Bad news for reefs

Ocean acidification could lead to collapse of coral reefs: To better understand the effect of acidification on coral growth decline, Hebrew University scientists led by Prof. Jonathan Erez and Prof. Boaz Lazar at the Fredy and Nadine Herrmann Institute of Earth Sciences, together with Carnegie Institute colleagues Dr. J. Silverman and Dr. K. Caldeira, carried out a community metabolism study in Lizard Island at the Great Barrier Reef in Australia.

The researchers compared calcification rates documented in 2008 and 2009 to those measured using similar techniques in 1975-6. Despite the fact that the coral cover remained similar, the researchers found that the recent calcification rates had decreased by between 27% and 49%. These lower rates are consistent with predictions that took into account the increase in CO2 between the two periods, suggesting that ocean acidification is the main cause for the lower calcification rate at Lizard Island.

While previous studies on individual reef building corals have shown that they lower their calcification rates in response to ocean acidification, in the present study this was demonstrated for the whole community. These findings suggest that coral reefs are now making skeletons that are less dense and more fragile. While they still look the same, these coral reefs are less able to resist physical and biological erosion.

According to Erez and Silverman, "The results of this study show a dramatic decrease in the calcification of the reef, and that it was likely caused by ocean acidification. When the rate of calcification becomes lower than the rate of dissolution and erosion, the entire coral ecosystem could collapse and eventually be reduced to piles of rubble. The collapse of this habitat would ultimately lead to the loss of its magnificent and highly diverse flora and fauna."

This strikes me as a pretty significant study, as I would expect that Lizard Island is a bit less affected by river run off issues than reefs further south. 

Real life ocean acidification

BBC NEWS | Science/Nature | Natural lab shows sea's acid path

Here's a very interesting recent report on some science being done in ocean areas near Italy that already are more acidic due to volcanic CO2 bubbling through the sea.

As expected, the news does not look good for corals, sea urchins, sea snails, and mussels. (I assume that oysters, although they don't get a mention, would also not fare well .) One thing that does well appear to do well is seagrass. I suppose that might mean that one winner out of ocean acidification might be dugong/manatees. I don't know whether they taste any good, though.

Here's the abstract in Nature, but the article itself is behind a paywall. Grrr.

It's also interesting to note the recent stories about the surprising number of bacteria found to be living in the earth's crust under the oceans. The exact role of these in carbon cycling is unknown, but would seem to be potentially very significant. Kind of hard to study bacteria that live best under great pressure, though.

I assume that bottom living bacteria would be very significant to the feared production of poisonous gas if the ocean becomes warm and acidic enough. All a worry.

UPDATE: I hope the tone of my post didn't sound too dismissive of concerns about this.

The Nature paper attracted attention in The Times and The Telegraph. Here's what one of the scientists said in the latter:

Dr Hall-Spencer said: "What we saw was very dramatic and shocking.

"All the predictions made in lab experiments about acidity causing the disappearance of species is coming true.

"When we looked in the field it was already happening.

I must admit I though a lot of the claims being made about species disappearing amounted to scaremongering but now I have seen it with my own eyes.

"Our field studies provide a window on the future of the oceans in a high CO2 world. We show the dramatic ecological consequences of ocean acidification including the removal of corals, snails and sea urchins and the proliferation of invasive alien algae."

"Our observations verify concerns, based on laboratory experiments and model predictions, that marine food webs will be severely disrupted and major ecological tipping points are likely if human CO2 emissions continue unabated."

Also, I note that, although there was a lengthy Sydney Morning Herald story on ocean acidification on 7 June, it did not mention this paper. In fact, I can't see from Google that it has been reported anywhere in the Australian media. Sort of odd, isn't it, given the implications for the Great Barrier Reef?

Discover magazine does ocean acidification in depth

There's a detailed article on ocean acidification just up at Discover magazine. (If you have read this article at Online Opinion, you may be surprised at how similar they are, but I have it on very strong authority that the Online Opinion piece was written without knowledge of the coming Discover article). Here's a lengthy section from Discover worth extracting:

Over the history of the planet, there have been many sudden peaks in CO2 related to volcanic eruptions, releases from hydrothermal vents, and other natural events. When the pH of the ocean dips as a result of absorbing this excess gas, bottom sediments rich in calcium carbonate begin to dissolve, countering the increase in acidity. This buffering process occurs over 20,000 years, roughly the time it takes for water to circulate along the bottom from the Atlantic to the Pacific and back up to the surface several times. Currently, however, we are pouring man-made CO2 into the atmosphere at 50 times the natural rate. “That overwhelms the natural buffering system for maintaining balance in ocean chemistry,” the Carnegie Institution’s Caldeira says. “To find any parallel in the earth’s history you would have to look to a sudden violent shock to the system far in the geologic past.”

One such event occurred 55 million years ago at the so-called Paleocene-Eocene Thermal Maximum (PETM), when 4.5 million tons of greenhouse gases were released into the atmosphere. Just what triggered this enormous emission is not known, but scientists suspect volcanic activity may have begun the process. That may in turn have caused the planet to heat up enough to melt deposits of methane frozen in sediments on the ocean floor (something, incidentally, that could happen again), discharging even more potent greenhouse gases into the atmosphere and further heating the planet in an escalating feedback loop.

Whatever the exact cause of the CO2 release at the PETM, the earth warmed faster than at almost any other time in its history. The average temperature soared 9 degrees Fahrenheit, entire ecosystems shifted to higher latitudes, and massive extinctions occurred on land and, most telling, at sea. The abrupt rise of CO2 acidified the oceans. James Zachos, a paleo-oceanographer from the University of California at Santa Cruz, analyzed sediment cores obtained from deep drilling in the ocean and discovered that bottom-dwelling creatures with shells disappeared from the fossil record for a period of more than 40,000 years corresponding to the PETM. And once the oceans turned more acidic, Zachos says, they did not recover quickly: It took another 60,000 years before sediments again began to show a thick white streak indicative of fossilized shells.

Drastic as the PETM was, the event is tame compared with acidification today. “Back then,” Zachos says, “4.5 million tons of CO2 were released over a period of 1,000 to 10,000 years. Industrial activities will release the same amount in a mere 300 years—so quickly that the ocean’s buffering system doesn’t even come into play.”

I wonder when any global warming sceptic is going to come up with convincing reasons why ocean acidification is not something to worry about. In fact, when are they going to give it any attention at all.

UPDATE: I've noticed that the figure of 4.5 million tons of CO2 being released during PETM must be an error. If you follow the link in the article (about PETM,) it indicates it should be 4.5 Gt. Disappointing to see an error like that turn up at Discover, but I'll email them now!

Report explained - news not good

Station ALOHA data reveal ocean acidification

A few posts back, I had a post updating some recent stuff on ocean acidification, and ended noting a study on waters near Hawaii that examined the 20 year history of pH levels. I said it was kind of hard to understand clearly, as at that time I only had a link to the paper itself, and scientists aren't all that good at writing clear summaries.

Anyhow, my guess as to what it meant was correct, as shown in this easier to understand summary linked above:

.....over the two decades of observation, the surface ocean grew more acidic at exactly the rate expected from chemical equilibration with the atmosphere. However, that rate of change varied considerably on seasonal and inter-annual timescales, and even reversed for one period of nearly five years. The year-to-year changes appear to be driven by climate-induced changes in ocean mixing and attendant biological responses to mixing events.

The authors also found distinct layers at depth in which pH declines were actually faster than at the surface. Dore and colleagues attribute these strata of elevated acidification rates to increases in biological activity and to the intrusion at Station ALOHA of remotely formed water masses with different chemical histories.

This seems to me to be a pretty important study, as it is confirmation from long term measurements that the predicted rate of ocean acidification is correct. (The fact that there are bumps along the way is, I suppose, like the difference between weather and climate.)

To the extent that they note that at depth, acidification at times seems to be happening faster than expected, is not good news.

A serious ecological consequence of global warming

Ocean acidification as a result of increasing CO2 doesn't get mentioned often lately, although it presumably continues to increase.   (There was, no doubt, some sloppily done lab based experimentation on this with fish and other creatures which I think has perhaps harmed its reputation amongst science journalists.  But the problem is still real.)  

The other big problem in the oceans from global warming is the increase in lack of oxygen as the water warms, and I have mention it from time to time over the years.  (You can search "ocean oxygen" in the search bar at the side, if you like.)

There was an article about it in Science recently, and yeah, maybe it will be a race between it and acidification as to which will cause the most serious ecological collapse within the next few decades.  Some extracts:

Climate change is leaching oxygen from the ocean by warming surface waters. Two other climate-related threats to the seas—ocean acidification and marine heat waves—get more attention from scientists and the public. But some researchers believe deoxygenation could ultimately pose a more significant threat, making vast swaths of ocean less hospitable to sea life, altering ecosystems, and pushing valuable fisheries into unfamiliar waters. As global warming continues, the problem is sure to get worse, with disturbing forecasts that by 2100 ocean oxygen could decline by as much as 20%. Sharks—fast-moving fish that burn lots of oxygen, sit at the top of food chains and crisscross huge ocean expanses—should be sensitive indicators of the effects....

SCIENTISTS FOR YEARS have documented oxygen-starved dead zones in places like the Gulf of Mexico and the Baltic Sea. There, pollution from nutrients running off the land, such as synthetic fertilizer, sparks algae blooms. Microbes feast on the rotting vegetation, consuming oxygen. A surge of low-oxygen water can flood an area so quickly that crabs, sea stars, and even fish suffocate before they escape. Low-oxygen zones also form naturally along the western edges of the Americas and Africa, where oxygen-depleted water that hasn’t seen daylight for decades wells up.

In the open ocean, currents and storms churn the water, keeping oxygen levels higher. Yet since the 1990s climate models have foretold that a warming climate would deplete oxygen there, too. Surface water warmed by rising air temperatures holds less oxygen, and the growing temperature contrast between surface layers and colder, deeper water slows the mixing that transports oxygen into the depths. At higher latitudes, melting ice can flood surface layers with fresh, low-density meltwater, strengthening the layering and reducing mixing.

In 2008, a paper in Science sounded the alarm. German and U.S. scientists found that the low-oxygen zones off Africa and the Americas were growing deeper and losing still more oxygen. Since the 1960s these areas had expanded by about 4.5 million square kilometers, close to the area of the European Union. In the waters frequented by Sims’s sharks off Africa’s northwest coast, the low-oxygen layer had nearly doubled in thickness over 5 decades, from 370 meters to 690 meters. By 2008 its top had risen to less than 150 meters below the surface. The global trend, the scientists warned, “may have dramatic consequences for ecosystems and coastal economies.”

In 2017, scientists delivered more troubling news in Nature. Overall, the world’s oceans had already lost some 2% of their oxygen since 1960, roughly double what climate models predicted.

For Andreas Oschlies, a biogeochemist at the GEOMAR Helmholtz Centre for Ocean Research Kiel and a leading expert on modeling oxygen in the ocean, the implications were staggering. If the trend continues, it could mean a potential loss of 20% by 2100, he says. That’s equal to going from sea level to more than 2000 meters elevation on land. “I thought ‘Wow!’” Oschlies recalls. “That’s the biggest change and maybe the most worrying change that we see in the ocean. Immediately I thought of (past) major extinction events.” For example, at the end of the Permian period 256 million years ago, rising ocean temperatures and an 80% plunge in oxygen levels helped drive the largest extinction in Earth’s history. Up to 96% of all marine species disappeared.

By comparison, the 2% drop in oxygen levels seen so far might not sound like much. But global averages can be misleading, warns Lisa Levin, a biological oceanographer at the Scripps Institution of Oceanography who has studied the effects of low oxygen on ocean ecosystems for more than 30 years. “There are places in the ocean where there’s been much bigger declines,” Levin says. “These changes are probably very important.”

 

 

 

Your bad ocean acidification news for the week

Poor Malcolm Turnbull. He sounds half reasonable to me on the topic of CO2 emissions but is caught in a bind. Even though the Rudd ETS is probably an extravagant waste of time from a scientific point of view, as is probably about 95% of all nations' approaches to greenhouse gases, people like the idea of doing something better than the idea of doing nothing. Politically something has to be done, but a divided Coalition is giving every reason for the public to think they can't be trusted to do a damn thing.

Why do no politicians talk of ocean acidification as an independent reason for taking action? Here's some more depressing news from the ocean acidification blog:

* two studies indicating bad news for corals due to effects on important symbiotic relationships

* some reef fish don't seem to like it either

* another study showing a couple of bivalves (clams and scallops) don't take lower pH well.

I saw Malcolm Turnbull on Insiders last Sunday arguing that action on AGW was the prudent thing to do given the weight of science. Quite right; but why not also mention ocean acidification, given that it appears increasingly well founded that future changes to ocean chemistry are a gigantic ecological crapshoot.

Ocean acidification update

It's been a while since ocean acidification has been mentioned here. There have been more studies reported, often with confusing or uncertain results:

* it was reported a month ago that tank studies with fish indicate that they grow bigger ear bones in more acidified water. This is the opposite of what was expected. Does it matter? No one knows, but there is speculation it might affect affect their navigation and orientation. Presumably, the studies to look into that are underway.

* The latest studies for coral are quite mixed. One tank study on a species of Mediterranean temperate coral indicates that it is not particularly sensitive to more CO2. (Although it is noted that this might be because it is relatively slow growing coral.) Yet, another study shows a mechanism for how a Hawaiian species can suffer more erosion under higher CO2. A third study, this time on an Atlantic species, indicated that it was indeed sensitive to decreased aragonite saturation (which is a consequence of increased acidification.) The overall picture then: still not good seems a fair conclusion.

Update: overnight, another paper has turned up indicating that coral around Bermuda:

...will experiences seasonal periods of zero net calcification within the next decade.... The Bermuda coral reef is one of the first responders to the negative impacts of ocean acidification, and we estimate that calcification rates for D. labyrinthiformis have declined by >50% compared to pre-industrial times.

* So, what about phytoplankton?, I hear you say. (Assuming you are still awake.) Well, this seems unexpected, but it seems some tank tests in coastal waters off Norway indicate that higher CO2 can lead to a phytoplankton bloom which then leads to more dissolved iron being in the water. (I don't quite follow how that works.) Anyhow, the abstract notes that this may be a good thing:

"If applicable to the open ocean this may provide a negative feedback mechanism to the rising atmospheric CO₂ by stimulating marine primary production."

Of course, whether this happens out in the deep ocean is not known. And are phytoplankton blooms in shallow areas necessarily a good thing? Certainly, some algal blooms are not good.

* On a related issue, if AGW does increase water temperatures, it seems that it will cause a significant shortening of the lifespan of many cold-blooded creatures:

“We were intrigued by the fact that that pearl mussels in Spain have a maximum lifespan of 29 years, while in Russia, individuals of the same species live nearly 200 years,” said Dr. Munch....

