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Blue-Green Algae, scientifically known as cyanobacteria, are among the oldest life forms on Earth and are believed to have played a crucial role in the formation of Earth’s oxygen-rich atmosphere through photosynthesis. Despite their common name, they are not true algae but photosynthetic bacteria (prokaryotes).
Under favourable environmental conditions, cyanobacteria multiply rapidly to form Harmful Algal Blooms (HABs), which degrade water quality, produce toxins, threaten aquatic biodiversity, and pose serious risks to human and animal health.
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Blue-Green Algae Meaning
Blue-Green Algae (Cyanobacteria) are photosynthetic bacteria found in freshwater, marine, and brackish water ecosystems. They use sunlight, carbon dioxide, and water to produce food, and many species can also fix atmospheric nitrogen, enabling them to survive in nutrient-poor environments.
Conditions Favouring Blue-Green Algal Blooms
Blue-Green Algal Blooms develop when environmental conditions favour rapid growth and multiplication of cyanobacteria:
- Warm Water Temperatures: Blooms are most common during summer and early autumn when water temperatures are high.
- Abundant Sunlight: Longer daylight hours accelerate photosynthesis and growth.
- Nutrient Enrichment: Excess nitrogen and phosphorus from fertilisers, sewage, and urban runoff stimulate rapid multiplication.
- Calm or Slow-Flowing Water: Stagnant lakes, reservoirs, and ponds provide favourable environments for cyanobacteria to remain near the water surface where sunlight is abundant.
Impacts of Harmful Algal Blooms (HABs)
Harmful Algal Blooms (HABs) adversely affect aquatic ecosystems, public health, and economic activities by degrading water quality, releasing toxins, and disrupting ecosystem functioning.
Ecological Impacts
- Oxygen Depletion: Bloom decomposition reduces dissolved oxygen, leading to fish mortality.
- Loss of Biodiversity: Dense blooms suppress aquatic plants and disrupt aquatic food chains.
- Reduced Light Penetration: Surface blooms block sunlight, limiting photosynthesis by submerged vegetation.
- Ecosystem Imbalance: Alters nutrient cycling and the structure of aquatic ecosystems.
- Human Health Risks: Exposure may cause skin irritation, eye irritation, vomiting, and illness from contaminated water.
Economic Impacts
- Higher Water Treatment Costs: Additional treatment is required to remove cyanotoxins from drinking water.
- Loss to Fisheries: Fish mortality and contamination reduce commercial and inland fish production.
- Decline in Tourism: Recreational activities such as swimming and boating decline during bloom events.
- Agricultural Losses: Livestock deaths and contaminated irrigation water reduce agricultural productivity.
Blue-Green Algae in India
India has witnessed increasing occurrences of harmful cyanobacterial blooms due to rapid urbanisation, nutrient pollution, and climate change. For example, sites like Bellandur Lake experience recurring cyanobacterial blooms driven by untreated sewage and nutrient-rich wastewater.
- Public Awareness: Issue health advisories and restrict recreational and drinking water use during confirmed Harmful Algal Blooms.
Government Initiatives
India has launched several programmes to improve water quality, reduce nutrient pollution, and conserve aquatic ecosystems, thereby lowering the risk of harmful algal blooms:
- National Water Quality Monitoring Programme (NWQP): CPCB monitors the quality of rivers, lakes, and reservoirs across the country.
- Namami Gange Programme / National Mission for Clean Ganga (NMCG): Reduces sewage discharge, improves wastewater treatment, and rejuvenates the Ganga ecosystem.
- National Plan for Conservation of Aquatic Ecosystems (NPCA) & Wetlands (Conservation and Management) Rules, 2017: Regulate activities that degrade wetlands and promote their sustainable management.
