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Serious ecological consequences of coral reef dredging

March 31, 2016

  • Serious Ecological Consequences of Coral Reef Dredging
  • Want to know where threatened species live? Look to the clouds
  • Hepatitis C virus uses Netrin-1 to hijack host cells


Serious Ecological Consequences of Coral Reef Dredging

Scientists have used satellite imaging of coral reefs in the South China Sea to highlight the dire ecological consequences of reef dredging to increase land area. While much has been made of the political significance of reef dredging and land creation activities in this area, the scientists conclude that the impact on these precious environments must also be considered and the international community must cooperate to prevent the destruction of these critical ecosystems.

Due to their isolation, the coral reefs of offshore distant atolls have historically been "protected" from direct human stressors. However, in an article publishing on 31st March in the Open Access journal PLOS Biology, researchers from the University of Hawaii document reef damage in isolated reefs due to dredging and land reclamation in the South China Sea (Note: reclamation is here defined as the creation of new land by filling submerged areas, with no connotation of ownership). The authors used remote sensing data from the Landsat 8 Operational Land Imager to quantify reef destruction and land creation in seven atolls in the Spratly Islands. Their results show that these seven atolls have effectively lost ~11.6 km2 (26.9%) of their reef area for a gain of ~10.7 km2 of land from February 2014 to May 2015. The study also shows that dredging has been a common practice among countries in the region, and calls for urgent international partnerships for the conservation of this disputed territory before further reclamation and destruction of atolls in the region.

"We see an urgent need to bring the issue to the attention of the scientific community and the general public before more unique atolls are irreversibly damaged," says study leader, Camilo Mora. The protection of coral reefs is extremely important, as not only are they home to an incredible number of species, but they provide food and protection to many coastal populations. Coral reef dredging is a disturbingly common practice across the globe. Previous studies of the impact of reef dredging have found that it can lead to near-permanent damage to the reef and its surrounding ecosystems, and result in local species extinctions. In the South China Sea, where the ownership of many atolls is disputed, the authors call for the international community to come together to create a mechanism for conservation. One possibility would be the establishment of a multinational marine protected area. Mora says, "We suggest the need for multinational cooperation in this disputed territory as a win-win situation, before the race for further development damages more unique environments."

"Countries bordering the South China Sea need to realize that the value of the Spratly Islands as a spawning ground for the same fish that support the lives and livelihoods of their citizens -- a source of larvae to replenish harvested fish populations throughout the region", says co-author John MacManus. The authors recommend looking to the formation of the Antarctica Protected Areas as a positive example of an ecologically important region saddled with multiple territorial claims.

In your coverage please use this URL to provide access to the freely available article in PLOS Biology: http://dx.plos.org/10.1371/journal.pbio.1002422

Contact: Camilo Mora, cmora@hawaii.edu, 1-808-956-7093

Citation: Mora C, Caldwell IR, Birkeland C, McManus JW (2016) Dredging in the Spratly Islands: Gaining Land but Losing Reefs. PLoS Biol 14(3): e1002422. doi:10.1371/journal.pbio.1002422

Funding: The authors received no specific funding for this work.

Competing Interests: The authors have declared that no competing interests exist.

Want to know where threatened species live? Look to the clouds

Study finds that cloud cover can help identify the size and location of important animal and plant habitats

BUFFALO, N.Y. -- Much of our planet's biodiversity is concentrated in hotspots, such as tropical mountains, where knowledge about the habitats and distributions of species remains too uncertain to guide management and conservation.

Scientists increasingly look to satellite remote sensing as a way to address this quandary, and a new study by University at Buffalo and Yale University scientists has now demonstrated the utility of an unconventional source of information: clouds.

The research, to be published on 31st March in the Open Access journal PLOS Biology, examines 15 years of data from NASA's Terra and Aqua satellites, which orbit and study the Earth. The comprehensive observations enabled the scientists to build a database containing two images per day of cloud cover for nearly every square kilometer of the planet from 2000 to 2014.

While clouds might seem an odd thing to probe when it comes to mapping species, these sky-bound entities influence factors such as rain, sunlight, surface temperature and leaf wetness that dictate where plants and animals can survive.

The study found that variations in cloud cover sharply delineated the boundaries of ecological biomes including tropical cloud forests, which harbor many species not found anywhere else in the world.

