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On India’s coasts, an unusual sight has become increasingly common: glittering blue button jellies, Porpita porpita, washing ashore in vast swarms. This year, Mumbai’s Juhu coasts were invaded by these rare guests just before the arrival of the monsoon - glittering, alien-like organisms, each one glowing electric blue against the sand. They look like forgotten jewels of the ocean, scattered in silence. These tiny marine creatures are actually not jellyfish at all, instead they serve as living barometers of the ocean and are rapidly becoming symbols of a much bigger problem, the intensifying impact of climate change on our oceans.
Their sudden mass appearances in Mumbai, Odisha, Tamil Nadu, Andhra Pradesh, and Gujarat signal profound changes underway in the marine environment. Rising sea surface temperatures, altered currents, coastal pollution, and cyclonic disturbances are driving these strandings, revealing how climate change is reshaping India’s coastal ecosystems. While they disrupt fishing, tourism, and local livelihoods, blue button jellies also highlight urgent questions about resilience, governance, and our preparedness to deal with changing seas. Their story is ultimately a warning: that when oceans drift out of balance, it is not just marine life, but coastal communities that bear the cost.
Blue button jellies or Porpita porpita are actually a group or colony of specialised polyps all working together in unison. Polyps are small cylindrical and vase shaped animals living in oceans with a mouth at the top surrounded by tentacles which resemble glove fingers. The tentacles are used for sensing the surrounding environment and for the capture of food. Polyps extend their tentacles, particularly at night, which contain coiled stinging nettle-like cells, which pierce, poison, and firmly hold living prey, paralysing or killing them. Polyp prey includes copepods (0ar-feet) and fish larvae.
The upper part of the colony looks like a thin disk that is blue or sometimes greenish-brown and is a gas filled float that keeps the group of polyps floating on the surface of the water as currents move it. around based on wind and sea flows. Some polyps specialise in gathering food from the water while others focus on warding off potential predators with their stinging cells. Porpita porpita individuals have both male and female reproductive structures, making them hermaphrodites that are capable of different forms of reproduction. New generations can appear if conditions are right, causing occasional clusters to show up unexpectedly on sunny beaches.
Blue button jellies are usually found in tropical and subtropical waters of Pacific, Atlantic and Indian Oceans. They float passively with currents and winds, feed on plankton using their tentacles and are not generally dangerous, but can cause mild irritation.
Changes in ocean temperatures and currents may explain why this small floater is popping up in places where it once was rare. Scientists and coastal observers alike are linking the mass strandings of these creatures to broader climate-driven changes in the marine environment.
Thus, warmer ocean temperatures fuel jelly growth and reproduction while shifting currents and wind patterns push jelly swarms toward land. Increased plankton biomass gives them more food to thrive while extreme weather like cyclones stir up their habitats, sending them drifting ashore.
However, these changes are not isolated, they reflect a destabilising ocean system influenced by greenhouse gas emissions and global warming. Anthropogenic activities leading to coastal pollution, eutrophication, habitat modification and overfishing are also adding fuel to fire triggering proliferation of blue button jellies across the beaches.
Recent blue button jelly swarming events occurred along the Astaranga Beach, Odisha, in September 2024 and was linked to warmer waters and a local depression in the Bay of Bengal. This gelatinous animal aggregation event caused massive beach pollution, hindered fishing operations, and hampered tourism.
Researchers at Visakhapatnam, Andhra Pradesh first recorded the presence of blue button jelly and shared their findings in a paper in 2023, marking a new distribution hotspot.
They inform, “The beach stranding of P. porpita was due to physical and oceanographic parameters, i.e. wind (16 km h-1), currents and tides. These factors might be a possible reason for offshore aggregation and swarming of the species. Furthermore, their occurrence was associated with higher water temperature (28.1 °C) and salinity (32.1) during the summer and monsoon seasons, which made Indian waters a favourable environment for the species aggregation or swarming”(p 200).
The same study also found that jellyfish can negatively affect fisheries because they compete with fish that eat zooplankton, prey upon fish eggs and larvae, and indirectly compete with other animals living in the waters by reducing the plankton available and thus disturb the ecological balance of the marine ecosystems by disturbing the food webs and thus need to be monitored.
