Coastal and Estuarine Risk Assessment - Chapter 1 potx

Hale CONTENTS 1.1 Introduction 1.2 Application of Risk Assessment in Estuaries 1.2.1 Water Quality Criteria 1.2.2 Sediment Quality Guidelines 1.2.3 Toxics Characterization 1.2.4 Relative

Overview of Ecological Risk Assessment in Coastal and Estuarine Environments

Morris H Roberts, Jr., Michael C Newman, and Robert C Hale

CONTENTS

1.1 Introduction 1.2 Application of Risk Assessment in Estuaries 1.2.1 Water Quality Criteria

1.2.2 Sediment Quality Guidelines 1.2.3 Toxics Characterization 1.2.4 Relative Risk Assessment 1.2.5 A Case Study of Risk Assessment in an Estuary 1.3 Forum Organization

References

1.1 INTRODUCTION

Ecological risk assessment is a logical process for objectively defining the probability

of an adverse effect to an organism or collection of organisms when challenged with

an environmental modification such as climatic change, xenobiotic exposure, infec-tion with a disease organism, or some other potential stressor The link between the parameter producing the effect (i.e., the stressor) and the organism(s) responding (i.e., the receptor) is accessible mainly by inference in the absence of full and detailed knowledge Long used in economics and health sciences, risk assessment has a shorter history of application to ecological systems and even a shorter history for estuarine and coastal systems

The risk assessment paradigm in general, and in ecological risk assessment in particular, involves (1) problem formulation, (2) parallel analyses of exposure and effects, and (3) risk characterization1–5 (Figure 1.1) Each aspect of the paradigm involves an integrative process connecting various inputs or data to one or more outputs or conclusions Initial assessments are often imprecise, pointing to data needs

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that, if fulfilled, allow more rigorous assessments of risk with improved certainty in the evaluation Problem definition includes a determination of a valued resource such as a population of commercially important species or keystone species, or

FIGURE 1.1 The environmental risk assessment paradigm as presented by the U.S EPA Information inputs are shown in boxes, processes in ovals, and outputs in circles (Modified from Reference 5 )

community structure In this step, one determines what assessment end point(s) will

be used, develops a conceptual model that links the end point(s) to exposure, and

an analysis plan that incorporates both the end point(s) and the model

The analysis phase involves collection of data on exposure, effects, and charac-teristics of the ecosystem of interest In coastal and estuarine situations, these parameters are particularly dynamic and the resultant gradients in salinity and other variables present special challenges to risk assessment The analyses of exposure and ecological responses occur in parallel, leading to exposure and response profiles Attention must be paid to environmental conditions in both analyses if the ultimate risk estimation is to be credible

The final stage in the process is risk characterization, resulting ultimately in a risk estimate To the extent possible, this characterization should be a quantitative probability statement, but this is not always achievable in complex and dynamic systems As depicted in Figure 1.1, the risk characterization may be deemed inade-quate, resulting in the need for additional data, reanalysis, and monitoring of the outcome for plausibility

Risk assessment is a practical management tool rather than a purely scientific endeavor It is useful for predicting the outcomes of activities such as chemical use or disposal, or species introductions, or for attributing observed effects to potential causes in a retrospective analysis Risk assessment can generate enough understanding to allow informed decision making relative to choosing among several remedial actions It is an especially important tool if the resources needed

to reduce risk are limited, if competing options exist, or if the relative value of each action is not obvious

This edited volume was developed to focus primarily on chemical exposure, effect measurement, and risk characterization in estuarine and coastal environments The chemicals of concern are those that are or may become toxic in these environ-ments This focus is important not only because of intense historical uses, but also because human use of the estuarine and coastal system continues to expand rapidly Historical human use has resulted in relic accumulations of chemical contaminants

in localized areas, and present human activities in coastal areas produces continued introductions of chemical contaminants either directly (e.g., from discharge pipes)

or indirectly (e.g., polycyclic aromatic hydrocarbon, or PAH, from atmospheric deposition as a result of vehicular emissions) Enhancing the importance of risk assessment in estuaries is the current rapid migration of people into the coastal zone.6

For example, the Chesapeake Bay watershed had a 19.3% increase in population between 1970 and 1990 Smaller coastal watersheds such as St Johns River (Flor-ida), Tampa Bay (Flor(Flor-ida), and San Diego Bay (California) had even larger popu-lation increases of 43 to 47%.7 With this population growth, the potential for sub-stantial increases in adverse impacts on estuarine and coastal environments is dramatically enhanced Conversely, as these populations grow, the resources in estuaries and coastal systems that serve as an inducement to human immigration are among those most likely to deteriorate as a result of human activity

