Lessons from the Past: How Cold-water Corals Respond to Global Warming

New MARUM study: Food and oxygen have the greatest impact on survival

Peer-Reviewed Publication


Large colony of the cold-water coral

Cold-water corals, and the species Lophelia pertusa in particular, are the architects of complex reef structures. They build the foundations of important habitats for deep-sea organisms that find protection as well as food within the structures. Coral reefs, however, react very sensitively to changing conditions. These include warming of the ocean waters, acidification, declining oxygen content, and the variable supply of food. A change in any one of these parameters, as a consequence of global climate change, for example, can impact the health of the total coral reef. According to the new study, therefore, it is important to understand exactly how these ecosystems react to environmental changes in order to be better able to protect them more effectively in the future.

First author Rodrigo da Costa Portilho-Ramos of MARUM – Center for Marine Environmental Sciences of the University of Bremen, with his colleagues, examined sediments from six cold-water coral locations in the North Atlantic and the Mediterranean in order to identify of the critical parameters that could trigger the mortality and ensuing proliferation of cold-water corals. Information providing insights to the environmental conditions of the past are stored in these sediments. This fact allows researchers to determine when and why cold-water corals flourished or not. The authors point out that the results could also be used to show how corals might respond to future climatic changes. The study analyzes the changes of the most important environmental factors over the past 20,000 years, the period of general global warming since the last glaciation, and compares them with the occurrence of the cold-water corals.

“We looked back into the past to understand how Lophelia pertusa reacted to environmental changes,” says Portilho-Ramos. The corals vanished from or returned to a region mainly when the food supply or the oxygen content of the water changed. Cold-water corals feed on microscopically small plankton and other particles that are transported by ocean currents. The temperature and salinity of the water had little effect on the mortality or proliferation of cold-water corals. As Portilho-Ramos points out, “we therefore assume that food supply and availability of oxygen are the primary factors that determine the life or death of cold-water corals.” It is not clear what kind of impact ocean acidification has over the long term because there is no paleoceanographic indicator for this parameter.

Acting as ecosystem ‘engineers’, cold-water corals contribute significantly to the formation of biodiversity hotspots in the deep sea. With their influence on food webs and nutrient cycles, their role as fish nurseries and their impressive biodiversity, cold-water coral reefs provide important ecosystem services. In order to continue these services in a future under the influence of climate change, the results of this study form an important foundation for developing knowledge-based management strategies for such deep-sea ecosystems. They also contribute significantly to the goals of the Bremen Cluster of Excellence, which is dedicated to the study of the ocean floor.

Original publication:

Rodrigo da Costa Portilho-Ramos, Jürgen Titschack, Claudia Wienberg, Michael Georg Siccha Rojas, Yusuke Yokoyama, Dierk Hebbeln: Major environmental drivers determining life and death of cold-water corals through time. PLOS Biology 2022. DOI: https://doi.org/10.1371/journal.pbio.3001628

About MARUM:

MARUM produces fundamental scientific knowledge about the role of the ocean and the seafloor in the total Earth system. The dynamics of the oceans and the seabed significantly impact the entire Earth system through the interaction of geological, physical, biological and chemical processes. These influence both the climate and the global carbon cycle, resulting in the creation of unique biological systems. MARUM is committed to fundamental and unbiased research in the interests of society, the marine environment, and in accordance with the sustainability goals of the United Nations. It publishes its quality-assured scientific data to make it publicly available. MARUM informs the public about new discoveries in the marine environment and provides practical knowledge through its dialogue with society. MARUM cooperation with companies and industrial partners is carried out in accordance with its goal of protecting the marine environment.


PLoS Biology




Major environmental drivers determining life and death of cold-water corals through time

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June 9, 2022 2:13 am

“The temperature and salinity of the water had little effect on the mortality or proliferation of cold-water corals.”. They are typically deep enough – eg. 700m in the photo caption – that global warming will ‘never’ affect them. Anyway, they have seen much larger changes over the last 20,000 years than they potentially face now (120m of sea level rise eg.).

Ron Long
June 9, 2022 2:14 am

“…quality-assured scientific data.” does not include utilizing the term “ocean acidification”. This looks like an attempt to find data for a conclusion and admitting the data supporting the conclusion couldn’t be found.

