John H. Gentile

Developing and applying a benthic index of estuarine condition for the Virginian Biogeographic Province

A benthic index of estuarine condition was constructed for the Virginian Biogeographic Province (from Cape Cod, Massachusetts, to the mouth of Chesapeake Bay, Virginia) with data collected during summers of 1990 through 1993 by the US EPA’s Environmental Monitoring and Assessment Program (EMAP). Forty-eight metrics, based on attributes of the macrobenthos, were considered for the index, including measures of biodiversity, community condition, individual health, functional organization, and taxonomic composition. Salinity was correlated significantly with some of the metrics. Therefore, some metrics were normalized for salinity. The data used to develop the index (the calibration data) included equal numbers of reference and degraded sites, distributed equally across three salinity zones ( 18‰). An independent set of data was used for validation. Linear discriminant analysis identified combinations of metrics that could best discriminate reference from degraded sites. The targets for correct classification were 90% of the sites for the calibration data and 80% for the validation data. Six combinations of metrics were identified. The final index was based on the ecological interpretation and relevance of the individual metrics and the ability to meet the calibration and validation targets. The final index consisted of three metrics: a positive contribution from salinity-normalized Gleason’s D (a biodiversity metric), and negative contributions from two taxonomic composition metrics, abundances of spionid polychaetes and of salinity-normalized tubificid oligochaetes. The index correctly classified 87% of reference and 90% of degraded sites in the calibration data and 88% of reference and 81% of degraded sites in the validation data. The index correctly classified sites over the full range of salinity (tidal-fresh to marine waters) and across grain sizes (silt–clay to sand).

A Framework for an Ecosystem Integrity Report Card

543 E cosystem management is a structured process for society to define what ecological condition is desired at each part of a region and to develop and implement management policies designed to achieve that mosaic of desired sustainable ecological conditions (US MAB 1994, IEMTF 1995a, 1995b, Christensen et al. 1996, Harwell et al. 1996, Harwell 1998). Ideally, the establishment of ecological goals involves a close linkage between scientists and decision makers, in which science informs decision makers and the public by characterizing the ecological conditions that are achievable under particular management regimes, and decision makers make choices reflecting societal values, including issues of economics, politics, and culture. Because ecosystem management is adaptive—that is, management is adjusted if necessary to achieve goals—the general public, the scientific community, resource managers, and decision makers need to be routinely apprised of progress toward achieving the desired ecological goals, that is, they need a “report card” on ecosystem condition or integrity. The concept of report cards or performance measurements to describe progress toward environmental goals has evolved over the past few decades as environmental legislation and the appropriation of public funds for environmental restoration, preservation, and management have increased. Over this time, reports have expanded from measurement of the effects of single initiatives (e.g., land acquisition goals for parks and protected areas) and progress toward pollution reduction in single media (e.g., reduction of air or water emissions) to encompass the broader and longer-term regional ecosystem management and restoration approaches that have been developing in highly valued ecosystems throughout the country (e.g., the Greater Everglades, San Francisco Bay, Chesapeake Bay, the Great Lakes, and the Pacific Northwest). These holistic, often multi-agency efforts to maintain accountability for regional ecosystem integrity and the progress of restoration activities stem in part from the proactive desire of resource managers to maintain public interest, support, and, consequently, funding for long-term environmental restoration and management efforts. They also stem in part from specific legislative or regulatory requirements to engage the public in the ecosystem management process (e.g., EPA/EC 1995, 1996, Chesapeake Bay Program 1996, NSTC 1996a, 1996b) or from direct requests from Congress, A Framework for an Ecosystem Integrity Report Card

Ecosystem management to achieve ecological sustainability: The case of South Florida

