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Description:
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Macrobenthos of the deep , northern Gulf of Mexico have been sampled with
large box cores along multiple cross -depth transects extending from depths of 200 m out
to 3700 m . Four major depth zones have been identified based on the faunal similarities
(beta diversity ) between geographic sites , with the two intermediate -depth zones being
divided horizontally down the middle of the basin . The input of food resources appears
to control the observed patterns . Each zone and sub -zone can be described by a
characteristic animal density , biomass and biodiversity (alpha diversity ) . Highest densities
and biomass occurred in two large submarine canyons , the Mississippi and De Soto
Canyon , but the two habitats are markedly different . The alpha diversity displays an
intermediate depth maximum . Species richness (gamma diversity ) is highest on east mid -slope ,
due , we suggest , to habitat complexity , but alpha diversity is lowest at the canyon head due
to extreme dominance by amphipods . Small mean individual size and low densities
encountered are a reflection of the meager surface water primary production , albeit with
exceptional isolated habitats in which detrital material is concentrated , such as canyons
on the upper continental slope . |