A caridean grass shrimp (Palaemonetes pugio Holthius) as an indicator of sediment quality in Florida coastal areas affected by point and nonpoint source contamination

Grass shrimp are one of the more widely distributed estuarine benthic organisms along the Gulf of Mexico and Atlantic coasts, but they were used infrequently in contaminated sediment assessments. Early‐life stages of caridean grass shrimp, Palaemonetes pugio (Holthius), were used in this baseline survey as indicators of sediment pore water quality for several Florida coastal areas affected by nonpoint and point sources of contamination. Static toxicity tests were conducted using 24 well culture plates assessing embryo and larval survival after 12 days exposure to pore water (interstitial water). Acute toxicity was observed in 28% of pore waters (15 of 53 samples) suggesting that sediment contamination was not widespread in the study area based on the response of this species. When toxicity was observed, grass shrimp pore water toxicity test was usually a more sensitive indicator of contamination than solid‐phase tests conducted with the epibenthic invertebrate, Mysidopsis bahia. P. pugio embryos were more sensitive than larval form and response of different brood stocks usually were similar (P>0.05) when exposed to same pore waters. Based on all considerations, this early‐life stage toxicity test shows promise being useful detecting pore water toxicity. This conclusion is based on availability of a test methodology which requires minimal space and effort, and the test species widespread geographical distribution. However, there are several remaining research needs, including the important issue of its sensitivity relative to that for other pore water test species as well as for species used in solid‐phase toxicity tests. © 2000 John Wiley & Sons, Inc. Environ Toxicol 15: 234–242, 2000     

Acute toxicity and bioaccumulation of aqueous and sediment-bound metals in the estuarine amphipod Melita plumulosa

The sensitivities of juvenile and adult amphipods to metals (Cd, Cu, Ni, Pb, and Zn) in whole sediment and water-only exposures were compared using a newly developed acute test with the estuarine species Melita plumulosa. Endpoints included survival and bioaccumulation in adults, and survival and growth (body length) in juveniles over 96 h water-only and 10 day sediment exposures. Juveniles were more sensitive than adults to metals, either bound to sediments or in the aqueous phase. Although LOEC values for copper and zinc in juvenile whole-sediment tests (820 and 2290 mg/kg dry weight, respectively) were high in comparison with interim sediment quality guideline values for individual metals (270 and 410 for copper and zinc respectively), they were generally within the range of concentrations found in contaminated sediments in local estuaries. Accumulation of metals, together with the low porewater metal concentrations in whole-sediment tests, indicated that the ingestion of sediment is an important source of zinc and copper and cause of toxicity in this species.     

Effects of Louisiana crude oil on the sheepshead minnow (Cyprinodon variegatus) during a life‐cycle exposure to laboratory oiled sediment

Determining the long‐term effects of crude oil exposure is critical for ascertaining population‐level ecological risks of spill events. A 19‐week complete life‐cycle experiment was conducted with the estuarine sheepshead minnow (Cyprinodon variegatus) exposed to reference (uncontaminated) sediment spiked with laboratory weathered South Louisiana crude (SLC) oil at five concentrations as well as one unspiked sediment control and one seawater (no sediment) control. Newly hatched larvae were exposed to the oiled sediments at measured concentrations of < 1 (sediment control), 50, 103, 193, 347, and 711 mg total polyaromatic hydrocarbons (tPAH)/kg dry sediment. Juveniles were exposed through the reproductively active adult phase at measured concentrations of <1 (sediment control), 52, 109, 199, 358, and 751 mg tPAH/kg sediment. Throughout the exposure, fish were assessed for growth, survival, and reproduction. Resulting F1 embryos were then collected, incubated, and hatched in clean water to determine if parental full life‐cycle exposure to oiled sediment produced trans‐generational effects. Larvae experienced significantly reduced standard length (5–13% reduction) and wet weight (13–35% reduction) at concentrations at and above 50 and 103 mg tPAH/kg sediment, respectively. At 92 and 132 days post hatch (dph), standard length was reduced (7–13% reduction) at 199 and 109 mg tPAH/kg dry sediment, respectively, and wet weight for both time periods was reduced at concentrations at and above 109 mg tPAH/kg dry sediment (21–38% reduction). A significant reduction (51–65%) in F0 fecundity occurred at the two highest test concentrations, but no difference was observed in F1 embryo survival. This study is the first to report the effects of chronic laboratory exposure to oiled sediment, and will assist the development of population models for evaluating risk to benthic spawning fish species exposed to oiled sediments. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1627–1639, 2016.     

