Bleaching of coral reefs reduced where daily temperature changes are large
By taking a closer look, UCI scientists find resilience in face of heat stress
Coral reef bleaching is stark evidence of the damage being inflicted by global climate change on marine ecosystems, but a research team led by scientists at the University of California, Irvine has found some cause for hope. While many corals are dying, others are showing resilience to increased sea surface temperatures, pointing to possible clues to the survival and recovery of these vitally important aquatic habitats.
“Field observations have shown a heterogeneity or patchiness of the bleaching process at the reef scale, which means that some corals are responding differently to heat stress,” said Aryan Safaie, lead author of a study published yesterday in Nature Communications.
“We know that some species are more thermally tolerant than others,” he added. “But our study shows additionally that certain locations within a reef might be more amenable to allowing corals to persist in the face of increasing water temperature.”
To reach this conclusion, Safaie, a Ph.D. student in UCI’s Department of Civil & Environmental Engineering, said it was necessary to examine reefs more closely in terms of both space and time, versus relying solely on satellite remote-sensing products. He and his collaborators analyzed decades’ worth of field data collected at 118 locations spanning five coral reef regions around the world, including the Great Barrier Reef near Australia and sites in the Indian Ocean, Pacific Ocean, Caribbean Sea and the Red Sea.
“Satellite images are indispensable in giving us the big picture and providing tools for long term projections of ocean health,” he said. “But, these spacecraft collect data only once or twice weekly, there just isn’t enough to provide a clear understanding of the daily and hourly variability of ocean conditions unless you’re looking at more frequently reported field observations.”
The team found that in reef locations with more high-frequency temperature variability – water temperature spiking during the day and dropping at night, day in and day out – severe bleaching was less likely to occur.
“We think of corals as these thermally sensitive organisms, and that temperature variability would mean they would have a harder time all the time,” said coauthor Kristen Davis, UCI assistant professor of civil & environmental engineering and Earth system science. “Instead, what we found is that higher daily temperature variability made corals stronger and more resilient when a thermal stress event came along.”
The upshot of this work, according to Davis, is that scientists now have a better way to predict the outcome of coral reef bleaching events, which can lead to better conservation strategies.
“As we move into a time when corals are threatened by global warming, if there are some living corals remaining on a reef after a bleaching event, there will be some genetic material to repopulate the reef with corals that are more thermally resilient,” she said.
Davis said further work is needed to identify where these super corals live, so that those areas can be protected from over fishing and development.
This project was funded in part by the UCI OCEANS initiative and the National Science Foundation and involved researchers from California State University, Northridge; UC San Diego; Wildlife Conservation Society (Bronx, N.Y.); Old Dominion University; Duke University; Stanford University; and Bangor University (United Kingdom).
The study: https://www.nature.com/articles/s41467-018-04074-2
(open access)
High frequency temperature variability reduces the risk of coral bleaching
Abstract
Coral bleaching is the detrimental expulsion of algal symbionts from their cnidarian hosts, and predominantly occurs when corals are exposed to thermal stress. The incidence and severity of bleaching is often spatially heterogeneous within reef-scales (<1 km), and is therefore not predictable using conventional remote sensing products. Here, we systematically assess the relationship between in situ measurements of 20 environmental variables, along with seven remotely sensed SST thermal stress metrics, and 81 observed bleaching events at coral reef locations spanning five major reef regions globally. We find that high-frequency temperature variability (i.e., daily temperature range) was the most influential factor in predicting bleaching prevalence and had a mitigating effect, such that a 1 °C increase in daily temperature range would reduce the odds of more severe bleaching by a factor of 33. Our findings suggest that reefs with greater high-frequency temperature variability may represent particularly important opportunities to conserve coral ecosystems against the major threat posed by warming ocean temperatures.
Ah, but this isn’t caused by temperature, it’s caused by ocean microdealkalinization.
Right on. A lot of people don’t recognize this if they don’t have any experience with corals. I can bleach every coral in my tank overnight if I just drop the alkalinity. Bleaching is visual manifestation of corals purging symbiotic zooxanthellae when conditions change drastically in an attempt to repopulate with a different clade of zooxanthellae more adapted to the new conditions. In healthy corals, the process is intense but easily survivable.
