Negatives and Positives: Contaminants and Other Stressors in Aquatic Ecosystems.

Published research is reviewed to provide examples of both positive and negative interactions of contaminants and: climate change; habitat change; invasive and introduced species; and, eutrophication including harmful algal blooms. None of these stressor interactions results solely in negative effects. Research must shift from examining contaminants or other stressors in isolation to considering potential positive and negative effects of interactions, with the ultimate goal of providing the necessary information for the effective management of ecosystem services.

Total Suspended Solids Effects on Freshwater Lake Biota Other than Fish.

Protective benchmarks for the effects of total suspended solids (TSS) on freshwater aquatic biota primarily focus on fish; whether these benchmarks will also protect their prey or co-existing lower trophic level aquatic biota was uncertain. We conducted an extensive literature review of TSS effects on those organisms comprising the food webs upon which fish living in lakes depend: phytoplankton, zooplankton, periphyton, and benthic invertebrates. The available literature indicates that TSS benchmarks that protect sensitive life stages of lake fish will also protect their supporting food webs; in other words, the function of lake aquatic communities will be protected and maintained.

Effect of Total Dissolved Solids on Fertilization and Development of Two Salmonid Species.

Some studies have shown that the early life stages of salmonids are particularly sensitive to elevated concentrations of total dissolved solids (TDS). We evaluated the effect of TDS released in treated effluent into Snap Lake (Northwest Territories, Canada) by the Snap Lake Diamond Mine on two salmonids native to Snap Lake: Salvenius namaycush (lake trout) and Thymallus arcticus (Arctic grayling). Exposures encompassed the embryo-alevin-fry early life stages and extended to 142 days for lake trout and 69 days for Arctic grayling. Such extended testing is uncommon with these two species. Two exposures were conducted with each species, one initiated prior to fertilization, and the other subsequent to fertilization. Fertilization, survival, and growth were not adversely affected for either species by TDS at concentrations >1400 mg/L, with the exception of survival of lake trout, which produced an LC20 of 991 mg/L in one test, and >1484 mg/L in the second test. For the specific TDS composition tested, which was dominated by chloride (45 %-47 %) and calcium (20 %-21 %), the early life stages of these two fish species were relatively insensitive. Although some authors have suggested lower TDS regulatory limits for salmonid early life stages, our study indicates that this is not necessary, at least for these two fish species and for the specific ionic composition tested.

Effects of an oil spill on the regrowth of emergent vegetation in a northern Alberta Lake.

Following a train derailment in August 2005, Wabamun Lake (Alberta, Canada) was exposed to approximately 149,500 L of bunker "C" oil, much of which became entrained in the abundant Schoenoplectus tabernaemontani (= Scirpus validus) beds in the eastern basin of the lake. We assessed the regrowth of emergent macrophytes during the subsequent two growing seasons. Postspill measures of productivity, including transect length, total cover, and biomass were within the variability of prespill data collected in 2001, with the exception of a few specific areas in which biomass appeared to be affected. We conclude that exposure to oil during the late growing season in August 2005 and through the winter senescent period and regrowth in the summers of 2006 and 2007 did not cause large-scale changes to S. tabernaemontani communities. Physical factors such as cleanup activities and vegetation management appeared to be responsible for the reduced regrowth observed at some locations. Few previous studies have been published on the effects of oil spilled into freshwater on macrophyte communities; thus, the results of this study are expected to provide useful information for the assessment of future freshwater oil spills.

The importance of benthos in weight of evidence sediment assessments--a case study.

Sediment quality in a Texas reservoir subject to point and non-point sources of contaminants was assessed using the Sediment Quality Triad weight of evidence approach. Fifteen stations were sampled plus a reference station which, unfortunately, comprised a different habitat type than the other 15 stations. Accordingly, standard comparisons between reference and exposed stations were inappropriate. Interpretation of potential relationships between benthic community structure and sediment-associated contaminants was also confounded by differences in habitat-related characteristics (e.g., water depth and total organic carbon) within the reservoir. Multivariate analyses of the benthic community identified two station groupings separated primarily by habitat-related differences rather than contaminant-related toxicity. Laboratory toxicity tests and chemical analyses, including measures of bioavailability, did not differ consistently between the two community-based station groupings, indicating that toxicity resulting from chemical contamination was not the primary factor in observed community structure in the reservoir, although alterations to the benthos due to chemical contamination could not be ruled out in the absence of an appropriate reference comparison. Appropriately giving highest weight to resident benthic community structure, followed by the results of laboratory toxicity tests, then chemical analyses, provided the best possible assessment of chemical pollution in the absence of a suitable reference comparison. The alternative approach of relying on only sediment toxicity and chemistry data, without considering the full weight of evidence, would have provided misleading information.

