Journal of Water Resource and Protection, 2013, 5, 611-623 doi:10.4236/jwarp.2013.56062 Published Online June 2013 (http://www.scirp.org/journal/jwarp) Copyright © 2013 SciRes. JWARP Assessment of Changes in the Algal Diversity of Chilika Lagoon after Opening of New Mouth to Bay of Bengal Debabrata Mohanty, Siba Prasad Adhikary Department of Biotechnology, Institute of Science, Visva-Bharati, Santiniketan, West Bengal, India Email: adhikarysp@visva-bharati.ac.in Received February 1, 2013; revised March 3, 2013; accepted April 3, 2013 Copyright © 2013 Debabrata Mohanty, Siba Prasad Adhikary. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT Eighty one algal taxa comprising of 24 species of Cyanophyta, 2 Rhodophyta, 19 Chlorophyta, 6 Euglenophyta and 30 Bacillariophyceae under Heterokontophyta were recorded in Chilika lagoon in different seasons of 2010-2011 in a sur- vey after opening of new mouth to Bay of Bengal. Of these Cyanobacterium diachlloros, Aphanocapsa marina, Micro- systis aeruginosa, Microsystis wesenbergii, Pseudanabena limnetica, Arthospira ambiguum, Oscillatoria perornata, Oscillatoria proteus, Oscillatoria simplicissima under Cyanophyta, Scenedesmus bijugatus, Urenema elongatum under Chlorophyata, Trachelomonas abrupt, Trachelomonas hispida under Euglenopyta and Coscinodiscus subtilis, Navicula amphirhynchus, Navicula major, Gomphonema micropus, Gomphonema olivaceu, Gomphonema sphaerophorum, Cyclotella meneghiniana, Pinnularia subsimilis, Pleurosigma javanicum, Stephanophyxis turris, Synendra tabulata, Stauroneis pusilla and Cymbella affinis under Bacillariophyceae of Heterokontophyta recorded in the survey have not been reported in the lake before opening of the mouth. Maximum number of algal species was observed in winter fol- lowed by summer and post monsoon seasons. Northern sector showed maximum algal diversity followed by Central, Southern and Outer channel sectors. The Cyanophytes followed by Chlorophytes were rich in Northern, Central and Southern sectors where as the diatoms were abundant in Outer channel sector and Northern sector. The agarophyte Gracilaria verrucosa recorded in the Outer channel sector of the lagoon for the first time showing extended distribution of the species due to increase in salinity coupled with consistent wave action in the lagoon after opening of the new mouth. Keywords: Chilika Lagoon; Algal Diversity; New Mouth; Salinity Gradient; Seasonality 1. Introduction Chilika lagoon in the east coast of India is the largest bra- ckish water lake with an average depth of approximately 2 m and an area varies from 1165 to 906 km 2 during rainy and summer seasons respectively [1]. It was decla- red as Ramsar site, a wetland of international importance in 1981. The fresh water input into the lagoon is from Daya and Bhargabi rivers, several other rivulets and also salt water from Bay of Bengal. Due to confluence of fresh and salt water, a distinct salinity gradient is main- tained in different seasons in the lagoon ranging from 1 - 33 ppt basing on which it is divided into four sectors i.e Southern, Central, Northern and Outer channel sector. Prior to 2001 in Southern sector the salinity was moder- ate (8 - 20 ppt), in Central sector showed a seasonal va- riation in salinity level (5 - 30 ppt) and in the Northern sector the salinity was low varying from (0.1 - 13 ppt) due to opening of several rivers. Due to tidal impact, coupled with closure of the mouth connecting to the sea the salinity level in the Outer channel sector was nearly similar to the seawater during most times of the year ex- cept the rainy season [1]. To restore the lagoon charac- teristics with appropriate flux of seawater into the lake a new mouth was dredged in 2000 in the Outer channel sector near Sipakuda area. Again in March 2008, a natu- ral mouth was opened near Gabakunda and was subse- quently widened [2]. Both these new openings to the sea facilitated extensive mixing of saltwater with freshwater resulting in a wide variation in the hydrology of the lake. Several authors have reported the changes in the phys- ico-chemical parameters of the lagoon after opening of these new mouths [2-7], however, assessment of algal diversity changes after 2001 has not been made so far. An assemblage of marine, brackish and freshwater eco- systems in Chilika lagoon encourages occurrence of di-