When people at the beach in Puducherry noticed the sea turning red recently, it raised safety concerns and prompted official investigations. The reason was eventually determined to be a Harmful Algal Bloom (HAB), a phenomenon made worse by pollution, climate change, and unregulated wastewater flow, according to officials. An alarming increase in harmful algal blooms (HABs), which are toxic algal overgrowths that threaten ecosystems and public health, is occurring in India's lakes, rivers, and coastal waterways in India.
What are Harmful Algal Blooms (HABS)? Why are they increasing in India?
Algal blooms are formed when algae that are normally found in water bodies suddenly grow out of proportion when water bodies get polluted due to nutrients, often nitrogen or phosphorus from untreated sewage discharge, industrial wastewater, or agricultural fertiliser runoff, and when the water is warm and slow-moving with an adequate amount of sunlight and carbon dioxide. Salinity variations in the water column and monsoon patterns also influence formation of algal blooms.
While not all algal blooms are harmful, a few types of algae produce toxins and Harmful Algal blooms (HABs) occur when toxin-producing algae grow excessively in a body of water. This toxin production can also be stimulated by environmental factors such as light, temperature, salinity, and pH.
HABs are predicted to rise as India pumps more and more untreated waste into its waters with urbanisation, industrialisation, and agricultural expansion and as temperatures rise due to climate change.
The rise in HABs in India is linked to a combination of these factors:
Nutrient overload:
The most important cause of algal blooms is the presence of excess of nutrients such as nitrates and phosphates in the water. For example, India generates large amounts of wastewater and more than 63 percent of it is left untreated and gets mixed with freshwater bodies. This wastewater contains untreated sewage from urban areas, chemical wastes from industries, agricultural runoff that contains excess fertilisers that drain into water bodies, overloading them with nutrients.
Increased nutrient flux:
Monsoonal changes can influence nutrient levels in water bodies and monsoon days have been found to lead to lower formation of HABs in India, but these could be due to lack of availability of data due to rough weather. Coastal upwelling can lead to the rise of cooler nutrient rich water to the surface in oceans, triggering algal blooms.
Higher temperatures:
Climate change is causing sea temperatures to rise, which are creating ideal conditions for the growth of algae that proliferate rapidly when the water is nutrient rich.
Turbidity:
Is caused due to suspended particles and organic matter in the water. Low turbidity helps sunlight pass through the water aiding growth of algae.
Salinity:
Low salinity can aid in proliferation of HABs.
How do HABs impact public health and ecosystems?
Threat to public health
A vast majority of the Indian population depends on coastal and inland waters for fishing, agriculture, bathing or cooking, and spiritual rituals. Algal blooms can pose a public health risk, endangering the lives of people.
For example, CyanoHABs (a type of blue-green algae) can release toxins in the water, poisoning humans who drink it as well as aquatic animals such as fish. These fish, when consumed by humans, can cause nausea, breathlessness, diseases triggered by neurotoxins and hepatotoxins such as dementia and Alzheimer's, gastrointestinal and respiratory problems, and adverse impacts on the liver and kidney functioning. Over the years, numerous people have been hospitalised in Tamil Nadu, Kerala, Maharashtra, and coastal regions of India owing to the effects of CyanoHABs, but many instances also go unreported.
Damage local economies: Impact on fisheries
HABs produce thick mats on water, which prevent sunlight from entering the water. The thick mats gradually decay, and bacteria break down this decaying mass using oxygen in the water, leading to oxygen depletion, killing fish and other animals in marine and inland waters.
Loss of biodiversity: Threat to aquatic ecosystems
Algal blooms prevent penetration of sunlight leading to coral smothering, bleaching and weakening reef ecosystems that support diverse marine life.
The HAB can kill smaller animals living in the water, leading to the starvation of bigger animals living and depending on the water bodies for their food.
“Algal blooms are bioindicators of imbalance in freshwater ecosystems and of high nutrient loads. They affect several water parameters, such as dissolved oxygen and pH, and can also add toxins to the water,” says Dr. Gurudas Nulkar, Director of the Centre for Sustainable Development, Gokhale Institute of Politics and Economics.
Where are HABs occurring in India?
A total of 218 HAB events have been documented in Indian waters by October 2022. The majority of these (88 percent) are caused by dinoflagellates or cyanobacteria (a type of algal species).
Coastal hotspots in India
Nine algal bloom hotspots have been identified along India’s east and west coasts that include Goa, Mangaluru, Kozhikode, Kochi, and Vizhinjam Bay along the west and Gopalpur, Kalpakkam, Palk Bay, and the Gulf of Mannar along the east.
Cities such as Kochi, Mangaluru in the coastal states of Kerala and Karnataka generate large amounts of industrial and agricultural runoff that drains into the sea, which when coupled with warmer sea temperatures and high humidity create favourable conditions for HABs. These states are reported to experience higher (67 percent) incidences of HABs, but this could also be linked to presence of more research institutes in the area that are working on HABs.