The ecosystems of South Florida are unique in the world. The defining features of the natural Everglades (large spatial scale, temporal patterns of water storage and sheetflow, and low nutrient levels) historically allowed a mosaic of habitats with characteristic animals. Massive hydrological alterations have halved the Everglades, and ecological sustainability requires fundamental changes in management.The US Man and the Biosphere Human-Dominated Systems Directorate is conducting a case study of South Florida using ecosystem management as a framework for exploring options for mutually dependent sustainability of society and the environment. A new methodology was developed to specify sustainability goals, characterize human factors affecting the ecosystem, and conduct scenario/consequence analyses to examine ecological and societal implications. South Florida has sufficient water for urban, agricultural, and ecological needs, but most water drains to the sea through the system of canals; thus, the issue is not competition for resources but storage and management of water. The goal is to reestablish the natural system for water quantity, timing, and distribution over a sufficient area to restore the essence of the Everglades.The societal sustainability in the Everglades Agricultural Area (EAA) is at risk because of soil degradation, vulnerability of sugar price supports, policies affecting Cuban sugar imports, and political/economic forces aligned against sugar production. One scenario suggested using the EAA for water storage while under private sugar production, thereby linking sustainability of the ecological system with societal sustainability. Further analyses are needed, but the US MAB project suggests achieving ecological sustainability consistent with societal sustainability may be feasible.

TOTAL SYSTEM CONCEPTUAL ECOLOGICAL MODEL

The total South Florida ecosystem encompasses all natural areas that were once interconnected and embedded within the vast Everglades basin that originally extended from coast to coast and from the upper Kissimmee basin headwaters to Florida Bay, Biscayne Bay, the Gulf of Mexico, and Caloosahatchee and Indian River Lagoon estuaries. Restoration of this system will be successful once defining characteristics of the pre-altered system are recovered. Defining characteristics of the ecosystem are 1) abundant large vertebrates and aquatic prey bases, 2) animals with large spatial requirements, 3) healthy, dynamically sustainable estuaries, 4) oligotrophic freshwater wetlands, and 5) complex landscape mosaics and interactions. These defining characteristics have been altered by three external drivers that create stressors on the system: water management, land-use management and development, and climate change and sea-level rise. Stressors on the South Florida ecosystem include loss of spatial extent; loss of connectivity; altered geomorphology and topography; altered volume, timing, and distribution of regional hydropatterns; input of nutrients; altered fire patterns; and introduction and spread of exotic plants and animals. The Total System Conceptual Ecological Model links stressors to changes in the defining characteristics through major working hypotheses of cause-and-effect relationships. The linkages (ecological effects) relate to hydroperiod and depth patterns, sheet flow, salinity gradients, nutrient status and dynamics, fire patterns, habitat availability, and marsh aquatic fauna prey bases. For each defining characteristic, key ecological indicators are identified to collectively track the decline and restoration of the ecosystem.

A science-based strategy for ecological restoration in South Florida

The Everglades and associated coastal ecosystems of South Florida are unique and highly valued ecosystems. One of the worlds largest water management systems has been developed in South Florida over the past 50 years to provide flood control, urban and agricultural water supply, and drainage of land for development. However, this system has inadvertently caused extensive degradation of the South Florida environment, resulting in the loss of more than half the historical Everglades system and elimination of whole classes of ecosystems. The U.S. Man and the Biosphere Program (US MAB) instituted a project to develop ecosystem management principles and identify requirements for ecological sustainability of South Florida. A strategic process developed by the US MAB Project illustrates how ecosystem management and ecological risk assessment principles apply to South Florida, including the development of societal goals and objectives of desired sustainable ecological condition, translation of these goals/objectives into scientifically meaningful ecological endpoints, creation of a regional plan designed to meet the sustainability goals, and development of a framework for evaluating how well the plan will achieve ecological sustainability of South Florida. An extensive federal, state, and tribal interagency process is underway to develop a restoration plan for restructuring the regional management system, essentially following the elements in the US MAB project process. The Florida Governors Commission was established as an institution to reflect societal values and define regional sustainability goals. The U.S. Army Corps of Engineers is developing a science-based plan for Congressional approval to restructure the water management system to achieve the societal goals. Thus, South Florida may become the prototype example of successful regional-scale ecosystem management.