Despite the focus on chemicals as the stressors of interest in most of this volume, one must recognize that ecological risk assessment is a tool with broader application, providing an objective approach to evaluate simultaneously the effects not only of

chemical stressors, but also other stressors such as habitat loss (e.g., submerged aquatic vegetation, salt marshes, or shoreline green ways), fishing pressure, or reduced freshwater inputs (resulting from reservoir construction) This is reflected

in two recurrent themes in the book, i.e., the need to apply a landscape context for assessment and the need to relate effects to stressors across all levels of ecological organization from bacteria and primary producers to top carnivores, and from indi-vidual organisms to communities

Estuarine and coastal systems develop at the interface between land, fresh water, and the oceans As such, they are characterized by gradients, most obviously a persistent salinity gradient These systems are also physically dynamic over a variety

of timescales Tidal cycles modify mixing regimes over different, but predictable, periods in many coastal areas; wind varies aperiodically and interacts with tide to further modify the flow of water and associated materials Seasonal changes in air temperature and precipitation are reflected in annual changes in temperature and salinity of the water As a result, these systems must be looked at in an ecotonal context, as a habitat in which there are unique groups of organisms, as well as those from freshwater or euhaline systems that have sufficient physiological tolerances to handle conditions within these mixing zones and that utilize estuaries as sources of food or as refuges from predators Biological communities are dynamic and often ephemeral during the year although recurrent over cycles of years

These variable conditions affect both stressor and receptor For there to be an impact, there must be co-occurrence of the stressor and receptor The degree of exposure must be sufficient in intensity and duration to produce an effect In less dynamic systems, the presumption of stressor and receptor co-occurrence is often reasonable over relatively long timescales And equally important as a presumption, the receptors must remain within the volume influenced by the stressor Some species inhabiting estuaries are highly mobile, and can move outside the region where a stressor occurs Other species may have evolved behavioral mechanisms to cope with the natural variability of the system by isolating themselves from a stressor until the stressor intensity has decreased; e.g., bivalves can close their shells, and some organisms can encase themselves in mucus or another protective agent Many organisms have enzymatic mechanisms that allow them to detoxify chemicals, mech-anisms that are induced by the presence of the chemical

The tools of risk assessment have been developed for optimal use in less dynamic systems Therefore, the various steps in ecological risk assessment may need to be modified to address dynamic estuarine and coastal conditions effectively Is proper consideration given to the effects of estuarine conditions on exposure concentrations during assessments of exposure? Specifically, is sufficient attention given to the effects of salinity, binding to sediment-associated or dissolved organic material, and isolation in water masses by density gradients? Is the temporal and spatial sampling utilized appropriate to the temporal and scalar variation in these dynamic systems?

Is the ecosystem context inherent in framing most risk assessments adequate for coastal and estuarine systems that are physical boundaries and ecotones receiving large amounts of materials, energy, and species from outside of the system for which risk is to be estimated? Does the evaluation consider adequately all ecological components including primary producers, secondary consumers, and saprophytes?

In assessing hazard, is sufficient consideration given to variability in degree of exposure or in rates of stressor input? Does the approach consider the inherent seasonal variations in the presence of a species, reproductive activity, and growth? Some of these issues are not unique to estuarine and coastal systems, and obviously have persistent and collective implications about the validity of any risk assessment Nevertheless, the implications of the estuarine environment on risk assessment need careful consideration

1.2 APPLICATION OF RISK ASSESSMENT IN ESTUARIES

Although the use of ecological risk assessment in aquatic, and especially estuarine, systems is a relatively new development, exposure and hazard evaluations have been used in these systems for some time These evaluations have been applied in setting water quality criteria and standards, definition of sediment quality guidelines, char-acterization of various segments of the estuaries with regard to toxicological effects, and the so-called relative risk assessment In each of these cases, frequent mention

is made of managing “risk” or the process being “risk-based,” yet many times no actual determination of risk probabilities is conducted

1.2.1 W ATER Q UALITY C RITERIA

Water quality criteria are primarily based on laboratory exposure and effects data

In collecting exposure and effects data, standard test designs require high consistency

of exposure over time and effects are monitored over timescales of days to months The intent is to achieve reproducible and precise data, even though these controlled conditions may not accurately reflect field scenarios From the laboratory data developed for an array of species, a statistical estimate is made of the concentration

of a material that will be protective of the “most sensitive species.” Account is taken

of the interaction between a limited number of environmental variables (hardness, acidity, or salinity) and the chemical of concern by modeling the relationships, again assuming time constancy in all these parameters A safety factor is then applied to account for environmental variability and uncertainty.8

