Diurnal fluctuations of O2, N2, and CH4 in the rhizosphere of Thalassia testudinum1

Abstract
Gas bubbles in the sediments and gases in the internal spaces of the rhizomes of T. testudinum contained O2, N2, and CH4. CH4 was a minor component. The percentage composition of the major components, O2 and N2, varied from 2.3% O2 + 94% N2 (sediment bubbles, early morning) to 30% O2 + 69% N2 (rhizome gases, midafternoon). The variations probably reflected changes in O2 content of the gases caused by diurnal variations in photosynthetic and oxidative activities of the seagrasses and sediments. Apparently there is a net transfer of O2 from T. testudinum, via its rhizome system, to the sediments.