Guard-crab diversity key to coral reef survival in French Polynesia
Coral reefs face a suite of perilous threats in today's ocean. From overfishing and pollution to coastal development and climate change, fragile coral ecosystems are disappearing at unprecedented rates around the world.
Despite this trend, some species of corals surrounding the island of Moorea in French Polynesia have a natural protector in their tropical environment: coral guard-crabs.
New research from the National Museum of Natural History's Smithsonian Marine Station scientist Seabird McKeon and the museum's predoctoral fellow Jenna Moore of the Florida Museum of Natural History has helped unravel the complex symbiotic relationship between these crabs and the coral reefs they live in and defend. Details from this study are published in the Sept. 30 issue of the open-access journal, PeerJ.
The new research highlights the role of diversity in the healthy functioning of coral reef ecosystems and shows that guard-crab species and size classes offer different kinds of effective protection against various threats to coral reefs.
"We found that diversity in both species and size of coral guard-crabs is needed to adequately fend off coral predators," said McKeon. "It is an example of how biodiversity is crucial to conserving reef environments and the essential resources they provide for thousands of species, including humans."
Coral guard-crabs belong to the genus Trapezia and defend their habitat in coral reefs from predators called corallivores in exchange for shelter and nutrition. In 2008 and 2009, four species of coral guard-crabs known to protect coral from predator sea stars were studied in a series of experiments to examine the effectiveness of different species and various sizes of crabs at repelling multiple corallivores. At the time, crown-of-thorns sea stars, which can grow to the size of a trashcan lid and decimate coral reefs, experienced a population boom on Moorea, threatening the entire reef community found there.
In one trial, the research team selectively removed the largest species of coral guard-crab, T. flavopunctata, from corals in the path of the army of sea stars and observed the effects. The results were dramatic; corals without guard-crabs, or with other species of guard-crab, were eaten—usually overnight.
"Seemingly small differences among crabs guarding their coral homes can have big effects on coral survival," said Moore. "Not only does the level of protection provided vary by species, but the smallest crabs were defending the coral from coral-eating snails, a threat that larger crabs ignored."
The team concluded that multiple lines of defense are a direct result of guard-crab diversity and will be necessary to keep coral reefs safe long-term. Additional surveys revealed that the host corals were not the only species that benefitted from the diverse guard-crab ecosystem. Small corals of other species sheltering in the shadow of the crab-coral symbiosis were also shielded from corallivore predation.
Coral reefs have long protected humans living in coastal areas, acting as barriers again storms, wave damage and erosion. They are also a rich source of food for people around the globe, providing habitat and nurseries for as much as one-quarter of all ocean species. As waters to continue to warm and ocean acidification changes the chemistry of the Earth's marine systems, corals, and the incredible diversity of life they support, are at risk of vanishing.
The Smithsonian Marine Station in Ft. Pierce, Fla., is a research center specializing in marine biodiversity and ecosystems. The Marine Station, a facility of the National Museum of Natural History, draws scientists and students from the Smithsonian and collaborating institutions to investigate the plants, animals and physical processes in the ocean and Indian River Lagoon.
Kathryn Sabella | Eurek Alert!
Despite government claims, orangutan populations have not increased. Call for better monitoring
06.11.2018 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig
Increasing frequency of ocean storms could alter kelp forest ecosystems
30.10.2018 | University of Virginia
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly
The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
15.11.2018 | Life Sciences
15.11.2018 | Materials Sciences
14.11.2018 | Materials Sciences