Inconvenient study: Higher temperatures could help protect coral reefs

A new study in the journal Behavioral Ecology, published by Oxford University Press, suggests that higher water temperature, which increases the aggressiveness of some fish, could lead to better protection of some coral.

In the face of global warming, recent years have seen an increasing number of studies predicting the future of corals. It is well established that higher water temperatures lead many corals to die. Over the past century, global temperature has increased by 1°F. Meanwhile, research has shown that coral recovery can be significantly influenced by the behavior of species living around coral reefs.

Researchers here evaluated the relationship between fish behavior and coral performance using a farmerfish-coral system. Farmerfish (stegastes nigricans) are aggressive damselfish found around coral reefs in tropical climates that defend gardens of algae from intrusion by other fish. This study tested the relationship between coral recovery rates and the level of aggression exhibited by farmerfish groups when defending their gardens. The researchers did so by planting small coral fragments into farmerfish territories with different levels of aggressiveness.

The researchers collected data from 29 farmerfish colonies in French Polynesia from 2016 and 2017. They evaluated the average aggressiveness of each farmerfish group as well as the group’s reaction when intruders entered the farmerfish group’s territory.

Stegastes nigricans, the dusky farmerfish, is a species of damselfish found around coral reefs at a depth of one to 12 meters, in tropical climates between 30°S and 30°N. They are known for farming monocultures of algae such as cyanophores and rhodophytes. Source: Wikipedia

Researchers found that more branching corals resided in the territories of aggressive farmerfish groups. In addition, corals experimentally planted into the territories of non-aggressive farmerfish suffered 80 percent more damage than the corals planted into the territories of aggressive groups.

Researchers also found that farmerfish groups composed of larger animals were more aggressive. However, follow-up analyses showed that group aggressiveness mattered more than group member size in determining coral success. Fish aggressiveness is therefore likely to be an important part of how coral reefs will grow and survive in future environments.

While warming oceans negatively impacts a variety of biological processes, this study hints that warmer temperatures, which often increase fish aggressiveness, could enhance the protective function of farmerfish for nearby corals.

“Predicting the future of corals will require a systems approach. Failing to account for broader ecological processes, such as species interactions, could lead us to issue the wrong predictions about how some corals will fare in future environments,” said the paper’s author, Jonathan Pruitt. “Heating up many corals even mildly can negatively impact a variety of physiological processes. However, this study shows that small increases could provide greater protection by resident fishes. Obviously this can’t go on for forever, though. At some point, all the protection in the world won’t matter anything if the corals can’t feed themselves.”


The paper “Collective aggressiveness of an ecosystem engineer is associated with coral recovery” will be available at: on October 16 at midnight EST.


The ecological impacts of animal groups may be different and predictable depending on their collective behavior. Farmerfish (Stegastes nigricans) live in social groups and collectively defend gardens of palatable algae. These gardens also serve as settlement and nursery habitats for corals because farmerfish mob corallivores that attempt to forage on corals within these gardens. We detected large among-colony differences in farmerfish collective aggression towards intruder fish that persisted across years. We further found that the territories of aggressive groups and territories containing larger farmerfish provided greater protection to corals: territories of aggressive groups naturally harbored more branching corals than nonaggressive groups, and experimentally outplanted branching corals experienced 80% less skeletal loss and grew larger over 25 weeks in aggressive territories than in nonaggressive territories. These findings hint that factors that increase farmerfish group aggressiveness (e.g., higher temperatures) could enhance the protective value of farmerfish territories for the replenishment of coral populations.


0 0 votes
Article Rating
Newest Most Voted
Inline Feedbacks
View all comments
John Tillman
October 16, 2018 6:02 pm

Corals thrived in Cretaceous seas a lot hotter than the hottest oceanic water today.

Robert W Turner
Reply to  John Tillman
October 17, 2018 8:01 am

It’s almost like warming water is coincident with, but not the cause of coral bleaching; it’s almost like when currents slow down and there is less water circulating through the reef then there is less nutrients available and this is why the coral extrudes its algae, and the water coincidently warms up as the currents slow. And it’s almost like the lack of major scleractinian coral reefs during glacial periods and their struggle to form at all below 20 C suggests some relationship with temperature but its just so hard to figure out, better just stick with the global warming causes coral bleaching meme.

