Ocean acidification: 'a stealth asteroid of environmental change'

Planktonic forams floating in the upper levels of the oceans sequester about one quarter of all carbonate produced in the oceans each year.

-- from Nature's Masons by Sean B. Caroll

Dosidicus gigas

To meet a [Humboldt] squid in the wild is one of life's great pleasures. They follow your movements with intelligent, saucer eyes. Their emotions are written on their skin in quick-fire colour changes that pulse and ripple in incandescent waves across their bodies. The Humboldt's uncertain temper adds a little frisson to any encounter. Divers have been roughed up by squid or had their masks or gear tugged. After the adrenalin rush has passed, most divers feel the animals were more curious than aggressive. If they had really wanted to hurt them, with their huge strength they could have done far worse.

-- Callum Roberts in Ocean of Life: How Our Seas Are Changing. [1]

Roberts notes that the Humboldt squid seems to have benefited from expansion of its low oxygen habitat and from the loss of big predatory sharks to overfishing. [2] According to Ron O'Dor, its range has expanded from South America all the way to Alaska as some 90% of large fish have been eliminated by Man. [3] So the species looks like a real beneficiary of the Anthropocene.

On the other hand Rui Rosa predicts the animal's metabolism will drop in future because there will be more carbon dioxide in the water."The squid will be more lethargic and so more vulnerable to their predators because they won't be able to escape them any more." [4] 

Could we, then, be witnessing a spectacular boom to be followed shortly by a spectacular bust in Humboldt squid numbers as a result of human impacts?  Is there a name for species such as this that ride the Anthropocene up and (perhaps) then crash? 

Notes

1. Reviewed in The Economist and the Financial Times. My interview with Roberts will be published in Mandarin and English by Chinadialogue
2. Invasive range expansion by the Humboldt squid
3. The incredible flying squid
4. Synergistic effects of climate-related variables suggest future physiological impairment in a top oceanic predator

The fish in the sea

A study suggests that most fish in the oceans today are descended from freshwater species. One possible implication of this, notes a report is that:

it is possible that seas may be more prone to extinctions than land, rivers or lakes; while rivers and lakes form an "arc of survival" that can reseed the oceans when marine species are lost. 

"I don't think our results show that seas are strongly inhospitable, but they may become so at certain points in time," [says study co-author John Wiens]. Unfortunately, the strong ocean acidification that is predicted for the near future means we may be heading for one of those times now, he adds. 

Today, however, rivers and lakes may not be healthy enough to help re-supply the oceans...

Ten thousand miles in the mouth of a graveyard

Knoll points out some disturbing parallels between today's crisis and a pulse of mass extinctions that occurred 252 million years ago, wiping out an estimated 96% of species in the oceans and 70% of species on land. A rapid increase in carbon dioxide in the atmosphere led, among other things, to ocean acidification. For animals that depended on calcium carbonate, "you had about a 90% chance of going extinct," says Knoll. "Corals, sponges, brachiopods, they all kicked the can."

Knoll doesn't expect human-driven mass extinctions to be as bad as that ancient one. But they could still be unimaginably huge. "If we lose half the species on the planet, our grandchildren are not going to see them restored," says Knoll. "It will take millions of years."

--Carl Zimmer On The Origin of Tomorrow. See Coral Bones passim.

Compound eye of Antarctic krill

Stabledoor, horse?

I didn't make it to the Royal Society meeting last night. This is from Alok Jha's report (emphasis added):

David Attenborough joined scientists today to warn that carbon dioxide in the atmosphere is already above the level which condemns coral reefs to extinction, with catastrophic effects for the oceans and the people who depend upon them.

If this analysis is correct then one of the few options left would to be scrub very large amounts of CO2 out of the atmosphere. But that doesn't look a likely prospect, does it?

See also the Inter-Academy Panel statement on Ocean Acidification.

My review of Veron's book is here.

Stars of future seas?

A species of starfish has confounded climate change doom-mongers by thriving as sea temperatures and acidity increase - a scenario that is likely as the world gets warmer...

...Pisaster ochraceus thrive in temperatures of up to 21 °C and atmospheric CO2 concentrations of up to 780 parts per million - beyond predicted rises for the next century.

DOI: 10.1073/pnas.0811143106.

The Angel

...Scientists say ocean acidity has increased 30% since the Industrial Revolution, the fastest change in ocean chemistry for at least 65 million years...

...The rate of increase [in atmospheric concentrations of CO2] is much faster than only 10-20 years ago...[1]

A Klee painting named ‘Angelus Novus’ shows an angel looking as though he is about to move away from something he is fixedly contemplating. His eyes are staring, his mouth is open, his wings are spread. This is how one pictures the angel of history. His face is turned toward the past. Where we perceive a chain of events, he sees one single catastrophe which keeps piling wreckage and hurls it in front of his feet. The angel would like to stay, awaken the dead, and make whole what has been smashed. But a storm is blowing in from Paradise; it has got caught in his wings with such a violence that the angel can no longer close them. The storm irresistibly propels him into the future to which his back is turned, while the pile of debris before him grows skyward. This storm is what we call progress.