"When we visualized the data, it was remarkable how clearly you could see many different biomes on Earth based on the frequency and timing of cloudy days over the past 15 years," says lead scientist Adam Wilson, who conducted the majority of the research at Yale University and is now an assistant professor of geography in the UB College of Arts and Sciences. "As you cross from one ecosystem into another, those transitions show up very clearly, and the exciting thing is that these data allow you to directly observe those patterns at 1-kilometer resolution."

Cloud cover also helped the researchers to better predict about where specific species live. By taking cloud patterns into account, the team was able to determine the size and location of habitats for the montane woodcreeper (a South American bird) and king protea (a South African shrub) in unprecedented detail.

That finding is particularly exciting because the technique could be used to research the habitats of threatened plants and animals, says co-author Walter Jetz, Associate Professor of Ecology and Evolutionary Biology at Yale University. "Understanding the spatial patterns of biodiversity is critical if we want to make informed decisions about how to protect species and manage biodiversity and its many functions into the future," Jetz says. "But for the regions that harbor most biodiversity, there's a real lack of data on the ground."

"When it comes to conservation of threatened species, policies and regulations are in large part determined by our understanding of how big those populations are and where they are," Wilson says. "We show that remote sensing combined with the right science can be an effective tool to help inform policy."

Remote sensing as a powerful tool in defining habitats

The authors say that the study demonstrates how remote sensing can be a powerful tool in monitoring ecosystems.

In the past, scientists interested in climate data had to rely on observations taken at weather stations scattered across the globe. This left large swathes of land unmonitored, which created serious limitations for research because many characteristics of ecosystems -- such as temperature and rainfall -- vary significantly across small regions.

Data from satellites enables researchers to conduct research without such gaps.

"That's one of the really exciting developments in the field today," Wilson says. "We now have decades of satellite observations that we can pull together to characterize the global environment. Our data are from two NASA satellites that have been up there in space, collecting two images per day, everywhere on Earth, for well over a decade. It is exciting to now be able tap into this large stack of detailed data to support global biodiversity and ecosystem monitoring and conservation."

In your coverage please use this URL to provide access to the freely available article in PLOS Biology: http://dx.plos.org/10.1371/journal.pbio.1002415

Press-only preview: https://www.plos.org/wp-content/uploads/2016/03/journal.pbio_.10024151.pdf

Contact: Charlotte Hsu, chsu22@buffalo.edu

Citation: Wilson AM, Jetz W (2016) Remotely Sensed High-Resolution Global Cloud Dynamics for Predicting Ecosystem and Biodiversity Distributions. PLoS Biol 14(3): e1002415. doi:10.1371/journal.pbio.1002415

Image: https://www.plos.org/wp-content/uploads/2016/03/Seasonality.tif

Image Caption: Seasonal cloud concentration: Fine-grain spatio-temporal cloud dynamics visualized with a metric of seasonal concentration, which combines the magnitude and timing of monthly fluctuations in cloud frequency derived from 15 years of twice-daily satellite observations. It illustrates the often remarkably sharp transitions between many of the world's terrestrial ecosystems. The hue indicates the month of peak cloudiness, while the saturation and value indicate the magnitude of the concentration ranging from 0 (black, all months are equally cloudy) to 100 (all clouds are observed in a single month). Coastlines shown in white, marine areas with no data are dark grey.

Image Credit: Adam Wilson

Please note that further images are available by contacting Charlotte Hsu (chsu22@buffalo.edu)

Funding: National Science Foundation (NSF.gov) to WJ: DBI 1262600, DEB 1026764, and DEB 1441737. National Aeronautics and Space Administration (nasa.gov) to WJ: NASA NNX11AP72G. Yale Climate and Energy Institute postdoctoral fellowship to AW. Publication costs were covered in part by the Julian Park Fund at the University at Buffalo College of Arts of Sciences. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

Hepatitis C virus uses Netrin-1 to hijack host cells

Hepatitis C virus (HCV) is a small, enveloped virus comprising an RNA genome encased in a protein capsid and surrounded by a lipid bilayer containing two glycoproteins. Acute infection can cause hepatitis but the virus usually persists as a chronic infection of the liver where it can cause inflammation and, eventually, hepatocellular carcinoma. How HCV subverts hepatocytes to turn them into virus-producing factories, has remained unclear.

