Citizens may be rejoicing about the recent spells of rain bringing relief from the sweltering heat, but the showers have turned out to be deadly for the fish in Ulsoor lake. Apart from depleting the dissolved oxygen (DO) level in the lake, the showers also led to the draining of garbage dumped in storm water drains into the lake, resulting in yet another fish kill on Monday.
This is the second fish kill reported in the lake this year, following the first in March.
Leo F. Saldanah, a coordinator at the Environment Support Group, said unless the inflow of sewage and solid waste through SWDs is stopped, fish kills will continue to occur.
B.E. Satish, chief engineer (lakes), Bruhat Bengaluru Mahanagara Palike (BBMP), said the waste dumped in SWDs upstream was washed into the lake, increasing the toxicity of the water. The site of the fish kill has visibly heavy concentration of mixed waste, including non-biodegradable plastic waste.
A recent study by T.V. Ramachandra and team from the Centre for Ecological Sciences, Indian Institute of Science, concluded that the inflow of sewage and draining of solid waste into lakes was the chief cause of fish kill. While a major portion of the dumped solid waste is bio-degradable, the nutrients seep into the water after they are broken down.
This, coupled with sewage, leads to an increase in ammonia concentration, depleting the DO in the lake and killing the fish, the report said.
