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Sample Collection

Sample Collection

Standardizing field methods is necessary to establish the validity and reliability of biological data used in an assessment.  A lack of standardization results in the use of diverse methods, which ultimately yields conflicting information.  Standardization is especially important when information will be used in later trend analysis.  Studies have shown that variability between habitat types (e.g., riffles versus depositional areas) can affect results in single habitat sampling efforts (Boyero 2003).  Gerth and Herlihy (2006) found that sample type differences were more pronounced between mid-Atlantic riffle and pool samples than between western U.S. reachwide and riffle samples.  Gerth and Herlihy (2006) stated that reachwide sampling  could be used with little risk to the quality of assessments in surveys covering large geographic areas where a single targeted habitat may not occur at all sites.

Thorough training of investigators, coupled with rigorous certification processes, enhances the ability to provide a consistent unit of effort.  Strong oversight of activities and supervision of apprentice professionals are critical.  QC procedures, such as field crew audits, replication at 10% of the sites, and site re-visits within an index period are important for ensuring data integrity.  Evaluation of methods is necessary to ensure the sampling techniques are appropriate for the aquatic ecosystem being studied.  Considerations for field sampling of macroinvertebrates, fish, algae, and aquatic macrophytes include habitat type to be sampled, gear type, number of samples required, reach length, and field methods.  For instance, Battle et al. (2007) found that caution should be used when different mesh sizes are involved in macroinvertebrate sampling in large rivers—it may be inappropriate to contrast data produced with different mesh sizes or to combine data from different mesh sizes to create a long-term perspective.  Most fish and macrophyte assessments are carried out in the field and do not require extensive laboratory analysis.  However, vouchering of these organisms is a necessary quality control (QC) function to verify accurate and consistent identifications. 

Field personnel must consider proper preservation (e.g., macroinvertebrate and algal samples) labeling, transport, and transfer to lab personnel.  The development of standard operating procedures (SOPs) for field and laboratory methods must include an effective quality assurance (QA) program with QC checks.  The development of an effective QA plan is essential to the success of the bioassessment program.  It should assign responsibility, define personnel qualifications, establish protocols, define preventative and corrective action, provide information tracking, and ensure that study objectives are met.  QA plans are especially important to regulate performance and maintain data integrity.  To minimize bias, reduce error, and maintain a high level of data integrity as prescribed by the measurement quality objectives (MQOs) (see Technical Element 10, Ecological Attributes), the SOPs and QA/QC plan must identify the specific procedures for all aspects of the biological program.  This information should be available for other parties to use as a reference in developing compatible monitoring projects.  USEPA has published a generic quality assurance project plan (QAPP) guide for programs using assemblage-level biological assessment in wadeable streams and rivers (USEPA 1995a).

Some Frequently Asked Questions

Question:  How does sample collection influence the rigor of a bioassessment?
Answer:  Sample collection is the genesis of bioassessment data; therefore how it is designed and executed influences the ability of a bioassessment to adequately and accurately describe biological quality.  However, bioassessment sample collection must be sufficiently cost-effective so as to produce a sample with 2-3 hours effort in the field.

Question:  How do I know which method is best for my biological indicator?
Answer:  The method should produce data of sufficient quality to discriminate multiple condition categories along the BCG.  Biological sample collection requires must be done by qualified professionals to attain Levels 3 and 4. 


References

Battle, J.M., J.K. Jackson, and B.W. Sweeney.  2007.  Mesh size affects macroinvertebrate descriptions in large rivers: examples from the Savannah and Mississippi Rivers.  Hydrobiologia 592(1):329-343.

Boyero, L.  2003.  Multiscale patterns of spatial variation in stream macroinvertebrate communities.  Ecological Research 18(4):365-379.

Gerth, W.J. and A.T. Herlihy. 2006.  Effect of Sampling Different Habitat Types in Regional Macroinvertebrate Bioassessment Surveys.  Journal of the North American Benthological Society 25(2): 501-512.

USEPA.  1995a.  Generic Quality Assurance Project Plan guidance for programs using community level biological assessment in wadeable streams and rivers.  Authors:  J.B. Stribling, C. Gerardi, and C. Faulkner.  EPA 841-B-95-004.  Office of Water, USEPA, Washington, DC.

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