Chronic Sediment Toxicity Research Articles

Amphipod acute and chronic sediment toxicity assessment in estuarine environmental monitoring: An example from Ria de Aveiro, NW Portugal

This paper presents a comprehensive estuarine sediment toxicity survey, using acute and full life-cycle tests with an indigenous species, the amphipod Corophium multisetosum. In the acute test, adult specimens were exposed to sediments from 144 sites for 10 days. In the full life-cycle test, 5–7 days old specimens, obtained in laboratory cultures, were exposed during 21 days to sediments from 56 sites. Three endpoints were considered: survival, for the acute and the chronic test and fecundity (number of gravid females per replicate at the end of the exposure) and growth (weight increase), for the chronic test. In the acute tests, adult survival was high overall and almost no stressed areas could be recognized in the estuary. This image was not reflected by the chronic endpoints, in particular growth and fecundity, which, corrected for the number of survivors, was the most affected descriptor. The chronic data could not be related to the baseline sediment variables analysed (grain-size, total organic content and redox potential), suggesting that these play no part in the biological responses. Results indicate that a tiered sediment bioassessment approach including an initial comprehensive ecotoxicological screening phase should not rely solely upon acute responses, although these are obtained from simpler and more rapid laboratory testing procedures.

An Integrated Case Study for Evaluating the Impacts of an Oil Refinery Effluent on Aquatic Biota in the Delaware River: Integration and Analysis of Study Components

ABSTRACT A series of statistical and graphical techniques incorporating a “weight of evidence” approach were used to interpret results from an integrated Triad case study designed to determine potential environmental impacts to aquatic biota in the Delaware River that may be linked to PAHs found in Motiva's oil refinery effluent. Sediment concentrations of various metals, PCBs and LMW PAHs exceeding both ERL and ERM sediment quality guidelines (SQGs) were reported in the study area. However, most chemical contaminants did not exceed their respective SQGs. Results from a long-term sediment coring study indicated that there was no evidence of significant historical PAH contamination of sediments related to Motiva's exceedences. PAHs comprising the Motiva “fingerprint” were found in the surficial sediments at four near-field sites but non-Motiva PAH concentrations (background) were shown to be significantly higher at other far-field sites (non-Motiva influence). Chronic sediment toxicity appears to have significant relationships to the patterns of most PAH isomers, certain PCB isomers, and certain metals. However, sediment toxicity does not appear to be related to the PAH isomers that are characteristic of Motiva's effluent nor to the near-field sites. Impacted benthic communities were reported in the study area, primarily at one near-field and two far-field sites. However, there were no apparent relationships between benthic community health and sediment contaminants. The status of benthic communities does not appear to be related to PAHs derived from the Motiva effluent. The “weight of evidence” analysis developed from a systematic and comprehensive series of statistical and graphical assessments indicates that, although the study area displayed some degree of sediment contamination, chronic sediment toxicity, and benthic health impacts, these environmental effects generally could not be related to Motiva's exceedences.

Multi-level assessment of chronic toxicity of estuarine sediments with the amphipod Gammarus locusta: I. Biochemical endpoints

We report on biomarker responses conducted as part of a multi-level assessment of the chronic toxicity of estuarine sediments to the amphipod Gammarus locusta. A companion article accounts for organism and population-level effects. Five moderately contaminated sediments from two Portuguese estuaries, Sado and Tagus, were assessed. Three of them were muddy and two were sandy sediments. The objective was to assess sediments that were not acutely toxic. Three of the sediments met this criterion, the other two were diluted (50% and 75%) with clean sediment until acute toxicity was absent. Following 28-d exposures, the amphipods were analysed for whole-body metal bioaccumulation, metallothionein induction (MT), DNA strand breakage (SB) and lipid peroxidation (LP). Two of the muddy sediments did not cause chronic toxicity. These findings were consistent with responses at organism and population levels that showed higher growth rates and improvement of reproductive traits for amphipods exposed to these two sediments. Two other sediments, one muddy and one sandy, exhibited pronounced chronic toxicity, affecting SB, MT induction (in muddy sediment), survival and reproduction. Potential toxicants involved in these effects were identified. The last sandy sediment exhibited some loss of DNA integrity, however growth was also enhanced. Present results, together with the organism/population-level data, and also benthic communities information, were analysed under a weight-of-evidence approach. By providing evidence of exposure (or lack of it) to contaminants in sediments, the biomarkers here applied assisted in distinguishing toxicants' impacts in test organisms from the confounding influence of other geochemical features of the sediments.

