Testing predictions from an environmental stress on macroinvertebrate diversity across rocky intertidal elevation gradients in Mumbai, India.

Abstract

Intertidal organisms distributed in different zones experience strong environmental stress due to various biotic and abiotic factors. Environmental stress model (ESM) predicted that overall species richness and diversity should follow a unimodal trend along the vertical elevation gradient. In the present study, species richness and diversity of macroinvertebrates (molluscs and crustaceans) were measured on a rocky shore of Mumbai, the west coast of India. Data on species abundance were collected for two years (January 2005 to December 2006) after fixing three transects from high-to-low-shore zones based on the tidal heights. Quadratic regression analysis was applied to examine the pattern of variation in overall species richness and diversity across the stress gradient. The analysis revealed that both the variables followed unimodal trends across elevations and suggested that ESM predictions can also be applied to taxonomic groups besides different functional groups of intertidal organisms. It was also found that ESM can be useful in predicting local species richness and diversity as a function of environmental stress and helpful in providing a better understanding of distribution and dynamics of communities at local scale.