Environmental management scenarios: Ecological implications

The measure of whether a management scenario is capable of establishing regional-scale ecosystem sustainability is the degree to which it recovers the historical characteristics of the regional landscape mosaic. This study examines the ability of alternate management scenarios to recover the defining ecological features of the Everglades and South Florida landscape. Five conceptual scenarios are evaluated for recovering and sustaining the ecological characteristics of the wetland systems in South Florida. First, the regional-scale physical characteristics are identified that created and supported the major organizing and driving forces in the predrainage Everglades and Big Cypress basins. Eight hypotheses are proposed to explain how human-caused modifications to these defining characteristics have been responsible for the substantial level of ecological deterioration that has been documented in South Florida wetlands during the last century. The restoration scenarios are evaluated on their proposed ability to correct the physical and biological problems identified by the hypotheses. Our assessment of the five scenarios shows that all would improve the problems addressed by the eight hypotheses, as all could more effectively move increased volumes of water across broader expanses of contiguous wetlands than do existing management programs. This would result in longer hydroperiods over larger areas, reflecting historical patterns. Two of the scenarios would be successful in increasing flows into Florida Bay and the Gulf coast estuaries because removing internal structures increases the spatial extent of the upstream areas that could be devoted to natural hydropatterns.The benefits of eastern boundary buffer zones include improved flow into the Taylor Slough basin. Using Lake Okeechobee as a site for increased water storage, followed by the addition of eastern buffer zones and portions of the Everglades Agricultural Area, would produce increased flexibility in providing the storage capacity required to meet sustainability goals. Scenarios with maximum areas of buffer not only are more successful in reducing groundwater seepage losses to the east but also are more likely to reduce the level of nutrients and other contaminants entering the natural wetlands.

A Quantitative Ecological Risk Assessment of the Toxicological Risks from Exxon Valdez Subsurface Oil Residues to Sea Otters at Northern Knight Island, Prince William Sound, Alaska

ABSTRACT A comprehensive, quantitative risk assessment is presented of the toxicological risks from buried Exxon Valdez subsurface oil residues (SSOR) to a subpopulation of sea otters (Enhydra lutris) at Northern Knight Island (NKI) in Prince William Sound, Alaska, as it has been asserted that this subpopulation of sea otters may be experiencing adverse effects from the SSOR. The central questions in this study are: could the risk to NKI sea otters from exposure to polycyclic aromatic hydrocarbons (PAHs) in SSOR, as characterized in 2001–2003, result in individual health effects, and, if so, could that exposure cause subpopulation-level effects? We follow the U.S. Environmental Protection Agency (USEPA) risk paradigm by: (a) identifying potential routes of exposure to PAHs from SSOR; (b) developing a quantitative simulation model of exposures using the best available scientific information; (c) developing scenarios based on calculated probabilities of sea otter exposures to SSOR; (d) simulating exposures for 500,000 modeled sea otters and extracting the 99.9% quantile most highly exposed individuals; and (e) comparing projected exposures to chronic toxicity reference values. Results indicate that, even under conservative assumptions in the model, maximum-exposed sea otters would not receive a dose of PAHs sufficient to cause any health effects; consequently, no plausible toxicological risk exists from SSOR to the sea otter subpopulation at NKI.

Strategies for Assessing Cumulative Ecological Risks

Assessing and managing the ecological risks from multiple stressors is becoming increasingly important as our environmental and regulatory focus moves from managing point sources to one of managing and trading risks from multiples sources over large geographic areas. There are important corollaries to this shift in focus and scale, one is the increased role and importance of non-chemical stressors in shaping and controlling ecological systems, the fact that these categories of stress are, for the most part, not regulated under the traditional legislative mandates, that we have limited knowledge regarding the interaction of chemical and non-chemical stressors, that at large scales we are faced with the integration of and trading of risks to multiple resource categories. This trend of increased attention to regional-scale environmental issues requires the development of new analysis and interpretive strategies and highlight the need for a systematic framework for addressing the ecological effects of multiple stressors at regional ecological scales. We propose that such a framework have three essential properties: it be risk-based; it be effects driven; and it have the flexibility to be used in both a retrospective and prospective manner. While several approaches have been proposed we believe that an ecological risk assessment framework satisfies these criteria, has been used successfully in regional assessments, and can readily be modified and adapted to serve a wide variety of problem settings.

