Methods

Review of BEST Methods Suite

By applying a standard suite of biomonitoring methods in its Large River Monitoring Network (LRMN) the BEST Project measures and assess the effects of contaminants on resident fish in inter-jurisdictional rives of the U.S.  The LRMN biomonitoring methods suite includes morphometric, biochemical, histological, and tissue residue endpoints.  The operational BEST LRMN methods suite was selected from a more inclusive list of habitat-appropriate techniques (BEST 1994). Both the original list of methods and the subset of those methods that were selected for use in the LRMN were chosen based on best professional judgment.  Since the initial application of the methods suite in 1995 a considerable knowledge-base has been developed regarding the technical characteristics of the methods.  In addition to developing a operational competency in applying and interpreting these methods, detailed technical assessments have been published for two of the techniques (EROD, H4IIE ref).  However, experience and operational competency is no substitute for a structured assessment of the performance of the methods individually, in combination, across all basins. 

In FY 06, the BEST Project will evaluate the “performance” of the LRMN methods using a holistic approach that goes beyond assessing traditional benchmarks (i.e., accuracy, precision, and detection limits)  The performance evaluation must also recognize and take into account critical nonnumeric characteristics like as interpretability, redundancy, turnaround, complexity, sensitivity, interference, implications of false positive and false negative signals, optimal sample timing, and information gaps.

Assessment of nonnumeric considerations will involve a iterative, consensus based approach. Principle Investagators will participate in developing and refining evaluation criteria (i.e., redundancy, cost, turn-around, simplicity, robustness, relative implications of false positives and false negatives, strength of correlations between endpoints and stressors, bias, known interferences, and magnitude of critical information gaps). A consensus weight for the evaluation criteria will also be established.  The operational methods under review will be ranked according to the consensus derived criteria and weight factors.  The group will then use this information, in combination with findings from the statistical analysis as the basis to recommend ways to optimize the operational LRMN methods suite.

For a comprehensive review of the methods used in the LRMN and its associated products please visit the Columbia Environmental Research Center at: http://www.cerc.usgs.gov/pubs/BEST/synthesis.htm

A brief summary of the methods used in the LRMN fish health assessments isprovided below. For a detailedexplantion on the methods used in the LRMN, select the report image to the right.

BIOMARKERS
Biomarkers are physiological changes in an organism which indicate exposure to a chemical. The BEST Program employs a suite of biomarkers as indicators of contaminant exposure and effects. Biomarkers of fish measured in the BEST Program include:

Necropsy-Based Fish Health Assessment
Gross assessment of external and internal abnormalities (e.g., lesions, parasites, tumors) which can indicate contaminant related stress.  Although this gross assessment is not considered a biomarker, it is used in conjunction with the histopathologic assessment.

Histopathologic Assessment
Cellular examination of specific tissues, organs, lesions and abnormalities. This biomarker used with other assessment methods provides for a more comprehensive diagnosis for contaminant related effects.

Ethoxresorufin-O-deethylase (EROD) Activity
An assessment to the induction of the cytochrome P450 enzymes. Several classes of planar halogenated and polycyclic aromatic hydrocarbon compounds induce cytochromes P450 including: PCBs, PAHs, dioxins, and furans. Measurement of EROD activity provides BEST with a rapid indication to exposure to these compounds.

Macrophage Aggregate Analysis
An immune system biomarker, macrophage aggregates in fish respond to the exposure of a variety of contaminants.

Condition Factor and Organo-Somatic Indices
Condition factors (weight to length) and organo-somatic indices (proportional size of organs) are good methods to determine organism-level responses to contaminant exposure. 

H4IIE Bioassay
This bioassay is a rapid and sensitive procedure to indicate the presence of dioxin and related compounds and provide estimates of the potential cumulative toxicity of these compounds to fish.

Vitellogenin
This method as an indication of exposure to endocrine modulating compounds.

Sex Steroids (estradiol and testosterone)
BEST uses this method as an indication of exposure to endocrine modulating compounds.