In the context of the ongoing CEC project ‘Dynamics and Assessment of Kenyan Mangrove Ecosystems’, this study was undertaken as a first step towards assessing the contribution of mangrove litter as a potential source of nutrients. Leaves were collected from five main mangrove species: Avicennia marina, Bruguiera gymnorrhiza, Ceriops tagal, Rhizophora mucronata and Xylocarpus granatum occurring at Gazi Creek on the East Coast of Kenya. They were analyzed for the determination of organic Carbon, Nitrogen contents and inter- and intraspecific variations among the five species. Statistical analysis of the data has shown that the five species differ significantly in C:N ratios. C:N ratios are, Avicennia 28±5, Bruguiera 76±8.9, Ceriops 74±4, Rhizophora and Xylocarpus 38±7. A field experiment with litter bags was also initiated to study the decomposition of yellow, senescent leaves of Ceriops tagal for 1, 3, 6, 9 and 15 days. A 16% loss in the dry weight after 15 days of decomposition was observed in Ceriops. C:N ratio in Ceriops leaves has changed from 74 (fresh leaves) to 219 in senescent leaves (leaves which are about to fall) showing nitrogen resorption of 69% by the tree. The need for further research on nitrogen fixation, production, leaching, decomposition and export rates of mangrove litter is stressed. Mangrove litter, together with seagrasses and algae, could be a source of nutrient rich organic matter for the lagoon and coastal ecosystems. |
