USING BENTHIC MARINE INVERTEBRATE COMMUNITY ASSEMBLAGES AS PALEO-BATHYMETRYIC PROXIES: A DIRECT TEST FROM RECENT COASTAL ECOSYSTEMS OF NORTH CAROLINA USING MULTIVARIATE ORDINATIONS
We evaluated modern macro-faunal associations of marine invertebrates along an onshore-offshore gradient in North Carolina to determine the relationship between community composition and bathymetry, compare the performance of various ordination techniques, and to evaluate whether differences in resolution between modern and paleontological data reduce the ability of ordinations to effectively capture ecological gradients. Axis 1 scores correlate with actual depth values of species and samples, confirming that communities ordinate along an axis that primarily reflects bathymetry and its environmental correlatives, producing analogous results with DCA, NMDS, CA, and PCO. Axis 1 scores also correlated significantly with depth for ordinations restricted to heavily biomineralized taxa, as did those excluding mollusks. Ordinations using only mollusk did not perform as well, however, limiting the analysis to robust mollusks improved the clarity of the bathymetric signal.
Some types of paleontological data should, therefore, accurately captured bathymetric gradients, and in coastal ecosystems of North Carolina, bathymetry appears to be a primary controlling factor. Although it is arguable that individual case studies such as this one can support broader generalizations, these results are promising and consistent with multiple paleontological studies. Fossil communities may provide robust quantitative estimates of bathymetry with potential applications to paleoecology and stratigraphy.