Environmental quality benchmarks-the good, the bad, and the ugly.

Environmental quality benchmarks (EQBs) such as water or sediment quality guidelines comprise one line of evidence for assessing the potential harm from chemicals and other stressors (physical, biological). They are useful but not perfect tools, should not always be used, and should never be used alone for final decision-making. The "good" can be designed to be situation-specific and can provide understandable scientific input to decision-makers. The "bad" includes perception that they are absolutes (i.e., definitive binary decision points), no or limited adaptability based on good science or common sense, and protection of individual organisms not populations of organisms. The "ugly" includes benchmarks based on simplistic indices (information loss, misleading results), misuse of biomarkers, and misapplication of EQBs. Other factors to be considered include the following: appropriately deriving EQBs, uncertainty, the laboratory is not the field, contaminant uptake and cause-effect, and specifics regarding sediment quality benchmarks (i.e., their specific "good," "bad," and "ugly" components). EQBs are not always needed or useful.

Toward harmonizing ecotoxicity characterization in life cycle impact assessment.

Ecosystem quality is an important area of protection in life cycle impact assessment (LCIA). Chemical pollution has adverse impacts on ecosystems on a global scale. To improve methods for assessing ecosystem impacts, the Life Cycle Initiative hosted by the United Nations Environment Programme established a task force to evaluate the state-of-the-science in modeling chemical exposure of organisms and the resulting ecotoxicological effects for use in LCIA. The outcome of the task force work will be global guidance and harmonization by recommending changes to the existing practice of exposure and effect modeling in ecotoxicity characterization. These changes will reflect the current science and ensure the stability of recommended practice. Recommendations must work within the needs of LCIA in terms of 1) operating on information from any inventory reporting chemical emissions with limited spatiotemporal information, 2) applying best estimates rather than conservative assumptions to ensure unbiased comparison with results for other impact categories, and 3) yielding results that are additive across substances and life cycle stages and that will allow a quantitative expression of damage to the exposed ecosystem. We describe the current framework and discuss research questions identified in a roadmap. Primary research questions relate to the approach toward ecotoxicological effect assessment, the need to clarify the method's scope and interpretation of its results, the need to consider additional environmental compartments and impact pathways, and the relevance of effect metrics other than the currently applied geometric mean of toxicity effect data across species. Because they often dominate ecotoxicity results in LCIA, we give metals a special focus, including consideration of their possible essentiality and changes in environmental bioavailability. We conclude with a summary of key questions along with preliminary recommendations to address them as well as open questions that require additional research efforts. Environ Toxicol Chem 2018;37:2955-2971. © 2018 SETAC.

Determining when contamination is pollution - weight of evidence determinations for sediments and effluents.

Contamination is simply the presence of a substance where it should not be or at concentrations above background. Pollution is contamination that results in or can result in adverse biological effects to resident communities. All pollutants are contaminants, but not all contaminants are pollutants. Differentiating pollution from contamination cannot be done solely on the basis of chemical analyses because such analyses provide no information on bioavailability or on toxicity. Effects-based measures such as laboratory or field toxicity tests and measures of the status of resident, exposed communities provide key information, but cannot be used independently to determine pollution status. Laboratory studies can be predictive, but are rarely realistic. Measures of resident communities include innate natural variability and cannot easily distinguish between adaptation to contamination (a genetic process) and acclimation (a physiological process that may decrease energy reserves, possibly reducing such critical population-level parameters as reproduction). Finally, contaminant effects may not only be direct but also indirect; predicting such effects requires knowledge of the system under study as well as appropriate use of lines of evidence (LOE) such as toxicity tests directed to key species. Consequently, in sediments, effluents or other inputs/environmental compartments, determining when contamination is or may in future become pollution, requires a weight of evidence (WOE) assessment using different LOE appropriate to the situation under investigation. WOE investigations provide two different types of information: definitive conclusions regarding pollution; or, information as to what additional, investigative studies are necessary for definitive conclusions. Effectively, a WOE assessment comprises an initial screening-level ecological risk assessment (ERA), which may be followed by a detailed-level ERA if key uncertainties need to be resolved.

