Oxygen consumption patterns in a mangrove swamp on the Pacific coast of Costa Rica

Abstract

Measurements of the oxygen consumption of the suspended organisms, the sediment biota and the prop root-epibiont system were made to determine the rate of decomposition of organic material in a mangrove swamp on the Pacific coast of Costa Rica. The tidal range in this area is about 2.5 m. The sediment consists mainly of clay with 12-1 5% organic material. The dominant mangrove species bordering the swamp channels was Rhizophora mangle. The O₂ consumption in the free water varies between 35 and 47 mg m^-3 h^-1. The oxygen uptake of the sediment lies between 8.4 and 3 7.2 mg m^-2 h^-1. The respiration of the root-epibiont system depends on the position of thy root in relation to the low water line. Values between 0.65 and 29.5 mg O₂h^-1 per 1000 cm² of root surface have been recorded.

In a transect between two tidal channels the O₂ consumption per sediment surface area and the percentage consumption by the three subsystems show a great range of variation depending mainly on the water depth at high tide and the period of water coverage. The mean oxygen uptake per square meter was 1310 mg per day. Of this 40.5% was consumed by the organisms suspended in the water column, 13.5% by the sediment biota and 46% by the epibiotic community on the prop, roots. Thus, the decomposition of organic material would be about 410 mg C m^-2 day^-1 (mean value).