Multi-level assessment of chronic toxicity of estuarine sediments with the amphipod Gammarus locusta: II. Organism and population-level endpoints

This study aimed to test the performance of the amphipod Gammarus locusta (L.) in chronic sediment toxicity tests. It constitutes part of a multi-level assessment of chronic toxicity of estuarine sediments, integrating organism and population-level endpoints with biochemical markers responses. Here we account for organism and population-level effects, while biomarker responses were reported in a companion article. Five moderately contaminated sediments from Sado and Tagus estuaries were tested, comprising 3 muddy and 2 sandy sediments. These sediments either did not show acute toxicity or were diluted with control sediment as much as required to remove acute toxicity. Subsequent chronic tests consisted of 28-day exposures with survival, individual growth and reproductive traits as endpoints. Two of the muddy sediments induced higher growth rates in the amphipods, and improved reproductive traits. This was understood to be a consequence of the amount of organic matter in the sediment, which was nutritionally beneficial to the amphipods, while concurrently decreasing contaminant bioavailability. Biomarker responses did not reveal toxicant-induced stress in amphipods exposed to these sediments. One of the sandy sediments was acutely toxic at 50% dilution, but in contrast stimulated amphipod growth when diluted 75%. This was presumed to be an indication of a hormetic response. Finally the two remaining contaminated sediments showed pronounced chronic toxicity, affecting survival and reproduction. The sex ratio of survivors was highly biased towards females, and offspring production was severely impaired. The particulars of the responses of this amphipod were examined, as well as strengths versus limitations of the sediment test. This study illustrates the utility of this chronic test for toxicity assessment of contaminated estuarine sediments, with potential application all along Atlantic Europe.

Evaluation of a Multi-species Test System for Assessing Acute and Chronic Toxicity of Sediments and Water to Aquatic Invertebrates: Effects of Pentachlorophenol on Daphnia magna and Chironomus prasinus (6 pp)

Single-species toxicity tests are currently used as main tools for assessing effects in ecological risk assessments. Nevertheless, in higher-tier evaluations, alternative ecotoxicological methods can be required. Alternative methods should cover more realistic exposure conditions and/or additional species or endpoints. Water/sediment systems can be considered for covering additional exposure routes. A typical feature of water/sediment systems is the modification of exposure levels with time. The simultaneous exposure of different species within the same system can cover differences in sensitivity and relevance of exposure routes. The aim of this study was to develop a water/sediment test that could detect relevant effects on two selected species and explore the relevance of sediment and waterborne exposure routes. This alternative method may provide relevant information facilitating the design of microcosm and mesocosm studies. A multi-species water/sediment system was designed using two invertebrates: Chironomus prasinus a benthic detritivore invertebrate and Daphnia magna a pelagic filtering invertebrate was designed. Seven static water/sediments systems were built up: two controls and five treatments where sediments were spiked with NaPCP at nominal concentrations of 1.25, 2.5, 5, 10 and 20 mg/kg, respectively. Each system contained caged and free (unrestrained) Daphnia magna organisms to consider differences in the exposure route (through sediment and/or water column) and Chironomus prasinus organisms. Fate and partitioning of PCP within the water/sediment compartments were assessed. Acute (lethality) and chronic effects (reproduction) for Daphnia magna were monitored after 48 h and 16 days of exposure, respectively. Adult emergence and oviposition success of Chironomus prasinus were monitored at the end of test (16 days). Mortality and reproduction inhibition of Daphnia magna occurred at the two higher doses, corresponding to maximum measured PCP water concentrations of 1.95 and 0.746 mg/l, respectively. Chironomus prasinus was less sensitive to PCP than Daphnia magna. Concentrations inhibiting reproduction and provoking almost 100% adult mortality in D. magna only reduced slightly the emergence and reproduction of chironomids. The experimental design focussed on suitability of the system for assessing simultaneously assessing effects on D. magna and C. prasinus instead of calculations of toxicity endpoints for PCP. The results indicate that this experimental design can be useful to the field of sediment/aquatic toxicity testing, particularly through the comparison with single- species results. Assessment of relative contribution of two exposure routes for Daphnia magna and complementary chronic endpoints derived from two different species can be achieved. Another advantage is that differences in reproduction strategies of selected species (sexual vs. parthenogenetic) should permit one to detect mechanisms of action associated to with endocrine disrupters. The feasibility of a two-species test built-up in an artificial sediment/water system has been demonstrated. This experimental design represents a cost/effective test which can assess effects through water and sediment pathways and incorporates several relevant chronic endpoints in a single assay. By building on the experience gained, improvements for further test designs are discussed. Test validation with a set of model chemicals will contribute to address the effectiveness of the test developed as comparing compared to single- species tests.

