New hope for endangered corals: Scientists take an important step towards sustainable restoration of Caribbean reefs
Researchers of SECORE International (USA, Germany), the University of Amsterdam (Netherlands) and the Carmabi Marine Research Station (Curaçao) have for the first time successfully raised laboratory-bred colonies of a threatened Caribbean coral species to sexual maturity. These findings have been published in the latest issue of the scientific journal Bulletin of Marine Science.
"In 2011, offspring of the critically endangered elkhorn coral (Acropora palmata) were reared from gametes collected in the field and were outplanted to a reef one year later", explains Valérie Chamberland, coral reef ecologist working for SECORE and Carmabi.
"In four years, these branching corals have grown to a size of a soccer ball and reproduced, simultaneously with their natural population, in September 2015. This event marks the first ever successful rearing of a threatened Caribbean coral species to its reproductive age."
Due to its large size and branching shape, elkhorn corals created vast forests in shallow reef waters that protect shores from incoming storms and provide a critical habitat for a myriad of other reef organisms, including ecologically and economically important fish species. An estimated 80% of all Caribbean corals have disappeared over the last four decades and repopulating degraded reefs has since become a management priority throughout the Caribbean region.
The elkhorn coral was one of the species whose decline was so severe that it was one of the first coral species to be listed as threatened under the U.S. Endangered Species act in 2006, and as critically endangered under the IUCN Red List of Threatened species in 2008. Consequently, measures to aid Caribbean reef recovery often focus on the elkhorn coral given its major decline and its ecological importance.
Since 2010, SECORE, Carmabi, and partners from aquariums around the world started a project aimed at developing techniques to rear larger numbers of elkhorn coral offspring so they could eventually be outplanted to degraded reefs throughout the Caribbean. "Our approach differs substantially from the one generally used by the large number of reef restoration groups that operate throughout the Caribbean", explains Dirk Petersen, coral reef expert and director of SECORE.
"These groups generally use the 'coral gardening' approach, where small fragments are harvested from coral colonies on the reef. The fragments are then grown in special nurseries to larger sizes before they are returned to the reef." Although this method has been applied throughout the Caribbean, it does not allow for new genetic combinations as the fragments harbor the same genes as the donor colonies and are therefore copies of their parents. "By contrast, SECORE developed a technique whereby male and female gametes are caught in the wild and fertilized in the laboratory to raise larger numbers of genetically unique corals", says Dirk Petersen.
Elkhorn corals reproduce only once or twice a year, generally a few days after the full moon in August. During those nights, Acropora colonies synchronously release their gametes into the water column. The project team collects a small proportion of these gametes by gently placing special nets around spawning colonies to collect the floating gamete bundles. After collection, the researchers produce coral embryos by in vitro fertilization, mixing sperm and eggs in the laboratory.
Coral embryos develop into swimming larvae within days and eventually settle onto specifically designed substrates. After a short nursery period, the project team outplants the substrates with the newly settled corals to the reef. Details on the techniques developed by SECORE during this project were recently published in the scientific journal Global Ecology and Conservation.
"We just learned that elkhorn corals can reach sexual maturity in only 4 years. This is exciting news, as we now know that offspring raised in the laboratory and outplanted to a reef can contribute to the natural pool of gametes during the annual mass-spawning of elkhorn corals within 4 years", says Valérie Chamberland. By using a restoration method based on sexual rather than asexual (or clonal) reproduction, the SECORE method also promotes the formation of new genotypes that could potentially cope better with the conditions on modern reefs than their already struggling parents. These sexually-bred corals therefore not only aid in the recovery of dwindling elkhorn coral populations by increasing the number of colonies, but also by increasing the genetic diversity of this critically endangered species, thus giving evolution the opportunity to play its part.
While these initial results provide some hope for the restoration of endangered elkhorn populations, restoration cannot perform miracles. "Our techniques can only support natural recovery, which means that conditions have to be appropriate to allow long term survival of outplanted corals and succession by other organisms to restore ecosystem functions. Hence, outplanting efforts have best chances for success in well managed areas where stress has been reduced, but where, for some reason, no natural recruitment occurs. We don't get around to protect coral reefs and to apply additional management tools to reduce overfishing, pollution and other threats to coral reefs", underlines Dirk Petersen. "So far, any restoration effort is restricted to small areas and involves costly and labor intensive hands-on work. We now need to take the next step forward to apply our findings on a larger scale in Curaçao and elsewhere in the Caribbean. For that purpose, we started a joint pilot project last August."
This work would not have been possible without the cooperation and support of SECORE's partner aquariums such as Curaçao Sea Aquarium, Columbus Zoo and Aquarium, Pittsburgh Zoo & PPG Aquarium, Shedd Aquarium, and Henry Doorly Zoo.
Four-year-old Caribbean Acropora colonies reared from field-collected gametes are sexually mature. (2016) Bulletin of Marine Science, Chamberland VF, Petersen D, Latijnhouwers KRW, Snowden S, Mueller B, Vermeij MJA
Restoration of critically endangered elkhorn coral (Acropora palmata) populations using larvae reared from wild-caught gametes. (2016) Global Ecology and Conservation, Chamberland VF, Vermeij MJA, Brittsan M, Carl M, Schick M, Snowden S, Schrier S, Petersen D
Carin Jantzen | EurekAlert!
When corals eat plastics
24.05.2018 | Justus-Liebig-Universität Gießen
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
24.05.2018 | Ecology, The Environment and Conservation
24.05.2018 | Medical Engineering
24.05.2018 | Physics and Astronomy