Reply to  Ron Long
June 9, 2022 7:32 am

But they reported the lack of support for the pet conclusion anyway rather than torturing the data into framing CO2.

Dave Fair
Reply to  Ron Long
June 9, 2022 8:18 am

I wonder if atmospheric CO2 concentrations could be used as a proxy of sorts for the current nonsense of ocean “acidification.”

Last edited 11 months ago by Charlie Skeptic
June 9, 2022 2:20 am

Skip. Done.

June 9, 2022 2:38 am

They really can turn a phrase – Acting as ecosystem ‘engineers’ – and true to form it’s full of clever sounding bolleaux.

“These include warming of the ocean waters, acidification, declining oxygen content”

Acidification? At well over pH8?  I wonder if they have considered concepts and analyses such as biological and chemical oxygen demand? I’m guessing they do not figure any more than issues such as hardness and alkalinity do.

Hubris corner…
…to be better able to protect them more effectively in the future.

H. D. Hoese
Reply to  fretslider
June 9, 2022 7:44 am

“Acting as ecosystem ‘engineers’, cold-water corals contribute significantly to the formation of biodiversity hotspots in the deep sea.” Don’t know all the history but may have originated with attempts to understand and maybe control ecosystems. Odum, H. T., et al., 1963, Experiments with engineering of marine ecosystems. Publications Institute Marine Science University Texas. 9:373-403. Up to date– “Currently, Morro Bay is dominated by flatfish and sculpins, and the longevity of this new ecosystem state will depend on future eelgrass recovery dynamics supported by ecosystem-based management approaches.” O’Leary, J. K., et al., 2021. Effects of estuary-wide seagrass loss on fish populations. Estuaries Coasts. 44(8): 2250–2264  https://doi.org/10.1007/s12237-021-00917-2  
6 authors, 98 +/- 2 references.

Last line in OA paper “Over time, it is conceivable that CWCs [cold water corals] may be able to regulate their physiology to mitigate the impacts of future changes as long as a sufficient amount of high-quality food is available. However, given the fast speed of the current global climate change, the rate of adaptation might be too slow, which would inevitably lead to mass mortality.” They are claiming that “high quality food” may compensate for hypoxia citing paper “Cold-water coral reefs thriving under hypoxia.” At least they put food into the equation, attached animals do have a problem. 107 references, 6 authors.

Reply to  H. D. Hoese
June 9, 2022 11:13 pm

re your quoted ‘last line’: Why do they only consider the one possibility, namely mass mortality? Given how the Arctic for example is now bursting with extra food supply, why don’t they consider the possibility of a massive increase in food supply and coral expansion? I suppose if they have to have a disaster, they could claim that corals would explode from over-eating like Mr Creosote, but I doubt people would buy that version.

Dave Fair
Reply to  fretslider
June 9, 2022 8:39 am

Calling oneself “Bremen Cluster of Excellence” does not ensure the quality of one’s work. It could easily be named “Bremen Cluster F..k.” I’ve seen many more organizations that are characterized by the latter description rather than the former.

June 9, 2022 2:43 am

They have no idea of the resilience of coral species. Just ask the average aquarium reef enthusiast about the range of conditions under which corals thrive.

Reply to  Streetcred
June 9, 2022 11:21 pm

Corals have survived for hundreds of millions of years in temperatures way higher than today’s and through changes many many times greater than anything we can chuck at them, but the point is that over those hundreds of millions of years the government research grants were too small to support corals so they had to survive on their own. Now, however, the corals can just sit back and let the grants wash over them. The corals are saved! (until they run out of other people’s money).

June 9, 2022 3:21 am

While welcoming the publication of the fact that cold water corals exist and are worthy of research, I am wary of anyone who talks of the “acidification” of sea water.

June 9, 2022 3:41 am

Way off topic, but worthy of mention

During a meeting with the Lords’ Environment and Climate Change Committee which explored the government’s record on mobilising behaviour change in the population to help tackle the climate crisis, environment secretary George Eustice defended rearing and eating livestock, and questioned the science which shows the scale of the detrimental impact livestock farming is having on the planet.