The contribution of cobalt and manganese to the acute and chronic toxicity of sediments from Lake Molnbyggen and adjacent lakes around Leksand, Sweden

A number of studies of pollutants and their effects on the fish fauna of Lake Molnbyggen outside Leksand, Sweden have been focused on leachate from the municipal landfill (Lindbodarna), which is located above the lake. The aim of the present study was to test the toxicity of sediment from Molnbyggen and some adjacent lakes, in order to see if this could explain the causes of the effects on the fish. The sampling sites were selected in co-operation with the project group at the Swedish Environmental Protection Agency to make the results more easily comparable with those from other studies on the fish fauna in the area. Both acute and chronic tests were made with the crustacean Ceriodaphnia dubia, and the sediment samples were equilibrated with standard reference water prior to exposure. The exposures were made under standard conditions in the laboratory to make them more readily comparable between the sampling locations and with previous studies. The effects on survival and reproduction were monitored during 8 days. After that a series of Toxicity Identification Evaluation manipulations of the tested waters were made in order to identify the cause(s) of the toxicity. The results from the Toxicity Identification Evaluation tests pointed towards heavy metals as the cause of toxicity, and the analytical results of heavy metals in the water phase showed that the concentrations of six metals (Cd, Co, Mn, Ni, Pb and Zn) were significantly correlated with toxicity. The concentrations of these metals were also correlated with each other making it hard to separate cause and effect among the metals. However, the concentrations of Cd, Ni, Pb and Zn were below the expected effect concentrations, but the measured concentrations of Co and Mn were high enough to be probable causes of the observed experimental toxicity. There was no indication that lipophilic compounds should have caused these effects. Therefore, the result of this study was rather surprising, showing that heavy metals like cobalt and/or manganese which are not generally considered as environmentally problematic may be of environmental concern. Potential effects of cobalt and manganese could be mediated through the olfactory system, because both these metals have been observed to affect this system in fish. However, the link between such effects and those observed on reproduction in Lake Molnbyggen is vague.

Cyst-based toxicity tests XIII--development of a short chronic sediment toxicity test with the ostracod crustacean Heterocypris incongruens: methodology and precision.

Experiments were carried out with neonates of the freshwater ostracod Heterocypris incongruens to verify and complete previous choices of test parameters for a new culture/maintenance-free solid-phase microbiotest for freshwater sediments. From trials with increasing volumes of reference sediment, it was concluded that 300 microL was the most appropriate amount of substrate to be put in 12-cup multiwell plates with 2 mL of standard freshwater. Tests in 3-9 replicates eventually showed that six parallels were needed to have good assay precision (repeatability). Application of the final test protocol to oil-contaminated sediments from the St. Lawrence River in Canada revealed that the 6-day chronic ostracod microbiotest had less variation in repeated tests than did the 10-day contact assay with Hyalella azteca and hence can be considered more precise. Based on the 95% confidence intervals for mortality and growth of the ostracods in the controls (reference sediment) of the 56 tests carried out for the Canadian project, a validity threshold of 20% for mortality was eventually selected, in analogy with the acceptability limits applied in many chronic bioassays. A minimum length of 600 microm in the control sediment after 6 days' exposure was also taken as the threshold for good health of the test organisms and for reliable test conditions. The new microbiotest has been tailored in a handy and user-friendly new toxkit, the Ostracodtoxkit, which is particularly suited for cost-effective routine monitoring.

Effects of temperature and salinity on life history of the marine amphipod Gammarus locusta. Implications for ecotoxicological testing.