Dana Riddle has hypothesized that corals utilize an enzyme called carbonic anhydrase to convert inorganic bicarbonate alkalinity as a carbon source to synthesize sugars. If true, that means when alkalinity drops rapidly and doesn’t quickly recover, the coral bleaches in an attempt to find a suitable clade of zooxanthellae that can provide enough energy for survival. If the coral cannot accomplish this task quickly enough, it literally starves to death due to a drop in alkalinity.
Now, the real question is why do ENSO events have such a large impact on alkalinity? It is likely that the temperature indirectly causes bleaching though large shifts in alkalinity. If temperature is so critical to corals, how can certain species thrive in shallow, clear tidal pools where the temperature can vary many degrees on a single day?
Carbonate is defined by the partial pressure of CO2. CO2 solubility in inversely related to temperature. As temperatures rise, the solubility of CO2 decreases. Alkalinity is affected by carbonates. How can the coral survive when near-coastal temperatures change during the day? Simple, they eat at night. How can some corals survive better? First thing to check is if they can utilize more than one kind of carbonate.
So organisms exposed to and evolving in a high variance environment can deal with the variance better? Who would have thought? Actually, good for them to even think of checking. Obviously most haven’t.
why on earth would you put in a funding application to conduct research into a coral resilience mechanism that would ‘reveal’ that there is really nothing to see…….
For PR window dressing.
Yeah, and why would any terrestrial life form that experiences 100 degree annual differences between the coldest nights of winter and hottest days of summer, and daily 30 degree differences between day and night be at risk from a couple of degrees of warming from seasonal averages? Makes no sense whatsoever that mild warming is dangerous.
The organisms that did not survive the environment changes are all dead, so obviously the ones that remain can tolerate the variability.
Perhaps they need to widen their thinking and ask why the coral around Cuba is in pristine condition and the coral at Bikini atoll is in pristine condition and growing like a forest.
Now I didn’t get paid a cent for this but the clue is Cuba does not use pesticides and no one visits Bikini atoll so free of pollution.
Amazing how climate change manages to miss those areas with no pollution from land.
Not true re pollution the most remote places have has severe bleaching- Christmas Island Kiribati had 14 months of continual bleaching and 99% of all corals died.
did this tie in with the oil spill at Kiribati?
“The environment in Kiribati has also been adversely affected by metals and chemicals from mining activities, and agricultural chemicals have polluted coastal waters. Phosphate mining was especially devastating, rendering the island of Banaba almost uninhabitable. The Banabans, who were forced to move to the Fijian island of Rabi, sued the owners of the mines and have won special compensation.
As i said pollution!!
Biggest problem is probably sediment load from nearshore. Second would be phosphate pollution leading to more algae blocking light making the water turbid.
Field biology, not computer modeling. What is this world coming to?
Spend your days snorkeling/diving the reefs in the Caribbean. I could do that, I even have some experience.
I know some excellent reefs around Barbados, along with fantastic reefs around Bonaire and Providenciales.
These reefs are just desperate for some marine biology types to come study them. I could work full time on the reefs five days a week, and spend weekends at the resort’s poolside swim up bar. I could also double up as the resort poolside bikini inspector.
And it is all good, because it is to Save the World.
Apply for a grant!
Seriously, where is everyone’s faith in Evolution?
Faith in Evolution. Now there’s an oxymoron.
An oxymoron is literally a pointed (oxy) stupidity (moron). The term used to describe a phrase that seems contradictory (like “cruel to be kind”) but upon reflection in fact has some wisdom in it. Almost everything called an oxymoron these days is simply contradictory but I think that “faith in evolution” might actually be an oxymoron. Well done.
Ohhhh … I always thought oxymoron meant two blithering idiots combined with three oxygen atoms — you know, brain trust rust.
Not at all. “Faith” isn’t magic, it simply means “trust in”. Trusting in a proven biological phenomenon is not illogical at all.
Yet again here in australia we are told that the gbr is in danger.
But if indeed the temperature m did rise, surly the reef would slllowly move soouth to cooler waters.
Also how do coral reefs survive in places like the red sea ?.
The answer must be that they adapt.
Mje
To hell with the GBR.
You guys have salt water crocodiles, poisonous sea snakes, box jellyfish and Great White Sharks.
If I was a marine biologist down under, I would stick to computer modeling too.
