Lethal dissolved oxygen level in the water of Gohira Dam here led to mass death of fish. The Fisheries department, which had collected water samples from the dam after a large number of fish were found dead a few days back, submitted its report to the district administration on Tuesday. While the Regional office of Odisha State Pollution Control Board (OSPCB) at Rourkela is yet to submit its report, the Fisheries department, Sambalpur, report found the dissolved oxygen level at 3.8 mg/litre against prescribed 4mg/l or more. They hinted at this as the reason behind mass mortality among fish. However, the pH level of water was found at 7.4 against the prescribed pH between 6.5 and 8.5. Dissolved oxygen concentrations are constantly affected by diffusion and aeration, photosynthesis, respiration and decomposition. While water equilibrates toward 100 per cent air saturation, dissolved oxygen levels fluctuate with temperature, salinity and pressure changes. The officials have advised enhancing the dissolved oxygen level by aeration, pumping and other methods for survival of fish in the dam.

2016, The New Indian Express.