A phytoplankton bloom is suspected to have changed the colour of the sea along the Kollam shoreline to greenish yellow on Sunday.
The green splash attracted a large crowd of visitors at the Kollam beach towards evening as the setting sun gave the waters an unusual dazzle.
Huge shoals of balloon fish were also seen washed ashore. Given the colour change, many were wary to wash their feet on the shoreline.
Former scientist attached to the Central Marine Fisheries Research Institute, K.K. Appukuttan, said that he suspects an overdose of phytoplankton to be the cause of the colour change.
Phytoplankton bloom is a post-monsoon phenomenon when the sea becomes nutrient rich through a process called upwelling.
But the blooms sometimes lead to an oxygen deficiency in the sea which in turn causes phytoplankton mortality, Dr. Appukuttan said.
The floating phytoplankton gives the colour change. The most important light-absorbing substance in the sea is chlorophyll, which phytoplankton use to produce carbon by photosynthesis.
Phytoplankton contains chlorophyll, and especially when exposed to sunlight, reflects the greenish yellow colour through the water, he said.
The oxygen deficiency caused also kills some pelagic fish and this could be the cause of dead balloon fish also getting washed ashore, he said.
It could be the impact of the chlorophyll filled phytoplankton that has given the greenish yellow tint, Dr. Appukuttan feels.
