inhibit the trysin-like activity in hepatopancreas of M. nipponense. The activities of pepsin, trysin-like, alkaline phosphatase in hepatopancreas of M. nipponense were higher under salinity of 14@1000 than under salinity of 7@1000 and 20@1000. It showed that the activities of digestive enzymes and alkaline phosphatase of shrimp increased gradually with increasing pH value from 7.6 to 9.8.

Fate and environmental impact of pesticides in plastic mulch production runoff: field and laboratory studies

Concentrations of copper, azinphosmethyl, chlorothalonil, and endosulfan sulfate ranged from less than 1 to greater than 1000 microg/L in runoff from tomato plastic mulch production. When this runoff entered local creeks, the copper concentration was as high as 22 microg/L, which exceeded the measured larval clam LC50 values of 21 and 12 microg/L Cu at 96 and 192 h, respectively. A greenhouse scale investigation of copper and toxicity demonstrated that sedimentation reduced total copper concentration in runoff by 90%, although the dissolved copper concentration was unchanged, averaging 139 +/- 55 microg/L. When runoff was applied to marine mesocosms containing grass shrimp and mummichog fish, unsettled runoff produced the greatest mortality, although even settled runoff caused more mortality than that in the control mesocosm receiving runoff without added copper. Desorption of soil-sorbed copper occurred quickly in saline water and contributed to toxicity. Copper toxicity in runoff can be reduced, but not eliminated, by sedimentation.

The use of salt dilution gauging techniques: ecological considerations and insights

The salt dilution (gulp injection) technique is a well established and widely used technique to measure stream discharge, flow velocity and water residence characteristics in small headwater streams. However, the impact of the technique on water quality and instream ecology has been largely ignored in field investigations. A series of experiments were undertaken in a regulated and groundwater-dominated river to examine the effects on aquatic invertebrate drift at high, medium and low discharges. In the groundwater-dominated river, drift significantly increased as a result of the introduction of the saline solution under all flows. Drift increased at the regulated site under low and intermediate flow but not during high flows, probably due to a natural increase in drift associated with spate conditions. Following the application of the saline solution several taxa absent or infrequently occurring in background samples, such as the cased caddisfly, Agapetus fuscipes, were recorded. The wider implications of the technique are discussed in relation to short-term pulsed pollution episodes and the management of riverine ecosystems.

Preliminary evaluation of cytotoxic properties of Laurus nobilis leaf extracts

n-Hexane, ethanol and water extracts of Laurus nobilis L. leaves were evaluated for cytotoxic properties using the Brine shrimp bioassay. Only the n-hexane extract exhibited cytotoxic activity.

Toxicity of methyl tert-butyl ether to marine organisms: ambient water quality criteria calculation

In response to increasing concerns over the detection of methyl tert-butyl ether (MTBE) in groundwater and surface water and its potential effects in aquatic ecosystems, industry and the United States Environmental Protection Agency (USEPA) began to collaborate in 1997 to develop aquatic toxicity databases sufficient to derive ambient water quality criteria for MTBE consistent with USEPA requirements. Acute toxicity data for seven marine species, chronic toxicity data for an invertebrate, and plant toxicity data were developed to complete the saltwater database. The species tested were Cyprinodon variegatus, Gasterosteus aculeatus, Callinectes sapidus, Mytilus galloprovincialis, Palaemonetes pugio, Rhepoxynius abronius, Americamysis bahia, and Skeletonema costatum. The toxicity tests were conducted in accordance with USEPA and American Society for Testing and Materials testing procedures and Good Laboratory Practice guidelines. Data developed from this study were consistent with existing data and showed that MTBE has low acute and chronic toxicity to the marine species tested. Based upon measured MTBE concentrations, acute effects were found to range from 166 mg MTBE/l for the grass shrimp to 1950 mg MTBE/l for marine mussel. The no-observed effect concentration for the reproduction and growth of mysids was 26 mg MTBE/l during the life cycle test. The toxicity of MTBE to saltwater organisms is comparable to its toxicity to the freshwater species tested. Reported MTBE concentrations in coastal waters are several orders of magnitude lower than concentrations observed to cause effects in marine organisms.

