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Our planet’s coral reef ecosystems are under threat from multiple threats. Anthropogenic CO2 triggered a rise in global mean sea surface temperatures, pushing coral reef survival beyond its upper thermal limits. Coastal development from industry, aquaculture and infrastructure generates sedimentation and increased turbidity in coastal waters, which increases levels of particulate organic carbon (POC). Additionally, sedimentation reduces photosynthetically active radiation (PAR), the much-needed sunlight absorbed by the symbiotic algae corals rely on for food.
With most of the world’s coral reefs under stress, “coral gardening” or “transplanting” has become a popular and promising solution for restoration. Transplantation involves transplanting nursery-grown coral fragments onto degraded reefs. When successful, transplantation helps build coral biomass and restore coral reef function; but even with thousands of corals being transplanted every year, the results are mixed. Newly established corals are particularly vulnerable to stressors such as pollution, unfavorable light conditions and temperature fluctuations. Therefore, identifying which stressors have the greatest influence on coral health and survival is critical to ensuring successful reef restoration.
A recent study published in Ecology of restoration Researchers at Arizona State University’s Center for Global Discovery and Conservation Science (GDCS) found evidence that POC levels are one of the most important factors in determining coral transplant survival. This finding suggests that potential coral transplant sites should be selected in areas where sedimentation levels are low, away from coastal development or where coastal development is carefully managed for reef conservation.
“New restoration protocols can use remote sensing data from multiple oceanographic variables to assess a site’s environmental history. This will help evaluate and optimize site selection and give their outplants the best chance of survival,” said Shawna Foo, author principal and postdoctoral researcher at GDCS.
The study was based on an analysis of coral transplant projects around the world between 1987 and 2019. The team evaluated satellite data on multiple oceanographic variables including POC, PAR, salinity, sea surface temperature. and surface currents to quantify and evaluate the relative importance of each environmental driver and influence on coral survival.
“Our results provide, for the first time, a clear set of conditions necessary to maximize the success of coral restoration efforts. The results are based on a vast global dataset and provide a critical compass for improving performance. coral outplants in the future, “said Greg Asner, study co-author and director of GDCS.
Specifically, the researchers observed better survival rates for corals transplanted farther from the coast by six kilometers. This discovery has implications for many restoration projections that are often found close to land for accessibility purposes, such as diving operations. Researchers also found better coral recovery in water deeper than six meters; corals transplanted into shallow water showed a high vulnerability to disturbance and bleaching. Overall, coral outplants had the greatest chance of survival in regions with stable PAR, lower levels of POC, minimal temperature anomalies, and greater water depth and distance from land. Researchers note that finding recovery sites with all of these characteristics could be a challenge in some areas, but a consideration of all drivers in combination will greatly help outplant survival chances.
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Materials provided by Arizona State University. Note: The content can be changed by style and length.
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