Estuaries Mangroves Coral Polyps
Estuaries are partially enclosed bodies of water along coastlines where fresh water and salt water meet and mix. They act as a transition zone between oceans and continents.
D.W. Pritchard (1967) define estuary as “An estuary is a semi-enclosed coastal body of water which has a free connection with the open sea and within which sea water is measurably diluted with fresh water derived from land drainage.”
Types of Estuaries
a) Coastal Plain estuary: Coastal plain estuaries were formed at the end of the last ice age. As the ice melted and the waters warmed, sea level rose. The rising seas invaded low-lying coastal river valleys. These valleys are usually shallow with gentle sloping bottoms.
b) Tectonic Estuary: The earth’s crust is constantly in motion. This motion causes large cracks or faults and folds to form in the crust. Often due to folding and faulting, the land sinks or subsides. Tectonic estuaries are created when the sea fills in the “hole” or basin that was formed by the sinking land.
c) Bar-Built Estuary: Bar-built estuaries are formed when sandbars build up along the coastline. These sand bars partially cut off the waters behind them from the sea. Bar-built estuaries are usually shallow, with reduced tidal action.
Importance of estuaries
Estuaries provide us with a suite of resources, benefits, and services. Some of these can be measured in dollars and cents, others cannot. Estuaries provide places for recreational activities, scientific study, and aesthetic enjoyment. Estuaries are an irreplaceable natural resource that must be managed carefully for the mutual benefit of all who enjoy and depend on them.
Thousands of species of birds, mammals, fish, and other wildlife depend on estuarine habitats as places to live, feed, and reproduce. And many marine organisms, including most commercially-important species of fish, depend on estuaries at some point during their development. Because they are biologically productive, estuaries provide ideal areas for migratory birds to rest and re-fuel during their long journeys. Because many species of fish and wildlife rely on the sheltered waters of estuaries as protected spawning places, estuaries are often called the “nurseries of the sea.”
Estuaries have important commercial value and their resources provide economic benefits for tourism, fisheries, and recreational activities. The protected coastal waters of estuaries also support important public infrastructure, serving as harbors and ports vital for shipping and transportation.
Estuaries also perform other valuable services. Water draining from uplands carries sediments, nutrients, and other pollutants to estuaries. As the water flows through wetlands such as swamps and salt marshes, much of the sediments and pollutants are filtered out. This filtration process creates cleaner and clearer water, which benefits both people and marine life. Wetland plants and soils also act as natural buffers between the land and ocean, absorbing flood waters and dissipating storm surges. This protects upland habitat as well as valuable real estate from storm and flood damage. Salt marsh grasses and other estuarine plants also help prevent erosion and stabilize shorelines.
Threats to estuaries
Human activities within an estuary (shipping, recreation, aquaculture), or within the lands surrounding the estuary (urbanization, agriculture, logging), may alter estuarine habitats either directly (shoreline alteration, channelization, landfill) or indirectly through such problems as excessive nutrients or introduction of invasive, non-native species.
Estuaries are coming under increasing pressure from:
• Estuary margin development – population growth and coastal settlement.
• Increased demands for recreational uses – such as boating and fishing.
• Development in estuaries – such as marine farms and marinas.
• Catchment development – such as forestry and agriculture.
• Land clearance and reclamation.
• Excavation and dredging for example for boat ramps and boat channels.
• Introduction of invasive species such as Spartina.
• Resource extraction – such as fishing.
• Long term climate changes including sea-level rise.
Mangroves are plants that survive high salinity, tidal regimes, strong wind velocity, high temperature and muddy anaerobic soil – a combination of conditions hostile for other plants. The mangrove ecosystems constitute a symbiotic link or bridge between terrestrial and marine ecosystems. They are found in the inter-tidal zones of sheltered shore, estuaries, creeks, backwaters, lagoons, marshes and mud-flats.
Mangroves constitute a heterogeneous group of plants with similar adaptations to a particular environment. They colonize tidal shores and brackish waters in the tropics and subtropics and in doing so not only stabilize shorelines but also create new land by trapping debris, silt and mud along their interlacing roots. Mangroves plants can survive high salinity, tidal extremes, strong wind velocity, high temperature and muddy anaerobic soil.
Mangroves in India
In World’s total mangrove vegetation, India’s share stands at 3%. Currently Mangrove cover in India is 4740 km² which is 0.14 % of the country’s geographical area. Sundarbans in West Bengal accounts for almost half of the total area. As compared to 2013 there is a net increase of 112 sq km in the mangrove cover.
