CHENNAI: A mysterious yellowish layer reported in coastal waters from Nellore in Andhra Pradesh to Pondicherry has sparked concerns among fishermen and marine scientists, with the Central Marine Fisheries Research Institute (CMFRI) collecting samples to determine whether it is a phytoplankton bloom or something unusual.
Scuba divers and fishermen along the coast have reported the phenomenon over the past few weeks. Divers have observed the yellowish material in waters at depths of around 3-4 metres, while fishermen have reportedly encountered it even in deeper waters.
Scuba diver Venkat from Ocean Delight Scuba in Kovalam, who observed the phenomenon underwater, said the layer was unusually thick and reduced underwater visibility.
“We saw bioluminescence last Sunday. Two days after, the sea area has turned like this. It is very rare. We haven’t seen anything like this before,” Venkat said to TNIE. He added that the material appeared to dissolve and turn the water yellow when disturbed by boat movement or when touched.
Joe K Kizhakudan, principal scientist and head of CMFRI’s Visakhapatnam regional centre, who is currently in Nellore, said, “Kasimedu fishermen are saying they have seen this in the deep ocean continuously for a month now. If it is continuing for a month and it is flowing down, some river source may be the cause,” he said, and added that increased productivity could lead to enhanced phytoplankton growth, but the persistent nature of the phenomenon warranted further investigation.
Joe said excessive nutrients such as phosphates or nitrates entering the marine system could potentially trigger an unusually large phytoplankton bloom. Such nutrients can originate from a range of sources, including urban wastewater and other land-based discharges, but he added that this remained a possibility that had to be verified.
Importantly, fishermen at Kasimedu have not reported fish mortality and fishing activity was said to be continuing normally. This, Joe said, meant there was currently no indication that the phenomenon was a toxic algal event. At the same time, he cautioned against immediately concluding that the material was algae. “It may not be algae either. It might even be material which has leaked from a ship, we don’t know for now,” he said.
CMFRI has therefore asked for samples from different locations, including Kasimedu and areas farther north and south. Scientists will examine the material to establish its composition and determine whether it is biological or potentially linked to another source.
