title: Cluster analysis of contaminated sediment data: nodal analysis.
abstract: The objective of the present study was to explore the use of multivariate statistical methods as a means to discern relationships between contaminants and biological and/or toxicological effects in a representative data set from the National Status and Trends (NS&T) Program. Data from the National Oceanic and Atmospheric Administration, NS&T Program's Bioeffects Survey of Delaware Bay, USA, were examined using various univariate and multivariate statistical techniques, including cluster analysis. Each approach identified consistent patterns and relationships between the three types of triad data. The analyses also identified factors that bias the interpretation of the data, primarily the presence of rare and unique species and the dependence of species distributions on physical parameters. Sites and species were clustered with the unweighted pair-group method using arithmetic averages clustering with the Jaccard coefficient that clustered species and sites into mutually consistent groupings. Pearson product moment correlation coefficients, normalized for salinity, also were clustered. The most informative analysis, termed nodal analysis, was the intersection of species cluster analysis with site cluster analysis. This technique produced a visual representation of species association patterns among site clusters. Site characteristics, such as salinity and grain size, not contaminant concentrations, appeared to be the primary factors determining species distributions. This suggests the sediment-quality triad needs to use physical parameters as a distinct leg from chemical concentrations to improve sediment-quality assessments in large bodies of water. Because the Delaware Bay system has confounded gradients of contaminants and physical parameters, analyses were repeated with data from northern Chesapeake Bay, USA, with similar results.
authors.affiliation: National Oceanic and Atmospheric Administration/National Ocean Service, Center for Coastal Monitoring and Assessment, 1305 East West Highway, SSMC4, N/SCI1, Silver Spring, Maryland 20910, USA. ian.hartwell@noaa.gov
authors.forename: S Ian
authors.initials: SI
authors.lastname: Hartwell
authors.forename: Larry W
authors.initials: LW
authors.lastname: Claflin
mesh_terms: D000818:Animals; D016000:Cluster Analysis; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D013045:Species Specificity; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical