🗞️ Why in News Research from IISER Kolkata reveals that microplastics are disrupting both the food web and the carbon cycle in the Sundarbans — the world’s largest mangrove forest and a UNESCO World Heritage Site. Microplastic concentrations surge approximately 40% during the monsoon season, with ~50% being textile fibres. “Plastispheres” — microbial communities that form on degrading plastic surfaces — act as artificial carbon sources, potentially reducing the Sundarbans’ efficiency as a blue-carbon ecosystem that captures and stores atmospheric CO₂.
The Sundarbans — Ecological Significance
What Makes Sundarbans Unique
The Sundarbans spans the delta of the Ganga, Brahmaputra, and Meghna rivers across India (West Bengal) and Bangladesh, covering approximately 10,000 sq km:
| Feature | Value |
|---|---|
| Total area | ~10,000 sq km |
| India’s share | ~3,483 sq km (West Bengal) |
| Bangladesh’s share | ~6,517 sq km |
| Forest type | Tidal halophytic mangrove |
| UNESCO WHS | 1987 (India’s Sundarbans NP) |
| Ramsar Wetland | 2019 (India’s Sundarbans); Bangladesh side: 1992 |
| Tiger Reserve | Yes — Sundarbans Tiger Reserve |
| Key species | Royal Bengal tiger, saltwater crocodile, Irrawaddy dolphin, Gangetic dolphin, Olive Ridley turtle |
Blue Carbon Significance
Blue carbon refers to carbon captured and stored by coastal and marine ecosystems — mangroves, seagrasses, and salt marshes. These ecosystems:
- Sequester carbon 3-5 times faster per unit area than tropical forests
- Store carbon for thousands of years in waterlogged sediments (anoxic conditions prevent decomposition)
- Provide storm surge protection, coastal erosion prevention, and fisheries nursery services
The Sundarbans stores an estimated 54-57 million tonnes of carbon — making it one of the most significant blue carbon stores in Asia.
The Microplastics Crisis
What Are Microplastics?
Microplastics are plastic particles less than 5 millimetres in size. They originate from:
- Primary microplastics — manufactured at micro-size (microbeads in cosmetics, pellets in plastic manufacturing)
- Secondary microplastics — fragmentation of larger plastics through UV radiation, physical abrasion, and biological degradation
Nanoplastics are sub-micron particles (< 1 micrometres) formed from further weathering of microplastics.
Sources in the Sundarbans
The Sundarbans receives plastic pollution from:
- Ganga river system — carrying plastic waste from densely populated Gangetic cities (Kolkata, Patna, Varanasi, Delhi)
- Local fisheries — discarded nets, ropes, and packaging
- Tourism — boats and visitor waste
- Coastal communities — inadequate solid waste management in the Sundarbans fringe
The monsoon surge of 40% in microplastic concentrations reflects the annual flush of accumulated river plastics into the delta during high-flow season.
The Textile Fibre Dominance
Approximately 50% of Sundarbans microplastics are textile fibres (polyester, nylon, acrylic). These originate from:
- Washing synthetic clothing — each wash releases thousands of fibres per garment
- Fishing nets and ropes — synthetic rope degradation
- These fibres are particularly problematic because they are difficult for organisms to expel after ingestion
The Plastisphere — A New Ecological Concern
What Is a Plastisphere?
A plastisphere is a microbial community that forms on the surface of plastic debris in aquatic environments. As plastics weather and fragment:
- Microbial biofilms colonise the plastic surface
- The plastic leaches dissolved organic carbon (DOC) as it degrades
- The DOC feeds rapid microbial growth
- These microbial communities can include pathogenic bacteria, antibiotic-resistant microbes, and novel species
The Carbon Cycle Disruption
The IISER Kolkata study found that plastispheres in the Sundarbans act as artificial carbon sources:
| Natural Cycle | With Plastispheres |
|---|---|
| Mangrove leaf litter → organic carbon → sediment storage | Plastic DOC → microbial respiration → CO₂ release |
| Carbon sequestration enhanced by anoxic sediments | Plastisphere microbes alter sediment chemistry |
| Stable long-term carbon storage | Carbon leakage from ecosystem |
In effect, plastics introduce non-natural carbon inputs that alter the microbial metabolism of the sediment, potentially converting the Sundarbans from a carbon sink into a partial carbon source.
Food Web Disruption
Microplastics enter the Sundarbans food web at multiple levels:
| Level | Organism | Impact |
|---|---|---|
| Primary | Phytoplankton, zooplankton | Ingestion reduces feeding efficiency; toxin accumulation |
| Secondary | Small fish, crustaceans, molluscs | Bioaccumulation; gut blockage; hormonal disruption |
| Tertiary | Larger fish, birds, dolphins | Biomagnification; reproductive impairment |
| Apex | Royal Bengal tiger, saltwater crocodile | Highest toxin loads from biomagnification |
Irrawaddy dolphins and Gangetic dolphins — both endangered species in the Sundarbans — are particularly vulnerable as they are at the apex of the aquatic food chain.
Regulatory Framework
India’s plastic pollution governance:
| Regulation | Provision |
|---|---|
| Plastic Waste Management Rules, 2016 (amended 2022) | Banned single-use plastics below defined sizes |
| EPR (Extended Producer Responsibility) | Plastic producers responsible for collecting and recycling |
| Plastic Waste Management Amendment Rules, 2024 | Strengthened EPR framework |
| Microplastics | No specific regulation yet — a governance gap |
No Indian law specifically regulates microplastics — a critical gap identified by environmental researchers. The EU has proposed microplastic labelling requirements for cosmetics and has restricted intentionally added microplastics.
UPSC Relevance
| Paper | Angle |
|---|---|
| GS3 — Environment | Microplastics, blue carbon, mangroves, Sundarbans ecology |
| GS1 — Geography | Ganga-Brahmaputra delta, Sundarbans geography, mangrove forests |
| GS3 — Economy | Blue economy, fisheries, coastal livelihoods |
| GS2 — Governance | Plastic regulation, EPR, environmental law gaps |
| Mains Keywords | Microplastics, plastisphere, blue carbon, Sundarbans, mangroves, EPR, Ramsar, UNESCO WHS, Irrawaddy dolphin |
Facts Corner
- Sundarbans area: ~10,000 sq km; India (~3,483 sq km), Bangladesh (~6,517 sq km)
- UNESCO WHS: 1987 (India’s Sundarbans National Park)
- Ramsar designation: 2019 (India’s Sundarbans Wetland); Bangladesh Sundarbans: 1992
- Microplastic monsoon surge: ~40% increase in concentration
- Textile fibre share: ~50% of Sundarbans microplastics
- Blue carbon: Carbon stored in mangroves, seagrasses, salt marshes — stored 3-5x faster than tropical forests
- Sundarbans carbon storage: ~54-57 million tonnes estimated
- Plastisphere: Microbial communities on plastic debris; leaches dissolved organic carbon
- Key endangered species: Irrawaddy dolphin (IUCNVulnerable), Gangetic dolphin (Endangered), Royal Bengal tiger
- Plastic Waste Management Rules, 2022: Single-use plastic ban; EPR framework
- Microplastics regulation gap: No specific Indian law — a critical governance absence
- IISER Kolkata: Indian Institute of Science Education and Research, Kolkata — a national importance institution under MoE
