The ecological forces that drive community structure of deep-sea benthic
communities are poorly understood, yet such communities rival in biological complexity
those of coral reefs or rainforests. Using components of the recently concluded DGoMB
project, local and regional-scale structure of benthic macrofaunal communities were
examined at thirty two locations throughout the continental slope of the northern Gulf of
Mexico. Controlling factors associated with sediment disturbance, food supply, and
faunal competition between functional ecological groups were evaluated for correlative
and relational patterns. A higher order taxonomic sufficiency approach was used to
calculate both alpha and beta diversity.
The results of this study indicate that macrofaunal communities are very patchy,
having wide variations in abundance at within-site, adjacent-site, and across-basin
scales, yet all sample areas possess a large richness of higher taxa. Declining abundance
was noted with increasing water depth and reduced particulate organic carbon levels.
Upper-slope submarine canyons possess some of the highest abundances. Less mobile
macrofauna, such as poriferans, bivalves, and scaphopods, dominate slope communities above the 500 meter contour. Sediments exhibiting intense megafaunal bioturbation
inhibit abundances of sedentary macrofaunal taxa, but such mixing is positively
associated with increased abundances of polychaetes and ambulatory crustaceans,
including peracarids, harpacticoids, and ostracods. Prominent sediment mixing was
noted at most sites, including portions of the Sigsbee Abyssal Plain. The western Gulf of
Mexico was less biologically active than the eastern Gulf of Mexico, which possesses
two extensive submarine canyons that appear to act as regional nutrient traps. I conclude
that the physiographic complexity of the northern Gulf of Mexico continental slope
influences macrofaunal community structure. Biological disturbance, in the form of
sediment mixing, is widespread throughout most slope depths, and the benthic
environment is food-limited. It appears that disequilibrium-type ecological processes
predominate in this area, supporting similar findings by previous studies in other regions
of the ocean, usually at far smaller scales and none representative at the basin-level. Use
of higher order taxonomy in lieu of genus or species-level faunal identifications for
diversity measurements was inadequate for detecting spatial patterns or environmental
responses.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/5947 |
| Date | 17 September 2007 |
| Creators | Ammons, Archie Wood |
| Contributors | Rowe, Gilbert, Wicksten, Mary |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 3248612 bytes, electronic, application/pdf, born digital |
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