Data for freshwater and saltwater species can be treated separately in this type

of analysis, leading to distinct water quality criteria for fresh water and salt water The derivation of distinct freshwater and saltwater criteria is clearly important for many inorganic and organic materials that exhibit different bioavailabilities in these two media Examples include chlorine and cadmium,9,10 but there are many others The analysis of exposure and effects data yields a concentration that notionally should not be exceeded in a specific aqueous medium if the specified acute or chronic effect is to be avoided This process is a valuable first estimate of the hazard concentration, but is not a risk assessment as defined herein, even though both exposure and effect information are central to any environmental risk assessment The risk of adverse impact cannot be determined from the criteria

The same effects data can be used to conduct a risk assessment as demonstrated

by Hall and his colleagues.11 In the problem formulation, they selected two specific chemicals, copper and cadmium, based on use patterns in Maryland waters They

then applied the broadest array of laboratory toxicity data available to determine the concentration of each of these metals that affected the most sensitive 10th percentile

of species, thus defining a concentration protective of 90% of the species If one desired a more protective concentration, one could derive that from the same data This value is conceptually the same as the criterion value derived by the U.S Environmental Protection Agency (U.S EPA), but obtained in a way that involves all data Measured concentrations in samples from specific locations can then be compared with the concentration that produces a specified degree of protection The concentrations may also be compared with the effect curve to estimate the probability

of an adverse effect at specific locations as a result of exposure to the specific compound for which the analysis was performed

The issue of multiple stressors including effects of unidentified stressors was not addressed in this example although the authors noted the concurrence of both stressors in some locations Hall et al.11 discussed the strong preponderance of fish and benthos information in the available data set and the paucity of plant and zooplankton data The importance of this observation cannot be assessed objectively

at this point, but if these groups are more sensitive than fish or benthos, the analysis

is clearly biased by the omission of such information This observation points to a definite need to expand the array of organisms routinely used for effects evaluations

to be more inclusive of important ecological components

1.2.2 S EDIMENT Q UALITY G UIDELINES

A variety of sediment quality guidelines (SQG) have been proposed in the past two decades.12–17 Different guidelines yield different answers about the concentration that may be protective All guidelines are based on exposure and effects data, and some incorporate both laboratory and field data Clearly, many geochemical param-eters can affect bioavailability and will vary from place to place The statistically derived values are considered guidelines rather than criteria because spatial variabil-ity in underlying conditions at any specific location may be different from those embodied in the data from which the guidelines were derived Despite the impreci-sion of these guidelines, if carefully applied, these values can be useful to managers faced with decisions involving sediment quality issues Exceeding guidelines is

prima facie evidence of a risk of sediment quality reduction and an attendant substantial, if not quantified, risk of adverse effects

With further manipulation, these guidelines can also provide a basis for estab-lishing remediation criteria Based on a sediment quotient value (SQV) (i.e., the sum of the quotient between a measured value and the appropriate SQG for each contaminant of concern), one can identify one or more levels of exposure that will, with some degree of confidence, reduce adverse effects below a selected level(s).18,19

The ratios identified at one site may then be cautiously applied as cleanup goals in other locations The approach has been used recently by the Army Corps of Engineers

in a feasibility study of sediment remediation in the Elizabeth River, Virginia.20

A risk analysis approach in this application analogous to that used for water would be a valuable endeavor The use of guidelines does not allow an estimation

of risk probability At present, the risk of an adverse effect resulting from exceeding

a guideline such as an effects range median (ERM) is undefined If the concentration was two or more times above the ERM, the increase in risk is at present indetermi-nate An analysis that includes all available data to estimate risk would provide valuable extensions to the present approaches

Just as in the previous example related to water column impacts, risk analysis for sediments as portrayed here would be accomplished one material at a time In reality, simultaneous exposure to multiple materials and other potential stressors is typical Better tools are needed to deal with this complexity

1.2.3 T OXICS C HARACTERIZATION

The sediment quality triad method is one approach used to characterize the impact

of chemical contaminants in estuaries It was developed originally for Puget Sound12,21 and subsequently applied in San Francisco Bay13 and elsewhere In this method, there is synoptic determination of chemical contaminants in the sediment, measurement of toxic end points in laboratory tests of the sediment, and an assess-ment of the benthic community To understand bioavailability of chemicals in the sediment, total organic carbon, acid-volatile sulfides, and other geochemical param-eters are measured on sediment samples From these three types of measures, one can assess the health of a system on empirical grounds The power of this approach lies in the contemporaneous nature of the measurements

