Effect of well-drilling fluids on the physiological status and microbial infection of the reef building coralMontastrea annularis

Abstract

The reef building coral,Montastrea annularis, was exposed continuously to suspensions of oil and gas well-drilling fluids at concentrations of 0.1, 0.01, and 0.001 μl/ml in flowing seawater at the U.S. Naval Stage I platform (30° 7.5′ N, 85° 46.3′ W). After six weeks of exposure, coral fragments of 12 to 65 cm2 surface area were broken off, rinsed in seawater, and extracted in a one-phase chloroform-methanol-buffer and returned to the laboratory where the extraction was completed and the phases separated. The lipids were fractionated with silicic acid and by thin layer chromatography. The total, diacylated, and plasmalogen phospholipid content, total lipid acyl linked fatty acids, triglyceride glycerol, triglyceride acyl-linked fatty acids, and wax ester alcohols were measured. The aqueous phase of the lipid extraction was analyzed for amino acid composition. Acyl fatty acid and alcohol composition was measured by capillary gas chromatography. Total phospholipid, triglyceride glycerol, total extractable fatty acids, triglyceride fatty acids and the wax ester fatty alcohols showed no consistent changes with exposure to the drilling fluids. Changes in free amino acid concentrations were detected as well as significant decreases in the recoverable diacyl phospholipid. Significant increases in plasmalogen phospholipids appeared with exposure, suggesting infection by anaerobic fermenting bacteria which can indicate disease. The evidence suggests that biochemical indicators of infection with anaerobic bacteria may be useful as sensitive markers for pollution-induced changes in reef building corals and for monitoring the health of coral reefs.