Effects of copper-contaminated sediments on Hyalella azteca,Daphnia magna,and Ceriodaphnia dubia: Survival,growth, and enzyme inhibition

The results of two newly developed sediment toxicity tests were compared to the standard, 48-h acute Daphnia magna and Ceriodaphnia dubia tests. The 14-day Hyalella azteca growth inhibition test is a definitive test of chronic exposure to toxic sediments. The rapid, fluorescent D. magna test, which is based on in vivo inhibition of enzymatic processes, has been suggested as a rapid screening tool. H. azteca mortality was the least sensitive bioassay endpoint, while H. azteca growth, D. magna fluorescence, C. dubia mortality, and D. magna mortality were equally sensitive to the effects of sediments spiked with CuSO₄. In sediments collected in copper-contaminated lakes, the standard, acute 48-h D. magna bioassay was the least sensitive test, while the D. magna fluorescence test and H. azteca growth reduction test were the most sensitive bioassays.     

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. Received: 8 March 2000/Accepted: 22 July 2000     

Mississippi Oxbow Lake Sediment Quality During an Artificial Flood

Surface sediment quality was assessed during a 35-day artificial flood in a shallow (<1.5 m) oxbow lake along the Coldwater River, Mississippi, using Hyalella azteca 28-day bioassays. Seventeen pesticides were monitored in sediments before, during and after flooding, with increases in atrazine and metolachlor concentrations coinciding with two unexpected storm events, 51 and 56 mm, during and after flooding, respectively. Mean 28-day H. azteca survival was >85% throughout this study. However, growth was affected at three sites during flooding with limited growth recovery after flooding. Patterns in observed growth impairment were associated with changes in atrazine (R ² = 0.524) and fipronil sulfone (R ² = 0.584) concentrations.     

Assessment of Toxicity Reduction in Wastewater Effluent Flowing Through a Treatment Wetland Using Pimephales promelas, Ceriodaphnia dubia, and Vibrio fischeri

Effluent toxicity is regularly assessed with Ceriodaphnia dubia short-term chronic and Vibrio fischeri toxicity tests. Condition factor and hemotocrit of fish have recently been used to assess fish health following exposure to xenoestrogens in complex municipal effluents. To assess the ability of a treatment wetland to reduce or remove toxicity of a municipal effluent, we compared C. dubia and V. fischeri bioassays to Pimephales promelas responses in situ. Final whole effluent was diverted to a constructed wetland and effluent samples were taken daily from four sites, at incremental distances from the inflow, for a 3-week study. Overlapping 7-day C. dubia tests and V. fischeri assays were conducted with samples from each wetland site concurrent with a 3-week fish exposure. C. dubia survival and fecundity were significantly (< 0.0001) reduced at the inflow, but steadily improved with distance from the inflow. Fish condition and hematocrit were lower (α < 0.05) at wetland sites closer to the inflow than other wetland sites and laboratory controls. However, effluent toxicity was not detected by V. fischeri bioassays. Our findings indicate that 7-day C. dubia bioassays were most sensitive to effluent toxicity and suggest that other bioassays should be used concurrent with V. fischeri assays for municipal effluent toxicity testing. Received: 20 November 2000/Accepted: 18 June 2001     

