Rising sea temperatures pose a threat to coral reefs: study

Education, Engineering, Science, Research,

Bengaluru, September 24 2019: The Indian coastline is home to an
ancient and diverse coral reef system that provides natural habitat for diverse
marine underwater ecosystem. Also, they hold importance in fisheries, tourism
and as a repository of medicinal, agronomical and industrial products.

A
team of Indian researchers has warned that rising sea temperatures due to
climate change could put these wondrous underwater systems under peril. Their
study, which analysed data of sea surface temperatures since 1982, has found that
three mass bleaching events occurred in 1998, 2010 and 2016, impacting five
major Indian coral reef regions, in Andaman, Nicobar, Lakshadweep, Gulf of
Mannar and Gulf of Kachch.

Oceans
act as massive sinks for the greenhouse gases emitted by anthropogenic
activities. However, as they absorb them, the oceans warm up and there are
changes in the seawater chemistry.

Corals are sensitive to temperature changes, which affect photosynthesis and calcification
of their structures, making them prone to diseases and even death.

“Sea
algae and corals share a symbiotic existence in the ocean.When the sea waters
turn warm in summers and remain so for more than 28days, the corals experience
thermal stress. Due to this, the corals expel the algae residing in their
tissues, and turn colourless or bleach,” explained Mohit Arora from Space Application
Centre (SAC), Ahmedabad, and first author of the study, while speaking to India Science Wire.

For their study, the team utilised the sea temperature data from the
National Oceanic and Atmospheric Administration (NOAA)’s Optimum Interpolated
Sea Surface Temperature database and analysed them for the period from 1982.

They used daily computation and index parameters obtained from advanced
satellite monitoring data under NOAA’s Coral Reef Watch. By analysing sea
surface temperature patterns, the thermal stress on coral reefs and
corresponding bleaching indices were computed based on information on magnitude, duration of thermal stress and
intensity experienced in these regions.

The
different regions experienced hottest summers at different times, with Andaman,
Nicobar and Gulf of Kachch being severely affected in 2010 while Lakshadweep
and Gulf of Mannar experienced a similar fate in 2016.

A
coral bleaching alert report protocol developed by SAC recorded that the years
1998, 2010 and 2016 witnessed mass bleaching in the five coral reefs. They
observed that   Andaman, Nicobar and Gulf of Kachchh regions recorded
an ‘alert level-2’ warning status in 2010, while the Gulf of Mannar recorded a
level-1 alert in 2016.Although coral reefs are known to recover from bleaching ina
decade or two, the severity of the bleaching event could overwhelm them and
hamper their ability to recover.

“There is a
likelihood of high-intensity coral bleaching events in the future also.Our study will be helpful to marine biologists
and can be used for early warning of coral bleaching in future,” said Arora.

The
team comprised Mohit Arora, Nandini Ray Chaudhury, Ashwin Gujrati (SAC);
and Ramesh Chandra Patel
(Kurukshetra University). The findings have
been published in Current Science.

By Susheela Srinivas  

(India Science Wire)

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