We’ve all heard the saying, “All that glitters is not gold,” haven’t we? The same applies to what is supposed to be a breathtaking experience of radiance in the backwaters of Kochi widely reported in mainstream media about three weeks ago. Clips of bioluminescent bloom lighting up Kerala’s coastal waters captivated onlookers with its glow. But behind the science of this natural phenomenon lies a deeper story of nutrient overload, plankton proliferation and the ecological imbalances brewing beneath the surface.
Some of Kerala’s most picturesque fishing villages and ethereal tourist attractions include Kumbalangi, Chellanam and Puthuvype. This integrated ecotourism setup offers glimpses into the culture, traditions and folklore of fishing communities, interwoven with sustainable practices unique to Kerala.
Another natural wonder it showcases is the mesmerising blue bloom of bioluminescence during the summer months. Locally known as kavaru in Malayalam, this shimmering effect is produced when water is disturbed, a phenomenon that first captured the public imagination with the 2019 film Kumbalangi Nights. Since then, people eagerly await this magical display each summer, usually occurring between March and May.
Scientifically, this phenomenon results from eutrophication — a consequence of nutrient overload, along with high salinity and turbidity — which can potentially wreak havoc on marine life. Similar occurrences have been observed along Thiruvanmiyur Beach (Chennai), Juhu Beach (Mumbai), Bangaram Island (Lakshadweep), and Betalbatim Beach (Goa), raising ecological concerns. While bioluminescence evokes a sense of wonder in tourists, it also demands urgent attention to the sustainability of our ecosystems. Beauty, when blinding, can carry its own ambivalence. It’s high time we looked beyond the enchantment and examined the harsh ecological reality this stunning spectacle may be warning us about.
What causes kavaru?
Bioluminescence is exhibited by certain bacteria, fungi and algae in coastal, estuarine and brackish waters, resembling the light emitted by fireflies. It is essentially a conversion of chemical energy into light. One of the primary organisms responsible is Noctiluca scintillans, a microscopic plankton. Its Latin name alludes to this phenomenon — noctiluca means ‘night light’ and scintillans means ‘sparkling’, which is why it’s also referred to as ‘sea sparkle’.
This glowing effect is caused by mechanical disturbances and shear stress acting on the organisms. Additionally, complex biochemical reactions occur in specialised structures called scintillons. The glow is usually blue, but can also appear red or brown depending on the species involved. These colours often reveal details about their feeding behaviour. When concentrations exceed half a million per litre, the phenomenon is known as a red tide. Studies indicate that ecological imbalances such as reduced rainfall, rising temperatures and increased discharge of industrial effluents (leading to high nitrate and phosphate levels) are major drivers of these events.
How is understanding plankton ecologically essential?
Plankton — mostly larval forms of marine species like prawns and mussels — are vital to aquatic food chains. However, in large numbers, they release substances like dimethyl sulphide, dissolved organic carbon and ammonium, leading to the deterioration of water quality through Harmful Algal Blooms (HAB). These can cause widespread marine mortality and loss of biodiversity. A common effect of HABs is hypoxia (low oxygen levels), which damages both natural ecosystems and fish farming operations.
Recent research has identified 12 phytoplankton species in Kumbalangi waters, with total counts exceeding 100,000 per litre — a worrying sign for ecological health and aquaculture. Salinity levels here range between 30-35 parts per thousand, a key factor in triggering blooms and bioluminescence. Despite ongoing research, there is still no advanced system to warn communities ahead of such occurrences.
Impact of blue blooms on economy, livelihood
While the shimmering waves are a visual treat, the danger they pose extends beyond marine ecosystems to human health and the economy. Algal blooms are symptomatic of climate change and nutrient enrichment in aquatic environments. The hidden threat lies in the harmful toxins released when these microscopic organisms aggregate, affecting both marine and human health.
High fish mortality, particularly among shellfish, can devastate local ecosystems. Furthermore, the quality and safety of fish for consumption is compromised when biotoxins accumulate, leading to reduced demand in local and export markets.
Although beautiful to observe, these waters can be perilous to enter, as oxygen levels drop drastically. Toxins like hepatotoxins, neurotoxins and dermatoxins can harm fishers entering the water. One such example is amnesic shellfish poisoning (caused by domoic acid), a neurotoxin that affects the hippocampus, resulting in gastrointestinal and neurological symptoms. Paralytic shellfish poisoning, caused by Alexandrium. a kind of dinoflagellates or algae, can lead to respiratory failure and neurological disturbances. While social media glorifies this natural spectacle, the reality for local fishing communities is one of despair. As the sparkle spreads, fish flee the area, leading to poor catches and diminished livelihoods.
Monitoring to prevent environmental destruction
Both international and national bodies, including state-specific agencies, are involved in monitoring and mitigating HABs. Notable among them are UNESCO’s IOC-HAB Programme and India’s INCOIS Algal Bloom Information System.
Key measures to alleviate toxic blooms include regulating coastal runoff, managing agricultural and urban waste and promoting sustainable aquaculture practices such as feed regulation. Mangroves and seagrasses, which act as natural nutrient filters, are being restored in areas where they have declined.
Advanced technologies like remote sensing and biotic algorithms are now used to predict and map the spread of blooms. Public engagement through citizen science — including workshops, popular articles and local committee meetings — ensures community awareness and encourages effective long-term control strategies.