A control chart approach to monitoring and communicating trends in tissue selenium concentrations.

A primary aim of monitoring programs is to determine changes relative to background conditions, which typically represent a distribution of values, not a single value, and which may be elevated naturally. Graphical inspection of the statistical distribution of background and subsequent data provides the best means to determine changes over time and the relative significance of those changes based on both their magnitude and trajectory. The control chart approach commonly used in laboratory and product testing is a useful tool that allows for such determinations in a manner that is transparent to both scientists and nonscientists. This approach can be used both with true baseline (i.e., pre-development) data and with operational baseline (i.e., post-development) data and is particularly relevant for monitoring selenium (Se) tissue concentrations.

Assessing and managing stressors in a changing marine environment.

We are facing a dynamic future in the face of multiple stressors acting individually and in combination: climate change; habitat change/loss; overfishing; invasive species; harmful algal blooms/eutrophication; and, chemical contaminants. Historic assessment and management approaches will be inadequate for addressing risks from climate change and other stressors. Wicked problems (non-linear, complex, competing risks and benefits, not easily solvable), will become increasingly common. We are facing irreversible changes to our planetary living conditions. Agreed protection goals and considering both the negatives (risks) and the positives (benefits) of all any and all actions are required, as is judicious and appropriate use of the Precautionary Principle. Researchers and managers need to focus on: determining tipping points (alternative stable points); maintaining ecosystem services; and, managing competing ecosystem services. Marine (and other) scientists are urged to focus their research on wicked problems to allow for informed decision-making on a planetary basis.

Integrating causation in investigative ecological weight of evidence assessments.

Weight of evidence (WOE) frameworks integrate environmental assessment data to reach conclusions regarding relative certainty of adverse environmental effects due to stressors, possible causation, and key uncertainties. Such studies can be investigative (i.e., determining whether adverse impact is occurring to identify a need for management) or retrospective (i.e., determining the cause of a detected impact such that management efforts focus on the correct stressor). Such WOE assessments do not themselves definitively establish causation; they provide the basis for subsequent follow-up studies to further investigate causation. We propose a modified investigative WOE framework that includes an additional weighting step, which we term "direction weighting." This additional step allows for the examination of alternative hypotheses and provides improved certainty regarding possible causation. To our knowledge, this approach has not been previously applied in investigative ecological WOE assessments. We provide a generic example of 2 conflicting hypotheses related to a mine discharging treated effluent to a freshwater lake: chemical toxicity versus nutrient enrichment. Integr Environ Assess Manag 2017;13:702-713. © 2016 SETAC.

Revisiting the basis for US ballast water regulations.

The transport and release of invasive organisms in ballast water has harmed ecosystems, economic activities and human health. Current US ballast water regulations intended to minimize the discharge of such organisms are based on results reported by a scientific advisory committee in 2011. Using the same methods, we re-analyzed the data evaluated by the committee as well as new data. We find that the committee's analysis was flawed, and that some treatment systems can meet limits that are 10 times (for zooplankton) or 1000 times (for phytoplankton) more stringent than the committee reported. These findings suggest that US ballast water standards, and similar standards in a recently ratified international agreement, should be re-evaluated.

Assessing and managing multiple risks in a changing world-The Roskilde recommendations.

