A comparison of acute and chronic toxicity methods for marine sediments

Development of a Sublethal Chronic Toxicity Test for the Northern Trout Gudgeon, Mogurnda mogurnda, and Application to Uranium, Magnesium, and Manganese

Many international guidance documents for deriving water quality guideline values recommend the use of chronic toxicity data. For the tropical fish northern trout gudgeon, Mogurnda mogurnda, 96-h acute and 28-d chronic toxicity tests have been developed, but both tests have drawbacks. The 96-h toxicity test is acute and has a lethal endpoint; hence it is not a preferred method for guideline value derivation. The 28-d method has a sublethal (growth) endpoint, but is highly resource intensive and is high risk in terms of not meeting quality control criteria. The present study aimed to determine the feasibility of a 7-d larval growth toxicity test as an alternative to the 96-h survival and 28-d growth tests. Once the method was successfully developed, derived toxicity estimates for uranium, magnesium, and manganese were compared with those for other endpoints and tests lengths within the literature. As a final validation of the 7-d method, the sensitivity of the 7-d growth endpoint was compared with those of 14-, 21-, and 28-d exposures. Fish growth rate, based on length, over 7 d was significantly more sensitive compared with existing acute toxicity endpoints for magnesium and manganese, and was similarly sensitive to existing chronic toxicity endpoints for uranium. For uranium, the sensitivity of the growth endpoint over the 4 exposure periods was similar, suggesting that 7 d as an exposure duration is sufficient to provide an indication of longer term chronic growth effects. The sensitivity of the 7-d method, across the 3 metals tested, highlights the benefit of utilizing the highly reliable short-term 7-d chronic toxicity test method in future toxicity testing using M. mogurnda. Environ Toxicol Chem 2021;40:1596-1605. © 2021 Commonwealth of Australia. Environmental Toxicology and Chemistry © 2021 SETAC.

Assessment of whole-sediment chronic toxicity using sub-lethal endpoints with Monocorophium insidiosum

A whole-sediment test with the infaunal amphipod Monocorophium insidiosum has been developed to assess the long-term effects exerted by sediment contamination on survival, growth rates and attainment of sexual maturity. Juvenile amphipods were exposed for 28 days to a control sediment (native sediment) and three sediment samples collected in sites of the Venice Lagoon, characterized by contamination levels ranging from low to moderate, and absence of acute toxicity toward amphipods. Growth rate was estimated as daily length (μm d^-1) and weight increments (μg d^-1). The long-term exposure to the test sediments affected significantly both growth rate and attainment of sexual maturity of the females of M. insidiosum. In contrast, survival was high and uniform among all the samples, despite the contamination gradient. The results suggest growth to be the more reliable and statistically relevant endpoint. Attainment of sexual maturity, although allowed the identification of detrimental effects, was affected by a higher among-replicates variance as compared with growth rates, and thus less reliable than growth for the identification of impairments. The significant impairments observed both on growth and attainment of maturity evidenced the need to address the monitoring, also in the Lagoon of Venice, towards the assessment of the long-term effects on benthic species.

Testing lagoonal sediments with early life stages of the copepod Acartia tonsa (Dana): An approach to assess sediment toxicity in the Venice Lagoon

The early-life stages of development of the calanoid copepod Acartia tonsa from egg to copepodite I is proposed as an endpoint for assessing sediment toxicity by exposing newly released eggs directly onto the sediment-water interface. A preliminary study of 5 sediment samples collected in the lagoon of Venice highlighted that the larval development rate (LDR) and the early-life stages (ELS) mortality endpoints with A. tonsa are more sensitive than the standard amphipod mortality test; moreover LDR resulted in a more reliable endpoint than ELS mortality, due to the interference of the sediment with the recovery of unhatched eggs and dead larvae. The LDR data collected in a definitive study of 48 sediment samples from the Venice Lagoon has been analysed together with the preliminary data to evaluate the statistical performances of the bioassay (among replicate variance and minimum significant difference between samples and control) and to investigate the possible correlation with sediment chemistry and physical properties. The results showed that statistical performances of the LDR test with A. tonsa correspond with the outcomes of other tests applied to the sediment-water interface (Strongylocentrotus purpuratus embryotoxicity test), sediments (Neanthes arenaceodentata survival and growth test) and porewater (S. purpuratus); the LDR endpoint did, however, show a slightly higher variance as compared with other tests used in the Lagoon of Venice, such as 10-d amphipod lethality test and larval development with sea urchin and bivalves embryos. Sediment toxicity data highlighted the high sensitivity and the clear ability of the larval development to discriminate among sediments characterized by different levels of contamination. The data of the definitive study evidenced that inhibition of the larval development was not affected by grain-size and the organic carbon content of the sediment; in contrast, a strong correlation between inhibition of the larval development and the sediment concentrations of some metals (Cu, Hg, Pb, Zn), acid-volatile sulphides (AVS), polychlorinated biphenyls (PCBs) and polynuclear aromatic hydrocarbons (PAHs) was found. No correlation was found with DDTs, hexachlorobenzene and organotin compounds.

