Comparison of Lakes with Hypersaline, Heliothermic, sub-surface Oxygen Maxima
The data set is a comparison of Meromictic Lakes which exhibit at least few characteristics among hyper-salinity, sub-surface temperature maxima (heliothermic) ,sub-surface oxygen maxima(metalimnitic) and oxygen supersaturation. Very few such lakes are reported so far with about thirty (30) lakes world wide which are meromictic and heliothermic. . Meromictic lakes are highly stratified which exhibit meromixis, a condition in which a lake does not mix completely. Nine such lakes are reported in Asia and this data reports first time from India, Pulicat lake which has all these characteristics. Interestingly, the embedded meromixis still sustains some species withstanding the large ranges of temperature and salinity in this region of Pulicat. the Pulicat Lake in southern India that attracts various aquatic, migratory birds like Greater & Lesser Flamingoes, Pelicans, Terns, Teals, Grey heron, Open Bill Stork, Black-Headed Ibis, spot-Billed ducks, painted stork and little Egret. The lake is a habitat 88 species of birds which include more than 5 endangered and threatened species. The salinity of the lagoon is extremely fluctuating, shifting regimes from fresh to hypersaline on seasonal scales. recording a maximum of 191 ppt. Such high salinity in the Pulicat have so far not been reported.
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The observations from Pulicat lake are measures as follows. The temperature and salinity are measured using a CTD. The accuracy of temperature measurement of the CTD is ±0.005 °C and that of conductivity is 0.003 mS/cm. Temperature, salinity, dissolved Oxygen (DO) and pH are also collected using a multi-parameter water quality (WQ) probe at different depths. Further salinity was also determined using the field water sample collected from a depth of 0.5 m by Mohr-Knudsen argentometric titration method. The WQ probe measurement accuracies for different parameters are: temperature: ±0.2 °C; salinity: ±0.1 psu; DO: 0–20 mg/L: ±0.1 mg/L or 1% of reading, whichever is greater; 20–50 mg/L: ±8% of reading and for pH: ±0.2 pH units. The details of other lakes are collected from literature and the details are provided in the data set itself.