The U.S EPA Chesapeake Bay Program has, for a decade or more, been working

on a toxics characterization of various strata within the bay and its tributaries The program has been concerned with both water column and sedimentary effects The method for characterizing these strata as a region of concern, region of emphasis, region with low probability for adverse effect, or region of insufficient or inconclu-sive data has been described in detail.22 The characterizations are based on available ambient chemical concentration data for water, sediment, and finfish/shellfish tissue and on effects information such as laboratory toxicity data for ambient water and sediment samples and indices of biological integrity for benthic invertebrates Data collected under the auspices of the U.S EPA Chesapeake Bay Program Office23–30

with contemporaneous data collection were used along with other available, although noncontemporaneous, data of certifiable high quality

These determinations are risk based in that strata are ranked based on an estimate

of adverse effect by a panel of experts using professional judgment to assess the likeli-hood of adverse impacts This approach can resolve “regions of concern” from “regions

of no probable effect,” but does not allow objective evaluations of greater resolution These characterizations have nevertheless proved useful in prioritizing specific regions for cleanup and in identifying the need for additional data in regions that cannot currently be characterized However, these characterizations alone do not provide a clear strategy for the remediation of specific regions Once a strategy has been developed, quantitative cleanup goals must be established Again, the charac-terizations do not provide objective criteria for cleanup Finally, if resolution among regions is imprecise using this approach, one must conclude that there is insufficient resolution to recognize the benefits derived from various cleanup options Thus, the use of these characterizations to guide management decisions is limited

An alternative approach to characterize strata, developed and used by Ian Hartwell in Maryland, involves a risk-ranking approach based on ambient toxicity results using a standard battery of water column and benthic tests, and some measure

of community health.31–33 A score is calculated for each sample site based on severity

of effect, degree of response, variability of each test, consistency among various effects measures, and number of effects measured This approach allows one to compare objectively data from multiple sites even if there were differences in parameters measured, number of effects studied, and species tested

In the sediment triad method, laboratory and field effects data are not always consistent with one another This inconsistency may be due to test conditions modifying bioavailability, or a parameter other than toxicity producing an adverse effect on communities Further, the sediment triad method deals only with the benthic component of the ecosystem The risk-ranking method of Hartwell is an imperfect, but nevertheless useful, way to address some of these concerns The method can utilize water column or benthic information, or both Site scores can

be compared with measures of community health such as fish or benthic indices

of biotic integrity Sites that show poor community health but minimal toxicity can

be examined for other risk factors such as physical conditions, food availability, or infectious disease impacts A site that is scored “toxic” can be subjected to further study to provide a chemical characterization, with the goal of identifying specific chemicals of concern Thus, the outcome of analysis may lead to another round of data collection, analysis, and risk characterization Such iteration is an inherent strength of the risk assessment process

1.2.4 R ELATIVE R ISK A SSESSMENT

Another tool in environmental management applied recently has been relative risk assessment.34 To implement this method, an assessment group is formed of environ-mental experts (e.g., research scientists, regulatory agents, environenviron-mental managers from business) and nonscientists (e.g., homeowners, educators, businesspeople) The group is organized into committees representing differing perspectives and expertise with the goal of differentiating the importance of various issues of concern among stakeholders All committees are charged with identifying the problems and issues that need to be addressed from their perspective, and then a consensus is sought across the stakeholders

To help build consensus, experts in each group are asked to compile available data on each issue and to inform the panels For example, what chemicals are present

in water or sediment? Is toxicity associated with water or sediment? Is rainfall directed from roads and parking areas treated to remove contaminants before release

to waterways? Is the air polluted and, if so, with what pollutants? What are the human health implications? What effects are likely known to occur in fish and other wildlife? The specific list of questions for which data are accumulated will depend

on the issues collectively identified and the technical concerns attendant to each Armed with this technical information, digested into a form that is understandable

to everyone, the group seeks to reach consensus about relative risks associated with each issue, and to rank these in terms of perceived risk

Although based ultimately on opinion, the consensus about relative risk for each issue is founded on the technical information accessible to the panelists All stake-holders have participated in the evaluation process and have a sense, if the process worked well, that their concerns were appropriately considered

The next step in the process is to identify and evaluate possible steps that can

be taken to reduce the perceived risks Remediation methods used in other locations may provide applicable solutions, but many times these cannot be used without further consideration of local conditions For example, capping of contaminated estuarine sediments, as was done at Eagle Harbor in Puget Sound, is not possible

in a shallow estuary such as the Elizabeth River in Virginia with shoals less than

