Effects of Monsoon Fluctuations on Marine Life in Bay of Bengal

Prelims (GS I) - Indian and World Geography-Physical, Social, Economic Geography of India and the World.

Mains (GS I) – Geographical features and their location-changes in critical geographical features (including water-bodies and ice-caps) and in flora and fauna and the effects of such changes.

Why in news?

A recent study published in the journal Nature Geoscience has revealed how monsoon patterns significantly impact marine productivity in the Bay of Bengal.

Despite covering less than 1% of the world's ocean area, the Bay of Bengal it provides nearly 8% of global fishery production.

Key Findings of the study

• Extreme Monsson conditions – The study found that both abnormally strong and weak monsoons throughout history caused major disruptions in ocean mixing.
• This mixing play important role in climate, marine life, and cycles carbon and oxygen in the ocean.

• Reduced food availability – Up to 50% reduction in food availability for marine life in surface waters.
• Historical trend – Significant declines happened in certain period when extreme monsoon weather was observed.
  • Heinrich Stadial 1 (a cold phase between 17,500 and 15,500 years ago).
  • Early Holocene (about 10,500 to 9,500 years ago).
• Impact on plankton growth – The ability of the ocean to support plankton growth is reduced which forms the base of the marine food chain.
• Impact on food security – The decline in ocean productivity reduces fish stocks and impacts food security for coastal communities.

Reasons for Disruption

• During strong monsoons – Increased rainfall leads to greater river runoff into the Bay and this excess freshwater creates a buoyant surface layer which prevents nutrient mixing from deeper waters.

Buoyant surface layer formed as a result of difference in density of water where warm, less dense water floats on top of cooler, denser water.

• During weak monsoons – Due to reduced wind-driven mixing that limits the upwelling of nutrient-rich deep waters.
  • Surface waters become starved of essential nutrients.

Reference

The Hindu| Changes in monsoon affect marine productivity