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!
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.
In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...
Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...
19.03.2018 | Event News
16.03.2018 | Event News
13.03.2018 | Event News
21.03.2018 | Physics and Astronomy
21.03.2018 | Materials Sciences
21.03.2018 | Life Sciences