Sediment quality triad assessment survey of the Galveston Bay,Texas system

To characterize the quality of sediments at key sites in the Galveston Bay Estuary, sediment samples were collected concurrently for chemical and physical analyses, toxicity testing and an assessment of benthic community structure. Significant toxicity, as determined by the sea urchin (Arbacia punetulata) pore water embryological development assay, was observed at 12 of the 24 sites investigated in this study. No toxicity was observed at any of the sites with the amphipod (Grandidierella japonica) solid-phase test. There were a number of sites with elevated levels of trace metals and petroleum hydrocarbons. The chemistry, toxicity and benthic data were ranked by station and a scaled rank sum was calculated to facilitate comparisons among the stations. Five sites exhibited strong evidence of contaminant-induced degradation, while 15 stations showed no evidence of contaminant-induced degradation. At eight additional sites the sediment quality triad (SQT) data indicated that unmeasured chemicals or conditions were stressing the system. Contaminant impacts could be reduced or eliminated by alternative regulatory and management practices, including the restriction of produced water discharges into coastal estuaries and the use of dredge material disposal practices that minimize the reintroduction of sediment-associated contaminants to the bays.     

Comparisons between microscale and whole-sediment assays for freshwater sediment toxicity assessment

The use of several microscale assays for evaluating freshwater sediment toxicity was investigated to develop a representative and cost-effective test battery. The bioassays evaluated (18 assays total) included microscale assays performed on solid-phase, pore water, and organic extracts as well as conventional standardized whole-sediment assays with Chironomus riparius and Hyalella azteca on 10 sediment samples collected in the St. Lawrence/Great Lakes system. Selected sediment physical and chemical characteristics were also conducted to aid in the interpretation of results. Benthic invertebrate assays such as C. riparius and H. azteca endpoints were found to correlate well to contaminant levels. Microscale assays such as ATP (adenosine triphosphate) measurement of sediment microbial biomass gave promising results to predict whole-sediment toxicity to benthic invertebrates. Most assays on pore water did not adequately represent whole-sediment toxicity, whereas organic extracts appeared to be more representative, alleviating some potential confounding factors such as interference due to toxicity caused by ammonia. © 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13 : 93–110, 1998     

Hyalella azteca 10-day sediment toxicity test: Comparison of growth measurement endpoints

Hyalella azteca are presently used in toxicity tests designed to evaluate adverse biological effects associated with exposure to contaminated sediments. Biological endpoints examined in a sediment test include changes in survival, as well as sublethal effects such as changes in growth, and reproduction. Length and weight, two methods used routinely to measure growth, were compared using H. azteca recovered from a 10-day sediment toxicity test. Length of individual organisms was measured using an image analyzer and dry weight of organisms was determined using an electronic microbalance. Statistical analysis was conducted using one-way analysis of variance to compare treatment sites. Length measures were shown to have greater power, a small minimum detectable difference, and smaller amount of underlying variability. The results indicate that length, measured using an image analyzer, was a more sensitive means to detect significant changes in growth and can be conducted with a greater degree of statistical confidence than use of weight measures. © 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13: 243–248, 1998     

Equilibrium partitioning as the basis for an integrated laboratory and field assessment of the impacts of DDT,DDE and DDD in sediments

Many of the most biologically productive portions of streams are backwater areas which support large populations of benthic macroinvertebrates. The sediments in these locations and their associated macroinvertebrate communities are frequently subjected to chemical inputs and physical perturbations. Historically, assessment of the effects of contaminants in sediments have emphasized chemical analyses and either laboratory toxicity tests or in-stream monitoring of benthic macroinvertebrate community structure. However, combining the chemical and biological approaches provides a more powerful assessment technique. Such an integrated approach, combining laboratory water-only and sediment toxicity tests with Hyalella azteca and Chironomus tentans, field surveys of benthic macroinvertebrate community structure and evaluation of chemical data using equilibrium partitioning theory was used to assess the effects of DDT, DDE and DDD (collectively termed DDTR) in the sediments of the Huntsville Spring Branch-- Indian Creek (HSB--IC) stream system in the southeastern USA. Benthic macroinvertebrate populations in the HSB--IC system still appear to be adversely affected by DDTR residues within the sediments even though DDT discharges to the stream were stopped over 20 years ago and a major remediation project was completed in the late 1980s. This conclusion is based on a weight of evidence approach which incorporates (1) the observed sediment toxicity to C. tentans and H. azteca in laboratory tests, (2) the identification of DDTR as the likely cause of effects observed during laboratory toxicity tests, (3) the absence of appropriate sensitive species from groups such as the Ephemeroptera, Plecoptera, Trichoptera and Amphipoda, (4) the presence of reduced numbers of both total individuals and species of chironomids and oligochaetes relative to nearby streams not contaminated by DDTR and (5) the observed distribution of benthic macroinvertebrates in relation to organic carbon-normalized concentrations of DDTR and equilibrium partitioning-based predicted sediment toxic units of DDTR     

