Index of biological integrity

Index of biological integrity

To quantitatively assess changes in the composition of biologic communities Indices of Biological Integrity (IBIs) are developed to accurately reflect the ecological complexity from statistical descriptions of sample species counts. There is no one universal IBI, and developing metrics that consistently give accurate assessment of the monitored population requires rigorous testing to confirm its validity for a given subject. Often IBIs are region specific and require experienced professionals to provide sufficient quality data to correctly asses a score. Because communities naturally vary as do samples collected from a larger population, identifying robust statistics with acceptable variance is an area of active research.

This is the most powerful tool existing to identify systemic impacts on the health of biological systems. IBIs are increasingly involved in the identification of impairment, and confirmation of recovery of impaired waters, in the Total Maximum Daily Load process required by the Clean Water Act in the USA.

Unlike chemical sampling, and Biological Oxygen Demand tests, which give brief snap shots of chemical concentrations, an IBIs capture an integrated net impact on a biological community structure. While complete absence, particularly sudden disappearance of, suits of indicator species can constitute powerful evidence of a specific pollutant or stress factor, IBIs generally do not resolve a specific cause of impairment.

It is possible to create IBIs for use for minimally trained monitoring personal; however, the precision obtainable is less, safe guards to assure robustness in spite of potential misidentification's or protocol variations require careful testing, ongoing quality control by established experts is needed to maintain data integrity, and the analysis of IBI results becomes more complex. This is however being pioneered by government agencies responsible for monitoring far more water bodies than they can send qualified personnel with adequate frequency and regularity to observe changes (eg the MN PCA WHEP program, and VSMP programs in MN (USA)). While IBIs from such a programs are legally admissible in USA courts, defending the validity of conclusions based solely on such results is unlikely to be feasible.

Agreement among multiple IBIs from data collected by established professionals can be more conclusive. A case in point is the phenomena that stream IBI scores indicate significant impairment, or partial ecological collapse where ever more than 20% of the immediately surrounding watershed is impervious due to development. Identifying reasons for this, and hopefully verifying some exception too this, are major research challenges for academics studying cumulative watershed effects, and innovators attempting to achieve Low Impact Development.

So far IBIs exist for fish, algae, macroinvertebrates, pupal exuvia (shed skins of chironomidae), vascular plants, and combinations of these.


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