For the study, the researchers looked at lifespan data from laboratory and field observations for over 90 species from terrestrial, freshwater, and marine environments.

They studied organisms with different average longevities-from the copepod Arcartia tonsa, which has an average lifespan of 11.6 days, to the pearl mussel Margaritifera margaritifera, which has an average lifespan of 74 years.

They found that across this wide range of species, temperature was consistently exponentially related to lifespan.

“It is interesting to consider how cold-blooded species are likely to react in the face of global warming. Because of the exponential relationship between temperature and lifespan, small changes in temperature could result in relatively large changes in lifespan. We could see changes to ecosystem structure and stability if cold-blooded species change their life histories to accommodate warmer temperatures but warm-blooded species do not,” said Salinas.

It surprises me that a consistent relationship between temperature and life span was not noticed before.

* Someone should tell scientists how to write more clearly. There is a lengthy paper here about pH testing of the ocean near Hawaii over a number of years, but I have trouble working out exactly what it concludes. I think it indicates that ocean surface pH is dropping as expected (subject to seasonal variability), but the picture at depth was more complicated than they expected.

Oceans going down

I see that Oceanography has a special issue out about changes to ocean chemistry, which means in large part it's about ocean acidification.

I think all of the articles are available as .pdfs, so I won't bother linking to individual ones.

But having a look at a couple of them, the take away messages are:

*  the oceans at all parts of the world are showing declining pH dues to increase CO2 in line with predictions

*  coastal oxygen free "dead zones" are increasing and are likely to continue increasing with warming temperatures.  (This has been predicted for some time too.)

I don't do many posts about ocean acidification lately, but looking through the Ocean Acidification blog, there is plenty of research still going on, much of it with worrying results.  It seems to be a frequent theme that both oysters and scallop growing areas in North America are already suffering due to coast water acidification.  Although there is a natural variation to pH in those areas anyway, the slow increase in surface acidification is obviously not helping.

Many studies look at developmental and behavioural changes displayed by various species under decreased pH, but it is obviously very difficult to work out how they will play out in the future oceans.   Some species indicate some adaptive ability, but the big picture is enormously hard to predict.

I still think the pteropods are like the canary in the coal mine on this issue.  A study in 2012, which was looking at pteropods taken in 2008, found that those in aragonite undersaturated waters were showing severe shell erosion already.    A future collapse in this extensive species which feeds many of the sort of fish we like to eat could be dire. 

So, for all of the talk of lower rates of temperature rise and when that will turn around, this is the issue that climate change deniers larger ignore or simply dismiss as another scientific disaster story told to ensure funding. 

They are ignorant and dangerous to the future of humanity.

Some (pretty rare) good news on ocean acidification?

Researchers discover oysters can adapt to climate change - ABC Rural (Australian Broadcasting Corporation)

From the article:

Sydney rock oysters can adapt to ocean acidification, a key effect of
increased carbon levels, within two generations, researchers have found.

Research on Sydney rock oysters and ocean acidification has been going on for years, I believe, although I bet that most of the public is not aware of it.

Two things make me cautious, though, about this apparent good news re adaptation:

1.   in the US, ocean pH has already been clearly implicated in widespread oyster die off in certain coastal parts where upwhelming deep water already causes big pH changes.  So, the thing is, while oysters may cope with gradual average changes in pH, I wonder whether even in Australia they might be made more susceptible to temporary drops in pH when  the average has gone down.

2.  I think the evidence from the last huge ocean pH change was always that clams dominated the ocean floor, so I am not surprised that bivalves might be able to adapt.  However, there is also little doubt that the last event involved acidification at a much slower rate than what we are doing, and still the oceans ended up having a huge extinction of species.   The success of oysters may well be not that much to celebrate, even if they are tasty.

Oyster and coral alert

Time for some ocean acidification news.

Oysters grown on the West coast of American have been having a hard time.  As this story noted in 2009:

In 2005, when most of the millions of Pacific oysters in this tree-lined estuary failed to reproduce, Washington’s shellfish growers largely shrugged it off.

In a region that provides one-sixth of the nation’s oysters – the epicenter of the West Coast’s $111 million oyster industry – everyone knows nature can be fickle.

But then the failure was repeated in 2006, 2007 and 2008. It spread to an Oregon hatchery that supplies baby oysters to shellfish nurseries from Puget Sound to Los Angeles. Eighty percent of that hatchery’s oyster larvae died, too.

Now, as the oyster industry heads into the fifth summer of its most unnerving crisis in decades, scientists are pondering a disturbing theory. They suspect water that rises from deep in the Pacific Ocean – icy seawater that surges into Willapa Bay and gets pumped into seaside hatcheries – may be corrosive enough to kill baby oysters.

Well, now it seems the suspicions of high CO2 having something to do with this may have been confirmed.  Someone had the good idea to actually takes measurements of the water used:

Increased pCO2 and decreased pH have been shown to negatively impact larval development in C. gigas (Kurihara, 2007). Periods of elevated pCO2 in May and June 2010 correlated with commercial losses at WCH.