John Tillman
Reply to  Robert W Turner
October 17, 2018 12:00 pm

Today, shallow water stony coral reefs are largely restricted to tropical waters, or to warm water in temperate zones. Their range must be even more restricted during glacial intervals.

I don’t think there is any evidence to suggest that “bleaching”, ie ejecting their dinoflagellate symbionts, is in any way connected to the air above them containing four instead of three molecules of vital plant food per 10,000 dry air molecules.

Clearly, corals like it hot. But a deep sea coral reef was recently discovered in the North Pacific:, so these cnidarians (kin to sea anemones) are adaptable:

With fronds like these, who needs anemones?

John Tillman
Reply to  Robert W Turner
October 17, 2018 12:03 pm

Coral reef geographic distribution:

comment image

comment image

Robert W Turner
Reply to  John Tillman
October 17, 2018 1:40 pm

A reef is any topographic high, like a ridge or mound, in the marine environment. It doesn’t even need to be biogenic. These studies and the coral-bleaching meme is specifically referring to tropical reef building organisms, not deep sea or high latitude reefs.

John Tillman
Reply to  John Tillman
October 17, 2018 4:00 pm


The map is specifically of coral reefs, which extend out of the tropics into those temperate waters warm enough for them to grow. Some of the hottest ocean water lies outside the tropics.

October 16, 2018 6:20 pm

Whilst working in the Solomon Islands (1969) and Tabar Islands (2006-2008) in the SW Pacific, I found the warmth of the water over luxuriant, pristine coral reefs quite remarkable.

IainC of The Ponds
October 16, 2018 6:29 pm

“Over the past century, global temperature has increased by 1°F. ” Isn’t the important parameter in this case more like: “over the past century, local water temperature at the average live coral depth has increased by xxx°F for the three major reef systems worldwide”?

Reply to  IainC of The Ponds
October 17, 2018 1:23 am

IainC of The Ponds

At a given moment in time, there may not be one single place on earth that conforms to the average temperature prescribed by the IPCC.

October 16, 2018 6:35 pm

Can someone tell me what Mann and other “climate scientists” agree are the authoritative answers to these two simple questions:

1. what is the exact right temperature for the planet?
2. what is the exact right level of carbon dioxide?

Kristi Silber
Reply to  bh2
October 16, 2018 7:03 pm


There is no ideal temperature or CO2, of course. What people fail to understand, evidently, especially when comparing the present day with the distant past, it that biota evolve and they form ecosystems that are in dynamic equilibrium, i.e., they change but they are fairly predictable over the short to medium term (the actual time of which is different for different communities). Ecosystems also “evolve” over the long term along with climate. But if climate changes too quickly, it throws things out of whack, and that’s when extinctions happen, or ecosystems change dramatically, sometimes losing their functional properties. This can have huge economic costs. Coral reefs, for example, are immensely important to the fishing industry, serve as coastal protection during storms, and in some places are the primary basis of tourism.

Johann Wundersamer
Reply to  Kristi Silber
October 16, 2018 7:29 pm

“Coral reefs, for example, are immensely important to the fishing industry, serve as coastal protection during storms, and in some places are the primary basis of tourism.”

And in times gone by they wrecked ships.

Pillage Idiot
Reply to  Kristi Silber
October 16, 2018 8:00 pm


You made quite a few assertions in your comment. They all sound very reasonable. Unfortunately, they seem to lack any historical basis whatsoever. Please list some well-studied events that document your assertions.

The temperature changes and sea level changes entering the Younger Dryas and then exiting the Younger Dryas appear to be much more rapid than anything we are experiencing now. I am not aware of significant extinction events or ecosystem collapse associated with this period of much more rapid change.

Patrick MJD
Reply to  Kristi Silber
October 16, 2018 8:02 pm

“Kristi Silber October 16, 2018 at 7:03 pm

But if climate changes too quickly,…”

Show us the current “climate” is changing too “quickly” due to aCO2 emissions.

Reply to  Patrick MJD
October 17, 2018 6:55 am

She can’t even show us that the current rate of change is higher previous warming or cooling spells.

Reply to  Kristi Silber
October 16, 2018 10:28 pm

This can have huge economic costs

IPCC AR5 evaluated the economic costs and determined that almost every other factor they evaluated were more or much more of an impact than climate change.

Hey, they’re the climate scientists. Who should I believe? Them? Or you?