In a paper publishing in the Open Access journal PLOS Biology on 31st March, a research team based in Lyon (France) finds a small secreted protein, Netrin-1, closely implicated in the lifecycle of this virus. Romain Parent and his collaborators report that HCV enhances expression of Netrin-1 in hepatocytes and, in turn, Netrin-1 increases both the amount of the viral RNA genome and the infectivity of the virus particles produced. What's more, the authors present evidence that Netrin-1 also promotes viral uptake into uninfected cells, perhaps by blocking internalisation of the epidermal growth factor receptor (EGFR) and so increasing the amount of this cofactor for viral uptake on the cell surface.

HCV replicates mainly in the hepatocytes of the liver. It enters these cells by complex interactions with several cell surface proteins and, once inside, replicates on intracellular membranes, in particular those of the endoplasmic reticulum (ER). These authors were drawn to study the possible role of Netrin-1 in HCV infection because of previous studies showing its involvement in several cancer types as well as in inflammatory diseases associated with cancer.

The researchers first looked at the amount of Netrin-1 mRNA in liver biopsy samples from patients with HCV and compared this to similar samples from virus-free patients. They saw a substantial (23-fold) increase in the amount of Netrin-1 mRNA in the infected samples, which was reversed by treatment of the patients with antiviral drugs. Likewise, HCV infection of primary human hepatocytes and a hepatocyte cell line in culture resulted in a large increase in the amount of Netrin-1 mRNA in the cells and newly translated Netrin-1 protein.

Netrin-1 mRNA is known to bind to the La-related protein LARP1, although the functional significance of this interaction is unclear. These researchers found that LARP1 also interacts specifically with one of the non-structural HCV proteins, NS5A, on ER membranes where it promotes translation of Netrin-1. Moreover, Netrin-1 levels correlate directly with the amount of HCV RNA produced in infected cells and with the infectivity of the virus particles produced in overexpression and knockdown studies, perhaps by binding directly to the HCV particles. Thus, the authors concluded that HCV infection promotes Netrin-1 production and, in turn, Netrin-1 promotes HCV production.

But this is not the only influence of Netrin-1 on the HCV lifecycle. The authors also report evidence that Netrin-1 expression increases the level of EGFR protein at the cell surface -- and the level of activated (phosphorylated) EGFR - by impeding its internalisation, and this seems to promote virus entry into the cells.

This positive feedback loop suggests how HCV converts hepatocytes into viral factories, but it doesn't explain how the virus limits infection and cell death to persist for years in liver cells. Netrin-1 might hold a clue to this too as it is an inhibitory ligand of the UNC5 family of so-called 'dependence receptors', which auto-activate and trigger apoptosis. So, enhanced amounts of secreted Netrin-1 might help to prevent the death of infected liver cells. Netrin-1 expression did not confer a pro-survival advantage to the cultured cells used in this study, but, as quoted by the authors, "Netrin-1-associated cell survival in the liver has been meanwhile observed by the same team during the unfolded protein response, a hallmark of chronic liver disease, in animals (Cell Mol Gastroenterol Hepatol 2016, in press). Given the frequency of dysregulation of the EGFR pathway in late stage chronic liver disease, this functional association between Netrin-1 and EGFR is of potential relevance in the onset of hepatocellular carcinoma too".

Additional information

Cancer Research Centre of Lyon http://www.crcl.fr

Department of Microbiology and Immunology, Stanford University School of Medicine http://microimmuno.stanford.edu

In your coverage please use this URL to provide access to the freely available article in PLOS Biology: http://dx.plos.org/10.1371/journal.pbio.1002421

Contact: Romain Parent romain.parent@inserm.fr

Citation: Plissonnier M-L, Lahlali T, Michelet M, Lebossé F, Cottarel J, Beer M, et al. (2016) Epidermal Growth Factor Receptor-Dependent Mutual Amplification between Netrin-1 and the Hepatitis C Virus. PLoS Biol 14(3): e1002421. doi:10.1371/journal.pbio.1002421

Funding: This study was supported by the European Union (Marie Curie International Reintegration Grant #248364; http://ec.europa.eu/research/mariecurieactions/), the Bullukian Foundation, the French National Agency for AIDS and Viral Hepatitis Research (ANRS, Grant #2011-379; http://www.anrs.fr), Ligue contre le Cancer, and the DevWeCan French Laboratories of Excellence Network (Labex, Grant #ANR-10-LABX-61, http://devwecan.universite-lyon.fr). The funders had no role in the design of the study, in data collection and analysis, in the decision to publish, or in the preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.
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