Artificial reefs can restore coral reefs and protect coastal communities

Coral reefs support vibrant marine ecosystems, stimulate tourism and fishing industries, and protect coastlines from tropical storms and erosion. But reefs around the world have been hit hard by pollution, overfishing and climate change, which is becoming increasingly frequent and severe. Coral bleaching.

Scientists to predict If greenhouse gas emissions are not reduced, 99% of the world's reefs will experience severe bleaching this century. Saving coral reefs requires major systemic changes – dramatic cuts in energy consumption, switching to renewable energy, managing overfishing and pollution, and restoring targeted reefs.

Restoration efforts have now become a priority for many scientists. This series looks at some of those efforts.

University of Miami Rosenstiel School of Marine, Atmospheric and Earth Sciences It sits on the shores of Florida's Virginia Key. Most of its buildings have views of the water. One of them even has its own sea.

This box Air wave tank, Alfred C. Glassell, Jr. Part of the SUSTAIN laboratory, it is 60 feet long, 7 feet high, and 23 feet wide. A jet engine generates winds of up to 170 mph and mechanical fins create waves; Combining the two can simulate a Category 5 hurricane. The tank is clear on all sides, high enough to walk down, and strong enough for the scientists to sit on top, so they can monitor the action inside.

A multidisciplinary team at the university is using the tank to study how artificial reef structures hold up against wind and waves and how corals survive and grow in those structures.

This work leads to a unique combination of “gray” or man-made infrastructure such as concrete seawalls and “green” or natural systems such as coral reefs – resulting systems that provide coastal protection and coral reef habitat. A collaboration between the university and the city of Miami Beach, the project is called engineered coastal resilience through hybrid reef restoration, or ecoreef.

Florida is the only shallow state in the continental United States Coral reefs Near its coast, it stretches from the Dry Tortugas at the tip of the Keys in the Gulf of Mexico to about 350 miles north of Palm Beach.

Studies show that shallow coral reefs absorb 97% of the energy from waves, reducing flooding and helping to prevent loss of life, property damage and erosion from storms. But almost 90% of these reefs have died due to climate change, hurricanes, diseases and human development.

In South Florida, combined with its low-lying topography and its location within the tropical storm zone, the resulting densely populated coastline is highly vulnerable to the effects of climate change.

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A simulated ocean tank
A simulated ocean tank enables researchers to study how coral reefs affect waves. Photo: University of Miami Rosenstiel School of Ocean, Atmospheric and Earth Sciences

For decades, ECoREEF has worked to restore Florida's coral reefs, which provide habitat for hundreds of marine species — including green sea turtles, parrot fish and stingrays — support the state's tourism industry and protect its shorelines and structures from wave energy. .

Reef restoration efforts include studying the idea Moves hard corals In degraded areas, planting Hand-raised pieces of coral on existing reefs connect corals to reproduce sexually laboratoriesand enhance nature Sexual reproduction of creatures in the forest.

„The idea behind EcoREEf is to establish structures that can host coral reefs, but also provide wave energy dissipation,” says Landolf Rode-Barbarikos, associate professor in the College of Engineering.

After testing the designs in the tank, the team set up two types of structures in 14 feet of water 750 feet off shore in Miami Beach in March. One design is a hollow trapezoid structure with limestone boulders on its outer surface to mimic the structure of coral reefs and attract marine life.

Another is a configuration of hollow, hexagonal units through which water has been perforated to allow water to flow, consistent with estuarine and marine revetments or Seas. Both are made of concrete.

It's less expensive to test and replace a model in a tank than an actual structure in the ocean, says Brian House, chair of the Rosenstiel School's Department of Marine Sciences. After testing, samples can be measured.

„The tank test gives us a model of how this system dissipates so much wave energy,” Rode-Barbarikos says. „We then use those findings in conjunction with mathematical models to design structures that can withstand real waves.”

There is growing recognition that green infrastructure is an effective and cost-effective alternative to gray infrastructure. But if green systems are lost or damaged, it can take a long time to restore them. Artificial infrastructure can help accelerate that restoration.

The physical structures are well developed at this stage, but the addition of living coral makes the system more complex – one reason for the multi-disciplinary nature of the project.

„We've blurred the lines between ecology and engineering, not just improving the structures, but also the types of corals we use,” Rode-Barbarikos says.