-- Walter Benjamin

Footnote

[1] (added 21.00) See also: Hit the breaks hard at RealClimate

Zapped

The official message is to stabilise CO2 emissions "at a safe level to avoid not only dangerous climate change but also dangerous ocean acidification".

The likely reality, according to James C. Orr, is that "the chemistry is so fundamental and changes so rapid and severe that impacts on organisms appear unavoidable. The questions are now how bad will it be and how soon will it happen."

I'm still trying to take on board what Orr told me in 2006: "Our children will no longer be able to see the amazingly beautiful things that we can. I tell my son, go to see the corals now because soon it will be too late."



P.S. 2 Feb: a post from Simon Donner on coral reefs, a high CO2 world and deep time

P.P.S 11 Feb: Tom Goreau writes:

tropical surface waters will be the LAST part of the oceans where limestone becomes under-saturated. ...Alarm about acidification effects on coral reefs is based on fundamental misunderstanding of the CO2 cycle in tropical surface waters. This is not to say that it is not an important long-term problem, but only that it is trivial compared to bleaching as a source of coral mortality and growth decline.

Getting lumpy on the GBR

Porites are seldom regarded as beautiful. They are, however, often among the most robust coral species. So the decline in calcification rates reported from the Great Barrier Reef looks like a real cause for concern. [1]


In December 2008, notes Elizabeth Pennisi, a 4-year assessment of the Status of Coral Reefs of the World said that 45% of the world's reefs were healthy with no significant threats from human activity on the horizon. [2] But looks can be deceptive. Anne Cohen of Woods Hole says "Even though the corals look healthy, some pretty dramatic changes are occurring beneath the surface." [3]

More on this by John Bruno and Ove Hoegh-Guldberg at Climateshifts.

Footnotes

1. Declining Coral Calcification on the Great Barrier Reef by Glenn De'ath et al. DOI: 10.1126/science.1165283 (See also Declining coral calcification in massive Porites in two nearshore regions of the northern Great Barrier Reef by Timothy F. Cooper et al. DOI: 10.1111/j.1365-2486.2007.01520).

2. Noted on this blog at A glass almost half full. For some background and context see Coral Bones.

3. Calcification Rates Drop in Australian Reefs DOI: 10.1126/science.323.5910.27. Pennisi reports that the role of acidification in this decline is "far from settled". Alina Szmant of the University of North Carolina concludes, "It's not clear that carbon dioxide enrichment will have negative effects on calcification rates." [Question: why did the calcification rate increase by 5.4% between 1900 and 1970 (before falling 14.2% between 1990 and 2005)?]

P.S. 4 Jan: a comment on resilience by Tom Goreau here.

A problem without a name

'Ocean oxygen deprivation', says Ralph Keeling, is the best phrase he has come up with so far to describe the diminution of dissolved oxygen in large areas of the oceans resulting from large-scale, rapid dumping of carbon dioxide into the atmosphere [1]. The impacts on ocean life, said Keeling (speaking at Malente XVII), are likely to be adverse and significant [2].

Keeling invited ideas for a term that would better communicate the nature of the phenomenon. I asked what he thought of 'ocean suffocation' -- arguably a sensational term, but no more so than 'ocean acidification' (which actually refers to a reduction in oceanic alkalinity) [3]. Keeling said he had thought about this, but thought it might excessively sensational. He wanted to hear from biologists [4].


Footnotes

[1] As a result of anthropogenic emissions, CO2 levels are way outside the normal range for at least the last several hundred thousand years, and increasing at least a hundred times faster than at any time during that period.

[2] He referred to Expanding Oxygen-Minimum Zones in the Tropical Oceans by L. Stramma et al. DOI: 10.1126/science.1153847. A news report here.

[3] P.S. 22 Oct: I created a wiki stub for 'ocean suffocation'. On 23 Oct, following discussion with some distinguished oceanographers, this was changed to ocean deoxygenation. 24 Oct: see also this post from Simon Donner at Maribo.

[4] Keeling also said he thought research into the consequences of deep ocean dumping of CO2, "where it may do less damage", should be on the scientific research agenda (although not necessarily on the political agenda) . He couldn't see why it was not as good or better than most options on the table. [For an overview of ocean sequestration see, for example, the ocean acidification network.] In response, Philip Chris Reid was emphatically doubtful, pointing to the rich benthic life that would be affected. A Dutch participant (whose name I missed) highlighted what he said were enormous uncertainties regarding how thousands of microbial species in the oceans, many of them dormant, would react, and suggested that the changes [already underway] might be comparable those of 55 million years ago (I presume he meant the PETM). Sylvia Earle articulated similar concerns to both Reid and the second respondent ["We need to recognise that millions of years evolution and fine tuning have put us where we are with a functioning environment. We should do no harm and protect natural systems. In particular, we don’t know how to put them back together again"]. [See also Seibel and Fabry, 2003.] Keeling answered that to the extent deep ocean CO2 dumping was acute it would be localized, and to the extent it was widespread it was inevitable as the CO2 was heading for the deep oceans and much of that life was probably doomed anyway. Right now, by contrast, CO2 was being dumped into the "most sensitive" top layers of the oceans, and "we may do much better for fish [in the upper layers] by pumping [the CO2] deep"...“We have a global crisis at hand. All mitigation options need to be on the table to assess their merit. This includes less acceptable options such as CO2 sequestration in the deep sea. It may be a bad one but it may be the least bad one.”

