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MEPS prepress abstract   -  DOI:

Macrofaunal diversity and community structure of the DeSoto Canyon and adjacent slope

Arvind K. Shantharam, Chih-Lin Wei, Mauricio Silva, Amy R. Baco*

*Corresponding author:

ABSTRACT: Northern Gulf of Mexico depressions are centers of organic matter accumulation and biodiversity, but studies of their finer-scale (sub-100 km) ecological patterns are scarce. Detailed sampling of macrofauna within the DeSoto Canyon was undertaken with sampling along three depth transects on the canyon wall, axis, and adjacent slope. Sediment, terrain, and water mass parameters were also compiled for the same stations. Within the canyon, macrofaunal abundance decreased, evenness increased, and richness followed the expected parabolic curve with depth, peaking at 1100 m. Cluster analysis identified three canyon depth groups that conformed to established bathymetric boundaries for the non-canyon GOM slope: Group I at < 500 m, Group II at 669 – 1834 m, and Group III at > 2000 m. Explanatory environmental models indicate canyon community structure was strongly correlated with oxygen concentration and fluorescence, with a weaker potential influence from any of salinity, particulate organic carbon (POC), sediment organic carbon, or slope. Comparisons of the habitats indicated that abundances were highest on the canyon wall. Slope community structure differed from either the canyon habitats. Explanatory environmental models consisted of single variables including oxygen concentration, sediment organic carbon, slope, and temperature with similar explanatory value. Community differences within the canyon and between the canyon and adjoining slope contradict previous findings of a single faunal zone for the whole study area. Factors that may contribute to inter-habitat heterogeneity include potential hydrocarbon seepage, organically-enriched sediment deposits along channels, or remnant influence from the Deepwater Horizon blowout, warranting more research into this dynamic ecosystem.