But reefs appear to be more resistant to one potential menace – seaweed – than previously thought, according to new research by a team of marine scientists from the United States and Australia.
Their study, published in the June issue of the journal Ecology, is the first global-scale analysis of thousands of surveys of individual reefs – in all, more than 3,500 examinations of about 1,800 reefs performed between 1996 and 2006.
“Until now, many scientists have concluded that the world’s coral reefs are being overrun by seaweed,” said John Bruno, Ph.D, associate professor of marine sciences at the University of North Carolina at Chapel Hill and lead author of the study. “Our findings show that’s not the case. Seaweed have taken over and are dominating some reefs, but far fewer than assumed.”
The problem with too much seaweed, researchers say, is that it can smother the baby corals, reducing the ability of reefs to recover from other disturbances such as hurricanes and disease outbreaks. Over recent decades, there have been several dramatic examples of such shifts, with one of the most widely known and striking cases occurring in the Caribbean in the 1980s. Following a series of events that disturbed the marine environment (including two major hurricanes, a disease outbreak and the loss of a seaweed-grazing urchin), coral cover on several reefs in Jamaica plummeted from about 70 percent to less than 10 percent, and macroalgae became the dominant life form.
So Bruno, along with colleagues Hugh Sweatman, Ph.D., from the Australian Institute of Marine Science and William F. Precht, a Florida-based marine ecologist, set out to determine how bad and how widespread the problem of seaweed-dominated reefs really is.
The team came up with a “phase-shift index” to determine the state of each reef. Pristine reefs where coral was still abundant had an index number of -2 to -3, while areas where macroalgae have overwhelmed reefs’ surfaces were given an index ranking of between 3 and 5.
They found that while there were moderate local increases in seaweed cover over the study period, only four percent of reefs worldwide were dominated by macroalgae – that is, more than 50 percent of a reef’s surface was covered in seaweed. Researchers also found overall “phase shift severity” decreased in the Caribbean, did not change in the Florida Keys and the Indo-Pacific, and increased slightly on the Great Barrier Reef due to moderate coral loss.
“Overall, our results indicate that there is no general recent trend (i.e., post-1995) toward marcoralgal dominance,” the researchers wrote.
“The results from this study question many of the prevailing paradigms that coral reef ecologists have developed over the past two decades,” Precht said. “These findings will change the way we view and manage these fragile yet resilient ecosystems.”
Said Sweatman: “I hope this study leads to clearer definition of what coral-algal phase shifts are and broadens our perspective on the serious loss of corals in many parts of the world. Australian reefs have been relatively lucky so far, but there is no reason for complacency.”
The study team noted that while their analysis suggests the threat posed by macroalgae has been exaggerated, individual case studies such as the degradation of Jamaican reefs have been invaluable warnings of the consequences of subjecting reefs to multiple natural and manmade disturbances.
The paper’s co-authors include UNC College of Arts and Sciences marine sciences department researchers Elizabeth R. Selig, Ph.D., and Virginia G. W. Schutte, who is now a doctoral student at the University of Georgia.
The study was funded by the National Science Foundation, the Australian Institute of Marine Science and UNC-Chapel Hill.
Ecology Journal Web site: http://www.esajournals.org/loi/ecol
Patric Lane | Newswise Science News
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)
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
In an article that appears in the journal “Review of Modern Physics”, researchers at the Laboratory for Attosecond Physics (LAP) assess the current state of the field of ultrafast physics and consider its implications for future technologies.
Physicists can now control light in both time and space with hitherto unimagined precision. This is particularly true for the ability to generate ultrashort...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
19.04.2018 | Materials Sciences
19.04.2018 | Physics and Astronomy
19.04.2018 | Physics and Astronomy