Re-tuning the sphere

[Peter Brewer and colleagues] calculated how much [the drop in ocean pH by 0.12 during the 20th century] would affect the absorption of sound waves at 0.44 kHz – the note "A" used to tune an orchestra. They found that by the early 1990s, sound was being absorbed 15% less than in the late 19th century.

Some studies predict ocean pH could drop by an average of 0.3 before the end of this century...The team calculates that this would cause a 40% decrease in the absorption of sounds below 1 kHz. More...

On balance

Few beings are more bizarre when you come to them for the first time than the Crown of Thorns Starfish (COTS). What could be stranger than an animal with multi-axis symmetry that digests living 'rock' (coral) by extruding its stomach? [1]

Monster Mash

Their role in a so-called 'balance of nature' ['dynamic system'?] has been debated (see, for example What is natural? by Jan Sapp). A recently published paper by Hugh Sweatman suggests that a 'healthy' coral reef, with plenty of small inverbrates to eat the juvenile starfish, copes better with COTS (press report). Good news, perhaps, until something bigger comes along.

Note

1. There's a useful Q&A on COTS by Peter Moran of AIMS

'Assisted colonization'

We must contemplate the possibility that some regions of the Earth will experience high levels of warming (>4°C) within the next 100 years, as well as altered precipitation and ocean acidity. Under these circumstances, the future for many species and ecosystems is so bleak that assisted colonization might be their best chance.

-- say Ove Hoegh-Guldberg et al in Assisted Colonization and Rapid Climate Change.

Coral 'extinction'

For some context on One-Third of Reef-Building Corals Face Elevated Extinction Risk see this review of A Reef in Time.

Yes, the shells and reefs dissolve and the 'weeds' take over

Ocean 'acidification' causes concern but understanding of how it may affect marine ecosystems and organisms is 'limited' because almost all studies have been in vitro, short-term, rapid perturbation experiments on isolated elements of the ecosystem [1]. A newish paper [2] about localised acidification caused by undersea volcanic vents seems to confirm best guesses to date:

coralline algal biomass was significantly reduced and gastropod shells were dissolving... The species populating the vent sites...indicate that ocean acidification may benefit highly invasive non-native algal species.

Elsewhere [3], it's noted that avoiding environmental damage from ocean acidification requires reductions in carbon dioxide emissions regardless of climate change:

Projected changes in ocean carbonate chemistry should serve as a guideline for policy protocols that identify CO2 emission targets to reduce the effects of human-made ocean acidification. For example, to avoid a surface ocean pH decline by more than 0.2 units, total emission targets would have to range from ~700 Pg C over 200 years to ~1200 Pg C over 1000 years. Such scenarios would be difficult to achieve, however, because they require immediate reductions in global emissions.

Image: a 'rainbow of death' - explanation here.

Footnotes

1. But field studies from the Southern Ocean have already turned up evidence. See this episode of ABC's Catalyst.

2. 'Volcanic carbon dioxide vents show ecosystem effects of ocean acidification' DOI:10.1038/nature07051

3. Carbon Emissions and Acidification DOI: 10.1126/science.1159124, with news report here.

Acid test

The great concern for scientists is the speed at which the changes are happening. "What [this study] does indicate is that [marine species] may not have time to adapt as we might have hoped for".

-- Caroline Turley, commenting on Evidence for Upwelling of Corrosive "Acidified" Water onto the Continental Shelf.

[See also Sea change and Poised for significant reorganisation.]

Sea change

Some coral species can be amazingly resilient even in the wake of massive nuclear explosions. But bad news about coral reefs and, more widely, the state of the seas remains the default state. In this 'official' International Year of the Reef, and unofficial [deep sea] Coral Week, what pointers for hope?

Andrew Baird and Jeffrey A. Maynard have argued that an analysis by Ove Hoegh-Guldberg et al does not present sufficient evidence to conclude that corals will unable to adapt to climate change and ocean acidification. Hoegh-Guldberg and co respond here.

A recently published study by Deborah Iglesias-Rodríguez suggests that an important organism, Emiliania huxleyi, may actually thrive in a high CO2 world. But Iglesias-Rodríguez says the "hopeful news for 'Ehux' does not overturn the gloomy predictions for corals or negate ocean acidification as an impending ecological disruption" (see also V. Fabry pdf). And Thomas Goreau says that the fact that the cultures were grown under high "nutrient-replete conditions” should be a "serious caveat".

Coral restoration efforts - such as these or these - may be the best hope, where also combined with expanded and effective protected areas.

[P.S. See also Expanding Oxygen-Minimum Zones in the Tropical Oceans, blogged on 6 May as Ocean 'deserts' are increasing as planet warms.]