Carriage of Vibrio species by shrimps harvested from the coastal waters of South West Cameroon

OBJECTIVES

To determine the prevalence of Vibrio spp in unprocessed shrimps and their susceptibility to antibiotics.

DESIGN

A prospective study of Vibrio spp associated with shrimps harvested from the coastal waters of South West Cameroon.

SETTING

A laboratory based study at the Department of Life Sciences, University of Buea. Two hundred and thirty six shrimps harvested from the coastal towns of Limbe and Tiko, Cameroon, were examined for the prevalence of Vibrio spp using standard microbiologic procedures. The antibiotic sensitivity of isolates was determined using the Kirby-Bauer disc diffusion technique.

RESULTS

Of the 236 shrimps examined, 73 (30.9%) were contaminated with Vibrio spp. Further, a total of 125 Vibrio strains were isolated from the contaminated shrimps. Of this number, 33 (26.4%) were V. cholerae, 55 (44%) V. parahaemolyticus, 34 (27.2%) V. alginolyticus and three (2.4%) V. vulnificus. Antibiotic susceptibility generally ranged from 68.8% for polymyxin B to 99.2% for gentamycin. Multiple resistant strains were noted, especially with V. parahaemolyticus and V. alginolyticus

CONCLUSION

Shrimps maintain a reservoir of potential Vibrio spp in the coastal area of South West Cameroon. This finding is of epidemiologic and clinical significance.

High grazer toxicity of [D-Asp(3),(E)-Dhb(7)]microcystin-RR of Planktothrix rubescens as compared to different microcystins

Planktothrix rubescens, the dominant cyanobacterium in Lake Zürich, is generally considered to be toxic to zooplankton. The major toxin was determined by NMR spectroscopy and chemical analysis to be [D-Asp(3),(E)-Dhb(7)]microcystin-RR. The compound was isolated in high purity, and its 24-h acute grazer toxicity was compared with microcystin-LR, microcystin-RR, microcystin-YR, and nodularin using a Thamnocephalus platyurus bioassay. Based on LC(50) values [D-Asp(3),(E)-Dhb(7)]microcystin-RR was the most toxic microcystin tested. Nodularin was slightly more toxic under the conditions of the assay. The large number of individuals available for the grazer bioassay allowed the determination of dose-response curves of the different microcystins. These curves showed marked differences in their steepness. Microcystin-RR, which had nearly the same LC(50) as microcystin-LR and microcystin-YR, exhibited a very flat dose-response curve. This flat curve indicates that, for some individuals, lower concentrations of this microcystin are much more toxic than are the other two microcystins. Mortality of 100% requires much higher concentrations of microcystin-RR, indicating the resistance of some animals to the toxin. The purified [D-Asp(3),(E)-Dhb(7)]microcystin-RR exhibited a higher molar absorption coefficient determined by quantitative amino acid analysis than the coefficients generally used for other microcystins. This observation has consequences for the risk assessment for microcystins and makes a structural determination of microcystins an absolute requirement. The presence of the dehydrobutyrine residue may be the reason for the higher specific toxicity of [D-Asp(3),(E)-Dhb(7)]microcystin-RR when compared to the N-methyldehydroalanine-containing microcystins.

The first glycosides isolated from propolis: diterpene rhamnosides

Two diterpene glycosides, ent-8(17)-labden-15-O-alpha-L-rhamnoside and ent-8(17)-labden-15-O-(3'-O-acetyl)-alpha-L-rhamnoside (new natural compounds) were isolated from propolis from El Salvador. The compounds showed significant antibacterial activity and moderate toxicity to Artemia salina nauplii. These are the first glycosides reported in bee glue.

