The necessity of bioanalytical tools for advancing water and sediment quality assessment

What do we really mean when we say “poor water quality” or “poor sediment quality”? What do these words actually describe about the health of a particular aquatic system? It is easy to intuitively grasp the meaning of these phrases in a very general, very qualitative sense, they mean something is wrong, something is polluted or problematic, something has been altered, probably something needs to be fixed or requires societal attention. However, from a scientific perspective, water quality and sediment quality are not general or qualitative statements, these statements reflect the specific status of biological conditions following exposures to composite concentrations of diverse mixtures of chemical, microbiological, and macromolecular (DNA, nanomaterials, radioactive materials) substances present in an aquatic system. Substances with the capacity to impact biological health are often ubiquitous at some concentration in the aquatic and benthic environment. Water and sediment quality metrics reflect the collective impacts of many thousands of possible aquatic substances, although analytical efforts and bioassay endpoints tend to be more frequently dominated by a few important constituents which (hopefully) are measured directly or indirectly via environmental surveillance. Poor water or sediment quality typically reflects exposure to excess concentration(s) of toxic or harmful contaminants such as pesticides or metals, or a deficit in concentration of a necessary constituent (e.g., dissolved oxygen) that impairs the chemical, physical and biological integrity of the system for ecological (e.g., biodiversity, ecosystem services) and human (e.g., swimming, fishing, potable water supply) uses. Unacceptable risks to proper biological function arise from the presence of one or more conventional pollutants or bioactive contaminants whose concentration and bioavailability are driving the potential for impairment, although there are cases where a suite of constituents share a common molecular initiation event or are interacting in an antagonistic, synergistic or otherwise unexpected manner. From a regulatory perspective, assessments of environmental quality are dependent on the structure and implementation of protection systems, the capacity to deliver essential services, and the use of various prospective and retrospective tools (e.g., analytical chemistry, in vitro or in vivo bioassays, biological assessment) to evaluate the status of ecological and human health. These efforts are collectively intended to protect ecosystems and public health from adverse impairments arising from exposures to diverse stressors, including anthropogenic chemicals.

In all of these cases, the underlying motivation for characterizing water or sediment quality is the potential for adverse biological outcomes resulting from an exposure to a mixture of environmental stressors of chemical and/or biological origin. As a research community, it is most important to recognize that biology is the critical context: the relationships between environmental quality and biological responses to stressors are what drive our efforts to understand anthropogenic impacts on our surrounding environment. At the most basic level, human societies are willing to allocate resources to understand chemicals and other anthropogenic substances in the environment because they have the potential to adversely affect the health of organisms. Determinations of water, air, soil, and sediment quality are significant exercises if and only if humans or other organisms demonstrate, or are likely to demonstrate, some type of adverse biological outcome following exposure. For humans, it is often enough to demonstrate an adverse effect to an individual. Yet for aquatic organisms, common ecosystem protection goals seem to be more conservative: we need to demonstrate adverse effects that are consequential for populations or higher levels of biological organization, and we must understand the potential for adverse outcome pathways across multiple affected species. An important exception is the case of threatened and endangered species requiring special status; these are examples where the protection goals can focus on adverse effects at the individual level and thus more often mirror approaches used for human health. It is also important to note that we are concentrating human populations and chemical discharges in an unprecedented manner around the world, fundamentally driving the potential for new unintended and adverse consequences to arise in exposed populations.

The scientific literature representing some relation to water and sediment quality is extensive, with many thousands of papers, reflecting many hundreds of thousands of hours of collective labor, published each year. It is clear that we have no shortage of data on environmental systems. And yet, it would still be quite difficult to successfully argue that we accurately understand our impacts on these environmental systems. As a scientific community, it is clear that we do not accurately understand what aspects of sample composition truly translate to observations of poor water and sediment quality. Particularly for sublethal effects, we are not really even sure what harmful actually represents. In some cases, we are even overwhelmed by environmental data, with techniques like genomic characterization of environmental microbiomes and high resolution mass spectrometry providing examples where only a small subset of collected data is typically analyzed and presented. Sadly, despite all of these research and characterization efforts, the majority of published papers are destined to end up with only a few readers and downloads, only yield influence to a few other research studies or systems, or only generate a couple of citations. Why does this occur so frequently? In many of these cases, the overly high probability that a scientific paper fails to reach a broader scientific or general audience often implies a failure in scientific study design or subsequent technical communication. While unfortunate, such failures also imply that there are clear opportunities to improve the collection, interpretation and use of data in environmental chemical sciences, particularly when these data can be coupled with biological responses.

