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Ecological Attributes
The biological indicator or set of indicators that a State or Tribe develops depends on their ability to measure the ecological attributes of the aquatic flora and fauna. Ecological attributes are those aspects of an aquatic assemblage or community that correspond to the structure and function of that assemblage or community for a given condition. The Biological Condition Gradient (BCG) represents a continuum of condition in response to human disturbance and is determined or measured by an understanding of these attributes (Davies and Jackson 2006, USEPA 2010, BCG Development Guide). Ten primary ecological attributes have been identified as the basis for evaluating the BCG and establishing a viable biological indicator (Davies and Jackson 2006). The first six attributes relate to taxonomic identity, composition, and tolerances. They are 1) historically documented, sensitive, long-lived, or regionally endemic taxa, 2) sensitive rare taxa, 3) sensitive ubiquitous taxa, 4) taxa of intermediate tolerance, 5) tolerant taxa, and 6) non-native taxa that tend to displace endemic taxa. Attribute 7) organism condition, provides information on individual health. The remaining three attributes are 8) functional integrity, 9) ecosystem connectance, and 10) spatial and temporal extent of stressors. These attributes are not directly measured by bioassessment, but rather are inferred from the condition and well-being of the aquatic biota; hence, they are not discussed herein.
Some Frequently Asked Questions
Question: I have a calibrated index; so, why do I need to consider the ecological attributes of the BCG?
Answer: The ecological attributes of a BCG (see Table below) and a calibrated biological index are not mutually exclusive. In most instances the components of an index reflect several of the ecological attributes. We have found that having biological information that correspond to the attributes aids in defining biological condition tiers along the gradient and in characterizing the highest expectation for the ecosystem. An agency can use the underpinnings of the attributes to improve a biological index.
Question: What if I don’t have enough information to address all of the attributes?
Answer: Refining bioassessments is a dynamic process. The matrix and description of the ecological attributes provides guidelines designing monitoring programs that procure data relevant to supporting a more robust bioassessment method. The goal should be to implement a bioassessment program robust enough to address the agency’s questions and needs.
References
Davies SP, Jackson SK. 2006. The Biological Condition Gradient: A Descriptive Model for Interpreting Change in Aquatic Ecosystems (PDF) . Ecological Applications: Vol. 16, No. 4 pp. 1251–1266 (16pp, 184 KB About PDF)