You forgot the tiger sharks. I used to snorkle the coral around Snapper Island just north of the Daintree River when younger. Never considered why it was called ‘snapper’ island, I probably should have, as snapper fish don’t occur there at all. I wouldn’t dive there now though as the whole area is croc infested. A woman got taken from a beach near there not long ago. All the wooded gbr lagoon Islands probably have crocs visiting them in the warmer months.
Meh … those salt water crocodiles are kind of puny …
It always makes me laugh when the MSM says things like the GBR is in danger and how fragile it is but they seem to forget that when the sea level dropped during the last glaciation The Great Barrier Reef spent around 130,000 years 400 ft up the side of a cliff. When the ice melted and the sea level came back up so did the reef. Sounds fairly robust to me.
Not just the GBR. Coral islands routinely have a ledge at 60-65 fathoms from the last ice age that ships use for anchoring. The face of the reef itself plunging into the abyss far beyond anchor depth.
This ledge marks the surface on the oceans 20 thousand years ago. Since then the oceans rose many many times faster than current sea level rise and the corals had no problem keeping up.
One might as well dump a load of topsoil on their lawn and argued that nothing will grow on it.
Also how do coral reefs survive in places like the red sea ?.
======
The red sea has some of the most fantastic corals on earth along with some of the warmest ocean waters.
What the red sea lacks is rainfall. Fresh water is deadly to coral.
That which does not kill us makes us stronger. Nietzsche If corals exist in a location, they have adapted to the stressors of that environment. Time after time the greenies fail to account for Mother Nature’s ability to adapt to changing circumstances.
Could be that the corals change their angle to the sun to reduce warm rays, they build thicker exoskeletons to absorb heat, they act more nocturally, and they built extensions to radiate heat. All sorts of possibilities that does not require genetic change, just behavioral change. “Stressing” just means they have time to build these adaptations.
I can’t believe “coral scientists” are still making the same mistakes…..this has to be on purpose
They are not “algal symbionts”….they are dinoflagellates……..zooxanthellae…and come in many clades that all have different tolerances to different temps and conditions
The coral does not decide anything…..the zoox decides..and the zoox decides if it wants to trigger the coral to expel it or not
….like corals have not had to deal with tide changes since the beginning of time
Exactly correct.
Thank you. I’ve been wondering about that from time to time. Do you happen to know how it was determined?
…the zoox are not damaged after expulsion….
Can’t find a page anywhere suggesting zooxanthellae aren’t algae (as well as dinoflagellates). You’d have to have a narrow definition of “algae”. Maybe the coral scientists aren’t really so clueless.
I was just reading in microwikipedia that after a bleaching event , when the corals recover they often have zoox that are more heat tolerant.
They aren’t algae, but they are photosynthesizing eukaryotes, albeit without the standard nucleus. Some dinoflagellates are strictly photosynthetic, others only heterotrophic and still others both. Some live free and others are symbiotic.
They are now classed as alveolates, a major clade within the SAR group of protists (unicellular eukaryotes).
Kristi….no “coral scientist” would ever refer to zoox as algae
Latitude,
True, but there was a time in the distant, benighted past in which coral symbionts were referred to as “algae”. But those were the dark days when cyanobacteria were also called “blue green algae”, and they aren’t even eukaryotes (although the ancestors of chloroplasts within algae).
…and the earth was flat
.no “coral scientist” would ever refer to zoox as algae
Latitude,
Not today, no.
But in the past, they did, because the dinoflagellates hadn’t been properly phylogenized.
As I noted, same goes for cyanobacteria.
As it was almost certainly warmer in the Medieval Warm Period, and various other periods for the past few million years, if coral could not adapt to temperature changes, coral would be long extinct. Another “water is still wet” study.
Don’t forget that suntan lotion also kills corals. Looks like two causes predominate: oxybenzone and octinoxate:
http://www.nature.com/news/2008/080129/full/news.2008.537.html
https://www.theguardian.com/environment/2017/apr/28/sunscreen-damage-coral-research-oxybenzone
https://link.springer.com/article/10.1007%2Fs00244-015-0227-7
“Four commonly found sunscreen ingredients can awaken dormant viruses in the symbiotic algae called zooxanthellae that live inside reef-building coral species.”
https://news.nationalgeographic.com/news/2008/01/080129-sunscreen-coral.html
Well, that’s the claim, but I would love to see a real scientific experiment that proves causation and identifies the levels and duration of exposure that causes harm and then shows the levels and duration of exposure at the reefs where damage is claimed. It’s hard to think open water reefs would have much in the way of exposure; some reefs in heavily used bays maybe, but having dived at and flown over both the GBR and the reef in Belize, and with a Chemistry degree, you need to show me some well controlled experiments and sampling to convince me of the concentrations actually present on the open reefs.
