MICROBIAL-DEGRADATION OF RHIZOPHORA-MANGLE LEAVES IMMERSED IN THE SEA

The leaching and degradation of senescent leaves of red mangrove (Rhizophora mangle) immersed in the water column adjacent to a mangrove stand on Virginia Key, Florida were investigated. During the first 70 days the carbon content decreased from 46·2 to 36·2% while the nitrogen content increased from 0·51 to 0·89%. This represented a decrease in the carbon: nitrogen ratio from 90·6 to 40·7. Readily leachable carbohydrates and tanninlike compounds were lost from the leaf material by the 14th and 28th days, respectively. These leachable organic compounds contribute to the dissolved organic matter in the water. A microbial population slowly built up on the leaf surface after the tannin was lost and the degradation of the structural material was observed using scanning electron microscopy. Changes in the caloric content of the mangrove leaves reflected their microbial degradation. Earlier reports emphasizing the role of micro-organisms in a detritus-based food web in an estuarine mangrove community are confirmed. © 1979.