For many site-specific cases in the field, improving robust linkages between data collection/interpretation and identification of the potential for biological systems to be affected would advance a broader understanding of contextual meaning associated with environmental science observations. Impact, the importance of a study to a scientific field and (maybe) to the larger society in general, derives by developing a clear and compelling relationship to a high-priority issue, often from several perspectives. Proper biological context is frequently the most significant contributor to study impact in the environmental chemical sciences. As researchers, we often seek to understand which chemicals, sources, and systems are detrimental to water or sediment quality, and which anthropogenic substances and actions are higher priority for mitigation and restoration efforts. We would argue that inclusion of strong bioanalytical tools can best accomplish these objectives and greatly improve the potential for higher scientific and societal impact to arise from research efforts. By providing clear quantitative and mechanistic links to adverse biological outcomes, bioanalytical tools implicitly integrate aspects of chemical composition and concentration to specific biological endpoints, enabling more effective prospective and retrospective assessments of hazard and risk, and causality for stressor–response relationships in an impaired system. Application of interesting bioanalytical tools as primary or complementary components of environmental work in general is a big step toward building a strong, high impact research study, and should be a clear priority for the environmental research community in general.

Today, it is with pleasure that we introduce you to this Themed Issue on “Bioanalytical tools for water and sediment quality assessment” in Environmental Science: Processes & Impacts, guest edited by Kyungho Choi, Ruth Marfil-Vega, Bryan Brooks, and ESPI associate editor Edward Kolodziej. We have a selection of invited papers that reflect a variety of approaches and possibilities for providing biological context to the assessment of water and sediment quality. Our emphasis on bioanalytical tools is precisely to recognize and advance the driving importance of understanding diverse biological endpoints and consequences for organisms when we characterize aquatic systems. This approach can help to identify the most critical chemical contaminants in a complex mixture, identify new biological endpoints for mechanistic studies of adverse outcomes, and inform many different types of comparative study designs to identify high priority systems, stressors, and receptors.

The challenge of chemical complexity has long been prominent in environmental chemical sciences and engineering. As we all know too well, many thousands of contaminants co-occur in environmental systems, making it a challenge to understand the chemical basis of an observed impact when so little is known about the potential for any specific compound to induce a specific type of biological interaction. Neale et al. (DOI: 10.1039/C6EM00541A) utilize a series of in vitro oxidative stress response assays to understand the mechanistic basis of the oxidative stress response in surface waters. By monitoring the relative formation of reactive oxygen species and glutathione in response to a series of chemical stressors, they helped to define the mechanisms responsible for activating the adaptive stress response in the bioassays, improving the selectivity of these tools and aiding the interpretation of experimental data from these assays. Extending a series of high throughput in vitro and in vivo bioassays to survey unexplained bioactivity on a regional basis, Mehinto et al. (DOI: 10.1039/C7EM00170C) examined surface waters throughout the greater Los Angeles basin, with a particular focus on aryl hydrocarbon receptor activity. Integration of the in vitro and in vivo assays, in combination with select targeted chemical analyses, suggested the existence of unexplained aryl hydrocarbon receptor activity in these surface waters, particularly those that were stormwater impacted. Such efforts can help direct chemical characterization efforts towards better understanding the presence of novel aryl hydrocarbon receptor agonists in these surface waters, and ultimately determine the appropriate engineering controls to mitigate problematic contamination events. Du et al. (DOI: 10.1039/C7EM00243B) reported the development of suspect and non-target screening methods based upon high resolution mass spectrometry analysis to help understand potential toxicant flows in urban waters. This study focused on the potential for endpoints linked to acute mortality in fish, conceptualizing an approach to integrate biological mechanisms of action into the screening workflow. In particular, the paired analysis of water samples and exposure fish tissues were used to help prioritize analytical detections for subsequent identification efforts; this approach resulted in a number of identifications, including novel contaminants, in urban stormwaters and highway runoff.