You should go visit about ten outer reefs on the gbr and note that on any given day there’s no one out there, almost never any one swimming or diving on it.
If you see even one other boat on the reef that you’re at would be rare. And note that you’ll often be between 30 km and 150 km from land, and the reef that you’re at is 5km to 20 km across. Until you go visit it you just can’t comprehend how big the reef is, and how remote from humans and the coast it is. Sun screens are not a problem for the gbr, never will be either, that’s just more dismal greenie media hysterics. Gimme more money.
“Coral reef bleaching is stark evidence of the damage being inflicted by global climate change on marine ecosystems”. Anthony, you didn’t write that, did you?
That statement jumped out as encompassing a number of unscientific, unproved assumptions. How any well trained scientist could write something like that is beyond me.
Anthony needs to make it clear that he is not the author of the press releases he posts.
Anthony does often make it clear that he runs the blog this way. I think it helps keep regular readers on the straight and narrow if they cannot make too many quick assumptions from just the title or opening sentence of an article as to whether it might be considered good, bad, or global-appalling.
Kristi: I read the line and immediately glanced up to confirm our host introduced with italics, and the text was another source. If you look real sharp, you can see it.
Let me take this opportunity to congratulate our host on his great good fortune, you have Kristi to look over your shoulder and give you advice that’s worth every cent.
The coal mining industry has killed every polar bear on the Great Barrier Reef,
I thought the rainbow mining industry was responsible?
Davis said further work is needed to identify where these super corals live…
=======================
Oh look!, I found them already – on youtube:
Narrated by David Attenborough on behalf of … Saudi Aramco
at ~ 5 min:
“The sea [Persian Gulf] is like a hot tub. It getshotter and saltier than any other open sea in the world. It’s surprising that corals can survive. They have miraculously found ways to cope – much to the excitement of scientists.”
What this study tell us is the “coral experts” don’t know near as much about corals as they thought the did. Surprise! The whole coral bleaching issue has been around for decades long before the supposed “dramatic increase in SSTs.” NOAA SST anomaly charts actually have a version showing what they now call
“coral bleaching alert areas.” Thirty years ago corals supposedly only occurred in the photic zone. Yet we now know they live below the zone. Corals are faced with a lot of stressors and their response to all stressors is to expel zooxanthellae. Why the “coral experts” have zeroed in solely on AGW is a bit bizarre. Of course right now that is where a lot of research dollars are going. Many of the areas where they document coral bleaching has seen some of the greatest human population growth in the world. Since most of these areas have resorts and you do not attract visitor if you have bugs I am certain mosquito control is high on the list of activities. With the increase in human population so goes the increase in domestic sewage. In the USA that is about 100 gallons per person per day. That means freshwater is removed from somewhere in the uplands and then rushed to sea as stormwater runoff and domestic sewage. Assuming the sewage receives tertiary treatment, and we know in most places it doesn’t, that is hundred gallons per person of freshwater be dumped in places where it has before. Tourist often exceed the hundred gallon average. Even with just primary treatment there will be chlorination which produces a list of trihalomethanes in the process, many of which are toxic.
Edwin don’t blame humans for coral bleaching, a drop in sea level is the trigger for such events and it only happens during strong El Nino.
Looking at the 1997-98 El Nino as an example, sea level fell in the western Pacific and caused massive bleaching in the coral triangle.
The Indian Ocean also had a drop in sea level and shallow corals bleached in Sr Lanka and other places on the African east coast.
no mention of UV radiation in this discussion? … yet, the most powerful element in our environment is the Sun … variation in solar UV radiation exposure is the key to coral ‘bleaching’ … during El Nino the large tidal range of the northern GBR is exaggerated and shallower corals are exposed to UV radiation for longer than usual … the corals get ‘sunburnt’ … an increase in water temperature just doesn’t compare to the severity of over-exposure to UV radiation … this is not good news for the bank balances of GBR academics, radical anti-coal activists and the Greens …
Thanks Dr Bob.
