Characterizing the distribution of benthic fauna of the Lower Bay Complex into two broad geographic regimes is, of course, an oversimplification and community structure is more complex. Detailed analyses by Diaz and Boesch (1979), Steimle etal. (1989), and NOAA-USACE (2001) describe between five and ten geographic subdivisions and up to six species groups. My own attempt to examine community structure in the regional studies using a common set of multivariate methods failed. Spatial or habitat relationships were not well represented by MDS ordinations or UPGMA clustering. In most cases, goodness-of-fit measures for the 1959-60, January 1973, and August 1983 data sets were unsatisfactory. These measures were only slightly better, in the fair to good categories, for 1986-87 and 1994-95 data sets. Using functional groups instead of species as descriptors did not improve the goodness-of-fit measures.
Relationships assessed by correlating the faunal and environmental databy Mantel test while significant were also weak (Table 18.5). Thus, interpreting spatial and faunal-environmental associations based on these multivariate techniques was determined to be problematic.
Inverse analyses to examine faunal associations also resulted in a large number of goodness-of-fit problems. Goodness-of-fit measures for analyses with species were either poor or fair. Repeating the inverse analysis using functional groups as descriptors improved the goodness-of-fit only slightly, but it was enough to merit detailed analyses. Several distinct functional group associations were present (Table 18.6). Assemblage A consisted of two epifau-nal, nontubiculous functional groups (ENMC and ENSS), a surface deposit feeding group (INMDs), and a suspension feeding group (ETSS). This assemblage was predominantly found in sandy
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