For last few weeks beaches in Goa have been inundated with jellyfish causing inconvenience to tourists and hardships to fishermen. While jellyfish is important component of the oceanic environment, their proliferation is linked to changing chemistry of the seas. Though most jellyfish species are harmful, some have irritating and even venomous stings which threaten to turn our beaches into no-go areas.
Jellyfish blooms have been observed on many beaches and coasts around the world specially Japan, Australia, Mexico, England, Scotland, Israel, etc. Recently jellyfish blooms clogged electric power stations in England & Scotland, while in Japan two nuclear reactors had to be temporarily stopped due to the arrest of their cooling systems which were supplied by sea water. Jellyfish blooms can play havoc with coastal desalination plants and disable ocean freighters. Commercial fishing industry in Japan has been badly affected by ‘nomurai’ species of jellyfish.
Jellyfish require warm and saline water to thrive and normally they spend most of their lives in the open seas. Researches say that they approach the beaches only when the coastal water which is colder and less saline stops acting as a barrier to their approach. This happens in many places where less and less fresh water from rivers is entering the seas due to droughts, dams and coastal constructions like ports, etc. Environmental experts link frequent jellyfish blooms over the last few years to human induced environmental stresses like habitat modification, overfishing, eutophication and climate change. Researchers say that global warming and warmer waters accelerate jellyfish growth, while overfishing of natural predators like sharks and bluefin tuna helps their proliferation.
Jellyfish have very high tolerance to oceanic environmental damage says Dr. Baban Ingole, Chief Scientist in Biological Oceanography at Panaji-based National Institute of Oceanography. While many fish varieties are either killed or are driven away by changing habitats, jellyfish can survive in damaged environments, he adds. According to an UNEP Report, acidification of oceans due to increased carbon emissions makes it difficult for corals and shellfish to make skeletons, which drives away many fish varieties depending on them for food. Since the Industrial Revolution acidity levels of the oceans have increased substantially because oceans absorb more than 30% of atmospheric carbon emissions. Decline in creatures with shells could trigger an explosion of jellyfish as they are more immune to acidification.
Jellyfish is attracted to polluted waters and is a strong indicator of ocean health. According to Dr. Nandakumar Kamat, Professor of Biology at Goa University, nitrification of the oceans due to fertilizer run-off and eutophication following discharge of untreated sewage into water bodies tend to favour jellyfish proliferation. Jellyfish are ‘scavengers’ of the ocean and survive in the oxygen-depleted ‘dead zones’ typically found near coastal cities. Dr. Nandakumar says because most organisms do not survive the ‘dead zones’, jellyfish face lesser or no competition for food, rather they thrive on the debris of ‘dead zones’
Researchers say that it is difficult to predict how much the worldwide population of jellyfish would increase, but do warn that if the proliferation continues, it would certainly affect fisheries and tourism sector badly. Fishing industries in Japan, Gulf of Mexico, Mediterranean Sea have already been affected, and local fishermen are complaining of lesser catch during periods of beach invasion by jellyfish.
To the extent that jellyfish blooms are caused by global warming and increased acidification of the seas, any action taken to fight climate change like use of renewable energies would help in management of jellyfish blooms.Steps needs to be taken to reduce pollution of rivers and seas and curb dumping of untreaated sewage and hazardous chemicals into water bodies. Reducing fertilizer run-off through use of natural manure and biological pesticide would certainly help. It is necessary to curb overfishing through fishing regulations so that damaged habitats are restored and natural balance among different species of fish is maintained. Periods of fishing bans should be strictly executed.
Jellyfish require warm and saline water to thrive and normally they spend most of their lives in the open seas where the water is warmer and more saline. Researches say that they approach the beaches only when the coastal water which is colder and less saline stops acting as a barrier to their approach. This happens in places where less and less water enters the seas from the rivers due to droughts, dams or coastal construction like ports, etc. Environmental experts link frequent jellyfish blooms over last few years to human induced environmental stress like habitat modification,