Ironicman, I don’t disagree, certainly natural events cause bleaching but environmentalists, and today many scientists, tend to only blame things that are really big with no immediate solution. Problems that will not be solved in their lifetime. Why? That is where the money is and they also have to take no responsibility for any of the management decisions. Often you ask a marine biologists what needs to be done and their first response will be we could tell you if we had more data, i.e., more research dollars.
Corals can be stressed to the point of bleaching by a lot of things both natural and anthropogenic. Many of the local anthropogenic stressors can be fixed or mitigated relatively cheaply compared to the cost of reaching the goals of Paris Climate Accord, etc. Often the local anthropogenic stressors are ignored because it comes down to local politics and spending local tax dollars. One of the things once under my purview was a national marine sanctuary program created to save coral reef habitat. I also had coral reef biologists under my administration. It was sort of like building a national park supposedly to protect a threatened resources in the middle of Los Angeles but not wanting to change how LA functioning. Locals and the state love the tourism dollars but has never wanted to spend the money or at least enough money fixing what are now well defined problems affecting the corals. All the things I listed in my first post are well documented problems that have been known for decades. They can be resolved by spending millions not necessarily billions or trillions.
further to my UV radiation comment at 5.04 pm … the widespread bleaching events in the northern GBR were not only about extreme low tides during an El Nino and a consequent increase in UV radiation exposure … concurrent with the extremely low tides, stationary-slow moving high pressure cells delivered long periods of hot, still, cloudless weather to the northern GBR … so, aside from high air temperatures, the lack of cloud cover contributed to an extreme UV radiation dose across the region …
‘Corals can be stressed to the point of bleaching by a lot of things both natural and anthropogenic.’
Bleaching has been around for eons, before humans began polluting. Irradiance on exposed coral and clear skies warming the waters, are side effects of a strong El Nino.
Do you also believe CO2 causes global warming?
I’ll add this to argue my point.
http://i36.tinypic.com/huiyko.jpg
The sea level connection was covered here last year by David Middleton. Repeating my comment from then:
The unmentioned factor is strong sunshine; ie, high UV and TSI during the 2014 sunspot maximum and 2015 TSI maximum, that powered the 2015-16 El Nino.
Solar Radiation As a Cause of Coral Bleaching – Summary
“The link between solar radiation and coral reef bleaching goes back nearly a century to when MacMunn (1903) postulated that ultraviolet radiation could be potentially damaging to corals. It wasn’t until half a century later, however, that scientists began to confirm this suspicion via laboratory and field studies (Catala-Stucki, 1959; Siebeck, 1988; Gleason and Wellington, 1995). ”
Ultraviolet radiation and coral bleaching
“Abstract
EPISODES of coral bleaching resulting from dissociation of endosymbiotic algae (zooxanthellae) from host coral tissues have occurred with increasing frequency over the past decade on reefs throughout the tropics. These episodes have usually been attributed to increases in sea water temperatures, but the mass bleaching events that occurred throughout the Caribbean during 1987 and 1990 were not readily explained by temperature alone. An additional factor that may have contributed to these bleaching episodes is ultraviolet radiation in the 280-400nm band. At many localities where bleaching occurred in 1987 and 1990, sea conditions were described as extremely calm with exceptionally clear water.”
1990 UV & TSI were higher than in 2016; ie, SC22 > SC24.
From Coral Bleaching, UV Effects, and Multiple Stressors in the Florida Keys, which indicates strong sunshine has it’s strongest effect closest to the surface, important under low sea level conditions as described in the post:
https://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.files/fileID/8809
ironic man, I think the bottomline is that corals can be stressed by a lot of different things, both anthropogenic and natural. You are correct coral bleaching has been around a long time. Yet we cannot ignore anthropogenic effects any more than we can ignore natural events. Heck the coral bleaching anomaly maps have been around several decades, long before the modern CAGW excuse arrived and we supposedly had dramatically increasing SSTs. Corals, like most marine organism have been around for a very long time and faced all kinds of climate change, many far more dramatic than we are seeing today. I still would recommend that you look at ALL the coral areas that have reported bleaching and look at local human population growth. The reefs off the Florida Keys are different from the Great Barrier which is different from the reefs off Belize which are different from the coral atolls. Darwin wrote a book about coral reefs, coral atolls, etc which is worth reading. Ironically it was discounted by even his supporters until the 20th Century.