In another study, decreased pH was shown to decrease shell strength of pearl oysters (although it doesn’t appear that they looked at the pearls themselves.)

And for corals, another recent study indicated that a combination of even modest water temperature increase and lower pH has a big effect on coral growth and survival:

Holger babysat 40 of the baby corals for 42 days under four different conditions: In the first tank, the researchers simulated 1C of ocean warming; in the next, they simulated ocean acidification by bubbling carbon dioxide through the tank to lower the pH by 0.25; the third combined this warming and acidification; and a fourth tank maintained current ocean conditions as a control.

“The different conditions had absolutely no effect on the ability of the larva to settle – to stick to the rock surface – which may be good news for people who are trying to grow coral gardens,” Aaron says.

But post-settlement, some of the young coral polyps were showing the effects ‘global warming’.

“The biggest surprise was that neither temperature alone, nor acidification alone had a big effect on the growth or survival rate [95%] of the coral, even though the warming prompted zooxanthallae expulsion as expected,” Aaron says. “Once we combined this moderate warming and acidification, though, we saw significant impacts: growth rate of the polyps – for both the skeletal and soft pulpy mass – plummeted to almost half of the rate seen under the other three conditions, and they were twice as likely to die [90% survival rate].”

The link to the actual study abstact is here.

And finally, if these Europeans have it right, the decrease in aragonite saturation (important for some corals and shellfish) is going to be on a rapid downward spiral this century right around the world:

If you want to read the tiny words, and look in more detail at the original, go here.

Ocean acidification continues

USF Study Shows First Direct Evidence of Ocean Acidification

Actually, that headline is misleading, in that studies off Hawaii and Iceland have already shown acidification at the rate predicted. The new point about this study is that it covered a wide area of ocean instead of looking at just one spot.

The abstract of the paper is not too long, and I may as well repeat it here:

Global ocean acidification is a prominent, inexorable change associated with rising levels of atmospheric CO₂. Here we present the first basin-wide direct observations of recently declining pH, along with estimates of anthropogenic and non-anthropogenic contributions to that signal. Along 152°W in the North Pacific Ocean (22–56°N), pH changes between 1991 and 2006 were essentially zero below about 800 m depth. However, in the upper 500 m, significant pH changes, as large as −0.06, were observed. Anthropogenic and non-anthropogenic contributions over the upper 800 m are estimated to be of similar magnitude. In the surface mixed layer (depths to ∼100 m), the extent of pH change is consistent with that expected under conditions of seawater/atmosphere equilibration, with an average rate of change of −0.0017/yr. Future mixed layer changes can be expected to closely mirror changes in atmospheric CO₂, with surface seawater pH continuing to fall as atmospheric CO₂ rises.

Now I'm a believer

I’m officially ceasing my sitting on the fence about greenhouse gases, but want to make a few things clear.

It is right to worry about greenhouse gases, and to worry quite a lot. For me, the most convincing reason for this is actually not directly the issue of global warming, which still carries uncertainty about its likely extent and its full consequences, but rather ocean acidification.

The recent Scientific American article I posted about here gives good reason to worry about the global situation if CO2 levels ever reach 1000 ppm. (Short explanation: if oceans or seas become sufficiently lacking in oxygen and warm enough, hydrogen sulphide producing bacteria might make enough gas to cause enormous deadly gas bubbles that could wipe out life on nearby land.) The problem is, as noted in my recent post here, the world could get up to 700 ppm by the end of this century, and despite what the Scientific American article says, it would seem it need not take another century beyond that to crack 1,000ppm.

Going back and looking at other articles on ocean acidification, it seems to me that the environmental effects of that are relatively easy to test and accurately predict. (It doesn’t take much to set up a large tank and change the Ph and see what it does to plankton or coral shells.)
As plankton plays a significant role as a CO2 sink in the deep oceans, surface acidification to an extent that would cause a decrease in plankton would also seem to be a major worry for accelerating the rate of increase of atmospheric CO2.

The other issue that gives me concern is that letting CO2 levels get close to 1000 ppm may make it extremely easy for some uncontrollable event to lead to a sudden disastrous global increase. (For example, a supervolcano system suddenly springing to life, or an asteroid hit or two. If I understand it correctly, anything that kicks up a lot of dust would initially cool the earth, but the greater greenhouse gases would eventually kick in.)

That’s my reasoning for deciding that there is not much point in nitpicking over the arguments about how much hotter increased CO2 levels may make the world. Seriously bad effects on the oceans seem certain with sufficiently high CO2 levels anyway.

Of course, Phillip Adams and his ilk are in full gloating “told you so” mode about the fact that politicians on the the Right are starting to sound more serious about the issue. (It seems to me that Adams is wanting to take far more credit for early recognition of the issue than his published columns indicate he deserves.) My impression is that ocean acidification issue has really only started attracting a lot of attention in the last couple of years anyway.