Comparison of Bulk Sediment and Sediment Elutriate Toxicity Testing Methods

Numerous methods exist for assessing the potential toxicity of sediments in aquatic systems. In this study, the results from 10-day bulk sediment toxicity test methods using Hyalella azteca and Chironomus tentans were compared to results from 96-h Pimephales promelas and Ceriodaphnia dubia renewed acute toxicity tests conducted using elutriate samples prepared from the same sediments. The goal of the study was to determine if the results from the elutriate tests were comparable to those obtained from the bulk sediment tests. Of the 25 samples analyzed, 16 were found to be toxic to at least one of the species tested, in either elutriate or bulk sediment tests. The C. tentans 10-day bulk sediment test was the most sensitive, with 12 sediment samples exhibiting toxicity to this species, whereas the H. azteca bulk sediment test and C. dubia 96-h elutriate test were the least sensitive, exhibiting toxicity in only 7 of the 25 sediments tested. The P. promelas elutriate test found 8 of the 25 sediments to be toxic. Based on the total number of sites found to show toxicity, results from testing indicate 96-h elutriate tests show a level of sensitivity comparable to 10-day bulk sediment tests in assessing toxicity quantitatively. However, the methods did not always find toxicity at the same sites, suggesting that the ability of elutriate tests to predict toxicity (quantitatively) is not statistically correlated with bulk sediment methods. This would indicate that a suite of toxicity test methods would provide the most complete measure of site condition; however, in circumstances where bulk sediment testing is not feasible, elutriate tests can provide a practical and credible alternative for toxicity assessment.     

Phototoxic Evaluation of Marine Sediments Collected from a PAH-Contaminated Site

The phototoxicity potential of PAH-contaminated field sediment was evaluated and compared to standard sediment toxicity test results. Marine sediments were collected from 30 sites along a presumed PAH sediment pollution gradient in Elliot Bay, WA. Standard 10-day acute and 28-day chronic sediment toxicity tests were conducted with the infaunal amphipods Rhepoxynius abronius and Leptocheirus plumulosus using mortality and the ability to rebury as endpoints. The survivors of these tests were then subjected to 1-h exposures to UV radiation with mortality and reburial again determined. The most highly toxic sediments identified in these experiments were evaluated further for toxicity and phototoxicity by serially diluting them with uncontaminated sediment and repeating the toxicity tests. Standard 10-day toxicity test results indicated that over 70% of the sites sampled in Elliot Bay exhibited measurable toxicity with nine sites being highly toxic to both species of amphipods. Results of standard 28-day chronic sediment toxicity tests were similar. In contrast, almost all of the sites were found to be highly phototoxic. Results indicated that exposure to UV increased toxicity five- to eightfold. This suggests that standard toxicity tests underestimate the potential ecological risk of PAH-contaminated sediments in animals exposed to sunlight. However, only when PAH contamination was between 0.05 and 1.0 toxic units would conducting a phototoxicity evaluation add information to that gained from conducting a standard sediment toxicity test alone. Received: 12 July 1999/Accepted: 18 October 1999     

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.     

Effect of Nutrition on Toxicity of Contaminants to the Epibenthic Amphipod <Emphasis Type="Italic">Melita plumulosa</Emphasis>

The amphipod Melita plumulosa is commonly used to assess the toxicity of contaminated sediments. Seven-day-old M. plumulosa are <1 mm in size, and during 10-day tests in sandy sediments with low nutritional value, starvation can cause >50% mortality. In sediment toxicity tests, therefore, it can be difficult to determine if toxicity is due to contaminants or starvation, particularly in contaminated sandy sediments. This study investigated the influence of amphipod age and food addition on amphipod survival in toxicity tests. The 4-day LC₅₀ increased linearly from 120 to 470 μg/L when M. plumulosa age at the beginning of the test increased from 5 to 30 days. The addition of food as algae or fish food did not significantly affect the sensitivity of 11-day-old M. plumulosa (11-d Mp) to dissolved copper over 4 days in water-only tests. The survival of 11-d Mp in water-only tests over 10 days was poor without feeding, but when fed fish food, the 10-day LC₅₀ was 76 ± 15 μg/L. In sediment tests, feeding 0.063 mg fish food/amphipod on days 3 and 7 of 10-day tests consistently resulted in greater than 80% survival of 11-d Mp for a range of clean, sandy sediments, which had low amphipod survival without added food. Algae were not always suitable as a food source, as their growth can be stimulated by nutrients released from sediment and was inhibited by contaminants. The toxicity of most contaminated sediments was not ameliorated by the addition of food, suggesting that food addition was suitable for inclusion in routine testing protocols for this amphipod. An erratum to this article can be found at     

