The Central Marine Fisheries Research Institute (CMFRI) has connected the mesmerizing bioluminescence phenomenon, locally known as Kavaru, to harmful algal blooms during summer months. This luminous blue glow serves as an indicator of these blooms, which release biotoxins into the water, potentially affecting fish, especially those with shells. The CMFRI has identified 4-5 types of algae in these harmful blooms.
Grinson George, principal scientist and head of the marine biodiversity and environment division, highlighted the lack of early warning systems due to the ability to study samples only when the bioluminescence occurs. To address this, the Indian National Centre for Ocean Information Services (INCOIS) has started issuing harmful algal bloom (HAB) warnings for the country.
In scientific terms, the bioluminescence is attributed to eutrophication, resulting from increased nutrients like nitrogen and nitrates, high salinity, and turbid water. This phenomenon has intensified in the Kochi backwaters, with unusual climatic changes triggered by a shortage of rainfall leading to substantial algal blooms that pose harm to fish.
A recent study of the March 2023 algal bloom in Kumbalangi revealed 12 phytoplankton species, with a total count of 1,22,060 cells/litre of water. Water quality analysis during the bloom period indicated elevated pH (7.4), salinity (17 ppt), turbidity (5.74 NTU), and total chlorophyll (36.04 mg m-3). Algal blooms have a negative impact on the aquatic ecosystem, influencing fish mortality and other natural resources in the affected area.
Jellyfish blooms have also been observed as a consequence of disturbed rainfall patterns. Grinson explained that during the rainy season, the influx of fresh water triggers the sardine run, where shoals of sardines rush towards the coast in search of food.
The CMFRI conducted a series of studies from 2015 to 2021, revealing an increasing frequency of harmful algal blooms. Notably, a bloom of Scrypsiella trochoidea, a harmful dinoflagellate, was observed off Kochi during the late summer monsoon of 2021, extending from 10m to 40m depth in certain sampling stations.
Source: The Times of India