Hormesis and ecological risk assessment: Fact or fantasy?

Abstract Hormesis is a widespread phenomenon across occurring many taxa and chemicals, and, at the single species level, issues regarding the application of hormesis to human health and ecological risk assessment are similar. However, interpreting the significance of hormesis for even a single species in an ecological risk assessment can be complicated by competition with other species, predation effects, etc. In addition, ecological risk assessments may involve communities of hundreds or thousands of species as well as a range of ecological processes. Applying hormetic adjustments to threshold effect levels for chemicals derived from sensitivity distributions for a large number of species is impractical. For ecological risks, chemical stressors are frequently of lessor concern than physical stressors (e.g., habitat alteration) or biological stressors (e.g., introduced species), but the relevance of hormesis to non‐chemical stressors is unclear. Although ecological theories such as the intermediate disturbance hypothesis offer some intriguing similarities between chemical hormesis and hormetic‐like responses resulting from physical disturbances, mechanistic explanations are lacking. While further exploration of the relevance of hormesis to ecological risk assessment is desirable, it is unlikely that hormesis is a critical factor in most ecological risk assessments, given the magnitude of other uncertainties inherent in the process.

Quantifying Population-Level Risks Using an Individual-Based Model: Sea Otters, Harlequin Ducks, and the Exxon Valdez Oil Spill

Ecological risk assessments need to advance beyond evaluating risks to individuals that are largely based on toxicity studies conducted on a few species under laboratory conditions, to assessing population-level risks to the environment, including considerations of variability and uncertainty. Two individual-based models (IBMs), recently developed to assess current risks to sea otters and seaducks in Prince William Sound more than 2 decades after the Exxon Valdez oil spill (EVOS), are used to explore population-level risks. In each case, the models had previously shown that there were essentially no remaining risks to individuals from polycyclic aromatic hydrocarbons (PAHs) derived from the EVOS. New sensitivity analyses are reported here in which hypothetical environmental exposures to PAHs were heuristically increased until assimilated doses reached toxicity reference values (TRVs) derived at the no-observed-adverse-effects and lowest-observed-adverse-effects levels (NOAEL and LOAEL, respectively). For the sea otters, this was accomplished by artificially increasing the number of sea otter pits that would intersect remaining patches of subsurface oil residues by orders of magnitude over actual estimated rates. Similarly, in the seaduck assessment, the PAH concentrations in the constituents of diet, sediments, and seawater were increased in proportion to their relative contributions to the assimilated doses by orders of magnitude over measured environmental concentrations, to reach the NOAEL and LOAEL thresholds. The stochastic IBMs simulated millions of individuals. From these outputs, frequency distributions were derived of assimilated doses for populations of 500 000 sea otters or seaducks in each of 7 or 8 classes, respectively. Doses to several selected quantiles were analyzed, ranging from the 1-in-1000th most-exposed individuals (99.9% quantile) to the median-exposed individuals (50% quantile). The resulting families of quantile curves provide the basis for characterizing the environmental thresholds below which no population-level effects could be detected and above which population-level effects would be expected to become manifest. This approach provides risk managers an enhanced understanding of the risks to populations under various conditions and assumptions, whether under hypothetically increased exposure regimes, as demonstrated here, or in situations in which actual exposures are near toxic effects levels. This study shows that individual-based models are especially amenable and appropriate for conducting population-level risk assessments, and that they can readily be used to answer questions about the risks to individuals and populations across a variety of exposure conditions. Integr Environ Assess Manag 2012; 8: 503–522.