Most of the blooms on the east and west coasts of India occur during the withdrawal of the south-west monsoon and pre-monsoon period when winds drive dense, cooler, and usually nutrient rich water from the deeper sea on to the surface or lead to high riverine discharge resulting in nutrient-enriched waters.
Affected inland water bodies of India
Algal blooms in inland waters of India have been reported from Udaisagar lake in Rajasthan, Dal Lake in Jammu and Kashmir, Upper Lake (Bhojtal) in Bhopal in Madhya Pradesh, Chilika lake in Odisha and in River Ganges at Varanasi.
Dr Karthick Balasubramanium, a scientist at Agharkar Research Institute (ARI), Pune and an expert in Diatom research informs that “While diatoms (a type of algae) do not produce big HABs, other algae such as microcystis (a type of freshwater cyanobacteria) are known to produce HABs in dams that receive large amounts of sewage from urban areas. I have personally observed algal blooms triggered by cyanobacteria in Ujani dam in Maharashtra that receives loads of sewage from cities such as Pune”
What is India doing to monitor and control HABs?
India has routine HAB or water quality monitoring programs, but these are scattered between multiple institutes and agencies. For example, Mumbai port and adjacent areas are monitored through a pilot initiative by the Global Ballast Water Management Program.
The National Centre for Coastal Research (NCCR) and INCOIS use several buoys and monitor water quality in the Arabian Sea and the Bay of Bengal. Sensors for phytoplankton pigment assessment are also being used along with nutrient monitoring sensors in the Arabian Sea and the Bay of Bengal.
A multi-national HAB research program with the Center for Marine Living Resources and Ecology (CMLRE), Kochi and other participating institutes has been initiated by the Ministry of Earth Sciences (MoES). Open ocean HAB dynamics, toxicology, coastal HABs, HAB retrieval algorithms, and modeling are being studied through this programme.
The INCOIS’ Algal Bloom Information Service (ABIS) in India is equipped to provide bloom alerts in four coastal and offshore hotspots, namely Kochi, Gulf of Mannar, Northeast Arabian Sea, and off Gopalpur in the coastal Bay of Bengal. It calculates the bloom index to determine the presence or absence of a bloom and also monitors parameters triggering blooms such as chlorophyll levels, sea surface temperature, abundance of phytoplankton etc. Based on this information, alerts are generated based on indicators such as—“normal,” “watch,” or “warning,”.
Researchers have recently developed a novel interactive cloud-based dashboard called “CyanoKhoj” in the Google Earth Engine, that uses satellite data to monitor HABs in Indian inland water bodies. This app can be used by water managers, scientists, lay people to constantly keep an eye on waterbodies for any ongoing or potential Cyanobacterial Harmful Algal Blooms (CyanoHABs) and take water quality and water management decisions accordingly.
However, there is a need for developing novel technologies for HAB research and monitoring in India in the future, creating integrated observation networks and ensuring better coordination across different central/state agencies and research institutes to understand and prevent HABs.
What are the solutions and policy actions that can be undertaken to control HABs?
Prevention is the best way out
Preventing industrial, urban and agricultural discharge from getting into marine and inland water bodies.
Reducing concentration of nutrients in coastal runoff generated from urban and agricultural areas by implementing rainwater harvesting and stormwater management.
Promotion of sustainable practices
Sustainable fishing and aquaculture by avoiding overfeeding in aquaculture farms and ensuring responsible waste disposal to minimise organic pollution.
Restoring mangroves and seagrass beds as these ecosystems act as natural filters, absorbing excess nutrients and preventing bloom formation.
Methods such as enhancing ocean water circulation by using aeration techniques, oxygenation, improving water circulation are also recommended by the US EPA to prevent HABs from proliferating and use of floating wetlands to reduce nutrient concentrations in water bodies.
Use new technology for early detection and monitoring of blooms
HABs can be monitored using satellite-based remote sensing and bio-optical algorithms to track, issue warnings and mitigate bloom occurrences in real-time. Technology can also aid in research on the causes and impacts of HABs .
Ensure that strict regulations are laid and followed
Ensuring that industries follow proper waste management guidelines and do not transfer untreated waste into water bodies, and communities follow regulations and prevent waste from entering into water bodies.
Build awareness and community participation
Educate communities on the causes, indications and effects of algal blooms .
Encourage citizen participation in early identification of HAB events to prevent risks to lives.
Create pressure groups that can drive policy level changes to prevent algal blooms from happening
Encourage action by undertaking measures at the individual and community level to limit nutrient pollution and uptake sustainable practices.
Implement policy driven changes
Establishing a framework that combines science, society and policy for tackling HAB issues in India is necessary.
The most successful example of policy changes to facilitate HAB research and monitoring is the US Congress’ authorisation of the Harmful Algal Bloom and Hypoxia Research and Control Act (HABHRCA) in 1998, which mandates federal investments in HAB research, control, and monitoring. Similar initiatives can be implemented in India.