Coral reefs have been so fundamentally damaged by climate change that decades of research into how to protect them may not even be applicable, scientists say.
In a study on coral for more than 20 years, UK scientists found that a warming climate has undone decades of knowledge about coral in protected areas, known as marine reserves.
These delicate and vital ecosystems have been used as a guide to rejuvenate biodiversity in other disturbed regions.
Tropical coral reef marine reserves cannot offer much defense in the face of impacts on climate change, which means that conservatives may need to emphasize their role & # 39;
The team advocates urgent reductions in global greenhouse gas emissions and poor land practices that leak pollutants into coastal waters to protect coral reefs.
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A recovering ridge in Seychelles. Scientists used data from 21 reefs over a 20-year period, spanning the 1998 pale event, to investigate how reefs have changed and how this has affected the role of marine reserves
& # 39; Climate change is fundamentally changing the structure and composition of coral reef ecosystems that the way the ecosystem functions and responds to common management and conservation approaches needs to be carefully evaluated, & # 39; said Professor Nick Graham at Lancaster University.
& # 39; The rules that we & # 39; re familiar with are no longer applicable. & # 39;
Coral bleaching occurs when seen to warm, making coral colored algae.
As the ocean's temperature rises, warmer waters coral, causing them to release algae that live in them, consuming up to 90 percent of their energy.
This event causes the vibrant-colored communities of coral to become white – an effect called coral bleaching.
Algal-dominated reef in Seychelles. Seychelles were heavily influenced by the global coral bleaching event in 1998, when about a 90 percent loss of live coral caused large short-term impacts on ecological structure and fish diversity. This photo shows seaweed (algae) that were buried in a reef after the corals died. The dead reef is down, but the seaweeds now dominate space and so new corals cannot regulate and grow
Bleached corals are not dead, but are at a higher risk of dying, and these pale events become more frequent under climate change.
While some coral reefs may recover in time, others are dominated by seaweed.
In & # 39; & # 39; For years, recurring coral bleaching is caused by warming seas disrupting marine ecosystems around the world.
This reduces the availability of food and shelter for many marine species that do not trust these coral structures, resulting in loss of biodiversity.
Marine reserves are less effective at protecting the tops of food webs after pale events, indicated by reduced numbers of carnivorous predators, such as grouper fish (pictured) and snapper species
A parrot fish that does not feed on degraded coral. Parrot fish have improved the growth rates following coral death events
For their study, scientists from the University of Lancaster focused on marine reefs of coral reef in Seychelles – an island nation off the east coast of Africa in & # 39; e Indian Ocean.
Seychelles coral reefs were hit by a bleaching event in 1998, when about 90 percent of the coral died in surrounding waters.
Scientists used data from 21 reefs that spanned more than two decades to investigate how "reefs" in the course of "# 39; times have changed and how it has affected the role of marine reserves.
Marine reserves have been used for decades to improve biodiversity and fish biomass by preventing damage and excessive exploitation by fishing.
& # 39; Our long-term Seychelles records & # 39; Coral reefs show that before bleaching marine reserves contained high coral cover, a high biodiversity range of fish, and high biomass of carnivorous and herbivorous fish, & # 39; said Professor Graham, chief author of & # 39; e study.
Bleaches acropora coral in the Sea of Seychelles. Acropora species tend to be as brown as green, but a few are bright in color
Picture taken in October 2016 shows coral bleaching at the Great Barrier Reef in Australia, a World Heritage Site
& # 39; After the bleaching event, the role of & # 39; a marine reserve substantially.
& # 39; They no longer support higher coral cover compared to adjacent fish areas, and their role in improving biodiversity is diminished. & # 39;
Plant-derived fish, such as rabbitfish and parrotfish, dominated fish communities after the pale event.
Both feed on algae and therefore increase in numbers as reefs shift to algae.
Marine reserves have not been as effective in protecting carnivorous predators, such as grouper and snapper species, which are near the top of the food chain.
The researchers attributed the drop of a predator population of this kind to lesser prey available after the loss of coral reef structures.
& # 39; Other fish, such as groups and snappers, decay as their prey – small fish – disappears as the living coral habitat goes, & # 39; said Professor Graham.
Pictured, a clownfish beeps from behind an anemone on the Great Barrier Reef. Fish are crucial for coral reefs to function as healthy ecosystems
However, the experts added that despite these climate-driven changes, the protected areas still have a role to play in the conservation of ocean.
& # 39; Although these re-ordered marine reserves are less biodiverse, they are still important to maintain, & # 39; said Gilberte Gendron of the Seychelles National Parks Authority, who was the co-author of the research document.
& # 39; This is because, compared to open fish, they protect even higher levels of biomass of fish of species that are important to our local fishery.
& # 39; For example, the protected herbivorous fish may slip into open fish and help support associated fishery. & # 39;
The research team, compromised with the University of Lancaster, Seychelles Fishing Authority and University of Western Australia scientists, said that new marine reserves may need to be made to coral reefs, where the warming rates are slowest or where the recovery is bleaching is more likely.
The study was published in the journal Nature Communications.
HOT OCEANS ATTACK CORAL BLACHING
Corals have a symbiotic relationship with a small marine algae called & # 39; zooxanthellae & # 39; that do not live and feed within.
As temperatures at sea surface rise, corals drive away the colorful algae. The loss of algae causes them to pale and become white.
These pale states can last for a maximum of six weeks, and although corals can recover as the temperature drops and the algae recede, coral remains die and are covered by algae.
In both cases, this makes it difficult to distinguish between healthy corals and dead corals from satellite imagery.
These bleaches recently killed up to 80 percent of corals in some areas of the Great Barrier Reef.
Bleaching events of this nature happen four times more often worldwide than before.
The ARC Center of Excellence in Australia previously estimates that only the southern third of the Great Barrier Reef is unknowingly escaping coral bleaching.
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