The vast and dream like Chilika Lagoon is situated on the east-coast of India. It is the largest brackish Water Lagoon with estuarine character that sprawls along the east coast. It is the largest wintering ground for migratory waterfowl found anywhere on the Indian sub-continent. It is one of the hotspot of biodiversity in the country, and some rare, vulnerable and endangered species listed in the IUCN Red List of threatened Animals inhabit in the lagoon for atleast part of their life cycle. The total number of fish species are reported to be 225 (Dean and Saaltink, 1991). Along with a variety of phytoplankton, algae and aquatic plants, the Lake region also supports over 350 species of non-aquatic plants (Panda and Pattnaik, 1988). By a recent phytodiversiy survey by CDA ( 2002) 710 number of plants identified from Chilika( within the waterbody, including the Islands and shoreline plants) . A survey of the fauna of Chilika carried out by the Zoological Survey of India in 1985-87 recorded over 800 species in and around the lagoon. This list includes a number of rare, threatened and endangered species, including the Barakudia limbless skink. On account of its rich bio-diversity, Chilika was designated as a "Ramsar Site", i.e. a wetland of International Importance. The Nalaban Island within the lagoon is notified as a Bird Sanctuary under Wildlife (Protection) Act, the National Wetlands, mangroves and coral reefs Committee of Ministry of Environment & Forests, Government of India, have also identified the lagoon as a priority site for conservation and management. The Lagoon is a highly productive ecosystem, with rich fishery resources. The rich fishing ground sustain the livelihood of more than 0.15 million fisherfolk who live in and around the Lagoon.
 

The water spread area of Chilika varies between 1165 to 906 sq.km during the monsoon and summer respectively. A 32 km long, narrow, outer channel connects the main lagoon
 

to the Bay of Bengal, near the village Motto. The mouth connecting the channel to the sea is close to the north eastern end of the lagoon. High tides near this inlet mouth drive in salt water through the channel during the dry months, from December to June. With the onset of the rains, the 52 river and rivulets  falling into the Chilika are in spate, causing fresh water currents which gradually push the sea water out. Due to littoral drift prevailing along the east coast the inlet mouth constantly changes position.
 

The lagoon itself can be broadly divided into four natural sectors based on salinity and depth: the southern zone, central zone, northern zone and the outer channel. A number of islands are present in the lagoon with habitation and without the habitation, prominent among which are Krushnaprasad, Nalaban, Kalijai, Somolo, Honeymoon, Breakfast and Birds Island.
 

Chilika supports some of the largest congregation of migratory birds in the country, particularly during the winter. Flocks of migratory waterfowl arrive from as far as the Caspian Sea, Lake Baikal, Aral Sea, remote parts of Russia, Kirghiz steppes of Mongolia, Central and South East Asia, Ladakh and the Himalayas, to feed and breed in its fertile waters. In 1989-90 an estimated two million birds visited the Lake.Recently based on the survey by the BNHS ( 2002) 205 species of birds were listed from the lagoon.
 

Flora :- Phytoplankton flora – 43 sp, algal communities – 22 sp, Vascular plants 711 sp.

Fauna :- Fishes – 225 sp, Protozoa – 61 sp, Platyhelminthes- 29 sp, NematodesNematodes – 37 sp, Polychaetes –31 sp, Mollusca – 136 sp,–   Crustacea m- 28 sp., Decapoda – 30 sp., Amphibian & Reptile – 37 sp, Birds – 205 sp, and Mammals – 118 sp.