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 oilrelated activities on the macrobenthic community. The objective was to determine the effect of oilrelated 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.

Discharged drilling waste from oil and gas platforms and its effects on benthic communities

“…A region-wide study provides information on the potential for cumulative effects where multiple wells are drilled in an area (Hernández Arana et al 2005). In the southern Gulf of Mexico, a regional shelf-wide study was conducted that sampled across an 8000 km 2 area that included 200 oil platforms with a range of functions.…”

“…Finally, for all 48 stations sampled, a fossil fuel pollution index was measured and The nearest distance to oil platforms for these stations ranged from 1300 to 22 500 m for stations in 1999 and 700 to 25 500 m for stations in 2000, indicating that the distance of effects for petroleum origin hydro carbons could range out to 25.5 km. It was therefore concluded that oil-related activities in the southern Gulf of Mexico have a significant effect on the macro faunal assemblages and that effects are com para tively extensive and occur at a regional scale (Her nández Arana et al 2005).…”

“…Results from ordination analysis clustered stations with high concentrations of oil hydrocarbon and metals to gether, independent of season, and these stations did not exhibit the ambient pattern of depth and grain-size gradients across and along the shelf. Specifically, the study grouped stations in relation to the number of oil platforms within a radius of 5 km from high density (4 to 12), low density (1 to 3) and no oil platforms and was able to demonstrate elevated barium and hydrocarbon concentrations with polycyclic aromatic hydrocarbons (PAHs) of petroleum origin detected at distances ranging from 700 to 25 500 m. Stations located in areas of high oil platform densities, or close to oil-related activities, had significantly lower abundance or biomass and different species composition than those stations located in areas of low platform density or farther away from oil-related activities (Hernández Arana et al 2005). These effects were generally independent of natural differences be tween the sampling dates.…”

“…Elevated concentrations of barium in tissues of polychaetes, brittle stars (primarily Amphioplus macilentus) and bivalves (primarily Lucinoma filosa) were detected as far as 1600 m from a single well discharging WBFs (Menzie et al 1980). These species cover a range of trophic modes including detritivores (brittle stars) as well as deposit-and suspension-feeding modes.A region-wide study provides information on the potential for cumulative effects where multiple wells are drilled in an area (Hernández Arana et al 2005). In the southern Gulf of Mexico, a regional shelf-wide study was conducted that sampled across an 8000 km 2 area that included 200 oil platforms with a range of functions.…”

“…Finally, for all 48 stations sampled, a fossil fuel pollution index was measured and The nearest distance to oil platforms for these stations ranged from 1300 to 22 500 m for stations in 1999 and 700 to 25 500 m for stations in 2000, indicating that the distance of effects for petroleum origin hydro carbons could range out to 25.5 km. It was therefore concluded that oil-related activities in the southern Gulf of Mexico have a significant effect on the macro faunal assemblages and that effects are com para tively extensive and occur at a regional scale (Her nández Arana et al 2005).Little information is available on recovery time scales for benthic habitats after exposure to WBFs. The few studies of benthic community change around single wells suggest that communities returned to baseline conditions 1 yr after the cessation of drilling (Currie & Isaacs 2005, Manou kian et al 2010.…”