Trace element accumulation and elutriate toxicity in surface sediment in northern Tunisia (Tunis Gulf, southern Mediterranean)

Metal concentrations in sediments were investigated in the Gulf of Tunis, Tunisia, in relation to anthropic activities along the Mejerda River and Ghar El Melh Lagoon, with effluents discharged into the gulf. Distribution of grain size showed that the silty fraction is dominant with 53%, while sand and clay averages are 34 and 12% respectively. Zn concentration increased in the vicinity of the Mejerda River while Pb was at its highest levels at the outlet of Ghar El Mehl Lagoon. Sediment elutriate toxicity, as measured by oyster embryo bioassays, ranged from 10 to 45% abnormalities after 24h, but no relation was found between metal concentration and sediment toxicity. The AVS fraction that represents monosulfide concentrations in the sediment was higher in the central part of the gulf than in the coastal zone. The results reveal the influence of AVS, TOC and grain size on metal speciation and sediment toxicity.

An integrated assessment of pollution and biological effects in flounder, mussels and sediment in the southern Baltic Sea coastal area

Organic and metal contaminants and biological effects were investigated in flounder, mussels, and sediments in the southern Baltic Sea coastal area in order to assess environmental quality status in that area. Four sites were selected, including two within the Gulf of Gdańsk (GoG). In biota and sediment at each site, DDTs dominated over PCBs and PBDEs were the least abundant among organic contaminants. Their concentrations decreased progressively outward from GoG. Among metal contaminants, the levels of Hg, Pb, and Cd were elevated in GoG. Biomarkers in flounder, EROD activity and DNA SB, showed moderate positive correlations with organic and metal contaminants. In flounder, the integrated biomarker index (IBR/n) presented a spatial trend coherent with chemical pollution index (CPI), but there was no clear spatial correspondence between IBR/n and CPI in mussels nor between sediment toxicity index (STI) and sediment CPI. The integrated assessment of contaminant and biological effect data against available assessment criteria indicated that in biota, the contaminant assessment thresholds were most often exceeded by CB-118, heptachlor, PBDE, and Hg (in the GoG sediments by p,p'-DDT, Hg and Cd), while of the biological determinants, the threshold was breeched by AChE activity in mussels in GoG. Applying the ICES/OSPAR traffic-light approach showed that of the 50 parameters assessed at each site, there were 18% of determinants in the red color category in the two GoG sites and 8% of determinants in the two sites outside GoG, which indicated that none of the four investigated sites attained good environmental status (GES).

Life stage sensitivity of the marine mussel Mytilus edulis to ammonia

Ammonia is an important contaminant to consider in all toxicity tests. It is especially important to consider the impacts of ammonia in test methods that use sensitive water column organisms exposed to sediments or sediment extracts, such as porewater and elutriate toxicity tests. Embryo-larval development toxicity tests, such as the 48-h method using Mytilus mussel species, are particularly sensitive to ammonia. To better understand the effect thresholds across different life stages of these mussels, 6 short-term (48-h) development toxicity tests and 3 21-d toxicity tests with different-sized juvenile mussels were conducted. Two of the juvenile mussel tests involved 21-d continuous chronic exposure to ammonia, whereas the third involved an acute 2-d ammonia exposure, followed by a 19-d recovery period. The embryo-larval development test method (50% effect concentration [EC50] = 0.14-0.18 mg/L un-ionized ammonia) was 2.5 times more sensitive than the juvenile mussel 21-d survival endpoint (50% lethal concentration = 0.39 mg/L un-ionized ammonia) and 2 times more sensitive than the most sensitive sublethal juvenile mussel endpoint (EC50 = 0.26 mg/L un-ionized ammonia). Further, it was found that the juveniles recovered from a 48-h exposure to un-ionized ammonia of up to 1.1 mg/L. The data generated suggest that the embryo development endpoint was sufficiently sensitive to un-ionized ammonia to protect the chronically exposed (21 d) juvenile mussels. Environ Toxicol Chem 2017;36:89-95. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Effects of harbor activities on sediment quality in a semi-arid region in Brazil

