The frequency and intensity of marine heat waves are increasing due to ocean warming, which is wreaking havoc on coral reefs.
Tropical corals are sensitive to high temperatures and display a stress response known as bleaching when the ocean temperature rises.
These corals live in symbiosis with tiny single-celled algae. Millions of corals have died as a result of widespread bleaching brought on by marine heatwaves over the past 40 years.
Due to this, reefs that can withstand heat stress, endure future warming, and serve as sources of heat-tolerant coral larvae to replenish affected areas naturally and through restoration are being sought after on a global scale.
Palau's Rock Islands harbor heat-resistant corals
Researchers have now discovered genetic subgroups of a common coral species that exhibit remarkable tolerance to the intense heat associated with marine heat waves, as per ScienceDaily.
Palau is an archipelago in the western tropical Pacific where reefs are being studied.
The researchers also discovered proof that these coral larvae are migrating from their birthplaces deep within Palau's lagoons to the outer reef, where they can survive, grow, and maintain their heat tolerance.
Researchers at the Woods Hole Oceanographic Institution (WHOI) say that a better understanding of the underlying mechanisms that enable these corals to tolerate heat as well as the larval corals' ability to disperse will significantly improve coral reef conservation and restoration efforts in the ocean of the twenty-first century.
The Rock Islands are a group of mountains that were formed by the uplift of a network of very old, fossilized reefs in Palau's main lagoon.
These formations create localized environments where the water temperatures are consistently higher than other regions of Palau's reefs because they slow the flow of water through and around them.
Porites lobata (lobe coral), a keystone species, was sampled by scientists all over Palau, including the Rock Islands.
They performed skeletal biopsies and checked the cores for stress bands, which are telltale indicators of coral bleaching, which is a stress response to high temperatures.
They discovered that corals from the Rock Islands bleached less than corals from other parts of the reef during the extreme 1998 heatwave, indicating increased thermal tolerance.
Surprisingly, the researchers discovered that the LB lineage was not unique to the Rock Islands. On the comparatively cooler outer reefs, they discovered some LB colonies as well.
These colonies maintained the thermal tolerance exhibited by their relatives in the Rock Islands, as evidenced by the fact that an examination of their bleaching histories once more showed fewer stress bands.
According to the researchers' paper "Palau's warmest reefs harbor thermally tolerant corals that thrive across different habitats," which was published in Communications Biology, a journal published by Nature, this suggests that the Rock Islands provide naturally tolerant larvae to surrounding areas.
Reef survival in the face of climate change in the twenty-first century depends on locating and safeguarding such sources of thermally tolerant corals.
Read more: Corals That Experience Heat Stress are More Likely to Tolerate High Water Temperatures
Understanding heat tolerance in corals
The Great Barrier Reef is home to hundreds of different species of coral, each of which has a unique genetic makeup, as per The Great Barrier Reef Foundation.
Researchers are mapping the locations of the corals that can withstand the most heat and identifying the genes responsible for this tolerance.
This is accomplished by removing tiny pieces of healthy coral from the Reef and putting them in aquarium tanks with warmer water or more light.
A rapid heat stress test like this one enables scientists to see how a specific coral responds to heat stress, such as whether it bleaches and at what temperature.
The DNA of the algae living inside each coral fragment is also extracted and sequenced. This enables researchers to pinpoint the genes associated with heat tolerance that will be passed down to future generations.
We are aware that corals cannot adjust quickly enough to the summertime increase in marine heatwaves on the Great Barrier Reef or the warming water temperatures brought on by climate change.
In order to better withstand the ongoing and escalating stress caused by climate change, corals' heat tolerance and resilience must be increased.
According to research, there are several ways we might be able to unlock and accelerate heat tolerance.
corals that are tolerant of heat are mixed with those that are less tolerant, either within the same species or across species.
Next-generation hybrid corals may have improved survival traits compared to uncrossed corals when they are born.
Corals must gradually condition and acclimate to a rise in water temperature before reproducing new, more tolerant generations.
corals are given specialized probiotics, diets, and other treatments that improve their health and increase their resistance to environmental changes.
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