Also, to be clear about my position, there are several things related to global warming of which I remain either dismissive or at least very sceptical:

1. the Kyoto Treaty;

2. wind power;

3. Carbon offset schemes which involve growing trees, especially if they are in areas where bushfires are a distinct possibility. (It is my suspicion that many companies promoting carbon offset schemes are selling snake oil when it comes to their long term effect.)

4. Environmentalists and politicians who claim Pacific Islands are already disappearing from increasing sea levels caused by global warming. (In another 30 years or so, maybe. But hey, just how viable is any 2 metre high island nation built in the middle of the ocean anyway.)

5. Politicians who resist nuclear power on principle.

6. Dismissal of the sun’s role as being possibly significant for temperatures over the next century.

7. Believing that the current Australian drought is necessarily related to global warming.

8. Arguing that current short bouts of surprising cooler weather are a sign that global warming is not true, and that greenhouse gases are not worth worrying about. (Sorry Tim Blair, they are funny, but I think no serious climate scientist is concerned about them disproving the theory.)

9. “The Day after Tomorrow” scenarios to do with the sudden “switching off” of the Atlantic ocean conveyor current. (Real Climate recently chided The Guardian for getting reporting of recent research on this completely wrong.)

10. The more excitable predictions about the number of birds, frogs, spiders, polar bears etc likely to be lost as a result of global warming.

The fact that Rupert Murdoch and me have suddenly reached the same conclusion is, of course, simply a sign that great minds think alike. He's a sharp old codger, isn't he?

Phytoplankton worry

Green wet stuff continues to make the news. A new study in Nature indicates a large decline in the amount of phytoplankton in the oceans over the last century:

Phytoplankton activity fluctuates widely according to season and location, making long-term monitoring of trends difficult. An earlier study², based on satellite observations of ocean colour, suggested a link between climate variability and ocean productivity, but this was limited to observations from 1997 to 2006. Boris Worm, a marine biologist at Dalhousie University in Halifax, Canada, and his team have now combined satellite-derived observations of phytoplankton with historical shipboard measurements stretching back to the pioneering days of oceanography.

The research reveals an unsettling centennial downwards trend, superimposed on shorter-term variability. The scientists found that the average global phytoplankton concentration in the upper ocean currently declines by around 1% per year. Since 1950 alone, algal biomass decreased by around 40%, probably in response to ocean warming — and the decline has gathered pace in recent years.

"Clearly, 40% is a huge number," says Paul Falkowski, an oceanographer at Rutgers University in New Brunswick, New Jersey. "This implies that the entire ocean system is out of steady state, slowing down.

Something to worry about? Well, yes:

"This is severely disquieting," adds Victor Smetacek, a marine biologist at the Alfred Wegener Institute of Polar and Marine Research in Bremerhaven, Germany. "One must really digest the very magnitude of this decline and its possible implications."

The culprit is believed to be ocean warming:

In most regions tested, the phytoplankton decline seems to be the result of a 0.5–1.0 °C warming of the upper ocean over the past century. The warming leads to enhanced vertical 'stratification' of ocean layers, thus limiting the supply of nutrients from deeper waters to the surface.

But ocean warming does not explain reduced productivity in regions, including the Arctic Ocean, where algal growth is mainly constrained by sunlight. So scientists must try to find out what other drivers, such as changes in wind and ocean circulation, might force the decline, says Falkowski.

No one is pointing the finger at ocean acidification yet, and (from memory) experiments with bubbling CO2 through phytoplankton have had mixed results. But there was this story recently that increased acidification may affect the availability of iron, which phytoplankton need to grow well. (There is more detail on that study at my earlier post.) So, I wonder if acidification over the last century is part of the explanation.

Ocean acidification and iron: bad for phytoplankton

Acidifying Ocean May Stifle Phytoplankton - Science News

Some people argue that increased CO2 will result in more phytoplankton blooms, which will help sink more CO2 to the bottom of the sea.

One study that appeared a couple of weeks ago in Science suggests that this may not happen due to the lower water pH that the increased CO2 is definitely already causing:

Research by oceanographer Dalin Shi and his colleagues at Princeton University hints that rising CO₂, instead of providing extra nutrients for phytoplankton, may actually curb the growth of these organisms, which form the base of the ocean’s food chain. The team reports these findings online January 14 and in an upcoming Science.

In their tests, the researchers studied how acidification, a decline in ocean pH, affects the ability of phytoplankton to take up dissolved iron, another nutrient required for growth. The scientists measured growth rates of four species of the marine microorganisms — including two that Shi described as “the lab rats of phytoplankton” — in ocean water with pH values that ranged from 8.8 to 7.7. On average, the pH of ocean surface waters today is about 8.08, says Shi.

Across large swaths of the ocean, phytoplankton are already starved for iron, Shi says. And the team’s research suggests that acidification will make things worse: If ocean pH drops by about 0.3 units over the next century — the acidification expected if CO₂ emission trends continue — iron uptake by phytoplankton could drop by between 10 and 20 percent, the data suggest. Ironically, even though more-acidic waters are able to hold increased amounts of dissolved iron, a larger percentage of that nutrient would be chemically bound to organic matter dissolved in the water and therefore unavailable to nourish phytoplankton, Shi says.

