Wednesday, May 20, 2009: 2:45 PM
Vandenberg B
An element of tiered aquatic life uses (TALU) is the establishment of the biological condition of natural or undisturbed resources. Setting these expectations on the Biological Condition Gradient (BCG) anchors assessments and permits comparison of site condition in relation to the natural state. However, determination of the biological condition of natural communities is hindered by a lack of extant examples of these communities in many regions with extensive and ubiquitous disturbance. Contemporary and historical data were used to establish biological condition under natural conditions for several classes of Minnesota streams. This analysis produced indicator species and community attributes for natural communities which could be used to set assessment guidelines and management goals. Two major limitations of historical data were apparent: 1) spatially and temporally variable collection efforts and 2) limited collection from pre-impact periods. For example, many species listed as state special concern in Minnesota may not have even been abundant and therefore, historical collections may under represent these species due to limited collection efforts. Historical information helped to identify species with declining distributions which could then be used to reconstruct natural communities, but best professional judgment was also needed as a result of limitations with these data.