BRACKISH WATER OSCILLATORIACEAE FROM NORTH 24-PARGANAS , WEST BENGAL , INDIA

The present communication enumerates 40 taxa of Oscillatoriaceae from the brackish water wetlands of North 24-Parganas district of West Bengal. Out of the reported taxa, 12 are from each of Lyngbya and Oscillatoria, 6 from each of Phormidium and Spirulina, 2 belong to Schizothrix, and Hydrocoleum and Katagnymene are represented by one species each. A close relationship was observed between seasonal water temperature and salinity levels of the wetlands in enhancing algal population. Introduction Blue-green algae (BGA) are the primitive photosynthetic microorganisms which have tremendous potential in environmental management, as soil conditioners, bio-fertilizer, bio-monitors of soil fertility, water quality, amelioratory agents, feed for animals and protein supplements and rehabilitation of degraded ecosystems through biosorption of metals (Whitton and Potts 2000). The family Oscillatoriaceae includes non-heterocystous filamentous forms of BGA. Tropical climate of West Bengal, India provides favourable environment for the luxuriant growth of BGA in different types of soil, freshwater bodies, brackish waters and estuarine habitats (Gupta 1965, 1975, Sen and Gupta 1987, 1998, Santra et al. 1988, 1991, Sen and Naskar 2002, 2003, Naskar et al. 2006, 2007). Taxonomic work on BGA from brackish water wetlands of West Bengal has long been ignored. The present communication is an outcome of the taxonomic investigation of algal flora from brackish water wetlands of North 24-Parganas district of West Bengal. This study has been made with a view to understand the distribution of different members of Oscillatoriaceae in brackish water environment, which is an initiative study for exploiting their innate potentials. Materials and Methods The present study was conducted during 2002 to 2005 in brackish water wetlands of North 24-Parganas district of West Bengal. The district is situated in the southern zone of the state West Bengal, India and lies between 22o11 ́6 ́ ́ N and 23o1 ́2 ́ ́ N latitude and Corresponding author. E-mail: nurmohammadnaskar@yahoo.com Department of Botany, Charuchandra College, Kolkata 700029, India.


Introduction
Blue-green algae (BGA) are the primitive photosynthetic microorganisms which have tremendous potential in environmental management, as soil conditioners, bio-fertilizer, bio-monitors of soil fertility, water quality, amelioratory agents, feed for animals and protein supplements and rehabilitation of degraded ecosystems through biosorption of metals (Whitton and Potts 2000).The family Oscillatoriaceae includes non-heterocystous filamentous forms of BGA.
Taxonomic work on BGA from brackish water wetlands of West Bengal has long been ignored.The present communication is an outcome of the taxonomic investigation of algal flora from brackish water wetlands of North 24-Parganas district of West Bengal.This study has been made with a view to understand the distribution of different members of Oscillatoriaceae in brackish water environment, which is an initiative study for exploiting their innate potentials.

Materials and Methods
The present study was conducted during 2002 to 2005 in brackish water wetlands of North 24-Parganas district of West Bengal.The district is situated in the southern zone of the state West Bengal, India and lies between 22º11΄6΄΄ N and 23º1΄2΄΄   N latitude and between 88º20΄ E and 89º5΄ E longitude.Out of 22 blocks of the district, 12 blocks include brackish water wetlands.The administrative units chosen for the present study were blocks, viz.Hingalganj, Sandeshkhali-I and II, Haroa, Hasnabad, Minakhan, Basirhat-I and II, Baduria, Barasat-II, Rajarhat and Deganga.These 12 administrative units have been divided into four zones based on the adjoining blocks.Zone I includes the blocks Hingalganj, Sandeshkhali-I and II; Zone II with Horoa, Hasnabad and Minakhan; Zone III with Basirhat-I and II and Baduria; and Zone IV with Barasat-II, Rajarhat and Deganga.
Algal collections were made during summer (March-May), monsoon (June-August), post-monsoon (September-November) and winter (December-February) seasons.All the collections were preserved in 4% formalin and deposited at the Central Inland Fisheries Research Institute (ICAR), Salt Lake, Kolkata.The materials were then examined microscopically and measurements were taken.Identification was mostly based on the identification keys given by Desikachary (1959) and some other workers (Santra et al. 1988, Sen and Naskar 2003, Sen 2005).

Results and Discussion
The study revealed 40 taxa belonging to seven genera of Oscillatoriaceae which are briefly described here alphabetically along with their spatial and temporal occurrence and abundance.species in summer (35 taxa) and the lowest in monsoon (9 taxa) and winter (3 taxa).The post-monsoon period showed absence of these algae.The taxa which appeared during winter were (viz.Lyngbya birgei, L. aestuarii and Spirulina major) also found in summer, but not in monsoon.The brackish water wetlands are fed with tidal waters of Hooghly-Matla estuarine system and its tributaries.The salinity distribution of the studied wetlands does not indicate specific salinity zones.The temperature range and salinity spectrum of all four studied zones (Zone I to Zone IV) are shown in Table 1.The salinity values of brackish water wetlands were maximum during summer and went down during monsoon showing minimum values.But salinity values were higher during post-monsoon and winter periods than monsoon.The Table 2 summarizes the zone-wise distribution of recorded Oscillatoriaceae species.