Agri Business

‘Rapid warming of Indian Ocean can turn it into an ecological desert’

Vinson Kurian Thiruvananthapuram | Updated on January 22, 2018

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May impact food security in rim countries and global fisheries market, says scientist





Rapid warming of the Indian Ocean may potentially turn this biologically productive region into an ecological desert, according to a new study.

Authored by Roxy Mathew Koll, scientist at the Indian Institute of Tropical Meteorology, and others, the study has been published in the journal Geophysical Research Letters.

Major decline

The study points to significant decline in the marine phytoplankton in the Indian Ocean – microscopic plants in the ocean which sustain the aquatic food web and drive the marine ecosystem.

In addition, they absorb the solar radiation and modulate the upper ocean heat flux, thereby influencing climate processes and biogeochemical cycles, particularly the carbon cycle.

The authors suggest that the rapid warming in the Indian Ocean is playing an important role in reducing the phytoplankton up to 20 per cent during the past six decades.

It may also impact the food security in the Indian Ocean rim countries and also the global fisheries market.

Over the tropical oceans, the Indian Ocean (especially the western region) hosts one of the largest concentrations of phytoplankton blooms in summer.

Ocean upwelling

This is because of the strong monsoonal wind forcing which leads to ocean upwelling, supplying nutrients from the subsurface to the surface, and supporting elevated rates of primary productivity.

Large-scale distribution of tuna and other fishes are associated with the phytoplankton availability and abundance.

FAO statistics show that the Indian Ocean accounts for 20 per cent of the total tuna catch, especially the most economically valuable bigeye tuna, making it the second largest supplier to world markets.

But the region in the Indian Ocean with the largest phytoplankton concentrations is also the region which exhibits the largest ocean surface warming.

Vertical mixing

The warming during the past century is up to 1.2 deg Celsius, which is very large compared to a global surface warming of up to 0.8 deg Celsius during the same period.

Rising ocean surface temperatures results in less dense water on the surface and denser water in the subsurface, which is known as stratification.

Such a stratified condition inhibits the vertical mixing of subsurface waters (which are usually nutrient-rich) to the surface.

The vertical mixing is a critical process for introducing nutrients into the upper zones where sufficient light is available for photosynthesis.

Published on December 24, 2015

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