Roskilde University (Denmark) hosted a November 2015 workshop, Environmental Risk-Assessing and Managing Multiple Risks in a Changing World. This Focus article presents the consensus recommendations of 30 attendees from 9 countries regarding implementation of a common currency (ecosystem services) for holistic environmental risk assessment and management; improvements to risk assessment and management in a complex, human-modified, and changing world; appropriate development of protection goals in a 2-stage process; dealing with societal issues; risk-management information needs; conducting risk assessment of risk management; and development of adaptive and flexible regulatory systems. The authors encourage both cross-disciplinary and interdisciplinary approaches to address their 10 recommendations: 1) adopt ecosystem services as a common currency for risk assessment and management; 2) consider cumulative stressors (chemical and nonchemical) and determine which dominate to best manage and restore ecosystem services; 3) fully integrate risk managers and communities of interest into the risk-assessment process; 4) fully integrate risk assessors and communities of interest into the risk-management process; 5) consider socioeconomics and increased transparency in both risk assessment and risk management; 6) recognize the ethical rights of humans and ecosystems to an adequate level of protection; 7) determine relevant reference conditions and the proper ecological context for assessments in human-modified systems; 8) assess risks and benefits to humans and the ecosystem and consider unintended consequences of management actions; 9) avoid excessive conservatism or possible underprotection resulting from sole reliance on binary, numerical benchmarks; and 10) develop adaptive risk-management and regulatory goals based on ranges of uncertainty. Environ Toxicol Chem 2017;36:7-16. © 2016 SETAC.

Global geographic differences in marine metals toxicity.

Biochemical reaction rates, metabolic rates, and other rates of biological activity increase exponentially with temperature. It has thus been hypothesized that toxicity to chemical contaminants may increase from polar to temperate to tropical species; however, until recently, polar data to test this hypothesis were not available. This study examined differences in the acute sensitivities of marine invertebrates to four metals (Cu, Cd, Zn, Pb) for polar, temperate and tropical species; data deficiencies for polar regions prohibited comparisons using chronic end-points or other chemicals. Differences between the three geographic regions were not predictable based on temperature (other factors such as differences in dissolved organic carbon concentrations also affect toxicity). There appears to be no universal, predictable pattern of increased toxicity from polar to tropical regions. Toxicity data from one geographic region will not be universally protective of other regions.

Development of a total dissolved solids (TDS) chronic effects benchmark for a northern Canadian lake.

Laboratory chronic toxicity tests with plankton, benthos, and fish early life stages were conducted with total dissolved solids (TDS) at an ionic composition specific to Snap Lake (Northwest Territories, Canada), which receives treated effluent from the Snap Lake Diamond Mine. Snap Lake TDS composition has remained consistent from 2007 to 2014 and is expected to remain unchanged through the life of the mine: Cl (45%-47%), Ca (20%-21%), Na (10%-11%), sulfate (9%); carbonate (5%-7%), nitrate (4%), Mg (2%-3%), and minor contributions from K and fluoride. The TDS concentrations that resulted in negligible effects (i.e., 10% or 20% effect concentrations) to taxa representative of resident biota ranged from greater than 1100 to greater than 2200 mg/L, with the exception of a 21% effect concentration of 990 mg/L for 1 of 2 early life stage fish dry fertilization tests (wet fertilization results were >1480 mg/L). A conservative, site-specific, chronic effects benchmark for Snap Lake TDS of 1000 mg/L was derived, below the lowest negligible effect concentration for the most sensitive resident taxon tested, the cladoceran, Daphnia magna (>1100 mg/L). Cladocerans typically only constitute a few percent of the zooplankton community and biomass in Snap Lake; other plankton effect concentrations ranged from greater than 1330 to greater than 1510 mg/L. Chironomids, representative of the lake benthos, were not affected by greater than 1380 mg/L TDS. Early life stage tests with 3 fish species resulted in 10% to 20% effect concentrations ranging from greater than 1410 to greater than 2200 mg/L. The testing undertaken is generally applicable to northern freshwaters, and the concept can readily be adapted to other freshwaters either for TDS where ionic composition does not change or for major ionic components, where TDS composition does change.

Critical predicted no effect concentrations (PNECs) should not be based on a single toxicity test.

