Natural and anthropogenic oil impacts on benthic foraminifera in the southern Gulf of Mexico

• Published in: Marine environmental research 2019-08, Vol.149, p.111-125
• Main Authors: Machain-Castillo, M.L., Ruiz-Fernández, A.C., Gracia, A., Sanchez-Cabeza, J.A., Rodríguez-Ramírez, A., Alexander-Valdés, H.M., Pérez-Bernal, L.H., Nava-Fernández, X.A., Gómez-Lizárraga, L.E., Almaraz-Ruiz, L., Schwing, P.T., Hollander, D.J.
• Format: Article
• Language: English
• Subjects: Anthropogenic factors; Aromatic hydrocarbons; Benchmarks; Benthic foraminifera; Benthos; Biodiversity; Carbonates; Distribution; Distribution patterns; Drilling rigs; Ecological monitoring; Ecosystems; Environmental health; Environmental Monitoring; Factor analysis; Foraminifera; Foraminifera - chemistry; Foraminifera - classification; Geologic Sediments - chemistry; Gulf of Mexico; Human influences; Hydrocarbons; Marine ecosystems; Marine sediments; Natural seeps; Ocean floor; Offshore; Offshore drilling rigs; Offshore platforms; Oil; Oil industry contamination; Oil pollution; Oil seepage; Organic carbon; Petroleum hydrocarbons in sediments; Petroleum Pollution; Platforms; Polycyclic aromatic hydrocarbons; Polycyclic Aromatic Hydrocarbons - analysis; Rivers; Sediment; Sediment samplers; Sediment samples; Sediments; Seepage; Seepages; Trace elements; Trace Elements - analysis; Trace metal contamination; Water depth; Water Pollutants, Chemical - analysis
• ISSN: 0141-1136; 1879-0291
• DOI: 10.1016/j.marenvres.2019.06.006

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. •Impact of oil related activities on ocean floor sediments was assessed.•Benthic Foraminifera (microbenthos) show impact of various oil derived sources.•Concentrations of As, Ba and Cu might be of potential ecological concern. .•Organic carbon and PAHs content are greater in oil exploitation and seep areas.•Campeche Bay is affected by multiple stressors, both natural and anthropogenic.