Top five states with maximum Mangrove cover are as follows:
• West Bengal (2106 km2)
• Gujarat (1107 km2)
• Andaman & Nicobar Island (617 km2)
• Andhra Pradesh (367 km2)
• Odisha (231 km2)
Importance of Mangroves
Mangroves are self propagating plants and if it is undisturbed, can grow quite easily in conducive soil and locations. These are the plants that grow in the inter-tidal zone along the coastline of India. They are very hardy plants that have adapted over millennia to grow in difficult conditions.
Mangrove ecosystems are rich in biodiversity and harbour a number of floral and faunal species (both terrestrial and aquatic) many of which, e.g. the tiger, gangetic dolphin, estuarine crocodile, etc. are endangered. They also act as nurseries for fin fish, shell fish, crustaceans and mollusks. Mangrove forests are regarded as the most productive ecosystems in the world on account of the large quantities of organic and inorganic nutrients released in the coastal waters by these ecosystems.
The mangroves besides providing a number of ecological services also play a major role in protecting coastal areas from erosion, tidal storms and surges (tsunamis). They help in land accretion by trapping the fine debris particles. They are also an important source of honey, tannins, wax, besides fish. Presently, these are one of the most threatened ecosystems on account of both anthropogenic factors (reclamation of land, discharge of waste etc) and natural factors like global warming.
Mangroves under threats
The satellite data shows a decrease in the mangrove area.
The natural threats to mangroves include the following:
• cyclones, typhoons and strong wave action especially in the geographically vulnerable Andaman and Nicobar Islands;
• browsing and trampling by wildlife (e.g. deer) and livestock (goats, buffaloes and cows), which are often left to graze freely, especially in areas close to human habitation;
• damage by oysters to the young leaves and plumules of Rhizophora and Ceriops plants;
• crabs, which attack young seedlings, girdle the root collars and eat the fleshy tissues of the propagules
• insect pests such as wood borers, caterpillars (which eat the mangrove foliage and damage the wood as well) and beetles;
The following are some of the human activities that have resulted in damage to mangroves
• indiscriminate tree felling and lopping, mainly for fuelwood, fodder and timber, especially in areas close to human habitation;
• indiscriminate conversion of mangroves on public lands for aquaculture (e.g. for prawn culture at Chorao, Goa), agriculture, mining (e.g. along the Mapusa estuary in Goa), human habitation and industrial purposes;
• encroachment on publicly owned mangrove forest lands, e.g. cultivation of paddy observed on government land, which involved uprooting of natural and planted seedlings;
• lack of interest of private landowners (village communities and individuals) in conserving and developing the mangroves on their lands;
• illegal large-scale collection of mangrove fruits for production of medicines, which hinders their natural regeneration;
• discharge of industrial pollutants into creeks, rivers and estuaries, which is a major problem in some regions of the world;
• obstruction and diversion of water for culvert construction.
Legal and Regulatory Approaches for Protection
At present, the mangroves are protected through a range of regulatory measures such as Coastal Regulation Zone Notification, 1991; Environment Impact Assessment (EIA) studies under the EIA Notification, 1994 for specialized industries; monitoring of compliance, with conditions imposed while according Environmental Clearance, by Regional Offices of the Ministry and State Pollution Control Boards; enforcement of emission and effluent standards by industries and other entities, and recourse to legal action against the defaulters. Mangroves located within the notified forest areas are also covered under the Indian Forest Act, 1927 and Forest (Conservation) Act, 1980.
Mangroves for the Future Initiative
Mangroves for the Future (MFF) is a unique multi- country, multi sectoral, partner- led initiative which builds on the long history of coastal management interventions and lessons learned during the course of post- tsunami reconstruction and rehabilitation. The initiative is founded on a vision for a more healthy, prosperous and secures future for all Indian Ocean Coastal communities, where all the ecosystems are conserved and managed sustainably and seeks to promote investment and action in ecosystem conservation for sustainable coastal development. MFF is being coordinated by International Union for Conservation of Nature, IUCN covering, initially, six Tsunami affected countries namely India, Indonesia, Maldives, Seychelles, Srilanka and Thailand. India has agreed to participate in the IUCN- MFF Initiative.
Mangroves for the Future have two objectives:
– To strengthen the environmental sustainability of coastal development.
– To promote the investment of funds and effort in coastal ecosystem management for sustainable development.
The initiative seeks to effect demonstrable changes and results across four key areas of influence: regional cooperation, national programme support, private sector engagement and community action using a strategy of generating knowledge, empowering institutions and people to use that knowledge and, thereby promoting good governance in coastal areas.
Coral reefs are found in circum-tropical shallow tropical waters along the shores of islands and continents. The reef substrate is mainly composed of calcium carbonate from living and dead corals. Many other invertebrates, vertebrates, and plants live in close association to the corals, with tight resource coupling and recycling, allowing coral reefs to have extremely high productivity and biodiversity, such that they are referred to as ‘the Tropical Rainforests of the Oceans’.