‘Yet we cannot ignore anthropogenic effects …..’
I can, coral bleaching is a natural phenomenon and humanity is not to blame in any way shape or form.
Do you believe CO2 causes global warming?
I rarely read the coral literature, but as noted above there is a body of information in the aquarium industry and field work is very old, especially after WWII. In a 1957 review there are over two dozen papers listed after 1948, plus Darwin, 1837, Mayer, 1918, Daly, 1910, Gravier, 1910, Orr and Morehouse, 1933, Umbgrove, 1939, Wood Jones, 1912 and Yonge, 1940. This paper references nothing predating the current ‘problem.’
Since the coral problem then was destruction from bombing, dredging and oil, the current work may be new, but the concept of static versus dynamic responses in marine animals is not. It is also true for cold.
This is interesting given the past events and work at Kwajalein Atoll. Again all recent literature review.
http://advances.sciencemag.org/content/4/4/eaap9741.full
Hmm, not buying it. It’s a ploy, they’re just pulling back from the excessive coral-doom and media hysteria circus as they’ve over-cooked the hype too much this time, and the wider public are on to them, so the Uni Departmental loonies and Professorial hystrics need to start acting all ‘scientific’ and feign being ‘circumspect’, and all ‘disinterested’ and stuff, until the next grand global freakout, about nothing out of the ordinary.
Or the next propaganda effort, for the next funding grant push. For sure it’s not genuine though, because this stuff has been well understood for decades. Just more spin, damage-minimising and PR salving.
Coral bleaching is the detrimental expulsion of algal symbionts
==========
Detrimental? Nonsense. If it was detrimental the coral wouldn’t do it.
Coral bleaching is the equivalent of kicking your good for nothing spouse out of the house because they won’t get off their ass and help out. And then changing you status on Facebook to single and looking.
Good for the layabout. But you won’t hear the coral complaining.
Or, maybe, as Latitude suggests upthread, coral bleaching is the equivalent of the tenants moving out in the middle of the night (presumably without paying the rent) as a result of the landlord’s failure to properly maintain the property.
Excerpted quote from published article:
Maybe coral reef “bleaching” has nothing whatsoever to do with “increased water temperatures” ……… but everything to do with the bi-daily cycling of the water temperature.
It is a fact of science that all life forms has to “eat” to survive, …… and I would assume that the bi-daily cycling of the water temperature over the coral reef could be responsible for an enhanced daily influx of carbon dioxide and zooplankton, both of which are required nutrients for coral survival.
Anthony Watts writes
Why not invite all the proof-by-assertion alarmists to make false statements on this blog?
Perhaps AW was paraphrasing or joking, everyone knows coral bleaching is a result of natural variables.
no, they don’t.
‘no, they don’t.’
Then they will need to be educated.
Perhaps this is a new approach where the editor is trying to be more inclusive, turning the place into a debating club. I support the idea in principle.
Leo: Please look again- I think the italics are Watts, text is “UCI researchers, right? Your quote is fine example of CAGW, but it’s not Anthony.
“scientists now have a better way to predict the outcome of coral reef bleaching events, which can lead to better conservation strategies”
Don’t interfere, you’ll only make it worse! Have they never heard of the law of unintended consequences?
How many millions of years have corals been getting on just fine without humans poking their noses in?
But superior enlightened people need to feel self-important, fully display their ideological perfection. It’s a heavy burden being an actual superhero who saves the world daily, but we’d be lost without their unsolicited and not at all free, services. Just be thankful they care for stuff more than anyone else. We need them, and they should have our money.
University of California, Irvine?
Sure it wasn’t Cal Polyp?
“Coral reef bleaching is stark evidence of the damage being inflicted by global climate change ” CO2 driven GW is too slow a process to bleach coral.
Exactly, my client CO2 is innocent of all charges.
“a Ph.D. student in UCI’s Department of Civil & Environmental Engineering”
I hope there was a marine biologist associated with this study.
As Prof Jim Steele showed, some bleaching events are caused by sea level fall.