Beach stranding reports of blue button jellies across the coast of Mandvi, Kutch were also reported during August 2021, along the Adri beach in Gujarat in 2010 and Puri (Odisha) during March-May 2016 during the summer season where satellite observations revealed that their drifting was favoured by shoreward monsoon currents and winds. It was also found that chlorophyll concentration starts increasing from the month of February helping in proliferation of phytoplankton that serves as food for the blue button jelly. In the west coast of India (Veraval), a large number of blue button jellies were found washed ashore in the monsoon season. In Tamil Nadu, mass beachings of blue button jellies were observed on the Chennai coast during the Gaja Cyclone in November 2018.
Blue button jellies also appeared on the beaches from Vadakadu to Olaikuda Coastline, Rameswaram Island, Gulf of Mannar, after the Nivar Cyclone hit from December 7 to 14, 2020.
The researchers who have reported this occurrence in their paper attribute this offshore swarming and drift away to the beach to shoreward water currents and wind speed. They add, “During the Nivar cyclone, severe winds of 120-130 kmph lashed across Tamil Nadu State, reaching 60 kmph in Rameswaram Island. The current mass beach stranding of P. porpita can be explained as offshore swarming, subsequent drift away and discrete patches along the coastline due to unusual shoreward water currents and wind speed”(p 258).
Newspaper articles have also reported recent sightings of blue button jellyfish along the coasts of Girgaum and Juhu in Mumbai and Chennai’s Marina beach following cyclone Gaja.
These incidents reveal that mass appearances are driven by a mix of environmental triggers such as:
Rising sea surface temperatures (28.8–30.5°C) due to climate change which boost reproduction
Wind and ocean currents push colonies toward shore, especially during cyclonic depressions
Phytoplankton blooms provide abundant food, attracting blue button swarms
Coastal pollution and eutrophication may also play a role in increasing jelly populations
These factors combine to create perfect conditions for proliferation and beach strandings of blue button jellies.
For fishers and tourists, these events are more than a visual spectacle—they disrupt livelihoods and alter beachside experiences. For example, blue button jelly mass swarming has been found to lead to disrupted fisheries due to clogging of nets thus impacting fish catches, led to tourism challenges because of stinky beaches and ghostly swarms; led to food web concerns as blue button jellies compete for plankton and change predator-prey relationships while also trigger oxygen loss due to decomposing blooms that can reduce oxygen and harm marine life. While their sting is mild, they can still cause skin irritation, especially in sensitive individuals.
Despite their nuisance during strandings, blue button jellies play a critical ecological role:
As food web regulators: They feed on plankton and serve as food for animals living in the waters and are preyed upon by sea slugs, snails, and juvenile fish
Climate indicators: Their increasing presence may signal warming seas and shifting marine ecosystems.
Aid nutrient cycling: They are also a part of organisms that live at the ocean’s surface and influence nutrient cycling.
Understanding their behavior helps scientists to:
Predict jellyfish aggregation events
Develop early warning systems for coastal communities
Monitor climate change impacts on marine ecosystems
Complete control is not feasible, but:
Predicting event occurrences in advance can be done through regular monitoring of sea surface temperature and currents
Tracking phytoplankton proliferation in oceans
Increasing public awareness to educate beachgoers and fishermen
Rapid cleanup protocols to minimise ecological and economic impact
Further research into their biology, reproduction, and ecological role
India’s diverse coastline, with its reversing monsoons, river discharge, and anthropogenic pressures, makes prediction complex but essential. The increasing strandings of blue button jellies along India’s coasts underline how closely our oceans are tied to human well-being. These organisms are more than curiosities of the tide; they embody the stresses of warming seas, disrupted food webs, and fragile coastal livelihoods. Each appearance is both an ecological signal and a socio-economic challenge, reminding us that ocean health directly shapes community resilience. By strengthening monitoring systems, protecting marine ecosystems, and aligning policy with science, India has the chance to turn these drifting warnings into a call for urgent, collective action.