The life history of Gammarus locusta was analysed in the laboratory under the following temperature and salinity combinations: 20 degrees C-33/1000, 15 degrees C-20/1000 and 15 degrees C-33/1000 (reference condition). Life history analysis comprised survival, individual growth, reproductive traits and life table parameters. Compared to 15 degrees C, life history at 20 degrees C was characterised by at least a four-week reduction in the life-span, lower life expectancy, shorter generation time, faster individual growth, anticipation of age at maturity and higher population growth rate. These temperature effects constituted an acceleration and condensation of the life cycle, compared to the reference condition. Concerning salinity effects, with few exceptions, results show that overall this amphipod life history did not differ significantly between the salinity conditions tested. Regarding ecotoxicological testing implications, findings from this study indicate that the range of temperature and salinity conditions acceptable for testing was substantially expanded both for acute and chronic assays. A temperature of 20 degrees C or higher (for a salinity of 33/1000) is suggested for routine chronic sediment toxicity testing with G. locusta, in order to reduce the life cycle and consequently improve cost-effectiveness and standardisation. Results also suggest that a multiple-response approach, including survival, growth and reproduction, should be applied in chronic toxicity tests.

Metal bioavailability and toxicity through a sediment core

Sediment cores from Richard Lake near Sudbury, Ontario, were sectioned and analyzed for total metal content, plus metal bioavailability and toxicity to Hyalella azteca (after equilibration with oxygenated overlying water). Strong and similar sediment profiles were observed for Cd, Co, Cu and Ni in the sediment. However, these differed from metal bioavailability profiles (bioaccumulation by Hyalella and metals in overlying water). Bioavailability profiles for Cu also differed from those for Cd, Co or Ni. The deepest sediment layers, deposited prior to industrial development, were non-toxic. Sediment toxicity was attributed to Ni dissolution into overlying water. Moreover, differential bioavailability of Ni in surface and deeper sediment layers was observed. This can affect the interpretation of toxicity data for sediments collected by different methods (e.g. core vs. grab samples). Based on Pb-210 dating and trends in Ni in the core, chronic toxicity of surface sediments from Richard Lake might approach non-toxic levels in about 15 years.

Laboratory to field validation in an integrative assessment of an acid mine drainage–impacted watershed

AbstractAn integrative assessment was conducted in the Puckett's Creek watershed of southwestern Virginia, USA, to investigate the environmental impacts of acid mine drainage (AMD) inputs. Twenty‐one sampling stations were categorized into groups based on five degrees of AMD input: (1) none, (2) intermittent acidic/circum‐neutral AMD, (3) continuous acidic AMD, (4) continuous circum‐neutral AMD, and (5) receiving system stations with at least two levels of dilution. Bioassessment techniques included water/sediment chemistry, benthic macroinvertebrate sampling, laboratory acute water column toxicity testing, laboratory chronic sediment toxicity testing, and in situ toxicity testing with Asian clams (Corbicula fluminea [Müller]). Group 3 stations had significantly altered water chemistry (low pH, high conductivity, and high water column metals) relative to the other groups and significantly higher sediment iron concentrations. Both group 3 and group 4 stations had significantly decreased ephemeroptera‐plecoptera‐trichoptera richness and percent ephemeroptera abundance relative to unimpacted stations. Group 3 stations also had decreased total taxon richness. Water column toxicity testing was sensitive to AMD impacts, with samples from group 3 stations being significantly more toxic than those from groups 2 and 4, which in turn were more toxic than those from groups 1 and 5. Similar results were observed for in situ toxicity testing. No differences in sediment toxicity test survival and impairment results were observed among the station groups. Stepwise multiple linear regression and simple bivariate correlation analyses were used to select parameters for use in an ecotoxicologic rating system, which was successful in differentiating between two levels of environmental impact relative to stations receiving no AMD input.

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.

Sediment toxicity testing using large water–sediment ratios: an alternative to water renewal

Deterioration of overlying water quality during toxicity tests with benthic invertebrates is a serious problem with some sediments. One solution is periodic renewal of overlying water. However, this is either labour intensive or requires construction and maintenance of special equipment. Furthermore, water renewal has the potential for flushing toxic chemicals out of the test chamber and establishes nonequilibrium conditions between the water and sediment. An alternative is testing under static conditions using atypical test vessels (e.g. Imhoff settling cones) with a large water volume (1 l) overlaying a much smaller sediment volume (e.g. 15 ml). This results in dramatic improvement of overlying water quality compared to standard static toxicity tests. Compared to water renewal, the test method is much simpler, all toxic substances leached from the sediment are retained in the test vessel, and contaminant concentrations in water and sediment have more time to equilibrate. Chronic sediment toxicity tests (10–28 days) have been conducted successfully under these conditions with Chironomus riparius, Hexagenia sp., Hyalella azteca and Tubifex tubifex.