Reply to  Kristi Silber
October 17, 2018 12:35 am

So you are rowing back from the argument that current or higher CO2 per se is problematic.
It’s now becoming a rate of change argument?

The palaeo record is low frequency – showing changes over centuries or millenia typically.
So we really can’t know if such fast changes happened in the past, except possibly from stomatal densities which do suggest that that CO2 fluctuated quite rapidly in the past.
This would negate the rate of change argument also.

Reply to  Kristi Silber
October 17, 2018 1:29 am

Kristi Silber

Albeit the resolution is somewhat lacking, please explain why rapid temperature fluctuations now are any different from the past.

If there ecological damage it has nothing whatsoever to do with humankind.

Reply to  Kristi Silber
October 17, 2018 5:40 am

“more branching corals “….when they start out this way…it’s a sure sign this is a generic paper
…branching corals are weeds

All of these papers are built on prior papers that have passed peer…and would not have stood up if “scientists” had gone back and tried to reproduce them

wordsmithing……”territories of aggressive groups naturally harbored more branching corals than nonaggressive groups”……
…branching coral colonies attract more damsel fish

The fish they are calling “aggressive groups” are a huge problem to coral farmers. They pick at the corals to kill places on them for algae to grow

Reply to  Kristi Silber
October 17, 2018 6:12 am

Afraid you have it backwards, Kristi. Coral reefs are not immensely important to the fishing industry; the fishing industry is immensely important to coral reefs because it’s well-known among reef scientists that overfishing is the primary cause of world-wide reef decline.

By focusing on a non-problem (CO2) we’re distracted from a real problem (overfishing.)

See here
and here

How can the atmosphere, which has 1/1000 the heat capacity of the oceans, significantly warm the oceans? Yet consensus climate science takes the true primary cause of reef decline– overfishing– and erases that cause and substitutes their own cause– global warming. Is that the new math or something? Or just pseudoscience in action?


Reply to  Kristi Silber
October 17, 2018 6:37 am

Kristi: ” … Coral reefs, for example, are immensely important to the fishing industry, serve as coastal protection during storms, and in some places are the primary basis of tourism. ..”

Kristi, it was not long ago that I remember you defending acid-ocean balderdash and now you’ll school-us on the basics of the last textbook you perused?

Look, let’s just make this very simple, the highest diversity of coral is at or within 10 degrees of the equator, the hottest parts of the oceans.

Now look at this link below. Notice how the coral plankton rich surface currents (the hottest currents at the equator mind you) tend poleward from the equatorial zone at a fairly rapid clip. And from there flow the length of the Great Barrier Reef and replenish it NATURALLY with ZERO HUMANS INVOLVED. Seeding with new equatorial planktonic gene-stock, all day and all night. And the ones that don’t make it often die because the water was a bit too cold along the Great Barrier Reef.,-17.225,141.240,4,i:pressure,m:dgtakdW

Not one dollar needs to be spent on saving GBR coral. It heals itself, if it needs to. it does it ALL the time. Not a single grandstanding ‘paper’-pusher time-waster full of fake concerns need be heard. Now let those currents and temps burn into your brain for 15 minutes, then write out a thousand times:

“Kristi must not promote bad science or crackpot notions any more.”
“Kristi must not promote bad science or crackpot notions any more.”
“Kristi must not promote bad science or crackpot notions any more.”
“Kristi must not promote bad science or crackpot notions any more.”

Just 996 more to go, that’s your homework.

Reply to  WXcycles
October 17, 2018 7:02 am

“Not one dollar needs to be spent on saving GBR coral. It heals itself, if it needs to. it does it ALL the time.”

of course…..first they make a big deal out of bleaching….if heat kills corals…why did they evolve a way to deal with it and survive

Reply to  Kristi Silber
October 17, 2018 6:54 am

Exactly how much “evolving” do plants undergo over 1000 years?

Reply to  MarkW
October 17, 2018 8:48 am

plants are evolving every time they reproduce…..commonly called ‘sports’…most don’t make it
….if conditions change, some will

Robert W Turner
Reply to  Kristi Silber
October 17, 2018 8:20 am

The myth that the climate is currently changing rapidly is the alarmist’s original lie. And one that is so easily refuted for anyone that has actually studied Earth history.

