The Liberation and Utilisation of Oxygen By the Population of Rock-Pools

Abstract

ABSTRACT A. P. Orr (1933), in the course of a study of the physical and chemical conditions prevailing in the sea near coral reefs, and in shallow pools on their surface, found that the oxygen content of the water in pools containing coral may rise to a very high figure (sometimes as high as a supersaturation of 278 per cent.) by the end of the period of low water during the daytime, falling to a low figure (e.g. 18 per cent, saturation) by the end of low water at night. Respiration by plants and animals uses up oxygen in both light and darkness; photosynthesis produces an excess of oxygen during daylight. The photosynthesis is due not only to free-living algae, but also (and in some places predominantly) to the symbiotic algae known as zooxanthellae which abound in the tissues of nearly all reef-corals. The effect can be detected in open water over coral, but is naturally much less marked there than in pools. C. M. Yonge, M. J. Yonge and A. G. Nicholls (1932) and S. M. Marshall (1932) studied the oxygen production of corals and their larvae experimentally. Oxygen determinations on coral reefs, and experiments on corals, have also been made by other authors—for references see Yonge, Yonge and Nicholls (1932) and Verwey (1931).