Sediment Toxicity Assessment: Comparison of Standard and New Testing Designs

Standard methods of sediment toxicity testing are fairly well accepted; however, as with all else, evolution of these methods is inevitable. We compared a standard ASTM 10-day amphipod toxicity testing method with smaller, 48- and 96-h test methods using very toxic and reference sediments. In addition we compared parallel exposures of single species, either the amphipod Ampelisca abdita or the mysid Americamysis bahia, to multiple species, mysid, and amphipod, cohabiting the same types of chambers. These comparisons were performed for both water-only and sediment-water tests. Results of the comparison of the standard ASTM 10-day amphipod test with the smaller, 48- and 96-h test chambers indicate that survival was high in both test designs using the reference sediment. With toxic sediments, complete mortality occurred in less than 48 h using the smaller experimental chambers and only after 96 h in the larger experimental chambers. We concluded that although time to death is shorter in the smaller, shorter exposure chambers, there was no overall change in mortality for the organisms, and that the smaller chambers were predictive of the results obtained with larger chambers and longer exposures. For multiple species testing in whole sediment exposures there was no change in toxicity to either the amphipod or the mysid when they cohabited the same chamber. In contrast, for water-only exposures, A. bahia demonstrated less sensitivity when cohabiting the same chamber as A. abdita. Therefore, during whole sediment testing we can add A. bahia and A. abdita to the same test chamber without changing the toxicity to either species; however, in our 10-ml water-only exposures, the species should be tested separately. Received: 16 November 1999/Accepted: 13 May 2000     

Effects of Copper Sulfate on Typha latifolia Seed Germination and Early Seedling Growth in Aqueous and Sediment Exposures

The vascular macrophyte Typha latifolia Linnaeus (common cattail) may be a sentinel for evaluating potential phytotoxicity to rooted aquatic macrophytes in aquatic systems. To further evaluate the potential utility of this species, T. latifolia seed germination, shoot growth, and root elongation were measured in 7-day aqueous exposures using mean measured aqueous copper concentrations of 10.0, 23, 41, 62, 174, and 402 μg Cu/L, which were ≥ 62% of nominal concentrations. Seed germination and seedling shoot growth were not significantly affected by any of these copper concentrations as compared to controls. Mean measured no-observed-effect-concentration (NOEC) and lowest-observed-effect-concentration (LOEC) for root elongation were 18.6 μg Cu/L and 35.0 μg Cu/L, respectively. Seven-day sediment tests were conducted by amending uncontaminated sediments with copper sulfate to mean measured concentrations of 7.9, 17.1, 21.0, 51.2, 89.5, and 173.5 mg Cu/kg, which were ≥ 84% of nominal concentrations. Seed germination was not significantly different from controls. Mean measured NOEC and LOEC values for seedling shoot growth were 89.5 mg Cu/kg and 173.5 mg Cu/kg, respectively, and mean measured NOEC and LOEC values for root growth were 14.0 mg Cu/kg and 19.7 mg Cu/kg, respectively. These results demonstrate that T. latifolia early seedling growth can be utilized for assessing aqueous and sediment toxicity of copper. Received: 21 March 2000/Accepted: 28 August 2000     

Influence of Aqueous Sediment Extracts from the Oder River (Germany/Poland) on Survival of Diplostomum sp. (Trematoda: Diplostomidae) Cercariae

Laboratory experiments were carried out to test whether the life span of Diplostomum sp. cercariae is affected by contamination of its aquatic environment. Freshly emerged cercariae therefore were exposed to either standardized water, Oder River (Germany/Poland) or Lake Odersee (Germany) extracts of aqueous sediments; mortality patterns and mean survival times (MSTs) were compared. Cercariae added to extracts of aqueous sediments from the Oder River and Lake Odersee exhibited impaired survival with significantly different mortality pattern and reduced MST compared to that of controls. A significant negative correlation (r =−0.843, p < 0.05) was found between MST and mercury content of sediments, indicating a potential impact of mercury on survival of Diplostomum sp. cercariae. The results indicate that contamination of freshwater habitats may influence the viability of free-living transmission stages of helminth parasites of fish and may thus be of epizootiological significance. Received: 11 June 2000/Accepted: 26 October 2000     

