Journal of the Marine Biological Association of India

Recent evolution of mangrove vegetation in the Cauvery Delta : A palynological study

Volume 29 Issue 1&2

C.Tissot

Abstract

Palynological analyses have been carried out on sequences of sediments, cored in two estuaries of the Cauvery delta (Tamil Nadu) and they are estimated to be about 2000 years old. A detailed account on this subject is already been given by C. Tissot (1980).

In Muthupet (southern part of the delta), the investigations were made near a lagoon far from the present shoreline. Four periods in the evolution of the mangrove vegetation may be recognized. These are in accordance with geomorphic processes of the estuary as well as the resulting sedimentation pattern, both being dependent on the seaward setting up of sand bars.

In Pichavaram (northern part of the delta), the cores were taken near the present shoreline and only three periods can be distinguished. In the two older periods, the evolution of the mangrove vegetation is the same as that of Muthupet. In the upper part of the sequences, the evolution is highly disturbed: decrease in pollen representation of the arborescent genera Sonneratia and Rhizophora; increase in the herbaceous taxa such as Suaeda.

These disturbances are obviously due to local human activity: selective wood cutting, grazing in the mangrove forest. The development of fresh water damming, widespread in inland areas, seems to have had a deteriorating effect on the mangrove vegetation, causing higher salinity in the soil as a consequence of diminished fresh water flow in the delta

Date : 31-12-1987