Some scientists have attributed this to the large mass of marine algae killed by lowering of salinity owing to influx of fresh water from rivers and run-off but another state-based researcher disagrees with it and said the phenomenon was due to seismic factors.
A team of researchers from Kerala University, which studied the phenomenon reported from coastal areas off Kollam and Thiruvananthapuram had held the foul smell was attributable to the bacterial decay of a possible algal bloom.
The researchers of the university's Department of Aquatic Biology and Fisheries led by A Biju Kumar have recommended to the government close monitoring of coastal waters to identify the presence of algal bloom that could produce toxins.
They said they reached the conclusion based on examination of various parameters like the colour of the sea, salinity, temperature, pH nutrients, plankton, microbes and fish mortality.
However, Dr Sainudeen Pattazhy, Associate Professor of Zoology in SN College Kollam, said the stench was linked to seismic phenomena like tremors of moderate intensity that had been experienced in several districts of Kerala and other states recently.
Even though parameters like salinity and temperature were within the optimum levels, there was no chance of occurrence of algal blooming, massive death and decay of algae. If algal blooming occurred, a thick scum would develop on the sea surface, which had not happened, Pattazhy told PTI.Anoxic conditions during the night, changes in water quality, pollution, upwelling, nutrient discharges, run-off from the land during the south west monsoon were all natural process but no foul smell had been felt, Pattazhy said.
"If massive death of plankton was due to lowering of salinity, then why did it not affect the fish fauna and other animals? No mortality of fish and other animals were observed during this period," Pattazhy, also president of Kerala Environmental Researchers Association, said.
Stench event and "red rain" were observed in 2000, 2001 and 2011 in Kerala. These events were preceded by low intensity tremors in several districts of Kerala, massive collapse of wells and land slips, he said.
The fundamental cause of stench from sea was attributable to geological changes under sea, he said. The December 12, 2000 quake and the lesser intensive tremors that occurred in 2001 were causing several perceivable changes in the earth as well as the atmosphere. The epicentre was stated to be in Meenachil Taluk in Kottayam district, he said.
The earth’s surface consisted of seven large rigid plates (continental plates). There were equal number of small plates. These were moving at the rate of four centimetres per year and these plates move slowly past one another, he said.
When ‘fault’ occurred under sea, hydrogen sulphide and other inert gases would escape from the sea surface, which was the reason for the foul smell and this had no connection with algal blooming, salinity and nutrient variations, he said.
At times, following the emission of gases from under the sea, molten lava would ooze to the sea surface. Some fisherman had recently reported that they had seen oozing of black fluid from the bottom to the surface of sea, he said.
If the stench was due to algal blooming, death and decay of algae, the foul smell would not spread to several kilometers.
Here the situation was different that the foul smell spread to several kms, he said. There was, however, no need for panic as these phenomena are temporary and when the fault under the sea corrects itself this would stop, he said.
