SHORT-TERM SEDIMENT ACCRETION DYNAMICS OF PICHAVARAM MANGROVE FOREST, TAMIL NADU, INDIA

The influence of mangrove systems in advancing the process of sedimentation is very well studied over the years. However, understanding the actual mechanism of accretion at a specific point within a mangrove forest is difficult, due to the stochasticity of sediment distribution and deposition. Factors that influence the rate of sediment accretion within the mangrove forest such as plant litter accumulation and bioturbation were investigated in Pichavaram mangrove forest, India. The annual rate of vertical accretion was recorded as 1.5 ± 0.9 cm year -1 for the site at elevation 0.4 m, and 0.9 ± 0.04 and 0.9 ± 0.05 cm year -1 for the other two sites which are at -0.8 and -1.2 m respectively. Results show that the sites were accreting sediments but at varying rates, inter-site variability was low but the factors influencing the processes were different. Plant litter contributed significantly to the accretion, and organic matter estimates also supported this observation. A higher rate of organic matter accumulation was observed in one of the sites, which is not regularly inundated by tides. On the contrary, in sites which were regularly washed by tides, accretion was seen in both allochthonous and autochthonous inputs and the annual rate of vertical accretion was almost the same.