Long‐ and short‐term effects of smothering and burial by drill cuttings on calcareous algae in a static‐renewal test

Abstract

Discharge of drill cuttings into the ocean during drilling of offshore oil wells can impact benthic communities through an increase in the concentrations of suspended particles in the water column and sedimentation of particles on the seafloor around the drilling installation. The present study assessed effects of water-based drill cuttings, barite, bentonite, and natural sediments on shallow- and deep-water calcareous algae in short-term (30 d) and long-term (90 d) experiments, using 2 species from Peregrino's oil field at Campos Basin, Brazil: Mesophyllum engelhartii and Lithothamnion sp. The results were compared with the shallow-water species Lithothamnion crispatum. Smothering and burial exposures were simulated. Oxygen production and fluorescence readings were recorded. Although less productive, M. engelhartii was as sensitive to stress as Lithothamnion sp. Mesophyllum engelhartii was sensitive to smothering by drill cuttings, barite, and bentonite after 60 d of exposure and was similarly affected by natural sediments after 90 d. These results indicate that smothering by sediments caused physical effects that might be attributable to partial light attenuation and partial restriction on gas exchange but did not kill the calcareous algae in the long term. However, 1-mo burial by either natural sediments or drill cuttings was sufficient after 60 d for both species to reduce oxygen production, and the algae were completely dead under both sources of sediments.

Identifying past petroleum exploration related drill cutting releases and influences on the marine environment and benthic foraminiferal communities, Goliat Field, SW Barents Sea, Norway

“…These adverse effects include stress to and eradication of benthic communities due to physical smothering by real-time sedimentation of released particles and/or subsequent reactivation/resuspension of previously settled particles (e.g. Olsgard and Gray, 1995;Hess et al, 2013;Reynier et al, 2015;Figueiredo et al, 2015;Järnegren et al, 2016). Discharge related pollutants [THC(Total Hydrocarbons), heavy metals, etc.)…”

A meta‐analysis reveals global patterns of sediment effects on marine biodiversity

“…The stronger physiological responses of macroalgae were attributable to either reductions in light levels (e.g., Liu et al, 2015) or enhanced sedimentation (e.g., Harrington, Fabricius, Eaglesham, & Negri, 2005). Furthermore, the impacts from sediments on algae ranged from strongly positive, such as studies observing species-specific proliferation of opportunistic foliose fleshy algae (Fabricius, De'ath, McCook, Turak, & Williams, 2005), to strongly negative, such as observations and experiments on coralline or fine filamentous forms (Reynier et al, 2015), which were less tolerant to sediment-stressed conditions. F I G U R E 6 Effect sizes (Hedges' d) comparing impacts on each habitat type (y axis) in relationship to undisturbed controls.…”

Assessing the potential impact of water-based drill cuttings on deep-water calcareous red algae using species specific impact categories and measured oceanographic and discharge data

“…1), these discharges may have a physical impact on the test organisms through sedimentation of particles. Reduced production of oxygen and reduced in vivo photosynthetic efficiency, reported by Reynier et al (2015) was primarily physical and due to the burial with drill-cuttings. Also sediment mimicking drill cuttings from the Peregrino oil field resulted in reduced in vivo photosynthetic efficiency in Mesophyllum and Lithothamnion Villas-Bôas et al, 2014).…”