Sea levels were rising by up to 60 mm/yr during the transition into the current interglacial period, that is what would be considered rapid climate change.

dodgy geezer
Reply to  bh2
October 16, 2018 10:21 pm

“1…… what is the exact right temperature for the planet?
2. what is the exact right level of carbon dioxide?…”

1 – Slightly different to whatever it is at the current time.
2 – Considerably different to whatever it is. at the current time.

The key point is that people working in any field need money. A lot of money has been spent on worrying about the climate, and so a lot of people are currently working in that field. They have families, dependents and homes, and they need a regular supply of money. So they need a justification for their work which will not leave them unemployed.

The problems we are having with Climate Change are not scientific or technical. They are social.

Steve O
Reply to  bh2
October 17, 2018 9:19 am

The answer is, “Whatever level causes the Global Climate Cycles to grind to a halt.”

Has anyone ever studied what might happen if we actually were successful in halting the global climate cycle? Isn’t it possible that the gradual changes the flora and fauna are made to endure are beneficial to the long-term viability of the ecosystem? If the Canadian tundra converts to farmland, and then back to tundra over the course of an extended period of time, isn’t it possible that such shifts are inherently beneficial?

Reply to  Steve O
October 17, 2018 3:40 pm

Steve O

In our primitive way we do the same, leave land to lie fallow.

Mother Nature is a better farmer than any man alive.

October 16, 2018 6:45 pm

When proper English is used and “aggressiveness” is replaced by “aggression” I might consider giving the paper a serious read.
Then I might discover if it is higher steady temperatures that affect the study topic, or higher peak temperatures, like a few extra-hot days in summer, that affect the critical mechanisms. Geoff

Kristi Silber
Reply to  Geoff Sherrington
October 16, 2018 7:27 pm


I disagree. Aggressiveness is a characteristic, aggression is what an aggressive fish displays.

The temperature thing seems kind of conjectural. Paper’s not available yet, so hard to say.

Reply to  Kristi Silber
October 16, 2018 9:52 pm

Looking forward to reading how one measures fish aggressiveness.

Reply to  Retired_Engineer_Jim
October 17, 2018 1:32 am


Easy peasy. You just count the increasing numbers of “I’m a climate alarmist” ‘T’ shirts the fish are wearing.

October 16, 2018 7:00 pm

I don’t know what Mann would say, and I don’t think he has the foggiest idea. But in answer to your questions, the relevant answers are:

1. what is the exact right temperature for the planet? About 3 degrees warmer.
2. what is the exact right level of carbon dioxide? About 1200 ppm.

So now you know.

Reply to  Dudley Horscroft
October 16, 2018 9:53 pm

No, no, no. The proper concentration of CO2 in the atmosphere is 350 ppmv. Exactly.

D. J. Hawkins
Reply to  Retired_Engineer_Jim
October 17, 2018 7:33 am

Absolutely. Otherwise at least one alarmist organization will have to change all their letterhead stationary.

Clive 08
Reply to  Dudley Horscroft
October 17, 2018 5:04 am

Exactly Dudley, excellent for plant growth for an expanding world population. Need coal fired power to give us that CO2. The cheap electricity would give all a high standard of living. No need for UN world government or a socialist world.

October 16, 2018 7:06 pm

Yeah, OK, so who was studying the aggressiveness of damsel fish 100 years ago when the ocean temperatures were 1F lower than today? And how do you compare the two? Were the study groups in French Polynesia 1F different from each other?

Reply to  Paul
October 16, 2018 9:53 pm

BTW, is it 1 degree F or 1 degree C?

Reply to  Retired_Engineer_Jim
October 17, 2018 1:39 am


According to Mr. McLean, the MET office and their HADcrut data don’t distinguish between the two..

Dismiss it as a kind of typo thingy. Along with sea temperatures recorded 90 Km inland. Location is also irrelevant.

Reply to  Paul
October 17, 2018 7:00 am

I would have said that you could use two tanks, 1C apart in temperature.
However, since Kristi pointed out that fish evolve, who knows how Damsel fish 100 years ago would have reacted to the then cooler waters. /sarc

Kristi Silber
October 16, 2018 7:21 pm

There should really be a comparable term for “alarmism,” but at the opposite end of the spectrum. Something like “complacencism.” “Denialism” would work quite well, but for the silly notion that it’s supposed to be associated with Holocaust denial.

The title of this post is a perfect counterpart to alarmism.

Yeehah! Instead of ALL coral reef communities being lost, there could be communites of farmerfish and branched coral left, if it doesn’t get too warm, and if aggression is really associate with temperature. Hot dang, we are saved!

