Weighing the evidence of ecological risk from chemical contamination in the estuarine environment adjacent to the Portsmouth Naval Shipyard, Kittery, Maine, USA

Abstract

In characterizing ecological risks, considerable consensus building and professional judgments are required to develop conclusions about risk. This is because how to evaluate all the factors that determine ecological risk is not well defined and is subject to interpretation. Here we report on the application of a procedure to weigh the evidence of ecological risk and develop conclusions about risk that will incorporate the strengths and weaknesses of the assessment. The procedure was applied to characterize ecological risk of chemical contamination in nearshore areas adjacent to the Portsmouth Naval Shipyard, located at the mouth of the Great Bay Estuary, New Hampshire and Maine, USA. Measures of exposure and effect were used to interpret the magnitude of risk to the assessment endpoints of pelagic species, epibenthic species, the benthic community, eelgrass plants, the salt marsh community, and avian receptors. The evidence of chemical exposure from water, sediment, and tissue and the evidence of biological effects to representative pelagic, epibenthic, benthic, eelgrass, salt marsh, and avian species were weighed to characterize ecological risk. Individual measures were weighted by the quality and reliability of their data and risk was estimated from the preponderance, magnitude, extent, and strength of causal relationships between the data on exposure and effects. Relating evidence of risk to hypothesized pathways of exposure made it possible to estimate the magnitude of risk from sediment and water and express the confidence associated with the findings. Systematically weighing the evidence of risk rendered conclusions about risk in a manner that was clearly defined, objective, consistent, and did not rely solely on professional judgment.

A Levels-of-Evidence Approach for Assessing Cumulative Ecosystem Response to Estuary and River Restoration Programs

“…In particular, tools from the science of ecotoxicology-systematic approaches to assess existing and potential impacts of stressors on ecosystems Yu 1999, Luoma et al 2001)-provide insights on how to begin to integrate cumulative effects in evaluating restoration success. Ecotoxicologists use a system of reasoning called weight of evidence to estimate the adverse effects on ecosystems caused by complex stressors, typically combinations of toxins (e.g., Johnston et al 2002, Staples et al 2004). Weight-of-evidence is a logical system used to relate measurable indicators in the ecosystem to a target assessment endpoint (Norton et al 1992, Menzie et al 1996.…”

Integrated Risk Assessments for the Management of Contaminated Sediments in Estuaries and Coastal Systems

“…This is because the approaches used to evaluate all the factors that determine ecological risk are often not well defined and are subject to interpretation (Johnston et al, 2002). Furthermore, due to differences in scientific basis, study design, and method sensitivity, different methods have different degrees of uncer tainty.…”

“…Furthermore, due to differences in scientific basis, study design, and method sensitivity, different methods have different degrees of uncer tainty. Johnston et al (2002) further refined this approach by developing a weighting proce dure which addressed how well the measurement data related to the assessment of stressor levels or ecological damage. Considerable consensus building and professional judgment are required to develop robust conclusions regarding risk.…”

Characterizing the risks to aquatic ecosystems: A tentative approach in the context of freshwater dredged material disposal

“…This procedure allows a rigorous consideration of the strengths and weaknesses and of the nature of uncertainty associated with each measurement. Although their conceptual framework was not developed specifically for sediments or dredged materials, it can be applied to this type of material, as Johnston et al (2002) have done for an estuarine site downstream of a former shipyard. This site‐specific study also provided a number of conceptual developments to the WOE approach initially proposed by Menzie et al (1996) and established a basis for designing the risk characterization step of ecological risk assessment frameworks of bed sediments or dredged materials.…”

“…The risk characterization approach proposed to the French authorities stems from the above‐mentioned papers by the Massachusetts WOE Workgroup (MWWG; Menzie, 1996) and Johnston et al (2002). Both effects and exposure data are converted and combined into classes of ecological risk.…”