Selection of an appropriate life-cycle stage of Chironomus riparius meigen for use in chronic sediment toxicity testing

The first larval instar was identified as the most suitable life-cycle stage of the insect Chironomus riparius Meigen with which to initiate chronic sediment toxicity studies utilising the emergence of adults as the test end-point. The emergence of adults from formulated reference sediment was recorded in three test systems seeded with either individual eggs, egg-rope sections or first instar larvae. Analysis of total adult numbers emerging revealed a significant difference between the three systems. The system seeded with individual first instar larvae resulted in 100% emergence of adults compared to 90% and 94% in the systems seeded with egg-rope sections and individual eggs respectively. In all three systems, the median emergence time (EmT50) for males was significantly less than that of the females in the corresponding system. Analysis of combined male and female EmT50 values demonstrated that adults arising from the system seeded with individual eggs emerged significantly earlier than their counterparts in the remaining two systems. The relevance of these results in relation to the standardisation of existing test procedures amongst various operating agencies is discussed.

Application of a benthic euryhaline amphipod, Corophium sp., as a sediment toxicity testing organism for both freshwater and estuarine systems.

The use of an as-yet-undescribed euryhaline Corophium sp. amphipod as a sediment toxicity testing organism was assessed. The species was found to be ubiquitous in many tidal areas of the Hawkesbury River catchment. The salinity of habitat sites ranged from 0.1 to 24 ppt, sediment total organic carbon (TOC) ranged from 0.4% to 3.5%, and the fines content (< 63 micron particle size) of the sediment ranged from 4.3% to 47.6%. Monitored populations ranged from a density of 59 to 6622 individuals per m2, with freshwater sites with a sediment fines content greater than 20% having the highest population densities. The sensitivity of the Corophium sp. was assessed by using copper chloride and ammonium chloride as reference toxicants in a 96-h static water-only test and a 10-day static sediment test. The LC50 for copper in freshwater-only exposures was 80 to 86 microg/L, using adult animals collected from the field. In contrast, the LC50 for copper in freshwater sediment and the sediment pore water were 840 mg/kg (dry weight) and 99 microg/L, respectively. The LC50 for ammonia (total) in freshwater-only at pH 7 was 5.5 mg/L. In contrast, the LC50 for ammonia (total) in freshwater sediment and the sediment pore water were 110 mg/kg (dry weight) and 6 mg/L, respectively. Laboratory cultures of 5 per thousand to 15 per thousand salinity were optimal for supporting the release of juveniles. Juveniles collected from laboratory cultures had a LC50 for copper in 5 per thousand and 10 per thousand salinity of 9 microg/L and 28.5 microg/L, respectively, in water-only exposures. The juveniles would be suitable for use in the development of a chronic sediment toxicity test with growth as the endpoint.

Environmental Health Assessment of the Benthic Habitat Adjacent to a Pulp Mill Discharge. I. Acute and Chronic Toxicity of Sediments to Benthic Macroinvertebrates

In this study, we assessed the acute and chronic toxicity of sediments contaminated by bleached kraft pulp mill effluent (BKME). Sediments were collected in August 1991 and 1992, and May 1993 from eight stations exposed directly to the effluent and from four reference sites.Acute toxicity was determined for five macroinvertebrates (Hyalella azteca, Daphnia magna, Chironomus riparius, Hexagenia spp., and Tubifex tubifex) using pore water, elutriate, and bulk sediment exposures. Chronic toxicity was assessed using C. tentans and H. azteca (growth and survival) and D. magna and T. tubifex (reproduction) in bulk sediment exposures. Mortality declined with decreasing proximity to the outfall; acute toxicity (>20% mortality after 48 h)was observed at the two stations closest to the outfall (300 and 400 m). At 300 m, pore water was consistently more toxic than elutriate or bulk sediment phases, resulting in 100% mortality for all invertebrates except T. tubifex (23%). Elutriate exposures were toxic to C. riparius (88%), D. magna (54%), and Hexagenia (47%), but not H. azteca. Bulk sediments were toxic to Hexagenia (100%) and D. magna(88%), but not to C. riparius or H. azteca. In chronic tests, mortality in H. azteca and T. tubifex was highest at 300 and 400 m, indicating that toxicity observed in the short-term aqueous exposures adequately predicted long-term toxicity in bulk sediments. In both acute and chronic tests, mortality was significantly correlated with the concentration of extractable organic chlorines (EOCl) in the sediment, with LC50 values ranging from 4500 to 5500 mg EOCl/kg organic carbon. Growth of C. tentans larvae was depressed at 300 and 400 m in August 91 but enhanced in May 93 relative to the reference sites. Growth of H.azteca also declined near the outfall in August 91 sediments and was approximately one half that observed in 92/93 sediments; however, growth did not differ among stations in 92 or 93. Reproductive output in D. magna (neonates) and T. tubifex (cocoons) was highest at 300 and 400 m. In T. tubifex, the number of hatched young was lowest at these stations. This study provides evidence that toxicity may occur in sediments exposed to BKME, and emphasizes the need to incorporate sediment toxicity bioassessment as part of efforts directed toward remedial action in the pulp and paper industry.