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A piece of coral three months after planting
A piece of coral three months after planting. Photo: University of Miami Rosenstiel School of Ocean, Atmospheric and Earth Sciences

He points out that the project's data can show the value of the mix. „This creates a different kind of argument for coral restoration. If we can link coral restoration and coastal protection, we have a stronger argument.

So far, the work clearly supports the argument for combining the two for coastal protection. A study showed Coral structures – the calcium-based skeletons these organisms create – can significantly improve the wave-reducing capacity of an artificial reef, depending on ocean conditions and structural characteristics.

A trapezoidal artificial reef model was found to reduce up to 98% of wave energy, with the coral contributing 56% of the total. Additional testing detected Including skeletons of staghorn corals (Acropora cervicornis) showed an additional 10% wave height and 14% wave energy reduction on submerged artificial reefs compared to those without coral reefs.

After the structures were placed in the water, marine scientists from the Rosenstiel School added live corals, including giant star, mustard mountain, bulbous brain and symmetrical brain corals. All of these species are stony corals that can form massive reefs over time.

„On July 19, we took about 500 corals from parent colonies and grew them here at UM or in our marine nurseries,” says Emily Esplandeau, a research associate at the school. Coral Reef Restoration Laboratory.

Many marine coral nurseries hang coral pieces from PVC trees using monofilament. Trays are easy to transport from nursery to testbed setup, he adds. Engineers are now incorporating plug screws into the design of artificial reef structures to make it easier to attach corals.

The team plans to pollinate 500 more corals until extreme temperatures hit Florida waters in late summer. Instead scientists found themselves bringing corals from their marine nurseries to land-based facilities.

„At a temperature of about 30.5 degrees Celsius (87 degrees Fahrenheit), corals cannot be planted or moved out of the ocean,” Esplandiu says. Planting is scheduled to be completed by the end of the year if temperatures drop for at least a week.

Meanwhile, scientists have already monitored the corals in the structures and documented 80% survival. However, as temperatures continued to rise, on Aug. 17, monitoring teams detected some baling (a precursor to bleaching), and on Sept.

But there was some good news: The scientists found differences in the amount of bleaching across species and genotypes within species. They plan to find the least susceptible and use hardier genotypes for future fragmentation and transplanting.

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For example, the original plantings included four or more genotypes of star coral, Esplandiu says, and one genotype was all bleached while the other was healthy.

House notes that the ultimate goal is to build a larger infrastructure to provide greater security. „Coastal restoration and dune restoration are not enough to cope with sea level rise,” he says. The initiative opens up new areas of coral reefs and historically reefs — good news for coastal residents and marine life.

Someone is measuring coral with a ruler
Coral Monitoring. Photo: University of Miami Rosenstiel School of Ocean, Atmospheric and Earth Sciences

„People are realizing it's a crisis, all of it—coral loss, climate change, sea level rise,” House says. „The goal is to create solutions that are environmentally friendly and actually help the ecosystem. Of course, it's not enough if we don't change. We have to stop the source of the problem because emissions are only going to get worse.”

For the coral restoration lab, the next step is to create thousands of pieces of coral to plant in additional structures. Working with engineers to design structures that work best for coral reefs is exciting, Esplandiu says.

„We know corals do better with high water flow because that flow brings nutrients. We know it's different to put a coral on top of a structure versus on the side. We can work together to find specific places in a structure that are best for placing corals.”

„Until now, the only plantings we've done in Florida have been on mostly disturbed natural reefs,” Esplandiu says. „We're seeing many restoration sites fail after three to five years because they're facing the same stresses that the corals had to begin with. The reef structure is a very important part of the reef, and we've lost many corals that can no longer build that structure.

Coral restoration efforts, scientists agree, will ultimately not succeed without continued efforts to change the things that cause coral loss, such as greenhouse gas emissions, overfishing and pollution.

But the experimental structures offer a way to replace some of the lost natural reefs, and they offer an alternative to restocking coral reefs on degraded reefs. The team has already documented a large fish community around the test structures.

A combination of artificial reefs and stress-tolerant coral reefs can contribute to the restoration of both coastal protection and marine habitats provided by healthy natural reefs. In other words, working in the university's indoor ocean helps cure the real ocean outside its windows.

This story was originally published Revealer and republished with permission.

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