Sediment contamination and biological effects in a Chesapeake Bay marina

Complementary measures of sediment toxicity, sediment chemistry and benthic community structure were evaluated at stations within and on the outside perimeter of an enclosed marina on the Bohemia River, a northeastern tributary to Chesapeake Bay. Sediment concentrations of polynuclear aromatic hydrocarbons, copper and tributyltin (TBT) were elevated at stations inside the marina basin. A 28 day partial life-cycle test with the amphipod Hyalella azteca indicated no significant lethal effects associated with test sediments. However, amphipods exposed to sediments collected from three stations inside the marina basin were significantly larger than amphipods from control sediments, possibly as the result of hormesis. Sediment pore water from two out of the three stations eliciting enhanced amphipod growth caused a reduction in light emission by luminescent bacteria in the Microtox^® assay. Furthermore, sediments from these two stations contained the greatest measured concentrations of copper and TBT. Benthic infaunal communities that typically reflect environmental degradation were found exclusively at stations within the marina basin. The area of environmental impact appears to be localized to the enclosed basin, as the marina design limits flushing and, hence, contaminant export.     

Sublethal effects of cadmium on arm regeneration in the burrowing brittlestar, Microphiopholis gracillima

To assess the sublethal effects of sediment-bound cadmium on arm regeneration of Microphiopholis gracillima, a burrowing brittlestar, experiments were conducted to quantify the tissue and morphology of regenerating arms, the uptake of cadmium in various tissues and the effect M. gracillima had on the cadmium pools in muddy sediments. Regenerated arms of cadmium-exposed M. gracillima are thinner, with proportionally less soft and skeletal tissue and a greater number of developing ossicles than animals held in sediment without cadmium. Microphiopholis gracillima decreased pore water cadmium concentrations in muddy sediments. Uptake of cadmium in tissues dominated by the calcium carbonate endoskeleton was proportional to the measured sediment cadmium concentration, while concentrations in whole regenerating arms were more closely related to the pore water concentration. Both calcium and cadmium are accumulated in the early stages of arm regeneration with an apparent interaction which interferes with ossicle construction. Sediment-bound cadmium has a negative effect on the organism's recovery from sublethal tissue loss and, ultimately, its long-term survival.     

Assessment of the impact of a bleached kraft mill effluent on a south‐central USA river

We initiated a multifaceted, integrated investigation of the general health of the aquatic environment near a bleached kraft pulp and paper mill. This southcentral U.S. mill discharges about 125,000 cubic meters of treated effluent per day into an adjacent river. The sampling sites for this study were 1.8 km upstream from the mill's discharge, 0.25 km below the mill's outlet, and 5 km downstream from the discharge area. No toxicity was observed using Ceriodaphnia dubia and Pimephales promelas in aqueous phase tests or with Hyalella azteca and Chironomus tentans in sediment phase tests. Field examinations of two small fish species and sediment macroinvertebrate communities from each sampling site revealed no significant adverse effects. Bluegill sunfish (Lepomis macrochirus) were exposed for 35 days to site sediments and were evaluated for ethoxyresorufin O‐dethylase (EROD) activity, cytochrome P4501A (CYP1A) content, DNA strand breaks, condition index, organ indices, gross pathology, and immune responses. No significant adverse effects were observed in sediments immediately below the mill's effluent outlet, though detoxification enzyme activity was elevated in liver tissue of bluegill sunfish exposed to site 3 sediment. Embryos of mosquitofish (Gambusia affinis) were evaluated for developmental and reproductive abnormalities following a static laboratory exposure of gravid females to sediments from the three study sites for 56 days. The embryos showed no significant effects on a suite of reproductive parameters among the three sites. We concluded that there was no significant evidence of adverse impacts on the receiving river or its biota attributable to treated bleached kraft mill effluent based on a comprehensive suite of bioindicators of exposure and effects. ©2000 John Wiley & Sons, Inc. Environ Toxicol 15: 28–39, 2000     

