Nav: Home

Double trouble for a coral reef

April 26, 2018

Organized over a period of almost three years, the Tara Pacific expedition has made it possible to study some of the most isolated coral reefs in the Pacific Ocean. Indeed, given their isolation, many of these reefs remain scantly documented. This is the case of the Samoan Islands in Polynesia. The scientists dropped anchor in November 2016 in Upolu, one of the islands of this independent state. Its geographic situation meant that there had initially been hopes of finding a well-preserved reef. The available data and satellite images also pointed to a rich diversity of coral ecosystems.

A very badly damaged reef

Yet, once there, the researchers found a coral reef in very poor health. That is why they decided to conduct a more extensive study of the reef than planned: instead of considering three sites, they selected 124 around Upolu--covering over 80 km of coastline--in order to inventorize their biodiversity. Each time, they noted their observations of the state of the corals and the behavior of fish. They also noticed that coral cover was below 1% in half of the sites they visited and below 10% in almost 80% of them. Another result, in most sites, was that the death of the corals was recent. According to the scientists, the coral cover might have been between 60% and 80% at some sites even just two years ago.

Stressed fish?

Moreover, by studying two species of fish they had encountered in previous places the schooner had moored (Moorea, Aitutaki, and Niue), the scientists observed that the Upolu fish were smaller and that the number of individuals in a shoal was on average four to eight times lower than in shoals around the three other islands. In addition, they observed a tendency for fish to flee, which is thought to reflect intensive fishing pressure.

The cause of this massive deterioration? On the one hand, global warming, which heightened a classic meteorological phenomenon (El Niño) in 2015-2016, entailing increased coral bleaching . On the other hand, local human activities, which are thought to exacerbate the effects of climate change.

Indeed, in those sites where there is significant anthropic pressure, 30% to 40% of the dead corals are already covered with macroalgae (this coverage ranges from between 0% to 3% in sites further away from any human presence). The release of chemical substances, sewage, and waste, as well as overfishing, could be having an impact on the capacity of already weakened or damaged corals to recuperate. In contrast, the scientists observed reefs in better health within marine protected areas, a sign of the effectiveness of certain forms of management.

These initial analyses will be followed by more in-depth investigations of the samples taken from Upolu. These samples will be fed into a database that, in time, will make it possible to compare the reefs and to distinguish and understand their capacities to resist environmental upheavals.
-end-
Initiated by the Fondation Tara Expéditions and the Université Paris Sciences & Lettres, the Tara Pacific expedition (2016-2018) is supported by the CNRS, the CEA, the CSM, KAUST, and many other public and private partners including agnès b., Veolia, Fondation Albert 2, BillerudKorsnäs, and the Region of Brittany.

CNRS

Related Global Warming Articles:

The ocean has become more stratified with global warming
A new study found that the global ocean has become more layered and resistant to vertical mixing as warming from the surface creates increasing stratification.
Containing methane and its contribution to global warming
Methane is a gas that deserves more attention in the climate debate as it contributes to almost half of human-made global warming in the short-term.
Global warming and extinction risk
How can fossils predict the consequences of climate change? A German research team from Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), the Museum of Natural History Berlin and the Alfred Wegener Institute compared data from fossil and marine organisms living today to predict which groups of animals are most at risk from climate change.
Intensified global monsoon extreme rainfall signals global warming -- A study
A new study reveals significant associations between global warming and the observed intensification of extreme rainfall over the global monsoon region and its several subregions, including the southern part of South Africa, India, North America and the eastern part of the South America.
Global warming's impact on undernourishment
Global warming may increase undernutrition through the effects of heat exposure on people, according to a new study published this week in PLOS Medicine by Yuming Guo of Monash University, Australia, and colleagues.
Global warming will accelerate water cycle over global land monsoon regions
A new study provides a broader understanding on the redistribution of freshwater resources across the globe induced by future changes in the monsoon system.
Comparison of global climatologies confirms warming of the global ocean
A report describes the main features of the recently published World Ocean Experiment-Argo Global Hydrographic Climatology.
Six feet under, a new approach to global warming
A Washington State University researcher has found that one-fourth of the carbon held by soil is bound to minerals as far as six feet below the surface.
Can we limit global warming to 1.5 °C?
Efforts to combat climate change tend to focus on supply-side changes, such as shifting to renewable or cleaner energy.
Global warming: Worrying lessons from the past
56 million years ago, the Earth experienced an exceptional episode of global warming.
More Global Warming News and Global Warming Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Warped Reality
False information on the internet makes it harder and harder to know what's true, and the consequences have been devastating. This hour, TED speakers explore ideas around technology and deception. Guests include law professor Danielle Citron, journalist Andrew Marantz, and computer scientist Joy Buolamwini.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.