text: The analysis of field effects on benthic organisms functions to assess the potential for community based effects resulting from the identified contaminants. This is done because benthic organisms are sessile and location specific, allowing them to be used as accurate markers of contaminant effect (Chapman, 1990). This is done through conducting field-based tests, which analyze changes in benthic community structures focusing on changes in number of species, abundance, and percentage of major taxonomic groups (Chapman, 1997). Changes in benthic communities are typically quantified using a principal component analysis and classification (Chapman, 1997). There is no one specifically defined method for conducting these field assessments, however the different multivariate analysis typically produces results identifying relationships between variables when a robust correlation exists.
  Knowledge of the site-specific ecosystem and the ecological roles of dominant species within that ecosystem are critical to producing biological evidence of alteration in benthic community resultant of contaminant exposure. When possible, it is recommended to observe changes in community structure that directly relate to the test species used during the sediment toxicity portion of the triad approach in order to produce the most reliable evidence.