Toxicity of elemental sulfur in sediments

Elemental sulfur occurs naturally in marine and limnic sediments. Elemental sulfur, brought in solution in aqueous media by using organic solvents such as methanol as carrier solvent, was toxic in a bacterial luminescence test, known as the Microtox test. Previously, it has been shown that the toxicity in the luminescence test of whole sediments also was correlated to i.a. elemental sulfur using multivariate statistical analysis. Organic solvent extracts of sediments obtained in receiving waters of effluents from a pulp and paper mill was toxic in the luminescence test, and using a toxicity evaluation procedure, the toxic substance was identified as octameric cyclic sulfur, S₈. The substance dominated the toxicity in extracts of both a contaminated sediment and a sediment from a control area. Since the toxicity in the Microtox test of aqueous solutions of S₈ decreased upon storage, a conversion process of the toxic form was indicated. Acute toxicity of S₈ was not limited to the luminescent bacteria in the Microtox test, but was observed in tests with fish larvae if tested with the transient form of elemental sulfur. Tests of acute toxicity with zebra fish and perch larvae were responsive to elemental sulfur. Probably, the toxic form of elemental sulfur is the single cyclic octamer, that due to low aqueous solubility, binding to particulate sediment material or aggregation is converted into a nontoxic form. Acute toxic effects may occur in sulfur containing sediments of varying redox potentials or where elemental sulfur deposits are turbated. © 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13: 217–224, 1998     

Chronic toxicity of Great Lakes sediments to Daphnia magna: elutriate effects on survival, reproduction and population growth

Seventeen Great Lakes sediments ranging in degree of expected toxicity were evaluated using a 21 day sediment elutriate bioassay with Daphnia magna. Sediments differed in their effects on survival, age at first reproduction, the number of broods produced and the total number of young produced per adult. Sediments producing low survivorship (50–60%) also had negative effects on reproduction. However, both positive and negative effects on reproduction were found among sediments producing high survivorship. To integrate all test end-points, a stochastic matrix population model was constructed and parameterized with survival and reproduction data from each sediment. By including estimates of variability in vital rates, the model output provided quantitative estimates of uncertainty in projected population size. Sediment effects on survival and reproduction translated into large differences in projected population growth; mean estimates of projected population size at day 28 of the simulations ranged over two orders of magnitude among the 17 sediments. Reproductive timing (e.g. age at first reproduction), followed by fecundity and survivorship, had the largest effect on population growth. Results of this study also indicate that the presence of suspended sediment in elutriates may confound toxicity evaluations using cladocerans. The concentration of total suspended solids was negatively correlated with age at first reproduction and positively correlated with measures of fecundity and population growth. In order to realize the potential benefits of chronic testing we must develop ecologically relevant ways of interpreting sediment bioassay results and expressing the uncertainty associated with our estimates of ecological risk.     

Effects of Substrate Salinity on Early Seedling Survival and Growth of Scirpus robustus Pursh and Spartina alterniflora Loisel

Rooted aquatic plants are being used increasingly to test the toxicity of sediments. However, effects of naturally occurring substrate constituents on most potential test species are not well understood even though their effects could affect the test results. The objective of this study was to determine the effect of substrate salinity (NaCl) on early seedling survival and growth of the emergent macrophytes, Scirpus robustus Pursh and Spartina alterniflora Loisel. Results of four 21- and 28-day toxicity tests, conducted in an artificial sediment, indicated interspecific differences in NaCl sensitivity when based on changes in shoot, root and whole plant dry-weight biomass. Concentrations of 7.8 g NaCl/ and 19.2 g NaCl/ first reduced early seedling biomass of S. robustus and S. alterniflora (P < 0.05), respectively, when compared to plants grown in sediment containing no measurable salinity. Seedling survival was not affected at average concentrations of 17.5 g NaCl/ or less for S. robustus and 22.3 g NaCl/ or less for S. alterniflora. The results indicate that substrate salinity is an important consideration in the selection of test species for laboratory phytotoxicity tests conducted with estuarine sediments, particularly if determination of chronic toxicity attributable to anthropogenic contamination is the primary objective.     

