Explanation:

Coral bleaching is a phenomenon that takes place when the symbiotic relationship between algae
(zooxanthellae) and their host corals breaks down under certain environmental stresses.
• Statement 1 is correct: 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 28 days, the corals experience thermal stress. Due to this, the corals expel the algae residing in their tissues and turn colourless or bleach. Corals are sensitive to temperature changes, which affect photosynthesis and calcification of their structures, making them prone to diseases and even death.
• Statement 2 is not correct: Although coral reefs are known to recover from bleaching in a decade or two,
the severity of the bleaching event could overwhelm them and hamper their ability to recover.
• 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 Kutch.
• Statement 3 is correct: Coral bleaching can take place even with a rise of temperature by1-2°C , during
summer months. To provide early warnings on the coral bleaching, the nocturnal Sea
Surface Temperature (SST) is an important parameter to assess the thermal conditions and intensity of the
bleaching. The coral bleaching Alert System (CBAS), a service initiated from Indian National
Centre for Ocean Information Services (INCOIS) since February 2011. This model uses the satellitederived
Sea Surface Temperature (SST) in order to assess the thermal stress accumulated in the coral
environs