• Skip to main content
  • Skip to secondary menu
  • Skip to primary sidebar
  • Skip to footer
Geographical

Geographical

Official magazine of the Royal Geographical Society (with IBG)

  • Home
  • Briefing
  • Science & Environment
  • Climate
    • Climatewatch
  • Wildlife
  • Culture
  • Geopolitics
    • Geopolitical hotspots
  • Study Geography
    • University directory
    • Masters courses
    • Course guides
      • Climate change
      • Environmental science
      • Human geography
      • Physical geography
    • University pages
      • University of Aberdeen
      • Aberystwyth University
      • Cardiff University
      • University of Chester
      • Edge Hill University
      • The University of Edinburgh
      • Oxford Brookes University
      • Queen Mary University of London
    • Geography careers
      • Charity/non-profit
      • Education & research
      • Environment
      • Finance & consulting
      • Government and Local Government
    • Applications and advice
  • Quizzes
  • Magazine
    • Issue previews
    • Subscribe
    • Manage My Subscription
    • Special Editions
    • Podcasts
    • Geographical Archive
    • Book reviews
    • Crosswords
    • Advertise with us
  • Subscribe

Scientists discover how coral skeletons can harm reefs in world oceans

1 October 2024
2 minutes

A single blue starfish on a dead coral reef. This reef was destroyed by a strong typhoon several years ago and has not regrown.
Image: Richard Whitcombe/Shutterstock

Skeletons that stay put after marine heatwaves can prevent new coral from forming and stop herbivores from clearing away algae


By Victoria Heath

A new study has found coral skeletons left behind in ocean ecosystems – often due to bleaching events caused by high temperatures – can significantly impact reefs and their ability to survive.

Traditionally, corals face threats due to powerful storms. When this happens, corals are damaged in such a way that their skeletons are either pulverised or removed entirely from the ecosystem. Eventually, these corals regrow – like in the case of a 2010 tropical cyclone storm in Moorea’s reefs, located off a volcanic island in French Polynesia. Within five years of the storm, the quantity of coral was back to previous levels.

But when marine heatwaves happen – an increasingly common occurrence due to rising temperatures on the planet – corals are bleached and killed, yet their skeletons remain intact.

After a bleaching event in 2019 at Moorea’s reefs – the same ones that recovered after a storm – scientists then carried out further analysis of the area in 2023, concluding an accumulation of skeletons actively hinders the growth of colonies.

coral skeleton closeup texture structure macro on white background
A close-up of a coral skeleton. Image: Shutterstock

Why can coral skeletons be harmful?

There are two main reasons why skeletons can harm the marine environment. The first is that they hinder the ability of herbivores within the ecosystem to control macroalgae, another plant that competes for space with coral. Since the skeletons conceal the macroalgae, they cannot be reached and eaten by herbivores. This macroalgae – which spawns multiple times a year compared to just once for coral – is then able to outcompete young coral and eventually colonise particular areas, reducing the quantity of coral.

However, if young coral arrives quickly after a bleaching event, the coral skeletons may offer some protection.

Difficulty in replenishing coral colonies arises with leftover coral skeletons too. Because the macroalgae then can dominate the marine ecosystem, it is difficult for new coral to settle. The macroalgae can even shade existing colonies, leading them to die anyway.

Concerningly, it is difficult to reverse an area overrun by macroalgae once it has taken over. This is why researchers are now considering ways to remove or even repurpose coral skeletons in the world’s oceans.

‘In coral reefs, this is a novel idea and strategy, said Kopecky. ‘But if you look to other ecosystems – like prescribed burns in forests to remove dead wood – people have been increasingly thinking about manipulating dead stuff in ecosystems for management purposes.’

Related articles:

  • Geo explainer: The threats to coral reefs
  • ‘Coral superhighway’ is discovered in the Indian Ocean
  • The business of conservation: Wakatobi Dive Resort
  • Algae-eating giant viruses could help stop ice melt at the poles
  • Geo Explainer: What is El Niño?

Filed Under: Briefing Tagged With: Climate, Oceans

Protected by Copyscape

Primary Sidebar

Subscribe to Geographical Magazine from just £4.99

Geographical subscriptions

Sign up to our newsletter and get the best of Geographical direct to your inbox

Popular Now

UK against trawling in protected seas in wake of Attenborough film

UK against trawling in protected seas in wake of Attenborough film

QUIZ: Name The Island!

QUIZ: Name The Island!

Death valley wandering rocks

Phenomena: Death Valley’s wandering rocks

QUIZ: Human Geography Trivia

QUIZ: Human Geography Trivia

A rotting apple on a white background

Nimble fingers to shrinking apples: Unlearning the junk science of school geography

Footer

  • Facebook
  • Instagram
  • LinkedIn
  • Reddit
  • TikTok
  • Twitter
  • YouTube

Geographical print magazine cover

Published in the UK since 1935, Geographical is the official magazine of the Royal Geographical Society (with IBG).

Informative, authoritative and educational, this site’s content covers a wide range of subject areas, including geography, culture, wildlife and exploration, illustrated with superb photography.

Click Here for SUBSCRIPTION details

Want to access Geographical on your tablet or smartphone? Press the Apple, Android or PC/Mac image below to download the app for your device

Footer Apple Footer Android Footer Mac-PC

More from Geographical

  • Subscriptions
  • Get our Newsletter
  • About Us
  • Contact Us
  • Advertise with us
  • Privacy policy
  • Terms & Conditions

Copyright © 2025 · Site by Syon Media