Evaluation of ameliorative effect of curcumin on imidacloprid‐induced male reproductive toxicity in wistar rats

This study was undertaken to investigate the toxic effects of imidacloprid (IM) on male reproductive system and ameliorative effect of curcumin (CMN) in male Wistar rats. For this purpose, IM (45 and 90 mg/kg, body weight) and CMN (100 mg/kg, body weight) were administered orally to the rats either alone or in combinations for a period of 28 days. At the end of experiment, male reproductive toxicity parameters (total sperm count and sperm abnormalities), testosterone level, steroidal enzymatic activity [3β‐hydroxysteroid dehydrogenase (3β‐HSD) and 17β‐HSD], and oxidative stress indicators were estimated in testis and plasma. IM treatments resulted in significant decrease (p < 0.05) in total epididymal sperm count, sperm motility, live sperm count, and increase (p < 0.05) in sperm abnormalities. Activities of gamma‐glutamyl transpeptidase, lactate dehydrogenase‐x, and sorbitol dehydrogenase were significantly increased (p < 0.05), while, 3β‐HSD and 17β‐HSD enzymatic activity along with testosterone concentration in testis and plasma were decreased significantly (p < 0.05) in IM‐treated rats. IM exposure resulted in significant increase (p < 0.05) in LPO and decrease (p < 0.05) in GSH level along with decreased activities of CAT, SOD, GPx, and GST. IM‐treated rats showed histopathological alterations in testis and epididymis. However, the reproductive toxicity parameters, oxidative stress indicators, and histopathological changes were minimized and functional restorations were noticed by co‐administration of CMN in IM‐treated rats. The results of this study suggest that IM‐induced male reproductive toxic effects could be ameliorated by CMN supplementation. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1250–1263, 2016.     

Use of the aquatic oligochaetes Lumbriculus variegatus and Tubifex tubifex for assessing the toxicity of copper and cadmium in a spiked-artificial-sediment toxicity test

A sediment toxicity test using the freshwater oligochaetes Lumbriculus variegatus and Tubifex tubifex was performed. We evaluated acute and chronic toxicity affects of copper and cadmium on reproduction in both species and the bioaccumulation of both metals by L. variegatus using artificial sediment. L. variegatus bioconcentrated copper 22-fold and cadmium 16-fold after a 14-day exposure to spiked artificial sediments with 0.02% organic content. The EC₅₀ for T. tubifex varied depending upon endpoint from 2.7 to 2.8 mg/L for cadmium and from 8.4 to 8.9 mg/L for copper. The EC₅₀ for L. variegatus was 2.2 mg/L for cadmium and 3.9 mg/L for copper. Based on these results, L. variegatus appears to be more sensitive to metal toxicity in artificial sediments than T. tubifex. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 271–278, 1999     

A Comprehensive Environmental Assessment of a Receiving Aquatic System Near an Unbleached Kraft Mill

A critical examination of an aquatic environment adjacent to the discharge from an unbleached kraft pulp and paper mill (UBKM) was conducted in 1995. The assessment involved sampling of sediments, water, benthic macroinvertebrates, and fish collected 1.6 km upstream from the mill, at the mill's outlet, and 2.5 km downstream. Field-collected blue catfish (Ictalurus furcatus) and bluegill sunfish (Lepomis macrochisus) exposed to site sediments in the laboratory showed no significant within-organism adverse effects as measured by EROD activity, benzo[a]pyrene hydroxylase activity, CYP1A content, DNA damage, condition factor, organ indices, differential blood cell counts, and histopathology, though DNA strand breaks increased at the most downstream site. No aqueous or sediment toxicity was observed using Ceriodapnia dubia and Pimephales promelas or Hyalella azteca and Chironomus tentans, respectively. Embryos of the mosquitofish (Gambusia affinis) were evaluated for reproductive potential following laboratory exposures of adult mosquitofish to river sediments and water for 90 days. No significant adverse reproductive effects were observed immediately below the BKME discharge site. Analyses of field-collected benthic macroinvertebrate samples revealed no significant effects in terms of taxa, taxa richness, and other measures of their status. Using a comprehensive suite of within-organism, whole-organism, and community level endpoints, our study demonstrates that this effluent, discharged following secondary treatment from an UBKM, had no significant adverse impacts on the receiving aquatic ecosystem.     

