Limnological Study on Lonar Lake: A Unique Brackish Crater Lake in India

Lonar lake is a inland saline crater lake of only one of its kind in Asia, which depicts unique limnology and biodiversity. Studies were undertaken to evaluate its unique ecosystem. Wetlands of this lake have archaeological significance. Due to its importance to the humans, studies were carried out with regard to its water quality in terms of physico-chemical characteristics, heavy metal concentration and phytoplankton population. Ground water samples in surrounding area were also collected and analyzed to see that whether seepage of lake water in groundwater table occurs. But well waters depicted no such facts and were suitable for human consumption, with all parameters within drinking water standards. Lonar lake was observed to support luxuriant bloom of phytoplankton dominated by Spirulina plantensis – a protein rich blue green alga of commercial importance. Apart from Spirulina, more algal species belonging to Chlorophyceae, Cynophyceae and Bacillariophyceae were also encountered in the lake water. Lake water depicted high salinity and alkalinity. Alkalinity showed wide variation and ranged between 1460-2230 mg/l in different parts of lake. Chloride and sodium concentration varied between 1881 and 2414 mg/l and 5668 and 5762 mg/l respectively. Lonar lake water was found to be very rich in mineral nutrients content. This lake can be used for exploitation of protein rich algal biomass, as well as for control irrigation of salt tolerant crops. A total of 11 phytoplankton species was recorded in Lonar lake. Total phytoplankton count per ml of lake water was observed to vary between 1832 cells to 30085 algal cells/ml. Cyanophyceae group was the dominant among the algae community with percentage composition of 98.8 to 100% at different sampling locations. Two species of Spirulina were observed in lake water, with a total density of 1750 to 27641 algae/ml. Spirulina is a well known indicator of brackish water or eutrophic lake water. No fish species was recorded from this lake. This paper discusses in detail the limological status of the Lonar lake.