ENVIS Centre, Ministry of Environment & Forest, Govt. of India

Printed Date: Saturday, November 28, 2020

cradles of ocean life

cradles of ocean life:
    The place where the river meets the Sea or Ocean is called Estuary. It connects us to the sea and ocean. It is used for transportation, fishing and it plays an important role in recreation.

1.What is an estuary?


    The place where the river meets the sea or ocean is called estuary.

2.What is so special about the estuary?

    Estuary is the ‘cradle of marine life’, ‘breeding and nursery ground’. It protects baby fishes and crustaceans from predators
    and provide them nutrition till they become adults and swim back to the sea.It connects us to the sea and ocean. It is used for transportation, fishing and it plays an important role in recreation.
    It supports abundant lives, ours too – despite their tininess when compared to the seas.
    Major cites of the world, like New York, Boston, San Francisco, Kolkata, Mumbai, Goa, have developed around estuaries.

3.What are the obvious characteristic features of an estuary?


    Has brackish water with large variation in salinity (0.5–35 ppt)
    Sediment here is rich in nutrients
    Has unique fauna – fishes, crabs, shrimps, mollusks, etc.
    Has unique plants – mangroves, seaweeds, sea grasses
    Shorelines of estuaries are the areas of dense human populations

4.How many rivers are there in India?


    Ca 162.
    (Source: <http://en.wikipedia.org/wiki/List_of_rivers_of_India>, retrieved on 2nd April, 2009.)

5.How many estuaries are there in India?


    Exact number not known! Because:
       1. Few rivers are not reaching the sea.
       2. Not all the estuaries are studied in India.
       3. Confused identity between estuaries and lagoons.
    But, the major estuaries studied so far in India are 50 (23  from east coast, 27 from west coast).

6.Which is the largest estuary in India?


    Chilka Lake, Orissa, is the largest estuary in India – 1100 sq km.
    (Source: <http://keralaarticles.com/lakes/some-wonderful-lakes-of-the-world/>, retrieved on 3rd April, 2009.)

7.Which is the largest estuary in the world?


    “The largest estuary in the world is the Saint Lawrence River [estuary] which connects the Great Lakes with the Atlantic Ocean …
    The majority of the estuary is located in Canada   but portions of the river do touch the borders of New York.
    The estuary is over 1,900 miles long and the watershed occupies  390,000 square miles …”
    (Source: <http://www.dnr.state.md.us/mydnr/askanexpert/estuary.asp>, retrieved on March 27, 2009.)

8.What are the uses of an estuary?


    Estuary is the depositories of organic nutrient-rich sediments and alluvial soils carried-in by water currents from the sea and freshwater inflow from land.
    Young ones and juveniles of many of the marine fishes and crustaceans migrate to estuaries for protection (from the big marine predators). They also appear to enjoy little less salinity of the estuaries.
    Estuary is source of fisheries – fishes, shrimps, crabs and molluscs, which support our lives.
    Some estuaries possess the sea grass beds seaweed meadows, which have great commercial value.
    Mangroves flourish on the marshy banks of the estuaries. You may visit our ‘Mangrove’ webpage to know its tremendous uses and other interesting information on them.
    Estuary with exposed tidal flats and mud flats with their vegetation serves as sanctuaries for migratory and residential birds.
    Estuaries support our lives with the fisheries.
    * Through it we can have easy access (transportation) to the sea.
    * The estuary with the beaches serves as great recreational and tourism spots – jolly boat-riding also.

9.Name the few common estuarine fishes, crabs and birds.


    Fishes: mullets, croakers, catfishes, sardines, anchovies, engraulids, gobioids, milk fishes, eels, sea bass ...
    Crabs: mud crab, dobi crab, hermit crab …
    Birds: herons, egrets, ibis, plovers, curlews, turnstones, godwits …

10.What is the present status of the estuaries?


    They are threatened by anthropogenic activities.

11.What are the threats the estuary faces?


    Threats to an estuary is a threat to our lives (also many other organisms on the earth).
    Ever increasing huge human population that is settling around estuaries and misusing them in many ways:
    disposing sewage and household wastes:
    disposing dangerous industrial effluents with hazardous chemicals into estuaries
    using shallow water estuaries for agricultural and aquacultural purposes
    constructing barricades and dams
    heating up earth’s atmosphere by pumping out greenhouse gases more and more, thereby inviting sea level rise, which will engulf the estuaries and deltas
    collecting all the larval fishes and shrimps for the aquaculture farms – overexploitation of the fishery resources

12.What will happen to us if we continue to let the estuaries suffer?


    Soon we will be in a position to prefer death than living!
    Shortly we may finish eating all the fishes, shrimps, crabs and other edible organisms from the estuarine water bodies by overfishing them
    Some will die due to the pollution. Even if they are alive, their tissues will be filled with all the hazardous pollutants,
    which we may have to consume without any  alternate choice  and   end up having deformation, growth retardation, incurable diseases, dangerous mutations.

13.Is there anything that we can do to save the estuaries, us too?


    Yes, to start with we can follow the following suggestions:
        1. Prevent dumping solid wastes, effluents and sewages into estuaries or any biologically productive water bodies; or, purify (‘treat’) them from dirt and chemicals before letting them into estuaries.
        2. Avoid overfishing and use net with appropriate mesh-size.
        3. Follow coastal zone regulations.
        4. Avoid further human settlement.
        5. Encourage more ecological analyses and biodiversity inventories.
        6. Barcode all the presently available organisms and discover new ones. Use the data generated using barcoding for monitoring the ecosystem to find out changes in biodiversity.
        7. We must take individual, as well as collective, effort to understand the values and functions of the ecosystem.
        8. We must try to understand the deeper values and meanings of the existence of rivers and estuaries in our ancient literature/scripture of sages. That way we may be able to realize the importance and significance of having such water bodies.
        9. We must try to educate each other about our surroundings, everything we consume or use.
        10.Create awareness of misusing our environments.
          And much more …

14.What is the role of our ENVIS Centre in conserving these natural water bodies?


    Spreading scientific knowledge on estuaries and other coastal ecosystems to implant the importance of them in people’s minds.