John Wiley & Sons, Ltd.

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

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Discharge of drill cuttings to 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 shows an assessment of water‐based drill cuttings, barite, bentonite and natural sediments on shallow‐ and deep‐water calcareous algae (CA) in short‐ (30 d) and long‐term (90 d) experiments, using two species from Peregrino's oil field at Campos Basin, Brazil: Mesophyllum engelhartii and Lithothamnion sp. The results were compared with the shallow‐water species L. crispatum. Smothering and burial exposures were simulated. Oxygen production and fluorescence readings were recorded. M. engelhartii, although less productive, was as sensitive to stress as Lithothamnion sp. M. engelhartii was sensitive to smothering by drill cuttings, barite and also bentonite after 60 d of exposure and was similarly affected by natural sediments after 90 d. These results indicate physical effects from smothering by sediments that might be due to partial light attenuation and partial restriction on gas exchange but did not kill the calcareous algae in the long term. However, one month burial either by 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. This article is protected by copyright. All rights reserved

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