Marine biodiversity and ecosystem functioning: a perspective

Biodiversity and community structure are now recognized to be important determinants of ecosystem functioning. In this regard the marine ecosystem has been studied to a much lesser extent compared to the terrestrial. This article discusses the various aspects of biodiversity in marine habitats, as determined by competition, nutrients, heterogeneity, keystone predation and climate and anthropogenic effects, keeping in mind the peculiarities of the mobile and dynamic nature of pelagic waters. Some hypothetical examples from the Arabian Sea are considered. It is an established fact that nutrient availability largely determines the diversity of primary producers. Competitive dominance is rare in pelagic phytoplankton communities and various hypotheses have been put forward to explain this. However, single species algal blooms are not uncommon in coastal waters. Top-down control mechanisms, such as keystone predation can often be a major determinant in maintaining diversity. Heterogeneity is considered an important factor in promoting deep-sea benthic diversity. For the pelagic zone, water column stratification in terms of density, nutrients and light may lead to diverse assemblages. Increasing climate and anthropogenic effects on the marine ecosystem, particularly of the coastal waters have lent a sense of urgency in understanding the role of biodiversity in ecosystem dynamics, so that appropriate predictive models can be developed to facilitate wise management of our waters. Many of these issues have not been sufficiently studied for Indian waters. Some of the important questions that need to be addressed in this context are the effects of biodiversity on the environment and, therefore, successional patterns of communities, the relationship between biodiversity at different trophic levels, and their overall importance in community stability and productivity