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APPLICATIONS OF A CONCEPTUAL MODEL (THE BIOLOGICAL CONDITION GRADIENT) TO DEFINE AQUATIC REFERENCE CONDITIONS
Citation:
Davies, S. P. AND D P. Larsen. APPLICATIONS OF A CONCEPTUAL MODEL (THE BIOLOGICAL CONDITION GRADIENT) TO DEFINE AQUATIC REFERENCE CONDITIONS. Presented at North American Lake Managers Society Meeting, Mashantucket, CT, November 4-8, 2003.
Description:
The United States Clean Water Act currently offers no definitions to interpret the Act's objective to "restore and maintain physical, chemical and biological integrity of the Nation's waters". Operative definitions, independent of differences in assessment methodologies, are needed for consistent interpretation of stages of biological degradation across the country. The Biological Condition Gradient (BCG) is a conceptual model, developed by a workgroup of the United States Environmental Protection Agency, that describes six progressively deteriorating categories of biological condition. Changes in ten ecological attributes are presented that characterize stages of deteriorating biological condition in response to increasing levels of human disturbance.
There is a critical need for scientific consensus about what biotic and physical characteristics constitute legitimate reference conditions. Quantitative characterization of reference conditions is a requirement of most approaches to the development of biological thresholds to distinguish biological condition categories. A powerful convergence of concepts results from presenting the BCG in the context of a similarly constructed human disturbance gradient (or a stressor specific gradient). Conceptual and graphical approaches that combine consideration of a y-axis depicting biological condition, in relation to an x-axis depicting a stressor or generalized human disturbance gradient have contributed enormously to clarifying the issues and providing a context for productive dialogue.
The Biological Condition Gradient conceptual model is consistent with ecological theory and accommodates empirically observed biological responses to human disturbance gradients. The conceptual model facilitates communication about the legal, scientific, and ethical implications of societal choices by objectively describing stages of anthropogenic biological degradation.