Gosset et al. (DOI: 10.1039/C7EM00159B) used a literature synthesis and critical review approach to assess the relative ecotoxicological hazard potentials of contaminants linked to urban wet weather discharges. By integrating observed concentration and ecotoxicity data, they concluded that pesticides (particularly pyrethroids), metals, and select pharmaceuticals were highest priority candidates for directed management efforts. They also highlighted some distinctions between different contaminant sources, with differential outcomes related to combined sewer overflows versus stormwater runoff and overland flow. Tremblay et al. (DOI: 10.1039/C7EM00073A) measured select metal concentrations and compared them to benthic community structure across a pollution gradient in a large coastal estuary. This analysis indicated the limitations of existing sediment quality guidelines in understanding the sources of adverse biological impacts in a multi-stressor system (a.k.a. all systems) and pointed to the importance of using field-based measures of ecological condition when evaluating anthropogenic impacts to estuarine sediments. Na et al. (DOI: 10.1039/C7EM00078B) evaluated observations of unintended toxicity to Daphnia magna in textile dyeing effluents, concluding that zinc contamination of low purity reagents used in Fenton processes for wastewater treatment were ultimately responsible for inducing toxicity in the in vivo system. The potential risk of bioactive, toxic, or harmful transformation products in environmental systems is an especially interesting and difficult issue for the aquatic sciences. Wang et al. (DOI: 10.1039/C7EM00111H) characterized the phototransformation mechanisms of ketoprofen, a common pharmaceutical. This work elucidated transformation pathways for this compound and evaluated the potential ecotoxicity of the treated solutions by employing Daphnia magna and V. fischeri as biological indicators. Results indicated an increased potential for toxicity in photoproducts relative to parent compounds, clearly indicating the need to apply bioanalytical tools to product mixtures of common environmental contaminants. And finally, Lee et al. (DOI: 10.1039/C7EM00125H) evaluated the endocrine disrupting potential of polyaromatic hydrocarbons and their alkylated analogues associated with oil spills by screening samples across two in vitro bioassays, one to evaluate estrogen receptor binding affinity (MVLN-luc cells) and the other (H295R, human adrenocortical carcinoma cells) to quantify alterations in sex steroid hormone production. This analysis suggested that the endocrine disrupting potential of polyaromatic hydrocarbons was mostly associated with the capability of these contaminants to alter steroidogenesis, and that the degree of alkylation, and thus weathering, were contributors to unexplained toxicity in these sample types.

This series of studies highlights the diversity in research capabilities and assessment approaches possible with the use of bioanalytical tools. These studies used bioanalytical approaches to define mechanisms of biological impact (e.g., Neale et al., Lee et al.), survey the occurrence of unexplained bioactivity in various receiving waters (e.g., Mehinto et al., Du et al.), highlight deficiencies in current assessment approaches (Tremblay et al.), detect toxicants and product toxicity (Na et al., Wang et al.), and prioritize specific contaminant classes in complex mixtures (Gosset et al.). We would argue that more studies would benefit from an increased focus on the integrated use of bioanalytical tools with advanced targeted and non-targeted analyses to greatly improve (and even create) the appropriate biological context and relevance around their system characterizations. Continued development of more sophisticated and capable bioanalytical tools is needed, especially with respect to in silico and predictive screening methods capable of addressing the large number of uncharacterized environmental contaminants and their transformation products, and underexplored biological endpoints as potential novel mechanisms of adverse impact. Such efforts will require new teams, new combinations of capabilities, to reach their full potential. We hope that our efforts to draw attention to the capabilities of bioanalytical tools and their relationship to advance high impact science will help to encourage more scientists to find ways to use these tools in their own research efforts.

Unfortunately, integrating chemical and biological data is often difficult and expensive. Multiple research teams using multiple experimental techniques, which are not always complementary in system requirements or experimental design, are required for a strong study design that effectively integrates chemical and biological data. These collaborative teams do not always speak the same “language” and are rarely formed due to limited multidisciplinary funding mechanisms in most countries. Also, study complexity and costs increase, the potential for study failure can increase, and these interdisciplinary teams often have very different objectives and approaches to scientific research and data interpretation. Frequently, it is difficult to get funding agencies to support such an integrated approach to data collection and interpretation, particularly when novel or emerging bioanalytical tools are not required by specific regulatory programs, and thus aspects of these integrated efforts can be perceived as superfluous and unnecessary. And yet, the rewards of such an interdisciplinary approach to water and sediment quality assessment can sometimes prove to be most profound because integrated mechanisms are the pathways to novel discoveries and insights concerning anthropogenic impacts on environmental systems. Fundamentally, these approaches are excellent possibilities for the advancement of high impact studies and discovery science (a strong motivation to scientific research!), along with their demonstrated capabilities for routine and comprehensive system characterization. Collectively, we would all benefit from the increased potential for high impact outcomes when we consider protection of public health and the environment within the context of a complex environment full of underexplored and unintended possibilities for adverse impact. The continued development of more sophisticated, mechanistically capable, and high throughput bioanalytical tools can provide improved biological and other interpretative context to environmental data collections. Further, wider use of bioanalytical capabilities can help to directly link contaminant flows and sources to myriad adverse outcomes in exposed organisms. Here, we hope to inspire some new ideas for bioassay development and spur the increased use and interpretation of bioanalytical tools, for there exist so many important questions and systems that will require their capabilities for us to understand and manage our societal impact on aquatic environments.

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