Invertebrate Assemblages and Ecological Controls on Topographic Features in the Northeast Gulf of Mexico
Abstract:Biological assemblages dominated by suspension-feeding, tropical hard-bottom organisms occupy a variety of topographic features between 53 and 110 m in the northeastern Gulf of Mexico between the Mississippi River and DeSoto Canyon. Though some features may have been formed by hermatypic organisms, present-day production of calcium carbonate is limited to an impoverished calcareous algae population on features cresting above 78 m. Deeper features are considered drowned reefs or relict features unable to sustain hermatypic organisms. Faunal assemblages are of low richness and depauperate on features with relief less than 2 meters. Both richness and abundance is higher on features of 2–6 m relief. All features with relief between 6 and 18 m (the highest relief observed) harbor dense assemblages whose composition varies with habitat type. Reefs with horizontal summits harbor large populations of sponges, tall antipatharians and gorgonians, and comatulid crinoids. Vertical or rugged surfaces are dominated by ahermatypic corals. Variation between epibenthic development on features is attributable, in many cases, to differences in the potential for sedimentation. The Mississippi River plume may limit hard-bottom community development up to 70 km east of the river delta, an area much smaller than that affected to the west of the delta. Communities on these features are most like those at similar depths on outer continental shelf banks in the northwestern Gulf of Mexico, at shallower depths on mid-shelf banks in the northwest Gulf, and on south Texas banks.
Document Type: Research Article
Publication date: May 1, 1992
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