Jellyfish population is abounding along the Kerala coast, threatening other species and creating havoc for fishing operations. Scientists studying the phenomenon feel that the proliferation of the species indicates the impact of human activities on the marine environment.

In the latest incident, a large number of dead jellyfish were washed ashore on the Thumba beach in Thiruvananthapuram in the last week of October.

“Mass mortality of jellyfish and fouling of beaches are becoming more frequent,” says A. Biju Kumar, Head, Department of Aquatic Biology and Fisheries, University of Kerala. “Coastal areas around the world are struggling with similar jellyfish blooms, as these population explosions are known. These blooms are increasing in intensity, frequency and duration,” he says.

A biodiversity survey carried out by the department along the southwest coast of India last year found that fishing trawlers were facing a difficult time during the post-monsoon season when their nets get clogged with jellyfish. The survey documented frequent occurrence of jellyfish blooms and the mass deposit of dead jellyfish on beaches. Huge masses of jellyfish have forced the shutdown of nuclear plants in several countries by choking the water intake filters.

Food chain hit

Jellyfishes are free-swimming marine animals with a gelatinous umbrella-shaped body and trailing tentacles. They can deliver a painful sting that could prove fatal in some cases. By devouring huge quantities of plankton, jellyfish may deprive small fish species of food and mess up the entire food chain.

The proliferation of jellyfish appears in large part to be related to human impact on the oceans, scientists feel. “Throughout history, the intricate lattice of ocean life has kept jellyfish in check,” says Dr. Kumar.

“Thanks to overfishing, pollution, and other factors, though, jellyfish populations are exploding into superabundance.”

The increase in jellyfish population along the southwest coast in recent years has been found to match the increase in the occurrence of algal blooms in the coastal waters, a consequence of the nutrient run off from land.

Dr. Kumar feels that the proximate causes of jellyfish blooms are difficult to deduce because of the complex effect of climate change at the ecosystem level. “Global warming and the decline in the population of predatory fish species and turtles due to overfishing could lead to the proliferation of jellyfish in Indian waters.”

He stresses the need for detailed studies to analyse the factors responsible for jellyfish blooming and its impact on the marine ecosystem.

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