Predicting chronic toxicity of sediments spiked with zinc: An evaluation of the acid‐volatile sulfide model using a life‐cycle test with the midge Chironomus tentans

AbstractThe development of sediment quality criteria for the cationic metals cadmium, copper, lead, nickel, and zinc has focused on the use of acid‐volatile sulfide (AVS) as the primary normalization phase for predicting interstitial pore‐water concentrations and bioavailability of the metals. To date, most of the research in support of AVS in this context has utilized short‐term laboratory exposures, with a relative paucity of information pertaining to long‐term exposures. The purpose of this study, therefore, was to investigate the use of AVS as a predictor of metal toxicity to a benthic organism in a long‐term laboratory exposure. Clean sediment was spiked with zinc to obtain nominal treatments ranging from −2.34 to 58.5 μg/g dry weight with respect to the molar difference between simultaneously extracted metal (SEM) and AVS. The test was initiated with newly hatched larvae of the midge Chironomus tentans and carried through one complete generation (56 d) during which survival, growth, emergence, and reproduction were monitored. When the molar difference between SEM and AVS (i.e., SEM – AVS) was &lt;0, the concentration of zinc in the sediment interstitial water was low and no adverse effects were observed for any of the biological endpoints measured. Conversely, when SEM – AVS exceeded 0, a dose‐dependent increase in the relative concentration of zinc in the pore water was detected. However, the absolute concentration of pore‐water zinc at each treatment declined over the course of the study, corresponding to an increase in sediment AVS and to a loss of zinc due to diffusion into the overlying water, which was renewed twice daily. Only when SEM – AVS exceeded 0 were significant reductions in survival, growth, emergence, and reproduction observed. Together, the chemical and biological data from this study compare favorably with observations made in short‐term exposures and thus support the use of AVS as a normalization phase for predicting toxicity in metal‐contaminated sediments.

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 a contaminated sediment on life history traits and population growth rate of Neanthes arenaceodentata (polychaeta: Nereidae) in the laboratory

AbstractThe effects of a highly contaminated sediment on life history traits and population dynamics of the nereid polychaete. Neanthes arenaceodentata Moore were assessed in a laboratory experiment Survival, growth and fecundity were measured for one generation of worms exposed to 40 and 10% Black Rock Harbor, Connecticut (BRH) sediment (a contaminated sediment), 100% reference (REF) sediment from central Long Island Sound (the control) and a no‐sediment treatment (to follow progress of pairing and reproduction) The BRH sediment did not affect survival or size of adults or number of broods Number of eggs per brood appeared to be lower in 40% BRH sediment than 10% BRH or REF sediment, but the difference was not significant (1,397, 1,621 and 1,556 eggs per brood, respectively) However, number of larvae per brood was significantly lower in the 40% BRH sediment than in 10% BRH or REF sediment (363, 770 and 850 larvae per brood, respectively) Number of juveniles appeared to be lower in 40% BRH than in the other sediment treatments, although the differences were not significant Size of juveniles did not differ in the sediment treatments The finite multiplication rate of population increase, λ, was the same for all treatments The lack of significant differences but the presence of some trends may indicate that 40% BRH sediment was not a high enough dose to produce significant effects Effects of BRH sediment on other species are discussed. In conjunction with an earlier study, this work demonstrates that population responses of life cycle tests with Neanthes arenaceodentata can be used to evaluate the chronic toxicity of sediments, which could provide comparative toxicological data to evaluate the relative sensitivity of this and other marine species and may serve as a model system to study questions in population biology