Ecological components

Stressor is a chemical, physical or biological agent that can cause adverse effects in non-human ecological components ranging from organisms, populations, and communities, to ecosystems (Smrchek and Zeeman,... 

Thompson, S., Treweek, J. R., Thurling, D. J. (1997). The Ecological Component of Environmental Impact Assessment — a Critical Review of British Environmental Statements. Journal of Environmental Planning and Management, 40(2), 157-171. 

COMPARATIVE MULTI-ELEMENTAL ANALYSIS OF MINERAL AND ECOLOGICAL COMPONENTS OF THE ECOSYSTEM "KARABASHTOWN" CO-EXISTING WITH A COPPER-SMELTING PLANT. PHYSICOCHEMICAL POINT OF VIEW 137 N.M. BARYSHEVA, N.V. GARMASHEVA, E. V. POLYAKOV, V.T. SURIKOV,V.N. UDACHIN... 

COMPARATIVE MULTI-ELEMENTAL ANALYSIS OF MINERAL AND ECOLOGICAL COMPONENTS OF THE ECOSYSTEM "KARABASHTOWN" CO-EXISTING WITH A COPPER-SMELTING PLANT. PHYSICOCHEMICAL POINT OF VIEW... 

Direct effect An effect resulting from an agent acting on the assessment endpoint or other ecological component of interest itself, not through effects on other components of the ecosystem. See also indirect effect. 

Littler, M.N. and Doty, M.S., 1975. Ecological components structuring the seaward edges of tropical Pacific reefs The distribution, communities and productivity of Poroli-thon. J. Ecol., 63 117-129. 

The second phase of the framework is termed analysis and consists of two activities, characterization of exposure and characterization of ecological effects. The purpose of characterization of exposure is to predict or measure the spatial and temporal distribution of a stressor and its co-occurrence or contact with the ecological components of concern, while the purpose of characterization of ecological effects is to identify and quantify the adverse effects elicited by a stressor and, to the extent possible, to evaluate cause-and-effect relationships. 

Some reviewers of earlier drafts of this interim framework proposed that the term "exposure" — which, as used in human health risk assessment, generally refers to chemical stressors — not be used for the nonchemical stressors that can affect a variety of ecological components. Other terms, including "characterization of stress," have been suggested. At this time, EPA prefers exposure, partly because characterization of stress does not convey the important concept of the co-occurrence and interaction of the stressor with an ecological component as well as exposure does. 

The need to evaluate spatial and temporal distribution and variation is inherent in many of these example characteristics. Such information is especially useful for determining potential exposure, that is, where there is cooccurrence of or contact between the stressor and ecological components. 

Ecological effects data may come from a variety of sources. Relevant sources of information include field observations (e.g., fish or bird kills, changes in aquatic community structure), field tests (e.g., microcosm or mesocosm tests), laboratory tests (e.g., single species or microcosm tests), and chemical structure-activity relationships. Available information on ecological effects can help focus the assessment on specific stressors and on ecological components that should be evaluated. 

Information compiled in the first stage of problem formulation is used to help select ecologically based endpoints that are relevant to decisions made about protecting the environment. An endpoint is a characteristic of an ecological component (e.g., increased mortality in fish) that may be affected by exposure to a stressor (Suter, 1990a). Two types of endpoints are distinguished in this report. Assessment endpoints are explicit expressions of the actual environmental value that is to be protected. Measurement endpoints are measurable responses to a stressor that are related to the valued characteristics chosen as the assessment endpoints (Suter, 1990a). 

The major focus of the conceptual model (Figure 2) is the development of a series of working hypotheses regarding how the stressor might affect ecological components of the natural environment (NRC, 1986). The conceptual model also includes descriptions of the ecosystem potentially at risk and the relationship between measurement and assessment endpoints. 

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