Chemical Analysis and Sediment Toxicity Bioassays to Assess the Contamination of the River Lambro (Northern Italy)

This study consisted of a 10-day whole sediment toxicity test with the chironomid Chironomus riparius and a 28-day sediment toxicity test with the oligochaete Tubifex tubifex at seven sites to assess the quality of the River Lambro (Italy), one of the most contaminated rivers of the Po Basin. Endpoints measured were survival and growth for chironomids and cocoon deposition and development of young worms for tubificid oligochaetes. Responses were evaluated in relation to the occurence of organic micropollutants (PCBs, DDT, HCB, and HCH) representative of the industrial and agricultural contamination of the area. Though survival of the organisms remained unaffected, sublethal effects were observed at all sites. The sediment sampled at the farthest upstream site differed from the control only in the number of cocoons deposited by the worms. Both test species in the next three sediments, where concentrations of PCB and DDT were in the range 21.9–39.5 ng g^–1 DW and 0.6–1.3 ng g^–1 DW, respectively, experienced greater toxicity in terms of growth and reproduction. Contamination was particularly high in the site closest to Milan, where the river receives untreated urban and industrial discharges. Levels of total PCBs and total DDT here were up to two orders of magnitude higher than those found at the other sampling locations, and chironomid growth and the reproductive endpoints of tubificids were significantly lower than in the control and the other sites. The test results for the next two stations showed improvement relative to that of Milan, although contamination was still evident. Sublethal effects were in agreement with the measured concentrations of the principal persistent organic pollutants and should be included as part of environmental monitoring efforts as a basis for assessing the recovery of the river. Received: 9 June 2002/Accepted: 24 January 2003     

Chemical extractions of heavy metals in sediments as related to metal uptake by grass shrimp (Palaemonetes pugio) and clam (Mercenaria mercenaria)

Sediments from four sites in the Hampton Roads Harbor and Elizabeth River system were subjected to solid phase bioassays usingPalaemonetes pugio andMercenaria mercenaria. Metal levels in both organisms after exposure to the sediments varied little between sites; there was no difference in metal uptake between organisms exposed to the test sediments and to the reference sediment. All of the test sites would be acceptable for ocean disposal with respect to the tested metals. Metals concentrations inPalaemonetes were generally greater thanMercenaria. The amounts of metals extracted from the sediments were in the order of Conc HNO₃+H₂O₂>1N HNO₃>DTPA. Differences in metal levels in the Conc HNO₃+H₂O₂ and DTPA extracts from different sediments were generally significant and related to sediment type and sampling location. Since there was no significant difference in the concentrations in tissue for either organism, there was no correlation of metal uptake with the sediment extraction method. Out of four sites and metals studied with two test organisms, there were only four instances of bioaccumulation. Data from sediment extractable metals and metal/Fe ratios indicatedPalaemonetes were enriched with respect to the sediment in Cr, Cu, Ni, Pb, and Zn;Mercenaria were enriched with Pb and Zn.     

Toxicity Evaluation of Waters from a Tributary of the River Po Using the 7-DayCeriodaphnia dubiaTest