Predicted no-effect concentrations (PNECs), which represent the concentration of a substance below which an unacceptable effect most likely will not occur, are widely used for risk assessment and in environmental policy and regulation. They are typically based on single-species laboratory toxicity tests; often, a single test result for the most sensitive endpoints drives the derivation of a PNEC. In the present study, the authors provide a case study emphasizing the importance of determining the reliability of those most sensitive endpoints. Five 21-d Daphnia magna toxicity tests conducted using the same procedures by 2 laboratories gave 20% inhibitory concentration responses to a specific ionic composition of total dissolved solids that varied from 684 mg/L to more than 1510 mg/L. The concentration-response curve was shallow; thus, these differences could have been attributable to chance alone. The authors strongly recommend that the most sensitive endpoints that determine PNECs not be based on a single toxicity test result but rather on the geometric mean of at least 3 test results to adequately assess and bound test variability, especially when the concentration-response curve is shallow.

Quantifying natural variability as a method to detect environmental change: Definitions of the normal range for a single observation and the mean of m observations.

The normal range has been defined as the range that encloses 95% of reference values; in practice this range has been defined as the reference mean ± 2 standard deviations (SD). When sample sizes are small and reference data are not normally distributed, the mean ± 2 SDs do not enclose 95% of data values. Prediction intervals (PI) calculated using sample statistics are used in the present study to define the normal range for a single observation and the mean of m observations. The PIs provide confidence limits for the next randomly selected observation (or mean of m observations) from a population. The PIs are defined using normally distributed reference data; normality can typically be achieved with transformations of the data. Covariates can be used to explain some of the variability in the reference distribution, increasing the ability to detect change. When assumptions of normality are not met, alternative methods of defining the normal range are provided. The normal range can be used to quantify natural variability and assess change from the reference distribution. It can be used as an early warning indicator of change in environmental monitoring to identify the need for further investigation.

Ecological risk assessment (ERA) and hormesis.

Based on our current state of knowledge, the significance and importance of hormesis is likely to be greater for ecotoxicology, a component of ecological risk assessment (ERA), than for the overall process of ERA. Appropriately determining the role of hormesis in ERA will require extension of hormesis beyond chemical stressors to abiotic (e.g. habitat) and biotic stressors (e.g. species introductions, organism interactions). It will also require determining for all stressors whether at both individual and higher levels of organization, hormesis has positive, neutral or adverse effects. This determination must be made for model organisms, populations and communities. Adverse effects are the least likely, however, neutral effects cannot be ruled out. Presently, consideration of hormetic effects in ERA is most appropriate in a detailed level ecological risk assessment (DLERA), the most complex form of ERA. It is not appropriate in either problem formulation or a screening level ERA (SLERA). Further, for hormetic effects to be recognized and accepted fully into ERA may require a paradigm shift. Three on-going paradigm shifts to which hormesis could be linked are: recognition of the low utility of no-observed effects concentrations (NOECs); recognition of the need for special treatment of essential element dose/concentration-responses, which are similar to hormetic responses; and, the replacement of environmental toxicology with ecological toxicology (ecotoxicology).

Testing sediment biological effects with the freshwater amphipod Hyalella azteca: the gap between laboratory and nature.

The freshwater amphipod, Hyalella azteca, is widely used in laboratory sediment toxicity and bioaccumulation tests. However, its responses in the laboratory are probably very different from those in the field. A review of the literature indicates that in its natural habitat this species complex is primarily epibenthic, derives little nutrition from the sediments, and responds primarily to contaminants in the overlying water column (including water and food), not sediment or porewater. In laboratory sediment toxicity tests H. azteca is deprived of natural food sources such as algal communities on or above the sediments, and is subjected to constant light without any cover except that afforded by burial into the sediments. Under these constraining laboratory conditions, H. azteca has been reported to respond to sediment or porewater contamination. In nature, contamination of overlying water from sediment is less likely than in the laboratory because of the large, generally non-static sink of natural surface water. H. azteca does not appear to be the most appropriate test species for direct assessments of the bioavailability and toxicity of sediment contaminants, though it is probably appropriate for testing the toxicity of surface waters. Toxic and non-toxic responses will be highly conservative, though the latter are probably the most persuasive given the exposure constraints. Thus H. azteca is probably a suitable surrogate species for determining sediments that are likely not toxic to field populations; however, it is not suitable for determining sediments that are likely toxic to field populations.