Diatoms Distribution and its Paleoenvironmental Implications in Pulicat Lagoon Tamil Nadu South East Coast of India

To know the rate of sediementation and eutrophication processes in the Pulicat lagoon, a short core with a length of 1m is retrieved from the lake and subsampled in to 35 subsamples with an interval of 3cm each. All the samples are subjected to standard microplaeontological techniques to the study. The study area consists of 35 species belonging to 35 genera, 25 families, 3suborder, 2 subclasses and 2 classes have been identified throughout the core. Grammatophora oceanica Cocconies heteroidea, Opephora swartzii, Mastogloia baldjikiana, Petroneis marina and Tryblionella hungarica were the abundant species and Nitzschia palea as well as Nitzschia sigma are least present in the entire core. On the basis of textural analysis, a litholog is prepared and divided into three zones i. e, Zone I, Zone II and Zone III from bottom to top. Zone I and Zone III are dominated by sand which indicates the higher energy condition and Zone II shows the calm environment. Zone II showing the dominance of clayey sand, may be due the distribution of mangrove during this period of deposition of sediments. Organic matter is relatively less, it may be because of higher accumulation of sand particle which are carried out by the river in to the lagoon. Deposition of sand in the lagoon favours the significant growth of diatom.