Seven-day toxicity tests withCeriodaphnia dubiawere used to assess ambient water toxicity in the River Lambro, a tributary of the River Po, and in the corresponding stretch of the main river located downstream from their confluence. About once a month, toxicity tests were conducted on water samples of the River Lambro, using as dilution water the water of the main river collected upstream from the confluence. With a lower frequency, the downstream stretch of the River Po was tested for ambient toxicity at four sites located at 6, 11, 16, and 21 km from the emission of the tributary. The River Lambro demonstrated variable toxicity in different time periods, although the most frequent effects were sublethal, on both reproduction and growth. Ammonia, nickel, and zinc can be indicated as possible toxicants. Acute toxic effects toC. dubiawere observed with spring samples only, when the action of some pesticides, likely insecticides, have to be taken into account. Tests conducted on downstream water gave limited results, seemingly because the dilution capacity of the River Po reduced Lambro toxicity to a level close to and often below the detection limit of the 7-day test. Accordingly, toxic effects at downstream sites could only be observed on the growth ofC. dubia,which was found to be the most sensitive endpoint. Fairly good agreement was found between predictions based on toxicity tests of the River Lambro and the effects observed for downstream samples.     

DDT Toxicity and Critical Body Residue in the Amphipod Leptocheirus plumulosus in Exposures to Spiked Sediment

The lethal and sublethal toxicity of dichlorodiphenyltrichloroethane (DDT) to the estuarine amphipod Leptocheirus plumulosus was determined using sediment spiked with ¹⁴C-labeled compound. Juvenile amphipods were exposed to concentrations up to 9.9 nmol/g dry weight (3.5 μg/g). Acute effects on survival were determined in a 10-day experiment. Chronic effects on survival, growth, and reproduction were assessed in a 28-day experiment. The DDT in the sediments transformed to dichlorodiphenyldichloroethane (DDD), dichlorodiphenyldichloroethylene (DDE), and polar metabolites during the 14-day sediment storage prior to exposing the amphipods. The mixture of DDT and its breakdown products (tDDT) was comprised mostly of DDT at the beginning of the exposures. DDD was the prevalent compound at termination of the 28-day exposure. Complete mortality occurred at sediment concentrations of tDDT as low as 7 nmol/g (2.3 μg/g) in both acute and chronic experiments. Most of the mortality appeared to have occurred within the first 4 days of exposure. No sublethal reductions in growth or reproduction were observed in the 28-day experiment. In the 10-day experiment, where amphipods did not receive supplemental food, growth was significantly increased in DDT treatments where survival was not affected. The concentration of tDDT in amphipod tissues was determined at exposure termination. In the 10-day experiment, a mean body residue of 14 nmol/g wet weight was associated with significant mortality (30%). Lower critical body residues were observed in the 28-day experiment, where the median lethal tissue residue (LR₅₀) was 7.6 (6.8–8.4, 95% confidence interval) nmol/g wet weight. Based on previous studies, the lethal critical body residue for L. plumulosus is similar to those determined for freshwater amphipods and substantially lower than those determined for cladocerans and polychaetes. Received: 8 November 2000/Accepted: 19 March 2001     

Bioaccumulation and elimination of Hg in the fireworm Eurythoe complanata (Annelida: Polychaeta) from Mazatlan, Mexico

Mercury accumulation and elimination by Eurythoe complanata were evaluated through two laboratory bioassays in the absence (bioassay A) and presence (bioassay B) of sediment. Ten individuals per treatment (three replicates) were exposed to Hg in solution (0, 1.5, 1.7, 3, 7.4, 8.7, 9, and 11 μg/L) for an 8-day exposure period. At the beginning of the elimination period, the solutions (both bioassays) and sediments (bioassay B) were replaced by seawater only and clean sediment, respectively. This period lasted 8 days. The effect of Hg concentrations on Hg accumulation by worms from bioassay A was confirmed by the Kruskal-Wallis test (H = 19.43, df = 7, χ² = 18.475, p = 0.01), whereas this effect was nonsignificant for bioassay B. Specimens from bioassay A accumulated about double the Hg than those of bioassay B. This indicates that sediment plays an important role in the bioaccumulation process. Mercury elimination was observed only on specimens from bioassay B, where 25% to 36% of the total Hg was eliminated during 8 days. This suggests that worms need a longer period of time to completely depurate the accumulated Hg. The Hg balance was performed at the beginning and end of the experimental periods. The total Hg percentage per aquarium decreased at the end of the experiment, which suggests that a considerable amount of Hg was evaporated or adhered to the aquarium walls. This first approach points out that experimental studies using E. complanata as a test species can be useful to evaluate the potential risk produced by Hg or other toxicants on marine biota inhabiting zones subjected to anthropogenic activities.     

