Assessing the impact of oil-related activities on benthic macroinfauna assemblages of the Campeche shelf, southern Gulf of Mexico

Abstract

Considering the long history of oil extraction and the numerous platforms that exist in the southern Gulf of Mexico, a regional approach has been used to investigate the impact of oil-related activities on the macrobenthic community. The objective was to determine the effect of oil-related activity in a region known to have a highly variable benthic community composition due to temporal and spatial variability of its natural environment. A transect design along gradients of natural variables and disturbance intensities, including active oil platforms, was implemented during the rainy and winter storms (‘northers’) seasons of 1999 to 2000. Univariate and multivariate statistical analyses were applied to a data set of 2 macroinfauna size fractions retained on 0.5 and 2 mm sieves, in conjunction with levels of metals, oil hydrocarbons and a range of natural sediment variables. A pattern of contamination existed, with increased levels of contaminants at stations close to rigs and in areas of high oil platform densities. At these sites, macroinfauna abundance and biomass were reduced. Regression analyses and matching of Biotic to Environmental multivariate patterns (BIO–ENV) indicated that a combination of metals and natural sediment variables best explained the variability in macroinfauna data for all sites. Meta-analysis at phylum level was employed to specifically assess disturbance. The results of this technique were inconsistent between sampling dates due to a complex influence of natural and anthropogenic disturbance. However, increased variability in community composition was linked to oil-related disturbance.