Retention of photosynthetic oxygen in algal mass elevates dissolved oxygen concentration in the Lake

摘要

The atmospheric and photosynthetic oxygen is the major sources of dissolved oxygen in water. The concentration of dissolved oxygen depends on the photosynthetic activities of the Chloroplast-bearing organisms. In case of water, mostly algae are responsible to regulate the oxygen concentration in the lake. The present study was conducted in one of the eutrophic lake, the Lower Lake, where exceptionally high concentration of dissolved oxygen was recorded at particular time and place. The particular sampling point was repeatedlyinvestigated to know the cause of higher concentration of the dissolved oxygen. The vast difference in the readings recorded with the different methods (Winkler’s & Electrochemical) confirmed that apart from the dissolved oxygen in water, the oxygen retained by the algal mass present at the site is mainly responsible for increasing of D.O. values. The analysis of algal mass further confirmed that additional input of the oxygen is due to presence of Cyanophycean algae Viz. Microcystis aeruginosa, Merismopedia sp. and also of Clorococcum species belonging to Class Chlorophyceae. These algal species particularly retain photosynthetic oxygen, which was released due to the use of fixatives i.e. application of Magnous sulphate and alkaline iodide in the sample. As the dissolved oxygen and biologically trapped oxygen get fixed with the action of fixative, the total value was observed to increase substantially.