Development of marine toxicity data for ordnance compounds

A toxicity database for ordnance compounds was generated using eight compounds of concern and marine toxicity tests with five species from different phyla. Toxicity tests and endpoints included fertilization success and embryological development with the sea urchin Arbacia punctulata; zoospore germination, germling length, and cell number with the green macroalga Ulva fasciata; survival and reproductive success of the polychaete Dinophilus gyrociliatus; larvae hatching and survival with the redfish Sciaenops ocellatus; and survival of juveniles of the opossum shrimp Americamysis bahia (formerly Mysidopsis bahia). The studied ordnance compounds were 2,4- and 2,6-dinitrotoluene, 2,4,6-trinitrotoluene, 1,3-dinitrobenzene, 1,3,5-trinitrobenzene, 2,4,6-trinitrophenylmethylnitramine (tetryl), 2,4,6-trinitrophenol (picric acid), and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The most sensitive toxicity test endpoints overall were the macroalga zoospore germination and the polychaete reproduction tests. The most toxic ordnance compounds overall were tetryl and 1,3,5-trinitrobenzene. These were also the most degradable compounds, often being reduced to very low or below-detection levels at the end of the test exposure. Among the dinitro- and trinitrotoluenes and benzenes, toxicity tended to increase with the level of nitrogenation. Picric acid and RDX were the least toxic chemicals tested overall.

Effect of probiotics on bacterial population and health status of shrimp in culture pond ecosystem

The artificially manufactured probiotics having beneficial bacteria, Bacillus spp. was applied regularly in a modified extensive shrimp (Penaeus monodon) culture pond, located on the bank of Vellar estuary, Parangipettai. The populations of total heterotrophic bacteria (THB), beneficial bacteria (Bacillus spp.) and pathogenic bacteria (vibrios) were monitored in water and sediment of the pond. The results were compared with a control pond, situated in the same location having same water spread area, stocking density, species managed with same technologies and optimum environmental parameters in which no probiotic was applied. The populations of THB and Bacillus spp. in the experimental pond increased and the vibrios decreased after each application of probiotics. But the result of the control pond showed an increasing trend of the populations of THB, Bacillus spp. and vibrios towards days of culture. The control pond had lower levels of THB and Bacillus spp. and higher levels of vibrios than the probiotic applied (experimental) pond. Also the probiotics maintained optimum transparency and low organic load in the experimental pond as compared to control. In general, water and sediment had almost equal number of Bacillus spp. and vibrios, but sediment had higher THB load than water. The applications of probiotics lesser pathogenic vibrios and enhance beneficial bacilli in the culture leading to improved water quality, promoted growth and survival rates and increased the health status of the shrimp without stress and disease outbreaks. Thus the application of probiotics could lead to disease-free and profitable shrimp culture operations which will be helpful for shrimp farmers as most of them are now-a-days severely affected by microbial diseases.

Determination of acute mortality in adults and sublethal embryo responses of Palaemonetes pugio to endosulfan and methoprene exposure

Adult grass shrimp (Palaemonetes pugio) were exposed to endosulfan or methoprene for 96 h and LC(50) values were calculated. Male and female P. pugio cohorts were also exposed to endosulfan for 96 h in an attempt to determine potential differences in sensitivity between the sexes. Results from the methoprene exposure indicated that this pesticide was not acutely toxic to adult grass shrimp at 1 mg l(-1). Due to the lack of sensitivity, sex specific tests with methoprene were not performed. The calculated LC(50) for a population of grass shrimp, including both males and females exposed to endosulfan, was 0.62 microg l(-1). The LC(50) determinations for the sex specific tests were 0.92 microg l(-1) for males and 1.99 microg l(-1) for females. Following these acute exposures, reproductively active grass shrimp were chronically exposed to 200 ng l(-1) endosulfan or 1 mg l(-1) methoprene and were allowed to produce embryos. The resulting embryos were assessed for potential sublethal toxicity. There were no observed differences in the percent successfully hatching or larval mortality 3-days post hatch among the treatments. However, endosulfan treated embryos had a significantly increased hatching time (9.76 days compared to 8.72 days in controls). Methoprene treated embryos also took longer to hatch (9.55 days), but this delay was not significantly different from controls. These findings suggest that endosulfan may preferentially affect male grass shrimp and exposed female grass shrimp may produce embryos with delayed hatching times.

