Environment › Protected areas and habitats › Others
Marine and coastal ecosystems
Two things are happening in the sea at once. India has finished a national reading of its deep water, naming the banks and slopes where life concentrates and where a fishing fleet could therefore do the most damage. Off Jeju in South Korea, meanwhile, soft corals are sagging for a second warm summer, a reminder that heat harms corals in ways other than bleaching.
UPSC has asked
- Prelims 2026: India's Deep Ocean Mission
- Prelims 2018: coral reefs
- Prelims 2014: where India has coral reefs
The layer below the light
- The mesopelagic zone, 200 to 1,000 m down, holds lanternfishes, deep-sea shrimps and squids.
Hard corals and soft corals
Hard corals
- Rigid calcium carbonate skeletons
- Build reefs
- Polyps in multiples of six
Soft corals
- No rigid skeleton
- Upright through internal fluid pressure
- Mostly octocorals, polyps with eight tentacles
Slumping, and what it is not
- Slumping is the sag and collapse of a soft coral when a change around it disrupts the internal fluid pressure that holds it upright.
- It is not coral bleaching, which is the loss of the symbiotic algae that feed the polyp.
- Heat stress can drive both, so a warm sea damages hard and soft corals by two different routes.
What has happened
8 Sep 2026
Soft corals off Jeju in South Korea, a habitat recognised by the United Nations Educational, Scientific and Cultural Organization (UNESCO), are slumping again after two years of rising temperatures.
- The triggers named are high water temperature, typhoons and heavy rain, along with the lower salinity that the Yangtze river's outflow brings.
The Hindu, 8 Sep 2026: Slumping: a soft-coral threat (opens in a new tab)
20 Aug 2026
The Ministry of Earth Sciences released a national report on deep-sea fishery resources, drawing on more than 400 cruises of the research vessel Sagar Sampada.
- It flags Kollam Bank, Angria Bank, the Mangalore slope, the Thiruvananthapuram terrace, Lakshadweep and the Andaman and Nicobar Islands as vulnerable areas.