Regenerative functions and microbial ecology of coral reefs. II. Oxygen metabolism in the regenerative system

Abstract

Measurements were made relevant to the oxygen metabolism of the internal zone of coral reefs. Oxygen demands of internal sediments by a dark bottle method yielded rates of 0.06 to 0.50 mg O₂ per gram sediment per hour. Antibiotics significantly lowered oxygen demands and bacterial counts, suggesting an important respiratory role of aerobic bacteria. Measurements of total oxygen consumption by two intact coral "deadheads" were compared to oxygen demands by their internal sediments. Oxygen consumption of these sediments in suspension was about 10% of the total O₂ consumption of intact heads.Water samples collected from within regenerative spaces in situ generally showed oxygen debts when compared to ambient reef waters. Oxygen debts of internal waters of (stressed) inshore reefs were higher than those of an offshore reef. A diurnal set of oxygen measurements on waters from within reef mass brought to the laboratory showed constant internal oxygen deficit relative to the oxygen concentration in ambient waters.Coral skeleton microcosms were apparently adapted to local conditions of aeration at different collecting stations. Oxygen stress of skeletal mass resulted in internal oxygen depletion and related changes in microbial metabolism destructive to the aerobic infaunal (metazoan) community.