3 m deep, and the need to maintain deepwater shipping channels Simple removal

of surface sediments in shoal areas may be an unacceptable resolution if the con-tamination penetrates deeply into the sediment However, removal of contaminated sediment to some depth and then restoring the bottom contours by capping with clean sediment combines two technologies to isolate any residual contamination under a cap without drastically changing the bottom contour of the system Modi-fications of waste discharge processes for both point and non-point sources may provide a long-term benefit, but must focus on the most significant sources of contaminants and fit the landscape and socioeconomic structure The assessment group, representing a broad array of stakeholders, can identify by consensus a cleanup strategy that is acceptable to the community Environmental managers can then further evaluate and implement the strategy, with some confidence that there

is acceptance of the proposed solutions, provided that the assessment group remains active and informed

This relative risk approach, although subjective and imprecise, can be an effective tool to guide management decisions It has the inherent advantage that data on exposure and effects are evaluated by all constituencies, which then participate in prioritizing factors of greatest importance and selecting among courses of action based on perceived risks This model was used by the Elizabeth River Project, Inc., in developing its Strategic Plan for the restoration of the Elizabeth River, an urban river and “region of concern” in the Chesapeake Bay

in Virginia.35,36

1.2.5 A C ASE S TUDY OF R ISK A SSESSMENT IN AN E STUARY

In 1993, the U.S EPA Office of Water and National Center for Environmental Assessment cosponsored five prototype case studies to demonstrate the utility of the risk assessment paradigm as a tool for environmental management of entire watersheds One of these pilot studies addressed an estuarine system, the Waquoit Bay watershed in Massachusetts This small estuary is a shallow coastal feature with a diverse surrounding landscape It was small enough to allow a manageable exploratory study, yet of sufficient scale that the application of formal risk assess-ment procedures in this system is likely to have relevance to larger estuarine systems.37 Waquoit estuary is a National Estuarine Research Reserve in which extensive partnering is possible to enhance research Stressors of concern in this estuary include nutrient enrichment, suspended solids, changes in water circulation

patterns, toxic chemical inputs, and habitat alterations Of particular interest are effects on submerged aquatic vegetation in the system Models are used to assess the risks associated with each of the stressors both singly and in combination Although reports on risk assessments in this estuary have not been identified, this

is a work in progress that bears watching

1.3 FORUM ORGANIZATION

The forum from which this book was developed was focused on scientific aspects

of contaminant exposure and effects, with emphasis on an estuarine and coastal context Presenters dealing with chemical exposures were asked to address not only issues such as analyte type and efficacy of analytical approaches, but also bioavail-ability in estuarine and coastal settings One concern that is often overlooked is that

of new use or otherwise unregulated chemicals History teaches that such chemicals may become significant contaminants before they are detected in water or sediment

if there are no overt impacts on biota, e.g., Kepone History also teaches that there may be chemicals periodically entering the estuary at high concentrations that may

be difficult to detect and evaluate for effects Therefore, a paper was solicited specifically on these issues

Presentations were also solicited concerning effects at various levels of bio-logical organization from biochemical to cellular to whole organism to population

to landscape levels At each level of organization, there are concerns over the sensitivity and precision of measurement tools and the predictive value of mea-surements at any given level for effects at higher levels of organization Can laboratory methods adequately portray effects in the environment? What role do various biomarkers play in risk assessment? Rarely, does one objectively study the consequences of exposure to multiple stressors Is this important to a mean-ingful risk assessment? And ultimately, although individual species are important because they have commercial or recreational value, aesthetic value, or key ecological roles, the real issue is the preservation of functional assemblages at a landscape level Does one incorporate all important ecosystem components into data collection and analysis? Where possible, presenters were asked to show how their data could be applied in a risk assessment Through such case studies, the forum hoped to show how one can include issues overlooked in less comprehen-sive analyses

This forum examined the science and tools of risk assessment, used both in the laboratory and in watersheds, but it also included the logical tools by which risk is evaluated in an objective fashion The intent was to juxtapose different approaches and views in a way leading to a better understanding of the critical features of estuaries that need to be considered in a successful environmental risk assessment The summary chapter examines how well this intent was met

This forum was a meeting of scientists speaking to peers using their own jargon and shorthand Readers of this volume will most likely be scientists and managers familiar with this language Yet ultimately, this tool will be used in a very public risk management and regulatory context As scientists, we must always recognize that the people we serve may not see the world as we do People often place more