Carbon dioxide-spewing volcano drives reef from coral to algae

New research provides early warning of ocean acidification effects

Date:: August 10, 2015
Source:: University of Miami Rosenstiel School of Marine & Atmospheric Science
Summary:: A dramatic shift from vibrant coral communities to carpets of algae has been documented by researchers in remote Pacific Ocean waters where an underwater volcano spews carbon dioxide.

These are high-resolution photomosaic images of a healthy coral reef (left) and a volcanically acidified algae-dominated habitat (right) at Maug Island, Commonwealth of the Northern Mariana Islands.

Credit: Image credits: C. Edwards and M. Fox

Scientists from NOAA and the Cooperative Institute for Marine and Atmospheric Studies at the University of Miami Rosenstiel School of Marine and Atmospheric Science (UM) have documented a dramatic shift from vibrant coral communities to carpets of algae in remote Pacific Ocean waters where an underwater volcano spews carbon dioxide.

The new research published online August 10 in Nature Climate Change provides a stark look into the future of ocean acidification -- the absorption by the global oceans of increasing amounts of human-caused carbon dioxide emissions. Scientists predict that elevated carbon dioxide absorbed by the global oceans will drive similar ecosystem shifts, making it difficult for coral to build skeletons and easier for other plants and animals to erode them.

"While we've done lab simulations of how increased carbon dioxide influences coral growth, this is the first field evidence that increasing ocean acidification results in such a dramatic ecosystem change from coral to algae," said Ian Enochs, a scientist with NOAA's Cooperative Institute for Marine and Atmospheric Studies at UM who led the research. "Healthy coral reefs provide food and shelter for abundant fisheries, support tourism and protect shorelines from storms. A shift from coral to algae-covered rocks is typically accompanied by a loss of species diversity and the benefits that reefs provide."

The research was conducted on Maug, an uninhabited volcanic island in the Commonwealth of the Northern Mariana Islands about 450 miles from Guam. This location allowed scientists to single out a small geographic area that experiences carbon dioxide levels that vary from present day to those predicted for a hundred years in the future. Maug also provided researchers with an area with few other human-made stressors for coral, such as overfishing and pollution from land.

By setting up underwater instruments to continuously measure the effects of carbon dioxide, scientists were able to use this natural laboratory to show that coral cover decreased under higher levels of carbon dioxide, giving way to less desirable algae-covered rocks near the volcano's vents.

Story Source:

The above post is reprinted from materials provided by University of Miami Rosenstiel School of Marine & Atmospheric Science. Note: Materials may be edited for content and length.

Journal Reference:

I. C. Enochs, D. P. Manzello, E. M. Donham, G. Kolodziej, R. Okano, L. Johnston, C. Young, J. Iguel, C. B. Edwards, M. D. Fox, L. Valentino, S. Johnson, D. Benavente, S. J. Clark, R. Carlton, T. Burton, Y. Eynaud, N. N. Price. Shift from coral to macroalgae dominance on a volcanically acidified reef. Nature Climate Change, 2015; DOI: 10.1038/nclimate2758

University of Miami Rosenstiel School of Marine & Atmospheric Science. "Carbon dioxide-spewing volcano drives reef from coral to algae: New research provides early warning of ocean acidification effects." ScienceDaily. ScienceDaily, 10 August 2015. <www.sciencedaily.com/releases/2015/08/150810123706.htm>.

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Volcanic vents preview future ocean habitats

Date:: August 10, 2015
Source:: University of Adelaide
Summary:: A world-first underwater study of fish in their natural environment has shown how predicted ocean acidification from climate change will devastate temperate marine habitats and biodiversity.

Healthy kelp forest in the present-day carbon dioxide levels.

Credit: Ivan Nagelkerken, University of Adelaide

A world-first underwater study of fish in their natural environment by University of Adelaide marine ecologists has shown how predicted ocean acidification from climate change will devastate temperate marine habitats and biodiversity.

Published in the journal Nature Climate Change, the researchers used natural CO₂ underwater seeps to study how entire ecosystems have been impacted by the resulting acidification of the water.

They compared ecosystems in the high-CO₂ levels found at volcanic vents in temperate waters in both the Northern and Southern hemispheres with adjacent ecosystems with present-day levels of CO₂. These underwater vents have specific sites that release CO₂ into the water at concentrations predicted for the end of the century.

"Human greenhouse gas emissions are rapidly acidifying our oceans," says project leader Associate Professor Ivan Nagelkerken, Australian Researcher Council (ARC) Future Fellow with the University's Environment Institute. "Using these CO₂ seeps, we've been able to get a unique preview of what the future ocean will look like under current projections for the end of the century -- and it's not good.

"Previous studies have largely looked at how single fish species are affected by acidification in laboratory experiments. But we used these 'natural laboratories' to see the effects on whole ecosystems, as well as how acidification affects the behaviour and physiology of individual species."

The study confirmed previous laboratory research which showed acidification of the water affects fish behaviour, for example, by reducing the escape response from predators.

But there were some surprising results. When the fish were close to shelter in their natural environment, this negative effect of acidification disappeared.

"We also found that some species were more abundant in the acidified waters. But these were common or generalist species such as gobie and triplefin fishes which doubled or even tripled in number to the detriment of other species," Associate Professor Nagelkerken says.

The most dramatic finding was the marked habitat shift found in the high-CO₂, acidified waters.

"As you swim from one area to the other you see a dramatic difference," says co-author Professor Sean Connell. "One minute you're in a kelp forest with one metre high kelp and lots of different fish. Then you move into the vent area where everything is barren with short turf algae, just a few centimetres high and devoid of the life and colour of the other areas.

"Ecosystems represent complex interactions between different species, and between species and their environment. Our research has given us a greater understanding of increasing CO₂ emissions as a driver of ecological change and what this might mean for future marine biodiversity and fisheries production."

Story Source:

The above post is reprinted from materials provided by University of Adelaide. Note: Materials may be edited for content and length.

Journal Reference:

Ivan Nagelkerken, Bayden D. Russell, Bronwyn M. Gillanders, Sean D. Connell. Ocean acidification alters fish populations indirectly through habitat modification. Nature Climate Change, 2015; DOI: 10.1038/nclimate2757

University of Adelaide. "Volcanic vents preview future ocean habitats." ScienceDaily. ScienceDaily, 10 August 2015. <www.sciencedaily.com/releases/2015/08/150810111227.htm>.