If you happen to see the coastal waters giving off an eerie, shimmering glow one of these nights, the ‘culprit’ is, in all likelihood, the Noctiluca scintillans, a marine planktonic organism.
Dubbed ‘sea fire’ and ‘sea sparkle,’ the bioluminescence looks cool, but it has also left marine scientists wondering. An increase in Noctiluca blooms can have a negative impact on coastal ecosystems and fisheries, according to A. Biju Kumar, head of the Department of Aquatic Biology and Fisheries, University of Kerala, which is monitoring the phenomenon as part of a collaborative research effort.
The recent bioluminescence reported along the Kerala coast is caused by the green form of Noctiluca scintillans. Red blooms are observed in the southwest coast during the summers. A marine planktonic dinoflagellate organism, Noctiluca scintillans is aptly named. Noctiluca in Latin means ‘night light’ and scintillans, ‘flashes of light,’ Dr. Biju Kumar said.
Closer investigation
He says Noctiluca blooms along the Indian coast has been increasing in frequency, which points to a “changing ocean.” And as such, it calls for closer investigation, he said.
Winter blooms along the Kerala coast occur due to eutrophication — higher nutrient content in water — and influx of oxygen-deficient waters. Eutrophication can be caused by nutrients leaching into coastal waters from land-based sources such as sewage and fertilisers.
Death of fish
Rapid blooms of Noctiluca lower oxygen level in the water, driving fishes away. Increasing blooms of Noctiluca scintillans in the Arabian Sea can lead to the displacement of diatoms which constitute the food of many commercially exploited species such as sardines. “The species, as such, is not toxic. But their blooms result in the death of fish and other invertebrates due to accumulative toxic levels of ammonia, which they discharge into the water,” he said.
Indian scientists are using satellite data and field studies to monitor the harmful algal blooms along the coast, Dr. Biju Kumar added.
