The coastal and marine ecosystems of the world are composed of oceans and major seas which make up 70.8 per cent of the Earth and cover an area of 362 million sq km., and also span a coastline measuring 1.6 million km.
Coastal and marine ecosystems are found in 123 countries around the world. The marine habitats include a wide range of ecosystems such as the shallow coral reef ecosystem, mesophotic reef ecosystem, soft sediment ocean floor ecosystem to coastal estuarine ecosystem, saline wetland ecosystem, mangrove ecosystem, gulf waters, creeks, tidal flats, deltaic plains etc.
Marine biodiversity includes these wide ranges of ecosystems from coastal areas to the deep sea. Being one of the 17 Mega-diverse countries, India represents 4 hotspots among the 32 biodiversity hotspots of the world. The geographical location of India between the Tropics of Cancer and Capricorn is among the most important reasons for the enormous biological diversity and supports them in accordance with conductive climatic factors.
India has a long coastline of 7516.6 km. (Mainland: 5422.6 km. and Island Territories: 2094 km.), with an Exclusive Economic Zone of 2.02 million sq. km, a continental shelf area of 372424 sq. km. and a territorial waters area of 193834 sq. km. spread across 9 maritime states, 2 Union Territories and 2 Island Territories. The coastal geomorphology of India includes 43 per cent sandy, 11 per cent rocky, 36 per cent muddy and 10 per cent marshy beaches in mainland adjoining areas.
The extensive marine biodiversity of India is mostly reported from the four major areas in coastal and island habitats such as the Gulf of Mannar and the Gulf of Kutch, Andaman and Nicobar Islands and Lakshwadweep. Inconsistent development, environmental changes, habitat degradation, over-exploitation of nature and natural resources are the prime threats to marine biodiversity. The contribution of marine biodiversity to the sustenance of human populations is immeasurable.
Mangrove ecosystems occur mostly in the inter-tidal region between mean sea level to the highest spring tide in the tropical and
subtropical regions of the world. India’s mangrove cover is sporadic with a total area covering 4,627.63 sq. km. among 12 maritime states and union territories. A total of 125 species including 39 species of true mangroves and 86 species of associates are recorded in India. The highest species diversity is recorded from Odisha with a total of 101 species while Gujarat harbors 40 species. Mangrove habitats serve as one of the best nursery grounds for the development and aggregation of several faunal species. A total of 3111 species of mangrove associated fauna were recorded from India.
Seaweeds are the marine macro algae under 3 phyla or divisions, namely, Brown Algae i.e., Phaeophyta, Red Algae i.e.,
Rhodophyta and Green Algae i.e., Chlorophyta. Most of the importance of seaweed is derived from its delicacy and being
adopted by coastal dwellers in several counties for consumption as food. They are a good source of nutrients and are used as fertilizer for agricultural purposes. Seaweeds contain plenty of minerals which can be extracted to meet the necessary requirements. The therapeutic applications of seaweeds cover a wide range where these are used for the purposes of treatment.
A total of 936 species of marine algae were recorded from Indian coastal and marine environments. This ecosystem provides massive infrastructure for many associated faunal communities but the studies do not span all of the coastal regions.
Seagrasses are commonly known as the flowering group of plants. A total of 14 species of seagrasses are reported in Indian waters. The ecological contribution of this ecosystem towards niche maintenance is remarkable in coastal waters situated at the continental shelf region. It increases the complexity of life and provides a healthy place to live for a wide range of species. It provides the basic strata for all the dwelling organisms as a nursery ground for reproduction, pre and post larval settlement as well as protection for those animals against oceanic currents and sedimentation. A total of 1059 species of animals belonging to 18 groups were reported from the seagrass ecosystems in the Indian seas which harbor 5.18 per cent of India’s marine fauna.
CORAL REEF ECOSYSTEMS
Coral reefs are among the most ecologically fragile environments of the globe. These biological organisms are abundant and very common in marine environments, and have been known to natural historians for millennia. Despite covering less than 0.2 per cent of the total area of oceans, coral reefs are noted for some of the highest levels of biodiversity on Earth and house 25 per cent of all marine creatures. It has been estimated that about 1-9 million species live on coral reefs.
The coral reef ecosystem contributes various services such as biological, ecological, physiological services and economic services for the sustainable development as well as protection of the marine and coastal habitats. India represents a total 57.10 sq. km. of coral cover. The major reef areas of India are the Andaman and Nicobar Islands, Gulf of Mannar and Palk Bay, Lakshadweep and Gujarat while small patches of reef have also been recorded from Gopalpur-on-Sea, Kerala, Netrani Island of Karnataka, Goa and Malvan coast. Most of the marine faunal communities are recorded from the reef habitats of India.
The exploration of marine biodiversity in India was initiated long back and it is perhaps the first among the Asian countries. The studies on the marine faunal communities of India were documented from the shallow regions of the ocean floor while ample areas of the seas are to be explored for the documentation of several unknown faunal communities. A total of 20,444 species of fauna have been recorded from India’s marine and coastal waters. India contributes to 6.43 per cent of global marine biodiversity and 7.01 per cent of global faunal diversity.
PROTECTED MARINE FAUNA
A total of 733 areas (103 National Parks, 532 Wildlife Sanctuaries, 26 Community Reserves and 67 Conservation Reserves) have been declared as protected areas in India. 18 biosphere reserves have also been declared to protect entire ecosystems. According to a series of notifications issued under the Indian Wildlife (Protection) Act, 1972 by the Ministry of Environment, Forest and Climate Change, Government of India, so far 1180 species are listed as protected marine animals of India.
THREATS TO COASTAL AND MARINE ECOSYSTEMS
NATURAL: Storms and wave energies may be seen as typhoons, quakes, and tsunamis. These are natural catastrophic events which may lead to the destruction of marine biodiversity.
ANTHROPOGENIC: Sedimentation from developmental activities, eutrophication from sewage and agriculture, physical impact of maritime activities, dredging, destructive fishing practices, pollution from industrial sources, climate change, introduction of invasive species, UV- radiation, carbonate mineral saturation, habitat alteration, unregulated tourism, chemical stress, oil spills, anchoring and bacterial effects.
WILDLIFE (PROTECTION) ACT, 1972: Provides protection to a wide number of animals against collection.
ENVIRONMENTAL (PROTECTION) ACT, 1986: Prohibits use of any parts of selected marine faunal communities against construction and other purposes.
COASTAL REGULATION ZONE NOTIFICATION, 1991: Regulates onshore development activities to protect coastal environments.
CITFS: Restricts the trade of threatened marine fauna in order to avoid unsustainable utilization under Appendix II.
UNCLOS, MARPOL, and the Stockholm Convention on Persistent Organic Pollutants: Regulation of marine pollution.
Source: DIRECTOR, ZOOLOGICAL SURVEY OF INDIA, KOLKATA