Nature of spatial heterogeneity of the coastal, marine ecoregions along the eastern coast of India
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Ó Indian Academy of Sciences (0123456789().,-volV)(0123456789( ).,-volV)
Nature of spatial heterogeneity of the coastal, marine ecoregions along the eastern coast of India MEGHA GUPTA1, SUBHRONIL MONDAL2,* , HINDOLITA CHAKRABORTY2 and PUNARBASU CHAUDHURI1 1
Department of Environmental Science, University of Calcutta, 35, B.C. Road, Kolkata 700 019, India. Department of Geology, University of Calcutta, 35, B.C. Road, Kolkata 700 019, India. *Corresponding author. e-mail: [email protected] 2
MS received 1 July 2019; revised 29 September 2019; accepted 15 October 2019
The global marine environment is highly heterogeneous although the nature of heterogeneity can vary spatially. In this study, the nature and extent of spatial heterogeneity of the coastal, marine ecoregions along the Central-Eastern and South-Eastern coast of India (parts of Andhra Pradesh, Pondicherry and Tamil Nadu) was studied, which represent two different – Central-Eastern, and South-Eastern – coastal ecoregions. Several environmental (e.g., salinity, temperature, and nutrients of the ocean water, etc.) and physical (e.g., substrate type, energy condition of the coast) parameters were measured (quantitative as well as semi-quantitative approach) and analysed by using several bivariate and multivariate methods. Our results clearly point out that the Central-Eastern, and South-Eastern marine, coastal ecoregions of India are highly heterogeneous among themselves, and even smaller ecoregions (i.e., sub-ecoregions) within each of these larger ecoregions are also different from each other. Thus, each of these ecoregions is internally highly heterogeneous. In addition, there is no consistent spatio-latitudinal change in the environmental variables along the eastern coast of India. Keywords. Indian molluscs; environmental variables; biogeographic provinces.
1. Introduction Ecosystem is a natural functioning system where the abiotic and biotic factors interact with each other. This speciBc multidimensional space, where organisms inhabit, is deBned by those biotic and abiotic variables. The major abiotic components of the marine environment include temperature, salinity, other chemical characters of water (Eh, pH), and different types of physical parameters (e.g., substrate, suspended sediment, energy condition, etc.), and primary productivity, among many others. Because each ecosystem differs in these abiotic and physical variables, each and every ecosystem differs significantly from others
resulting in environmental heterogeneity (i.e., ecosystem heterogeneity). In the marine realm, because many of these aforementioned environmental factors (e.g., primary productivity, temperature, salinity) vary with latitudes as well as ocean basins, along with many other local variables, marine environmental heterogeneity is a global phenomenon and has been documented to vary spatially from local to global scale (Spalding et al. 2007). For example, the annual rainfall and sea surface temperature show spatio-latitudinal variation (NASA; https://www.nasa.gov/). T
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