Continental shelf benthic biomass in the western Gulf of Mexico

Benthic biomass of the soft-bottom community of the continental shelf in the western Gulf of Mexico reveals a significant space and time variability according to data obtained in three cruises during 1988 and 1989. This system is highly influenced by the hydrographic regime defined by anticyclonic ring interactions, convective mixing, and river runoff and fronts. Total benthic biomass varied among cruises and spatially by almost three orders of magnitude. High values (2.01-1.22 g C. m−2) were found in April 1989 and September 1988 (stratified period), and low values (0.33 g C. m−2) were found in November 1989 (mixed period). The northerly winter wind stress promotes coupling between pelagic and benthic compartments with the refurbishing of the benthic community with surface water carbon food sources. Small scale variability, due to either hydrological or sedimentological factors, accounts for the patchy distribution observed and large standard deviation recorded. Shelf benthic biomass was inversely related to depth: total benthos (r2 = 0.70), epibenthic macrofauna (r2 = 0.82), and infauna (r2 = 0.71). Largest total biomass values were obtained in areas influenced by river runoff and showed a northward increase in biomass during the stratified condition and southward in the period of mixing. These trends were likely related to wind transport of organic matter from riverine sources or production stimulated by riverine nutrient fluxes. Biomass values reported here are similar to others from similar depths in the Gulf of Mexico and worldwide.