Tropical marine environments are rich in biodiversity and the presence of harbor activities in these areas can harm the coastal ecosystems. In this study, we assessed sediment quality of two harbors from a tropical region in Brazil by applying multiple lines-of-evidence approach. This approach included the integration of results on: (1) grain size, organic matter, organic carbon, nitrogen, phosphorus, trace metals, polycyclic aromatic hydrocarbons, linear alkylbenzenes, and tributyltin; (2) acute toxicity of whole sediments and chronic toxicity of liquid phases; and (3) benthic community descriptors. Our results revealed that the main contaminants detected in sediments from Mucuripe and Pecém Harbors were chromium, copper, nitrogen, zinc, and tributyltin. These toxicants arise from typical harbor activities. However, the changes in benthic composition and structure appear to depend on a combination of physical impacts, such as the deposition of fine sediments and the toxic potential of contaminants, especially in Mucuripe. Thus, apart from toxicants physical processes are important in describing risks. This information may assist in management and conservation of marine coastal areas.

Effects of novobiocin and methotrexate on the benthic amphipod Ampelisca brevicornis exposed to spiked sediments

The marine amphipod Ampelisca brevicornis was used as model organism of benthic macrofauna to assess the possible adverse effects of pharmaceuticals bound to sediments. Organisms were exposed to sediment spiked with novobiocin (NOV) and methotrexate (MTX) for 10 days in order to estimate the acute toxicity (lethal effects) produced by the two compounds. The surviving organisms were pooled and analyzed to determine their sublethal responses associated with different phases of metabolism (enzyme activities in phases I and II), oxidative stress (antioxidant enzyme activities and lipid peroxidation), and genotoxicity (DNA damage in the form of strand breaks). No lethal or sublethal effects were observed in the amphipods exposed to NOV. For organisms exposed to sediments spiked with MTX the results were found to calculate the concentration that was lethal to 50% of the organisms exposed in the toxicity tests (LC₅₀ of 30.36 ng/g). MTX also induced the metabolism of enzyme detoxification activities in phases I and II. Oxidative stress and DNA damage in particular were also observed, indicating responses associated with MTX's mechanism of action. Both mortality and the set of applied biomarkers allowed for the assessment of bioavailability, oxidative stress, and genotoxicity of NOV and MTX. The information obtained in this investigation can assist in ecological risk assessment of marine sediments contaminated by pharmaceuticals.

Challenges for using quantitative PCR test batteries as a TIE-type approach to identify metal exposure in benthic invertebrates

The epibenthic amphipod Melita plumulosa shows unique gene expression profiles when exposed to different contaminants. We hypothesized that specific changes in transcript abundance could be used in a battery of quantitative polymerase chain reaction (qPCR) assays as a toxicity identification evaluation (TIE)-like approach to identify the most relevant stressor in field-contaminated sediments. To test this hypothesis, seven candidate transcriptomic markers were selected, and their specificity following metal exposure was confirmed. The performance of these markers across different levels of added metals was verified. The ability of these transcripts to act as markers was tested by exposing amphipods to metal-contaminated field-collected sediments and measuring changes in transcript abundance via qPCR. For two of the three sediments tested, at least some of the transcriptomic patterns matched our predictions, suggesting that they would be effective in helping to identify metal exposure in field sediments. However, following exposure to the third sediment, transcriptomic patterns were unlike our predictions. These results suggest that the seven transcripts may be insufficient to discern individual contaminants from complex mixtures and that microarray or RNA-Seq global gene expression profiles may be more effective for TIE. Changes in transcriptomics based on laboratory exposures to single compounds should be carefully validated before the results are used to analyze mixtures.

The mismatch between bioaccumulation in field and laboratory environments: Interpreting the differences for metals in benthic bivalves

Laboratory-based bioaccumulation and toxicity bioassays are frequently used to predict the ecological risk of contaminated sediments in the field. This study investigates the bioassay conditions most relevant to achieving environmentally relevant field exposures. An identical series of metal-contaminated marine sediments were deployed in the field and laboratory over 31 days. Changes in metal concentrations and partitioning in both sediments and waters were used to interpret differences in metal exposure and bioaccumulation to the benthic bivalve Tellina deltoidalis. Loss of resuspended sediments and deposition of suspended particulate matter from the overlying water resulted in the concentrations of Cu, Pb and Zn (major contaminants) becoming lower in the 1-cm surface layer of field-deployed sediments. Lower exchange rates of overlying waters in the laboratory resulted in higher dissolved metal exposures. The prediction of metal bioaccumulation by the bivalves in field and laboratory was improved by considering the metal partitioning within the surface sediments.

