An Ecological Study of some Intertidal Algae of the Visakhapatnam Coast

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Abstract
The seasonal and yearly changes in the growth of some common algae occurring in the intertidal region of the Visakhapatnam coast in the period from May 1960 to April 1963 are described and their relationship to the changes observed in the environmental factors are discussed. The tidal behavior associated with the seasonal changes in the mean sea levels and seasonal changes in the sand levels on the beach are found to exert a great influence on the algal growth. Distinct zonation in the distribution of the different organisms observed on this coast corresponded well with the three basic zones in the Universal Scheme of Zonation proposed by Stephenson and Stephenson (1949). The seasonal and yearly variations in the vertical distribution of some common algae growing in different zones and the changes in their band formations observed are described. The tidal behavior is examined in detail and the seasonal changes in the algal growth, vertical zonation and the yearly variations observed in the period of this study are found to be associated with the variations in the durations of exposure and submergence of the different levels on the shore. The results of experiments conducted by artificially exposing algae growing in the different zones to air are given. The importance of tides in determining the vertical distribution of the intertidal organisms is indicated by the existence of a correlation between the critical periods observed in the experiments and the exposure values estimated for the different levels on the shore from the tidal curves.