Reply to  Kristi Silber
October 17, 2018 7:02 am

In an effort to insult others, Kristi once again manages to prove just how little she actually knows.

She actually believes that claiming that all coral are dying is a valid argument.
There isn’t a shred of evidence that the so called global warming is stressing any coral, but she’s been taught that any warming must be bad, so she goes off the deep end. Again.

Reply to  MarkW
October 17, 2018 11:36 am


Judging by the GBR, coral enjoys the shallow end with warmer water so, as usual, Kristi is jumping in at the wrong end.

Were coral so sensitive to thermal variation, wouldn’t it exist only in the deep oceans where temperatures are more stable?

Robert W Turner
Reply to  Kristi Silber
October 17, 2018 8:14 am

Try to pay attention. Scleractinian coral is a warm water Order of cnidaria that have been the dominant reef building organism on Earth since shorty after the start of the Cenozoic. Earth’s oceans were much warmer at this time, possibly the warmest in the entire history of the planet. Since the Earth has entered into the Cenozoic Ice Age ca. 30 mya, these reefs have barely been able to stay extant during glacial periods and then quickly reform during the relatively warm interglacial periods, some which were over 1 C warmer than today.

David Chappell
October 16, 2018 7:36 pm

Someone is a genius at writing grant applications – getting finance for a 2-year holiday in the South Pacific watching fish!

Pillage Idiot
Reply to  David Chappell
October 16, 2018 8:07 pm

It was probably the other Dave Chappelle.

He was burned out from his show on Comedy Central and took a two year break. Nobody was exactly sure where he went. I like your theory – a two-year holiday on a reef in the South Pacific sounds pretty relaxing!

(He is definitely a good enough writer to fill out that grant application.)

October 16, 2018 8:55 pm

Even in the warmest equatorial ocean waters they have found no coral dead zones.
Warming has just increased the area suitable for coral growth further north and south.

October 17, 2018 12:21 am

In the Eemian, the previous interglacial, global temperatures were 2-4 C higher than today:

Coral reefs and everything else were just fine.

This fact alone destroys the CAGW alarmist conjecture and the 1.5 C nonsense/scam.

Reply to  Phil Salmon
October 17, 2018 1:43 am

Phil Salmon

Judging by your surname I’ll take your word over any scientific study. 🙂

October 17, 2018 12:39 am

So sudden warming will wipe so much sea life into extinction.
Maybe sea life is far more robust than all the snowflakes believe …

Umm, …

… Bikini Island

October 17, 2018 12:42 am

If as we now know from Prof Jim Steele’s research, coral bleaching events are caused by sea level fall, not rise, then it would be indeed expected that higher temperatures should minimise sea level fall, and thus reduce the risks of bleaching events linked to sea level fall. So it makes sense.

Reply to  ptolemy2
October 17, 2018 1:46 am


Logic, the nemesis of climate alarmists.

October 17, 2018 1:47 am

The warmers like to scare us over coral bleaching. They chose to say that coral bleaching means th coral is dying. Not so, its the creatures s which live on the coral which die if a shallow water and a low tide occur on a hot day. The white coral is still alive and over time is re-populated again.

The GBR is a a North South thing, the North end is far hotter than the South end. . Eggs are released every year and whenever the conditions are right they settle and grow.

I spent some months at Madang in PNG. Its closee to the Equator and is hot. But the coral growth is wonderful.

The Read Sea corals are doing just fine. and that is a hot place. Coraals have been around for millions of years and are doing just fine.


October 17, 2018 1:59 am

Not only temperature, but the small current fairly steady rise in sea level is probably ideal for corals to grow.

R Davis
October 17, 2018 5:09 am

Interesting article:
ALETHO NEWS – The dark Story behind Global Warming aka Climate Change by F William Engdahl.

October 17, 2018 6:53 am

“It is well established that higher water temperatures lead many corals to die.”

Bleaching is not dying.

HD Hoese
October 17, 2018 7:59 am

“It’s time to develop visual rhetoric that shocks viewers into understanding their personal responsibility for our deteriorating ocean while supplying them with immediate information on how to alleviate that impact.”
Bleached coral in aquarium due to “acidification.” Out of Scripps no less.

Zoos and aquaria need to get their act together. From the publication of the former “Scientific Honor Society.”

%d bloggers like this: