Coral Reefs Feel the Heat
- School of Fish in Kenya Photo
- Reef stability is essential to the balance of marine ecosystems
- ©R Graham
Climate change affects life in every biome, from the apex of the Arctic food chain to the tropical sea floor. The tiny creatures that are the building blocks of coral reefs are particularly vulnerable to rising ocean temperatures. During prolonged periods of surface warming, many coral species discharge the algae that live within their tissues—the same organisms that give them their stunning colors—and “bleach.” This leaves the reefs white and sickly. If the stress is not too severe and lessens, the affected corals can regain their algae and recover. But if it persists, the corals will die. Researchers still have much to learn about the long-term impacts of this phenomenon.
Challenges
Because reefs contain some of the most diverse life on the planet, including tropical fish, marine turtles, and sharks, their stability is essential to the balance of marine ecosystems. But both rising sea temperatures and overfishing have wrought havoc on reefs from Belize to Madagascar, in Fiji, and throughout the Coral Triangle. Reefs located in waters with stable but high temperatures are most susceptible to fatal bleaching. Those subject to overfishing will lose their zooplankton, an essential coral food, and can also bleach.
Goals
- Continue to determine which corals are most sensitive to climate change and likely to be eliminated or go extinct.
- Study how corals adapt to climate change through their relationship with symbiotic algae.
- Identify sites that may survive climate change without big disturbances.
- Map the global stress on corals throughout their range.
- Determine which types of fishing methods will exacerbate climate change disturbances to reefs, and conversely which types can be tolerated by reefs.
What WCS is Doing
WCS scientists studying the reefs in the Indian Ocean off Africa’s east coast have found that corals with the best chances of survival live in seas with wide-ranging seasonal temperatures. These hardier reefs tend to be located in the “shadow” of islands, protected from the oceanic currents that keep temperatures stable in more fragile reef ecosystems. Our scientists are now mapping the global stress on corals in the Indo-Pacific Ocean.
WCS researchers are also determining how human communities living adjacent to reefs in southern Kenya, Tanzania, Seychelles, Mauritius, and Madagascar adapt to the impacts of climate change. When reefs die off, their valuable fish stocks disappear and tourism dollars dry up. WCS is working to improve coral reef fishery management to relieve stress on these ecosystems. Ultimately, conservationists hope to help provide wider economic opportunities to local communities dependent on reef fishing.
In addition, WCS researchers are finding ways to help reduce the negative impacts of climate change and potentially increase the resilience of marine ecosystems by managing fishing gear. Different types of equipment used by artisanal fishers target fish with various effects on the coral reef ecosystem. At our study sites in Papua New Guinea and Kenya, WCS has observed that traps and spear guns target many species that are highly susceptible to coral mortality, based on their role in the food chain and their reliance on the reef for shelter and other needs. Conservationists hope that by selectively banning or restricting certain fishing gear that damage coral reef ecology, they can develop a powerful tool to combat the detrimental effects of climate change.
From the Newsroom
A new study says that banning certain types of fishing gear can help save coral reefs from the damaging effects of climate change, by protecting key fish populations that help stressed reefs recover.
In the face of warming ocean waters due to climate change, some coral reefs off East Africa are demonstrating unusual resiliency. A WCS study shows that successful fisheries management is key.
WCS researchers find that coral reefs next to middle class communities in East Africa have far fewer fish than the reefs in either poor or affluent communities.
A combination of improved management and natural regeneration is helping corals stage a rapid comeback in Indonesia following the December 2004 tsunami.
A WCS study finds that the prospects of coral reefs in the age of climate change have improved. Reefs living in sites with variable temperatures are better able to survive warm water.
In the longest running study of its kind, WCS scientists found that to maintain a healthy coral reef, heavily exploited fish need a long break from nets and lines.