The “coral garden” or “plantation” has become a popular and promising solution for restoration.
Arizona State University Center for Global Discovery and Conservation Science
Our planet’s coral reef ecosystems are threatened by multiple threats. Anthropogenic CO2 triggered an increase in global average sea surface temperatures, pushing reef survival beyond its upper thermal limits. Coastal development from industry, aquaculture and infrastructure generates sedimentation and increased turbidity in coastal waters, which increases particulate organic carbon (COP) levels. Additionally, sedimentation reduces photosynthetically active radiation (PAR), the much-needed sunlight absorbed by the symbiotic algae on which corals depend for food.
With most of the world’s reefs under stress, “coral gardening” or “explanting” has become a popular and promising solution for restoration. Planting consists of transplanting fragments of coral grown in a nursery on degraded reefs. When successful, planting helps build coral biomass and restore reef function; but even with thousands of corals transplanted each year, the results are mixed. Newly settled corals are particularly vulnerable to stressors such as pollution, unfavorable lighting conditions and temperature fluctuations. Therefore, identifying the stressors that have the greatest impact on coral health and survival is crucial to ensure successful reef restoration.
A recent study published in The ecology of catering by 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 explant survival. This finding suggests that potential coral plantation sites should be selected in areas where sedimentation levels are low, far from coastal development, or where coastal development is carefully managed for reef conservation.
“New restoration protocols can use remotely sensed data from several oceanographic variables to assess the environmental history of a site. This will help assess and optimize site selection and give their explants the best chance of survival.” , said Shawna Foo, senior author and postdoctoral fellow. researcher at GDCS.
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The study was based on an analysis of coral plantation projects around the world between 1987 and 2019. The team assessed satellite data on several oceanographic variables, including POC, PAR, salinity, surface temperature of sea and surface currents in order to quantify and assess each relative environmental factor. importance and influence on the survival of coral explants.
“Our results provide, for the first time, a clear set of conditions necessary to maximize the success of coral restoration efforts. corals in the future, ”said Greg Asner, study co-author and director of GDCS.
In particular, the researchers observed better survival rates for corals transplanted more than six kilometers from the coast. This finding has implications for many restoration screenings that are often located close to land for accessibility purposes, such as diving operations. The researchers also found better recovery of corals in water deeper than six meters; corals transplanted in shallow waters have shown a high vulnerability to disturbance and bleaching. Overall, coral plantations had the best chance of survival in regions with stable PAR, lower POC levels, minimum temperature anomalies, and increased water depth and distance to land. The researchers note that finding restoration sites with all of these characteristics could be a challenge in some areas, but taking all of the factors together will dramatically increase the chances of explant survival.