Polybrominated Diphenyl Ethers (PBDEs) and Polychlorinated Biphenyls (PCBs) in 0+ Juvenile Cyprinids and Sediments of the Po River

PBDE and PCB content has been determined in 0+ bleak (Cyprinus alburnus), nase (Chondrostoma soetta), gudgeon (Cyprinus gobio), chub (Cyprinus cephalus), and barbel (Barbus sp.) as well as in bed sediments sampled from the River Po upstream and downstream of the confluence of a tributary draining a highly industrialized and urbanized subbasin. Both groups of chemicals were present at higher levels in fish and sediments downstream from the confluence. In addition, whole-body concentrations of PBDEs and PCBs were different among species despite the young specimen age. The fact that PBDEs and PCBs were higher in benthivorous versus planktivorous fish, as well as in carnivorous versus herbivorous species, suggests that feeding behavior is a major controlling factor that may help differentiate the accumulation levels of 0+ juveniles. Of the five species, the pelagic/planktivorous cyprinid bleak (C. alburnus) showed the lowest concentrations (111 ng PBDE/g lipid weight [l.w.], 2016 ng PCB/g l.w.), whereas the benthic dweller and feeder barbel (Barbus sp.) had the highest concentrations of both groups of chemicals (259 ng PBDE/g l.w., 4785 ng PCB/g l.w.). The rank order of species contamination was essentially stable upstream and downstream from the tributary, and the congener contribution of PBDEs was also similar. In general, BDE-47 was the dominant congener, followed by BDE-100, -154, -153, and -28. BDE-209 dominated the PBDE congener profiles of sediments but was not found in any fish sample. Conversely, an unidentified hexa-BDE congener, which was not detected in sediments, was found in all fish species. The levels of PBDEs and PCBs determined in adult goby (Padogobius martensii), a small demersal predator also examined in the same river stretches, provided additional useful insights with which to interpret results.     

Chronic Effects of the Herbicide Diuron on Freshwater Cladocerans, Amphipods, Midges, Minnows, Worms, and Snails

The chronic effects of the herbicide diuron on survival and reproduction of Daphnia pulex, and survival and growth of the amphipod Hyalella azteca, the midge Chironomus tentans, juvenile and embryo/larval fathead minnows, Pimephales promelas, annelid worms, Lumbriculus variegatus, and snails, Physa gyrina, were determined in laboratory static and static-renewal tests. D. pulex 96-h and 7-day LC50 values were 17.9 and 7.1 mg/L; 7-day LOAEL and NOAEL values based on mortality and reproduction were 7.7 and 4.0 mg/L. H. azteca 96-h and 10-day LC50 values were 19.4 and 18.4 mg/L; 10-day LOAEL and NOAEL values based on survival and reduced weight were 15.7 and 7.9 mg/L. C. tentans 10-day LC50 value was 3.3 mg/L; 10-day LOAEL and NOAEL values based on growth were 7.1 and 3.4 mg/L, and 3.4 and 1.9 mg/L based on mortality. Juvenile fathead minnows had a 10-day LC50 of 27.1 mg/L and 10-day LOAEL and NOAEL values based on growth of 3.4 and <3.4 mg/L. The fathead minnow embryo-larval test had a 7-day LC50 value of 11.7 mg/L and 7-day LOAEL and NOAEL values based on reduced growth of 8.3 and 4.2 mg/L. L. variegatus had 10-day LOAEL and NOAEL values based on reduced weight of 3.5 and 1.8 mg/L. P. gyrina had 10-day LOAEL and NOAEL values based on reduced weight of 22.8 and 13.4 mg/L. Laboratory effects concentrations were higher that those found in normal field application situations, except in areas of localized pooling after recent herbicide applications, indicating that there would probably be little harm to these fish and invertebrates from diuron exposure in the field. Received: 18 January 1998/Accepted: 28 March 1998     

