Abstract
The Campeche Sound is the major offshore oil producing area in the Southern Gulf of Mexico (SGoM). To evaluate the impact of oil related activities in the ocean floor sediments, we analyzed the geochemical (major and trace element, organic carbon and hydrocarbon concentrations) and biological (benthic foraminifera) composition of 62 superficial sediment samples, from 13 to 1336 m water depth. Cluster and Factor analysis of all the variables indicate that their distribution patterns are mainly controlled by differences between the terrigenous and carbonate platforms in the SGoM. Benthic foraminiferal assemblages were abundant and diverse, and their distribution patterns are mainly determined by water depth and sedimentary environment. However, most of the abundant species are opportunistic and/or low-oxygen tolerant, and many of their tests show oil stains and infillings, characteristic of oil polluted locations, suggesting the environment has been modified by natural seepage or oil-related activities. To determine if these conditions are natural or anthropogenic in origin, pre - industrial settings should be studied. Organic carbon (Corg) content (0.6–2.9%) and total hydrocarbon concentrations (PAHs 1.0–29.5 μg kg−1) were usually higher around the oil platforms area, the natural hydrocarbon seeps (“chapopoteras”) area and offshore rivers, but there is no accumulation of oil related trace elements in these areas. However, the comparison with international sediment quality benchmarks indicates that Cd, Cr and Ni concentrations are above the threshold effect level, and also As, Ba and Cu are above the probable effect level benchmarks, which indicate that these element concentrations might be of potential ecological concern. Comprehensive studies involving different proxies, and assessing pre-industrial conditions, must be undertaken before assessing environmental health of marine benthic ecosystems.
Highlights
Oil exploration and production activities often cause enrichment of hydrocarbon and trace element concentrations in aquatic environments, which might result in acute and/or chronic effects to biota (Peterson, 2001; Mojtahid et al, 2006)
In this study we investigated the characteristics and spatial distribution patterns of total BF, and their relationship to Corg, Polycyclic aromatic hydrocarbons (PAHs) and trace element concentrations in the sediments, with the purpose to assess their present - day status and to establish the basis for later studies of pre-industrial conditions in the area
2 Most of the specimens included in this taxon are similar to E. discoidale forma translucens (Poag, 2015, pl. 35, Fig. 2)
Summary
Oil exploration and production activities often cause enrichment of hydrocarbon and trace element concentrations in aquatic environments, which might result in acute and/or chronic effects to biota (Peterson, 2001; Mojtahid et al, 2006). Sources of chronic oil exposure include oil seeps, operational discharges of produced water and drill cuttings, as well as non-point runoff from land - based facilities (RuizFernández et al, 2016). Metals and metalloids may be naturally found in the crude oil, and concentrations may be enhanced by oil related activities (such as production, transportation and storage) owing to operational discharges of produced waters and drill cuttings (including chemical additivities) or accidental spills (including chemical dispersants) (Ruiz-Fernández et al, 2019).
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