More care needed

Crucial ocean-acidification models come up short : Nature News & Comment

Interesting article here, noting that a lot of the uncertainty in working out the ecological effects of ocean acidification  comes from experimenters (especially those at the start of research into this) not being careful enough with the experimental set up. 

I had noticed myself that, over the years, after the initial flurry of reports about the dire effects on different organisms, there followed a lot of considerably more ambiguous reports from tank experiments.   And, yes, it had been noted before that how the water chemistry is altered is important.

But do the researchers writing this paper think this means there is not a serious problem for the oceans?  Nope:

Cornwall says that the “overwhelming evidence” from such studies of the
negative effects of ocean acidification still stands. For example,
more-acidic waters slow the growth and worsen the health of many species
that build structures such as shells from calcium carbonate. But the
pair’s discovery that many of the experiments are problematic makes it
difficult to assess accurately the magnitude of effects of ocean
acidification, and to combine results from individual experiments to
build overall predictions for how the ecosystem as a whole will behave,
he says.

 This article also notes that not enough experiments have looked at the combination of warming water and decreasing pH together.

Your weekly ocean acidification news

Comment on "Phytoplankton Calcification in a High-CO2 World" -- Riebesell et al. 322 (5907): 1466b -- Science

Readers interested in my ocean acidification posts* will recall that there was a big surprise earlier this year when one study suggested that one species of calcifying phytoplankton actually got substantially heavier with more CO2 in the water.

The suggestion was that this may work as an important new CO2 sink, and was quite contrary to previous studies which showed the coccolithophore shells getting smaller with increased ocean acidity.

There was some muttering at the time by other scientists that this study could have been flawed, and now, see the link for a detailed comment by a group of scientists who think they have the problems with the experiment.

The comment is worth reading as setting out the basic issues with acidification and calcification.

Basically, this group still sounds very pessimistic about the "winners" outweighing the "losers" in ocean acidification.

* and who knows if there are any? - no one ever comments on those posts, which just encourages me to continue grinding my teeth about how most of the world is ignoring this issue.

Ocean acidification continues apace, with hardly anyone noticing

From Nature Climate Change:

The uptake of anthropogenic CO₂ by the ocean decreases seawater pH and carbonate mineral aragonite saturation state (Ω_arag), a process known as Ocean Acidification (OA). This can be detrimental to marine organisms and ecosystems^{1, 2}. The Arctic Ocean is particularly sensitive to climate change³ and aragonite is expected to become undersaturated (Ω_arag < 1) there sooner than in other oceans⁴. However, the extent and expansion rate of OA in this region are still unknown. Here we show that, between the 1990s and 2010, low Ω_arag waters have expanded northwards at least 5°, to 85° N, and deepened 100 m, to 250 m depth. Data from trans-western Arctic Ocean cruises show that Ω_arag < 1 water has increased in the upper 250 m from 5% to 31% of the total area north of 70° N. Tracer data and model simulations suggest that increased Pacific Winter Water transport, driven by an anomalous circulation pattern and sea-ice retreat, is primarily responsible for the expansion, although local carbon recycling and anthropogenic CO₂ uptake have also contributed. These results indicate more rapid acidification is occurring in the Arctic Ocean than the Pacific and Atlantic oceans^{5, 6, 7, 8}, with the western Arctic Ocean the first open-ocean region with large-scale expansion of ‘acidified’ water directly observed in the upper water column.

Oceans and Plimer

Most Australian readers would probably know already of the global warming skeptics excitement about a new hefty book by geologist Ian Plimer that (apparently) sets out with lots of footnotes his opinion as to why the great majority of climate scientists are wrong.

While we are waiting for some climate scientist types to review it in detail, I am curious as to whether he makes any attempt at addressing ocean acidification. As remarked here many times, this is an issue skeptics just like to wave away with a few dismissive snorts, and that's about the extent of their analysis. (Yes, I am aware of Plimer's previous short contributions to the issue, such as this one noted last year at Marohasy's blog. Anyone who has bothered to read about the issue can readily spot that this was a disingenuous attempt at dismissing it, and does not address the reasons why it is believed to be a serious problem regardless of the oceans surviving past periods of high atmospheric CO2.)

In fact, I haven't posted anything new about ocean acidification for a few weeks, but there have been quite a few papers of note, such as:

* some new calculations indicate that ocean "dead zones" will increase:

increases in carbon dioxide can make marine animals more susceptible to low concentrations of oxygen, and thus exacerbate the effects of low-oxygen "dead zones" in the ocean.

Brewer and Peltzer's calculations also show that the partial pressure of dissolved carbon dioxide gas (pCO2) in low-oxygen zones will rise much higher than previously thought. This could have significant consequences for marine life in these zones.

* (if I am reading this right) some lab tests indicate that phytoplankton in nutrient poor ocean areas (such as the Southern Oceans, which will be affected first by lower .pH) don't do well with increased CO2.

