Warming Indian Ocean may pose threat to global fisheries market: study


A view of the Indian Ocean from the cruise ship MSC Opera on November 7, 2014.

CAPE TOWN - A recent study published by the Indian Institute of Tropical Meteorology (IITM) has found that the amount of microscopic plants in the Indian Ocean has declined by 20 percent in the last decade, potentially destabilising the marine food chain.

The study, published in the journal Geophysical Research Letters by a collaboration of authors from various international universities, led by Mathew Koll Roxy (IITM), proposed the reduction was due to surface ocean warming.

Marcello Vichi, a biogeochemistry expert and researcher who took part in the study from the University of Cape Town (UCT), explained that more data still needed to be collected. “We are not able to quantify this clearly, this is just the start.

“This is what the data simulations predict, that there is a declining trend,” said Vichi.

Phytoplankton (microscopic ocean plants) form the basis of the marine food web. A decline in phytoplankton may pose a risk to the global fisheries market, explained the study, with countries along the Indian Ocean particularly vulnerable.

“We can’t say for certain that there’s going to be a disruption, but it’s likely to disrupt the fisheries market in the future,” said Vichi.

The study has shown a 50-­90 percent decrease in tuna catch rates over the past 50 years, with decreased phytoplankton being a possible cause.

The culprit behind the surface warming has been linked to climate change.

The study explained that the Indian Ocean had absorbed excess heat in the atmosphere caused by greenhouse gases.

The warming surface temperature of the ocean interferes with conditions favourable for photosynthesis, a process necessary for microscopic plants to grow, according to the study.

Due to the ocean having a 1,000-year timescale, Vichi explained that the changes were set.

“The heat absorbed by the ocean is unlikely to go away soon,” said Vichi, who added that “we’re unlikely to go back to pristine conditions”.

According to the study, the Indian Ocean has experienced the most significant amounts of warming.

“Future climate projections suggest that the Indian Ocean will continue to warm, driving this productive region into an ecological desert.”

The warming, which was focused in the North-Western Indian Ocean, was most prominent during the summer season, when a monsoon driven bloom in phytoplankton also occurs.

A rise in temperatures of as much as 1.2 degrees Celsius has been recorded over the past century.