Corals live in very nutrient poor waters and have certain zones of tolerance to water temperature, salinity, UV radiation, opacity, and nutrient quantities.
Zooxanthellae live symbiotically within the coral polyp tissues and assist the coral in nutrient production through its photosynthetic activities. These activities provide the coral with fixed carbon compounds for energy, enhance calcification, and mediate elemental nutrient flux. The host coral polyp in return provides its zooxanthellae with a protected environment to live within, and a steady supply of carbon dioxide for its photosynthetic processes. The symbiotic relationship allows the slow growing corals to compete with the faster growing multicellular algaes because the tight coupling of resources and the fact that the corals can feed by day through photosynthesis and by night through predation.
The tissues of corals themselves are actually not the beautiful colors of the coral reef, but are instead clear. The corals receive their coloration from the zooxanthellae living within their tissues.
Geographical Conditions Required
• Corals generally flourish in clear tropical oceans usually between 30°N and 30°S of the equator.
• They grow best in the brightly lighted water about 5 to 10 meters deep. The suspended particles interfere with feeding.
• Corals live in saline water (27%).
• Coral reef can from to depth of 90 meters, but growth rate declines rapidly after 5 to 10 meters depths.
• The reef building corals are found within the 21°C isotherm.
• Corals are not near the mouths of rivers.
• Temperature below 18°C causes their death.
• Individual coral organisms are however, found in some cold, high latitudes waters as well (Norway and Cap Verde Island and off New Zealand and Japan)
Uses of coral reefs
• Remove and recycle CO2 a greenhouse gas
• Protect the shore from erosion by storms and floods
• Are home to over 4,000 species of fish, 800 species of coral and thousands of other forms of plant and animal life, all of which will not survive without the reefs
• Account for 12% of the marine fish catch
• Could provide important medicines including anti-cancer drugs and a compound that blocks ultraviolet rays
• Coral skeletons are being used as bone substitutes in reconstructive bone surgery
Coral reefs are threatened by
• Destructive fishing practices, such as dynamite or cyanide fishing and trawling in deeper waters, cause direct physical damage to corals.
• Widespread over fishing leads to very low levels of herbivorous fish, which check coral killing algae.
• Nutrient-laden sewage released near the shore causes algal blooms which block sunlight, stunting coral growth and interfering with reproduction.
• Shoreline construction disturbs sediments, which smother corals.
• Tourism and tourists cause physical damage to reefs by construction activities, trampling, boat abrasion and the removal of corals “souvenirs”.
Conservation of coral reef
• The coral reefs of India come under the jurisdiction of the department of forests and wildlife and it is their responsibility to monitor, manage and conserve these fragile eco-system.
• The Ministry of Environment and Forests is responsible to develop an action plan to manage the reef resources and issue guidelines for the sustainable utilization of coral reefs.
• Ministry of Environment and forests has taken charge of Marine national Parks which have coral reefs in them.
• The National Committee constituted for conservation and management of wetlands and mangroves advises the Government on policy issues related to conservation and management of coral reefs. State level steering committees have been set up for the formulation and implementation of the Management Action Plans for the identified coral reef areas.
• Management plans for the Gulf of Kutch Marine National Park and Sanctuary has been prepared by the Conservator of Forests in 1994. Recently the Ministry of Environment and Forests has sanctioned preparation of management action plans for the Andaman and Nicobar and Gulf of Mannar coral reefs.
• The coastal regulation zone notification 2011 offers the only legal protection to all coral reefs and In this coral reef areas come under the CRZ1 category. A special category CRZ 4 has been prepared for the Islands of Andaman, Nicobar and Lakshadweep. Norms for regulation of activities within the CRZ state that corals and sand from beaches and coastal water shall not be used for construction and other purposes. Dredging and underwater blasting in and around coral formations shall not be permitted. Notification also states that construction of beach resorts/hotels shall not be permitted in ecologically sensitive areas such as marine parks and coral reefs.
• The Union Ministry of Environment and Forests is currently undertaking a UNDP supported pilot project, “Management of Coral Reef Ecosystem of the A&N Islands” for developing a full project to ensure the conservation and management of A&N Islands’ reefs. An Indian Coral Reef Monitoring Network has also been established for the purpose. Besides, the Wildlife Institute of India is engaged in a project to develop a management plan for the Mahatma Gandhi Marine National Park at Wandoor, which is one of the few marine national parks in India. In 1996, the Department of Environment and Forests of Andaman and Nicobar Islands notified three islands in the Ritchies Archipelago, comprising Outram Island, Henry Lawrence Island and John Lawrence Islands and the coastal waters surrounding them, as the Rani Jhansi Marine National Park.
• Though monitoring of reefs remains poor in India, the WWF-India project has, hopefully, provided the impetus for all concerned to take the right step for the preservation of our coral reefs.