Can death assemblages provide meaningful estimates of diversity, relative abundance & other aspects of local communities across multiple higher taxa simultaneously? Although most fossil assemblages consist of multiple higher taxa, we lack a clear understanding of whole assemblage fidelity, i.e., relative taphonomic biases across multiple higher taxa. Studies comparing living communities to death assemblages have been fruitful in assessing biases induced by the fossilization process, & quantifying the expected fidelity of the resulting fossil record. However, these types of analyses are typically restricted to a single taxon, primarily more heavily calcified organisms such as mollusks. In an effort to quantitatively assess taphonomic biases across multiple marine invertebrate groups with variable biomineralization (bivalves, gastropods, echinoids, decapods, & chelicerates) we are targeting the subtidal benthos of coastal North Carolina.

Field collections from 55 localities & 221 samples resulted in the identification of 11,248 live individuals, & 94,964 dead individuals, representing 231 species (Figure 1). Our data suggest that taphonomic filters can alter relative abundance of higher taxa. While mollusk-based fidelity analysis provides a powerful tool for assessing anthropogenic changes, other groups with lower fossilization potential, may be less informative or more difficult to interpret in terms of human impacts on ecosystems (Figure 2). In addition to enhancing our understanding of the quality of the fossil record, this project also provides an important reference baseline for conservation biology where the assessment of anthropogenic changes in local ecosystems is essential for reconstructing pristine communities that existed prior to human-induced disturbances.

 In addition to the main project outcomes described above, these data were also used to examine whether environmental conditions associated with increasing water depth such as temperature, salinity, & nutrients should result in fundamental differences in invertebrate marine communities. Whether depth & its related environmental parameters control faunal composition has previously not been directly tested. If depth is a widespread primary control on community structure, & can be readily inferred from paleontological data, this would have significance for stratigraphic patters of fossil occurrences.

We evaluated modern macro-faunal associations of marine invertebrates along an onshore-offshore gradient in North Carolina to determine the relationship between community composition & bathymetry, compare the performance of various ordination techniques, & to evaluate whether differences in resolution between modern & paleontological data reduce the ability of ordinations to effectively capture ecological gradients. Communities do ordinate along an axis that primarily reflects bathymetry & its environmental correlatives, producing analogous results with a variety of ordination techniques (Figure 3 & 4). This relationship was strong using heavily biomineralized taxa, & when excluding mollusks; Ordinations using only mollusks did not perform as well, however, limiting the analysis to robust mollusks improved the clarity of the bathymetric signal (Figure 5).

Some types of paleontological data should, therefore, accurately capture bathymetric gradients. 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 & consistent with multiple paleontological studies. Fossil communities may provide robust quantitative water depth estimates with applications to paleoecology & stratigraphy.

Finally, beta diversity (β) is often ...

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