An analysis of deep-sea benthic communities in the northeastern Gulf of Mexico

Abstract

The abundance and distribution of 142 benthic species from 39 Skimmer stations in the Northeast Gulf of Mexico were analyzed using cluster analysis. Five deep-sea communities were defined: (1) Upper Continental Slope (203-476 m), (2) Middle Continental Slope (565-918 m), (3) Lower Continental Slope (1061- 1829 m), (4) Lower Mississippi Cone (2103-2734 m), and (5) Abyssal Plain (2744-3256 m). The Bray-Curtis dissimilarity measure was used to group the stations in these communities, and these groups were checked for internal homogeneity by means of Horn's measure of overlap. Species diversity and equitability calculations for the four major taxa (Pisces, Crustacea, Mollusca, and Echinodermata) in each community indicated a general decrease in diversity with depth. The distribution of the benthos is compared to similar studies in the Gulf of Mexico. The results are comparable once allowances are made for differences in sampling and technique of analysis. The distribution of the benthos in DeSoto Canyon is compared to the surrounding slope distributions, and no difference was found in either species composition or abundance. Food, hydrostatic pressure, and biological interaction are discussed as possible limiting factors for the deep-sea benthos. Sanders' Stability-Time Hypothesis is discussed and compared with later theories to explain high species diversity in the deep sea. The Stability-Time Hypothesis is not the entire answer to species diversity, but may be a prerequisite before the other causes such as predation and environmental "grain-size matching" can take place.