Asked by Baroness Rosie Boycott about the lack of messaging from the government on reducing meat consumption, which she said was among the “single most important things we can do as individuals”, Mr Eustice said the government would “not be launching an advertising campaign” on the issue.

Baroness Boycott said despite the importance of cutting meat consumption, there remains “such an ambivalence from government about the way they handle meat”.

She asked: “Is the government going to stay on the fence about this?”

Describing the issue as “complex”, and suggesting the science around calls for reduction in meat consumption “is disputed”, Mr Eustice said: “It’s to do with the proper appreciation of the more holistic role of livestock in the farmed landscape and the environment.”

He also told the committee: “It’s quite depressing when people say “livestock are bad, therefore eat less meat’.”

“We are ultimately omnivores – in our natural state we will have meat and animal products and proteins as part of our diet… That’s the natural state of us as a species. But of course, some people will choose to be herbivores and that’s a choice that they can take.”



Dave Fair
Reply to  fretslider
June 9, 2022 8:30 am

It is the proper role for the population mobilizing behavior change in government rather than the other way around. Anti-tyranny, anybody? In the U.S. we have the Bill of Rights in our Constitution which was designed to guard against government overreach. Its too bad that many people believe in the infallibility and benevolence of powerful, centralized governments.

Right-Handed Shark
Reply to  fretslider
June 9, 2022 9:46 am

I detect the faint glow of common sense and logic in Mr. Eustice, so rare in a politician. This, of course, will not be tolerated.

June 9, 2022 5:33 am

Plants and animals constantly evolve to fit a constantly changing environment. It’s what they do. Nothing in the biosphere is ever permanent.

Besides, there is no such thing as “ocean acidification”. Making a basic solution less basic does not “acidify” the solution. That is a completely made up non-scientific term used by so-called “scientists” who do not know their asses from a hole in the ground when it comes to physical chemistry or biochemistry.

Reply to  Duane
June 9, 2022 5:37 am

Claiming that a slight reduction in pH of ocean waters – if it is happening, which it is not – “acidifies” the oceans is like saying that a violent criminal who used to rob, rape, and then shoot his victims dead has decided to drop the rape part is now “pacifying”.

June 9, 2022 7:36 am

Coral reefs, however, react very sensitively to changing conditions.”

I take it they could have written “….react very ADAPTIVELY to changing conditions”

Right-Handed Shark
June 9, 2022 9:53 am

“It is not clear what kind of impact ocean acidification has over the long term because there is no paleoceanographic indicator for this parameter.”

Maybe because it never actually happened, nor is it happening now. And, in all probability, never will.

Reply to  Right-Handed Shark
June 9, 2022 11:23 am

It is a chemical or physical process. As far as I know, pretty much all paleo data depends on measurement of chemical or physical (including nuclear) traces left by these processes. The reasonable interpretation of “no paleoceanographic indicator for this parameter” is that there are no known chemical or physical process that can leave a trace. Thus there is no way to make or estimate the change (or lack thereof) from the data.

Reply to  AndyHce
June 9, 2022 11:37 pm

All they have to do is to examine tree rings from coastal trees. Everything is recorded, and can be extracted from the one measure – tree ring width. It tells you the temperature, the amount of precipitation, cloud cover, wind speed and direction, atmospheric dust content, local flora competition, local animal population, seaspray salinity and alkalinity, and anything else you want. Past surfing conditions? Yup, that is in the tree rings. I don’t know why they bother with Be10 for example, as a proxy for cosmic rays, when they could use tree rings. NB. Bristlecones are best.

Andy Pattullo
June 9, 2022 11:50 am

The article makes it sound as if the researchers found temperature and salinity were not correlated with coral success, but they did not find oxygen and food supplies were causative either – they just assumed that to be the case – half science, half pseudoscience.

Reply to  Andy Pattullo
June 9, 2022 9:14 pm

How much O2 is available/dissolved at 700 meters down? Can’t be very much.

June 12, 2022 1:56 am

the results of this study form an important foundation for developing knowledge-based management strategies for such deep-sea ecosystems.

I’d be curious to know how they would propose to implement management strategies in deep sea.

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