Life history characteristics of the freshwater ostracod Cyprinotus incongruens and their application to toxicity testing

The biology of ostracod crustaceans suggests that this group could be a useful model for sediment toxicity testing. We examined life history characteristics of the freshwater ostracod Cyprinotus incongruens in the laboratory (25°C), then used length after 10 days as a response variable in a sediment toxicity test. Life history results indicated that both fecundity (0–64 total eggs per female), and egg development time (1->157 days), were highly variable. In contrast, juvenile development time showed less variation (7–16 days), and thus body length after 10 days was chosen as a sublethal bioassay character. A bioassay experiment using sediments isolated from mine-impacted cobble streams indicated that C. incongruens had a higher sensitivity to variation in sediment quality than the cladoceran Ceriodaphnia dubia. Surprisingly, the results indicated no correspondence between concentration of metals and toxicity in either C. incongruens or C. dubia. Overall our results indicate that ostracods are a good candidate taxon for sublethal toxicity tests of contaminated sediments.     

Embryonic and developmental toxicity of the ionic liquid 1‐methyl‐3‐octylimidazolium bromide on goldfish

The embryonic developmental toxicity of the ionic liquid (IL) 1‐methyl‐3‐octylimidazolium bromide ([C₈mim]Br) on the goldfish Carassius auratus was evaluated in this study. First, the 72 h 50% lethal concentrations (72 h‐LC₅₀) for [C₈mim]Br in goldfish embryos at the stages of cleavage, early gastrula, closure of blastopore, and heart beating were determined by preliminary acute toxicity tests. After that, fish embryos in different developmental stages (cleavage, early gastrula, closure of blastopore, and heart beating) were exposed to 10.4, 20.8, 41.6, and 104 mg/L of [C₈mim]Br until their hatching stage. The results of the acute toxicity tests showed that 72 h‐LC₅₀ values at the early cleavage, early gastrula, closure of blastopore, and heart beating stages of development were 208.96, 187.1, 245.03, and 298.33 mg/L, respectively. In the subchronic tests, [C₈mim]Br exposure prolonged the duration of embryo dechorionation and decreased the hatching rates of the treated embryos compared to control embryos. In addition, [C₈mim]Br treatment also caused remarkable increases of embryonic malformation and mortality ratio in most treatment groups. Finally, we also found that the embryonic and developmental toxicity of [C₈mim]Br on fish embryos was dose‐response and developmental stage‐specific. These results indicate that [C₈mim]Br has toxic effects on the early embryonic development of goldfish, and the risk to aquatic ecosystem by ILs leaking into the water body must be evaluated in the future. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010.     

Manganese-induced Parkinsonism in mice is reduced using a novel contaminated water sediment exposure model

Heavy metals enter the aquatic environment and accumulate within water sediments, but these metal-sediment interactions remain to be explored within toxicity studies. We developed an exposure model in mice that encapsulates the aquatic microenvironment of metals before exposure. Male and female C57/BL6 mice were exposed via their drinking water to manganese contaminated sediment (Sed_Mn) or to manganese without sediment interaction (Mn) for six weeks. Sediment interaction did not alter weekly manganese ingestion from water in males or females. We analyzed motor impairment, a common feature in manganese-induced Parkinsonism, using the beam traversal, cylinder, and accelerating rotarod tests. Sed_Mn mice performed better overall compared to Mn mice and males were more sensitive to manganese than females in both Sed_Mn and Mn treatment groups. Our study indicates that metal-sediment interactions may alter metal toxicity in mammals and introduces a new exposure model to test the toxicity of metal contaminants of drinking water.     

Sediment Toxicity in the St. Lucie River Watershed and Everglades Agricultural Area

DDD, DDE and ametryn were the most frequently detected pesticides in sediment in the St. Lucie River Watershed (SLR) and Everglades Agricultural Area (EAA). Concentrations of organochlorine compounds typically exceeded NOAA (SQuiRTs) TELs for freshwater sediment. Microtox BSPT EC50s from sediments in the SLR and EAA were lower than other sediment samples and reference controls. Single-species 10-day toxicity tests with Hyalella azteca and Chironomus tentans and whole sediment sample exposures from the SLR and EAA showed no effects on survival or growth of both species. However, in 28-day tests with H. azteca, survival was reduced at two sites compared to a reference control and a third sampling site. There were no correlations between contaminant concentrations, EC50s and toxicity test results.