ABSTRACT
Ecosystems comprise biological communities and their ambient physico-chemical parameters within a specific habitat. Tropical coastal ecosystems are diverse, with each characterized by unique features, biotic community, and ecological processes. The coexistence of these ecosystems within a given locale promotes heterogeneity, and interactions between their respective communities enhance species diversity. These ecosystems, in terms of their products and services, are comparable to tropical forests.
The near-shore coastal waters of Goa, along the central west coast of India, include coral reefs, estuaries, mangrove wetlands, sandy shores and rocky substrates within a radius of about 11 km. The uniqueness of this environment is well sustained coupling among these ecosystems that support better interactions among biotic communities. These processes are of great importance in the functioning of one of the biologically richest entities in the Indian Ocean region. In this region of the west coast of India, coral reefs occur in thick patches (31% coral cover) surrounding Grande Island, Goa. Moreover, the occurrences of reef fishes in trawl catches suggest the existence of patchy reefs in the region. The occurrence and distribution of reef patches in this region enhance the species composition and their representation in these areas to support highly diverse biological communities. Further, the occurrence of reef patches also supports associated fauna. The present coastal region is dissected by 237 km of estuaries, whose lower stretches are fringed by mangrove vegetation covering a total area of approximately 20 km2. The mangrove vegetation, represented by 13 species, is dense in the Mandovi–Zuari estuarine complex. These ecosystems harbour numerous species of vertebrates, including migratory birds, and serve as nursery grounds for commercially important fishes and invertebrates.
Sandy beaches and mud flats extend along most of the 105 km shoreline. Mud flats rich in organic matter support a detritus-based food chain, and in shallow water there is coupling between pelagic and demersal food chains. This coupling among food chains plays an important role in enhancing the productivity of the system as long as it occurs within the mixed layer depths. Several burrowing invertebrates inhabit the sandy substratum. Moreover, this region is also a popular tourist destination and serves as a major source of livelihood of the coastal population. Rocky substrates are sporadically spread along lower reaches and mouths of the major Goan estuaries and off the cape regions. These are important habitats for several demersal and reef-associated fishes and invertebrates. Rocky shores in tropical regions exhibit a distinct zonation pattern mainly mediated by physical and biological factors. Tidal inundation also plays an important role in the distribution and abundance of rocky shore communities. The disposal of untreated sewage, mining wastes, and industrial effluents represent potential threats to the resident biota, with lasting effects on their biological processes that have implications for the commercially exploitable fish and invertebrate stocks in the region. On the other hand, altered monsoon systems could affect coastal productivity. The persistence of such a scenario is perilous to both the existence of coastal ecosystems as well as the socio-economic structure of the indigenous coastal populations. These ecosystems require adequate management strategies for their conservation because they are subjected to intensive exploitation for timber and nutrition (fisheries and aquaculture). Rapid changes in land-use patterns to meet the ever-increasing demands of the burgeoning coastal and tourist populations are exerting immense pressures on these fragile ecosystems. Furthermore, the ecosystems are largely being used as dumping sites for different sources of waste material from continuously changing land-use patterns.
In view of the foregoing discussion, it is imperative that the coastal ecosystems be managed in a sustainable manner. It is proposed that the management strategy should basically involve a three-tier approach. The primary stage should involve the creation of a baseline inventory. The second stage should involve dissemination of scientific knowledge on ecosystem products and services and information regarding the legal aspects of coastal regulations through training and awareness programmes. The final stage should focus on the enforcement of coastal zone regulations including the closure of certain sensitive ecosystems to minimize human interference.