The role of biomarkers in the assessment of aquatic ecosystem health

Ensuring the health of aquatic ecosystems and identifying species at risk from the detrimental effects of environmental contaminants can be facilitated by integrating analytical chemical analysis with carefully selected biological endpoints measured in tissues of species of concern. These biological endpoints include molecular, biochemical, and physiological markers (i.e., biomarkers) that when integrated, can clarify issues of contaminant bioavailability, bioaccumulation, and ecological effects while enabling a better understanding of the effects of nonchemical stressors. In the case of contaminant stressors, an understanding of chemical modes of toxicity can be incorporated with diagnostic markers of aquatic animal physiology to help understand the health status of aquatic organisms in the field. Furthermore, new approaches in functional genomics and bioinformatics can help discriminate individual chemicals, or groups of chemicals among complex mixtures that may contribute to adverse biological effects. Although the use of biomarkers is not a new paradigm, such approaches have been underused in the context of ecological risk assessment and natural resource damage assessment. From a regulatory standpoint, these approaches can help better assess the complex effects from coastal development activities to assessing ecosystem integrity pre- and post development or site remediation.

Development of acute and chronic sediment bioassays with the harpacticoid copepod Quinquelaophonte sp

Reliable environmentally realistic bioassay methodologies are increasingly needed to assess the effects of environmental pollution. This study describes two estuarine sediment bioassays, one acute (96 h) and one chronic (14 d), with the New Zealand harpacticoid copepod Quinquelaophonte sp. utilising behavioural and reproductive endpoints. Spiked sediments were used to expose Quinquelaophonte sp. to three reference compounds representing important categories of estuarine chemical stressors: zinc (a metal), atrazine (a pesticide), and phenanthrene (a polycyclic aromatic hydrocarbon). Acute-to-chronic ratios (ACR) were used to further characterise species responses. Acute sediment (sandy and low total organic content) 96 h EC50 values for the sublethal inhibition of mobility for zinc, atrazine and phenanthrene were 137, 5.4, and 2.6 µg/g, respectively. The chronic EC50 values for inhibition of reproduction (total offspring) were 54.5, 0.0083, and 0.067 µg/g for zinc, atrazine, and phenanthrene, respectively. For phenanthrene, a potentially novel mode of action was identified on reproduction. Quinquelaophonte sp. was found to be more sensitive than several other estuarine species indicating choice of test organism is important to characterising the effects of environmentally relevant levels of contamination. The bioassay sediment results demonstrate the sensitivity and suitability of Quinquelaophonte sp. as a tool for the assessment use of estuarine health.

Slow avoidance response to contaminated sediments elicits sublethal toxicity to benthic invertebrates

Advanced analytical techniques have identified the heterogeneity of sediments in aquatic environments which may impact the exposure of benthic organisms to contaminants. Acute and chronic toxicity associated with short, intermittent exposure to four field-collected contaminated sediments were assessed for the epi-benthic amphipod Melita plumulosa and the harpacticoid copepod Nitocra spinipes. Increasing the duration of exposure caused a decrease in survival of M. plumulosa and N. spinipes during 10-d bioassays. Increasing the frequency of exposure to a total exposure time >96-h resulted in a significant toxicity to M. plumulosa. Reproduction decreased for both species from exposure to contaminated sediment. For M. plumulosa, reproductive effects occurred for shorter exposures than the time taken to sense and avoid contaminant exposure. Thus, while avoidance behaviors may prevent acute lethality, slow responses may not prevent sublethal effects. Exposure of M. plumulosa to contaminated sediment appeared to cause a physiological change in females which reduced fecundity. This study indicates that sediment toxicity methods which utilize static continuous exposures may overestimate the toxicity that would occur at a field location. However, by preventing organisms from avoiding unfavorable sediments, these methods provide a precautionary assessment of possible effects, which is usually the aim of most assessments frameworks.

