Microplastic Infiltration in Oceans

• 08 May 2025

Source: DTE 

Why in News? 

A recent study published in Nature reveals that microplastics are not just surface pollutants but are now embedded deep within the ocean, impacting the planet's biogeochemical and carbon cycles. 

What are Key Findings of the Study? 

• Microplastic Infiltration: Microplastics are widespread across the ocean, dominating marine ecosystems and reaching depths of up to 100 metres in ocean gyres. 
  • While larger plastic fragments (100 to 5,000 micrometres) were typically concentrated near the ocean surface, smaller particles were discovered embedded as deep as 100 metres within ocean gyres. 
  • Gyres, slow-moving, circular ocean currents, trap and concentrate plastics. 
• Quantity: The total plastic input from 1950–2015 was estimated at 17–47 million metric tonnes. 
  • Fishing gear made of nylon and polyester is a key source of dense plastics like Polyethylene Terephthalate (PET) in the ocean, with over 56 polymer types detected. 
• Impacts: The water column, vital for biogeochemical cycling, is increasingly affected by microplastics, potentially disrupting the ocean’s carbon cycle. 
  • Carbon Cycle Interference: Plastic pollution adds external carbon (called allochthonous carbon) to marine ecosystems, with microplastic carbon rising from 0.1% of total particulate organic carbon (POC) at 30 m to 5% at 2,000 m in subtropical gyres. 
    • It could make marine samples appear 420 years older. 
  • Biogeochemical Impacts: Microplastics alter microbial nitrification and denitrification and release metabolites that disrupt nutrient cycles. 

What are Microplastics? 

• About: Microplastics, defined as plastics less than five millimetres in diameter, can be harmful to oceans and aquatic life. 
  • Solar UV radiation, wind, and ocean currents break down plastics into microplastics (<5 mm) and nanoplastics (<100 nm). 
• Classification:  
  • Primary microplastics: They are tiny particles made for commercial use, like microbeads, plastic pellets, and microfibers from clothing. 
  • Secondary microplastics: They form when larger plastics like bottles break down due to sunlight and ocean currents. 
• Concerns: Microplastics can attach to red blood cells, reducing oxygen transport, and have been found in placentas and fetal organs.  
  • They can damage human cells, and young children are especially vulnerable to such exposure. 
• Applications: It is used in drug delivery, industrial cleaning, and as exfoliants in personal care products like scrubs and toothpaste. 
• Regulations Related to Microplastics:  
  • Global: United Nations Environment Programme (UNEP) Plastics Treaty 
  • India: Ban on Single-Use Plastics, Plastic Waste Management Rules, 2016, Plastic Waste Management (Amendment) Rules, 2024. 

UPSC Civil Services Exam, Previous Year Questions (PYQ) 

Q. Why is there a great concern about the ‘microbeads’ that are released into environment? (2019)

(a) They are considered harmful to marine ecosystems. 

(b) They are considered to cause skin cancer in children. 

(c) They are small enough to be absorbed by crop plants in irrigated fields. 

(d) They are often found to be used as food adulterants. 

Ans: (a)