The effect of mercury and PCBs on organisms from lower trophic levels of a Georgia salt marsh

We examined several indicators of salt marsh function, focusing on primary producers, microbes, and grass shrimp, at a Superfund site (LCP) contaminated with mercury and polychlorinated biphenyls (PCBs) and a reference site (Cross-River) in Georgia. Primary production of Spartina alterniflora was assessed by measuring peroxidase activity (POD), glutathione concentration (tGSH), photosynthesis (A(net)), and transpiration (E). Microbial populations were assessed by measuring living-fungal standing crop (as ergosterol) and Microtox(R). Grass shrimp (Palaemonetes pugio) reproductive potential was determined by measuring individual egg mass, average egg area, brood size, and brood mass of gravid females. Comparison of the sites suggested that P. pugio reproduction was affected at the LCP site, but we were unable to document clear negative effects on other organisms we investigated. Due to natural environmental gradients, the Cross-River site may not have been a perfect control for the LCP site. Therefore, data from just the LCP site were reanalyzed using multiple regression. Fungal biomass was related to methylmercury concentrations, but the direction of the relationship differed between wholly dead shoots (positive) and partially dead shoots (negative). S. alterniflora POD was positively related to methylmercury concentrations. S. alterniflora A(net) and E were negatively related to elevation and salinity, respectively. Despite high levels of contamination at the LCP site, our results provided only suggestive evidence for impacts on organisms at lower trophic levels.

The relevance of rooted vascular plants as indicators of estuarine sediment quality

Toxicity assessments and numerical quality assessment guidelines for estuarine sediments are rarely based on information for aquatic plants. The effect of this lack of information on contaminated sediment toxicity evaluations is largely unknown. For this reason, the toxicities of whole sediments collected from 15 sites in three urbanized Florida bayou-estuaries were determined for the benthic invertebrates Mysidopsis bahia and Ampelisca abdita and the plants Scirpus robustus Pursh (saltmarsh bulrush) and Spartina alterniflora Loisel (saltmarsh cordgrass). The results of the bioassays, conducted for 7 to 28 days, were compared for interspecific differences and to effects-based, sediment quality assessment guidelines. A variety of inorganic and organic analytes were detected in the estuarine sediments, and concentrations of as many as 7 analytes exceeded the sediment guidelines at the 15 sampling locations. Toxicity occurred at 2 of the 15 sampling stations based on invertebrate survival. Twelve of the 15 sediments had either a significant stimulatory or inhibitory effect on early seedling growth relative to a reference sediment (p < 0.05). The phytoresponse was specific to the location, test species, and plant tissue. There was no consistent trend between the sensitivities of the plants and invertebrates exposed to the sediments collected from the same sites. Of the 12 sediments that significantly affected seedling growth, 10 were not acutely toxic to the invertebrates. Consequently, the plant test species provided information that would have been missing if only animal test species were used. For this reason, the phytotoxicity database needs to be expanded for contaminated sediments to further evaluate interspecific sensitivities and to provide perspective on the environmental relevancy of proposed sediment quality criteria and effects-based assessment guidelines for which this information is usually missing. However, additional test method development and field validation are needed to support this effort, which includes the identification of sensitive plant test species, response parameters, and the chemical and physical sediment factors that influence plant growth.

Acute toxicity of locust insecticides to two indigenous invertebrates from Sahelian temporary ponds

During desert locust plagues large amounts of insecticides are used for control operations. Drift from these treatments and accidental overspraying may contaminate small surface waters such as temporary ponds. The present study describes methods for static acute toxicity tests with two abundant organisms that occur in temporary ponds in the African Sahel region: the fairy shrimp Streptocephalus sudanicus Daday (Branchiopoda, Anostraca, Streptocephalidae) and the backswimmer Anisops sardeus Herrich-Schåffer (Hemiptera, Notonectidae). The organisms were captured in the field and 48-h static toxicity tests were conducted in the laboratory. The assays were used to screen the toxicity of 11 formulated synthetic insecticides used in desert locust control and of spores of the mycopesticide Metarhizium anisopliae var. acridum. Most of the synthetic insecticides tested were highly toxic to both organisms (LC50 or EC50<1 mg/L). Exceptions were the toxicity of diflubenzuron to A. sardeus (moderately toxic: 1<LC50<10 mg/L), and that of fenitrothion (moderately toxic) and malathion (slightly toxic: 10<EC50<100 mg/L) to S. sudanicus. M. anisopliae var. acridum was moderately toxic to S. sudanicus and only slightly toxic to A. sardeus. EC50 values of the insecticides for S. sudanicus were not significantly correlated with L(E)C50 values for Daphnia magna collected from the literature. For A. sardeus a significant correlation with D. magna was found, but even in this data set the two species had widely differing sensitivities to some insecticides.