Selection of methods for assessing sediment toxicity in California bays and estuaries

Toxicity tests are often used in sediment assessment programs. However, the choice of methods has been largely limited to acute tests. Where sublethal methods have been used, there has been little consistency among programs in the types of the sublethal tests used. The goal of this study was to develop a method for choosing a suite of acute and sublethal tests for use in a California statewide assessment program, and to develop a set of method-specific thresholds for classifying the degree of toxicity within a multiple line of evidence framework consisting of sediment chemistry, benthic community structure, and sediment toxicity. A group of candidate methods was evaluated using feasibility and performance criteria. Toxicity thresholds were calculated based on test variability and sensitivity. As a result of the evaluation, 3 acute toxicity methods using amphipods (Eohaustorius estuarius, Rhepoxynius abronius, and Leptocheirus plumulosus), and 2 sublethal methods using a polychaete and mussel embryos (Neanthes arenaceodentata growth and Mytilus galloprovincialis embryo development at the sediment-water interface) were selected for recommendation. Thresholds for toxicity categories corresponding to Nontoxic, Low Toxicity, Moderate Toxicity, and High Toxicity were developed for each test method. Although these toxicity categories and thresholds provide a consistent framework for the interpretation of test results among different methods, additional research is needed to determine their effectiveness for predicting impacts to benthic communities.

An assessment of three harpacticoid copepod species for use in ecotoxicological testing

The relatively short life cycles of harpacticoid copepods makes them appropriate animals for use in tests that rapidly assess the acute, sublethal, or chronic effects of sediment contaminants. In this study, four harpacticoid copepod species (Nitocra spinipes, Tisbe tenuimana, Robertgurneya hopkinsi, and Halectinosoma sp.) were isolated from clean marine sediments, and procedures for laboratory culturing were developed. Halectinosoma sp. was abandoned due to handling difficulties. For the remaining species, the influence of food type and quantity on life-cycle progression was assessed. A mixed diet, comprising two species of algae (Tetraselmis sp. and Isochrysis sp.) and fish food (Sera Micron) was found to maintain healthy cultures and was fed during laboratory tests. Water-only exposure to dissolved copper (Cu) showed that the times (range) required to cause 50% lethality (LT(50)) were 24 (22-27) h at 50 μg Cu/l for T. tenuimana; 114 (100-131) and 36 (32-40) h for 200 and 400 μg Cu/l, respectively, for N. spinipes; and 119 (71-201) and 25 (18-33) h for 200 and 400 μg Cu/l, respectively, for R. hopkinsi. 96-h LC(50) (concentration causing 50% lethality) were also determined for adult N. spinipes exposed to cadmium, copper, zinc, ammonia, and phenol. A ranking system was generated based on the ease handling and culturing, rate of maturity, food selectivity and sensitivity to Cu. From this ranking, N. spinipes was determined to be the most suitable species for use in developing sediment-toxicity tests. The measurement of total reproductive output of N. spinipes during 10-day exposure to whole sediment was found to provide a useful end point for assessing the effects of sediment contamination.

Performance and sensitivity of rapid sublethal sediment toxicity tests with the amphipod Melita plumulosa and copepod Nitocra spinipes

Sublethal whole-sediment toxicity tests are an important tool for assessing the potential effects of contaminated sediments. However, the longer duration required for evaluating potential chronic effects may increase endpoint variability and test costs compared to survival endpoints. In the present study we compare the performance and sensitivity to contaminants of 10-d sublethal sediment toxicity tests with the amphipod Melita plumulosa and harpacticoid copepod Nitocra spinipes. For both tests, sublethal effects were consistently observed when sediment contaminant concentrations exceeded sediment quality guideline (SQG) concentrations. The response of these bioassays in metal-contaminated sediments was shown to conform ideally with respect to the mean SQG quotient calculated on the basis of the Australian and New Zealand lower SQG trigger value, with toxicity being observed only in those sediments where the mean quotient exceeded one. Better predictions of nontoxicity were obtained when dilute acid-extractable rather than total metal concentrations were used. Using the upper SQG, toxicity frequently occurred at mean quotients below one. The effects were generally consistent with predictions from the acid-volatile sulfide and simultaneously extracted metal model. Effects on reproduction of M. plumulosa were detected for sediments that did not cause effects on survival and highlighted the environmental relevance and importance of using these sublethal endpoints. When using four replicates for M. plumulosa and five replicates for N. spinipes, the endpoint variability (standard error) was less than 10%. Variations in sediment particle size and organic carbon content did not affect endpoint variability. Both species are relatively easily cultured in the laboratory, and the estimated effort and cost of achieving the sublethal endpoints is 1.5 times that of the acute survival test endpoints.