* A paper notes the wildly conflicting results of different lab tests on whether a certain type of phytoplankton will get heavier or lighter with more ocean acidification. However, even if they do in nature get heavier, they will not make a significant reduction in CO2 levels in the atmosphere:

...it should be recognized that the direct impact of calcification changes on atmospheric CO2 through the remainder of this century is relatively small compared to anticipated annual emissions as well as to other carbon cycle feedbacks.

(Hence, if AGW is true, you can't expect the carbon incorporating phytoplankton to save you.)

* more research indicating pteropods (which feed a lot of fish) don't do well with increased acidfication. The researchers note:

A decline of their populations would likely cause dramatic changes to the structure, function and services of polar ecosystems.

Not exactly cheery news.

Kevin and Penny don't spread the word

Magnetic Island News - Magnetic Island, North Queensland, Australia

Late last week on the TV news we saw Kevin Rudd and Penny Wong going for a look at a bit of a look at the Great Barrier Reef, and afterwards talking about how global warming will harm it.

I see from that famous newspaper, The Magnetic Times, that Rudd was told about more than global warming. It would appear that ocean acidification got a detailed mention too. From the above link:

Katharina Fabricius, a Principal Research Scientist from the Australian Institute of Marine Science (AIMS), who, along with fellow Magnetic Islanders, Dr Glenn De'ath and spatial analyst Stuart Kininmonth, is involved in a soon-to-be released web-based atlas of the reef, told Magnetic Times, "Sheriden had three hours to brief the Prime Minister who then gave a twenty minute speech in the Council Chamber that showed he really got the message. It went really well.” ....

Dr Fabricius described the serious effects of climate change on the reef which has prompted the making of the Atlas. “Climate change is already evident on the reef in two forms. One is water temperature which, from records which go back to the 1870s, shows that the ocean's water temperature has increased by 0.7 degrees C in the last hundred years. Corals have a low tolerance to only minor increases in water temperature, and hot water has led to the mass bleachings that have begun to happen in the last twenty years.”

“Of even greater concern is ocean acidification. The world's oceans absorb about half of the atmosphere's CO2. With increased CO2 in the sea water it becomes more acidic. Models predict that the pH (the measure of acidity and alkalinity) has already declined by 0.1 units which means that shellfish, crustaceans, corals and other marine creatures which utilise the carbonate in the water are less able to calcify.”

Well, why on earth in the evening TV news grabs don't we hear the PM, Penny Wong and others talking specifically about ocean acidification as a vital issue if Australia wants to preserve its extensive coral reefs? They clearly know about it, yet for some reason it still gets little media attention.

It also remains the issue that Andrew Bolt never mentions, I suspect because he can't find any credible ocean scientist type who can rebut the dire concerns other than by saying "it's all a conspiracy, everything will be alright, you just wait and see."

Plimer's oceans (and why salmon matter more than you think)

When it first came out, I was led to believe by a radio interview that Ian Plimer's "Heaven + Earth" did not address ocean acidification in detail.

It turns out that was a mistake. Someone at Marohasy's blog, where I occasionally enter the fray, pointed out that Plimer had a section of about 8 pages (from memory) on the topic.

Over the weekend, I was in Adelaide (travelogue post to come) and was able to browse quickly through Plimer's book in the Museum of South Australia bookshop. (!) Indeed, he does address the topic, but from my quick look, I am certain that a very thorough Fisking of that section could easily be done by anyone who has actually read things such as the Royal Society 2005 paper.

However, there's no way I am forking out $40 for the privilege of doing that.

If anyone knows how I could get my hands of those pages from the book, I would be happy to hear from you.

[Now for my attempt to be "fair and balanced", just like my favourite TV news network. (Well, I do like quite a lot of it.) It is definitely the case that popular media reporting of ocean acidification is increasingly using terms which suggest that the ocean will actually become acid in future. This is completely misleading and inaccurate, but it gives Plimer a straw man to complain about. (By the way, I could see from my quick browse of his book that Plimer spends a lot of time repeating what he briefly says in that link, namely, that the oceans can't go acidic. Yes, Ian, we know that.)

The scientific concern has never been that humans burning carbon can turn the oceans' .pH from the alkaline side of the scale into acid. Rather, the reduced alkalinity alone has sufficient effect on the ocean's carbonate chemistry to have effects on its ecology. There's no way the ocean is going to go completely sterile, but the worry is that pretty damned big changes are underway, as has happened in the past.*

I can understand Plimer and the skeptics being annoyed at the way the media is reporting it, but by the same token, it is disingenuous of him to spend time arguing how the oceans cannot "turn into acid" when that was never the issue.]

* I heard for the first time, in a recent nature documentary on the ABC about the salmon breeding cycle in North America, about how the massive number of salmon that die far inland after spawning are now believed to provide a lot of the nitrogen that the huge conifers there need to grow. So, it would seem a reasonable assumption that, if future acidification reduces salmon food and decreases that population, the coastal forests of North America are going to suffer in the long run too. It's a good example of why it is prudent not to just take the attitude that the ocean ecology will sort itself out and we don't have to worry about it.