Abiotic and biotic contributions to decomposition dynamics of Bruguiera cylindrica

Abstract

The decomposition of mangrove leaf litter is a highly important process in nutrient cycling, through which essential nutrients are regenerated and made available to mangrove ecosystems. Abiotic and biotic processes, such as leaching and microbial degradation, act as pathways for the decomposition of mangrove leaf litter. Using a laboratory based experiment, a study was undertaken to examine the decomposition dynamics of Bruguiera cylindrica, a common species found in Singapore. Leaves of Bruguiera cylindrica were incubated in either autoclaved seawater (ASW) or seawater (SW) to expose the leaves to different processes. Throughout the 90-day experimental period, rates and magnitudes of percentage dry mass loss, total nitrogen, total phosphorus, and total organic carbon, were monitored for both treatments. The main aims of the experiment were to 1) quantify contributions of leaching and microbial degradation to the decomposition of leaf litter of Bruguiera cylindrica, and 2) to determine how the contributions or significance of leaching and microbial degradation change over time. Results from the experiment showed rapid decreases in dry mass and rapid increases in nutrient contents in leachates during the initial period of the experiment, with rates slowing down as the experiment proceeded. ASW and SW treatments showed a significant difference in final dry mass, with higher losses observed for SW treatments. All nutrients in the leachate showed an overall increase in concentration. It is hoped that this research would aid future decomposition studies in Singapore, and enable the better management of our mangroves.