Coral bleaching

Definition

Coral bleaching is a phenomenon where corals lose their vibrant colors and turn white due to stress, primarily caused by elevated water temperatures, changes in salinity, or pollution. This process occurs when symbiotic algae called zooxanthellae, which provide corals with nutrients and their color, are expelled from the coral tissue. When bleached, corals are more susceptible to disease and can lead to significant ecosystem impacts.

5 Must Know Facts For Your Next Test

1. Coral bleaching can occur when sea surface temperatures rise just 1-2 degrees Celsius above normal levels for prolonged periods.
2. When corals are bleached, they lose their ability to obtain food from sunlight and may eventually die if stressors persist.
3. Coral reefs support about 25% of all marine species despite covering less than 1% of the ocean floor, highlighting their ecological importance.
4. Increased carbon dioxide emissions not only warm oceans but also cause ocean acidification, both of which threaten coral health.
5. Restoration efforts for damaged coral reefs often involve techniques like coral gardening and artificial structures to promote recovery.

Review Questions

• How does the loss of zooxanthellae during coral bleaching affect the overall health of coral reefs?
  • The loss of zooxanthellae during coral bleaching directly impacts the health of coral reefs because these algae provide essential nutrients through photosynthesis. Without zooxanthellae, corals struggle to obtain adequate energy to survive, making them more vulnerable to diseases and reducing their ability to reproduce. This loss not only threatens individual corals but also destabilizes the entire reef ecosystem, which relies on healthy corals for structure and biodiversity.
• Discuss the relationship between climate change and coral bleaching, emphasizing how rising temperatures contribute to this phenomenon.
  • Climate change significantly influences coral bleaching as rising global temperatures increase sea surface temperatures. When water temperatures exceed the threshold that corals can tolerate, they expel their symbiotic zooxanthellae, leading to bleaching. This warming trend is linked to human activities that increase greenhouse gas emissions, exacerbating the frequency and severity of bleaching events. Consequently, the ongoing effects of climate change pose a dire threat to coral reefs globally.
• Evaluate the implications of coral bleaching on marine biodiversity and ecosystem services provided by coral reefs in the context of environmental change.
  • Coral bleaching has severe implications for marine biodiversity and the ecosystem services provided by coral reefs. As corals decline due to bleaching, the habitats for numerous marine species diminish, leading to decreased biodiversity and altered community structures. Additionally, healthy coral reefs offer critical services such as coastal protection, tourism opportunities, and fisheries support. The ongoing environmental changes threaten these ecosystems' stability and resilience, underscoring the urgent need for conservation efforts and climate action.

Related terms

Zooxanthellae: Symbiotic algae that live within coral tissues, providing essential nutrients through photosynthesis and contributing to the coral's coloration.

Ocean acidification: The process by which increasing levels of carbon dioxide in the atmosphere lead to higher concentrations of carbonic acid in the oceans, affecting marine life, including corals.

Marine ecosystem: A complex network of interactions among marine organisms and their environment, where coral reefs play a critical role in supporting biodiversity and providing habitat.