Effects of Benzo(a)pyrene and Size of Organic Matter Particles on Bioaccumulation and Growth of Asellus aquaticus

The effects of sediment-bound toxicants to aquatic invertebrates may vary due to differences in bioavailability, food quality, or food structure. The equilibrium partitioning theory (EPT) assumes that organic matter content of sediments and not structure of organic matter is relevant for biological effects of polycyclic aromatic hydrocarbons. To test this hypothesis effects of benzo(a)pyrene (B(a)P) and size of sediment organic matter particles on the bioaccumulation and growth of the waterlouse Asellus aquaticus were studied in laboratory microcosms. Sediments and A. aquaticus were both sampled in an unpolluted, spring-fed pond. The sampled sediment was divided into two portions. From one portion the size of the organic matter particles was mechanically reduced. One set of each sediment fraction (fine and coarse) was spiked with B(a)P and incubated for 3 weeks resulting in a concentration of 70 mg B(a)P per kg sediment. Bioassays of 32 days were performed in a 2 × 2 factorial design with four replicas of each treatment. The results showed that the growth of A. aquaticus was mainly influenced by the size of organic matter particles. Growth was significantly less (27%) on finer sediments than on coarser sediments. The increase in length was 9–14% lower in the spiked sediments, but this difference was not significant. The reduced growth of A. aquaticus on finer sediments may be due to a change in the availability and/or quality of food together with a change in feeding behavior. The coarse and fine spiked sediment types did not differ significantly with respect to the sediment water partition coefficient, the organic carbon water partition coefficient, and the bioconcentration factor. In contrast, the biota to sediment accumulation factors were significantly 15% higher in the cosms with coarse sediments than in cosms with fine sediments. However, this difference is too small to conflict with EPT. Received: 9 November 1999/Accepted: 3 May 2000     

Ecotoxicity Assessment of Contaminated Dredged Material with the Marine Amphipod Corophium volutator

The incorporation of toxicological data from bioassays can improve the present system of sediment quality criteria in the Netherlands. The use of acute lethality toxicity tests alone does not however provide sufficient discrimination and sensitivity for predicting ecological effects of slightly and moderately contaminated dredged material. Sublethal endpoints are needed for the assessment of environmental hazards of such dredged material. In this study, two approaches were used to identify toxicity of marine sediments collected from 16 locations classified as “slightly and moderately contaminated” on the basis of chemical data: (1) a comparison of growth vs. mortality as different endpoints in the marine amphipod Corophium volutator (Pallas); (2) an investigation on the use of sediment dilutions to characterize the degree of toxicity. The influence of sediment storage time on toxicity was also evaluated. In four out of 16 locations, mortality over 10 days of exposure ranged 80–100%; in two out of 16 locations mortality ranged 40–60%. In the other 10 locations, mortality was below 15%. Results on growth showed that in all locations final dry weight values were significantly lower (a factor of 1.5 to 3) than in controls. Results of dilution experiments showed that if sediments were diluted with a reference sediment of similar physicochemical characteristics, total concentrations of metals, mineral oil, and PAHs decreased as expected and so did the effects on C. volutator. In the 100% contaminated sediments growth was reduced by 32–60% compared to controls. The dilution rate necessary to reduce toxicity to the EC₁₀ value for growth of C. volutator was considered an appropriate endpoint for the evaluation. When sediments were stored for a period of 3–5 months at 4°C and retested, effects on mortality and growth decreased, although some effects on growth were still measured after 5 months of storage. The experiments illustrate the usefulness of ecotoxicity assessment to evaluate contaminted dredged material. Received: 10 March 1997/Accepted: 6 November 1997