Tag Archives: Ocean acidification

“More acidic ocean could spell trouble for marine life’s earliest stages”

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EurekAlert!, 31st July 2008

Increasingly acidic conditions in the ocean—brought on as a direct result of rising carbon dioxide levels in the atmosphere—could spell trouble for the earliest stages of marine life, according to a new report in the August 5th issue of Current Biology, a publication of Cell Press. Levels of acidification predicted by the year 2100 could slash the fertilization success of sea urchins by an estimated 25 percent, the study shows. " If other marine species respond similarly—and there’s no evidence yet that they don’t—then we’re in trouble," said Jon Havenhand of the University of Gothenburg in Sweden. "The analogies are quite simple: we observed a 25 percent reduction in fertilization success at reduced pH, which is equivalent to a 25 percent reduction in the spawning stock of the species. Apply equivalent changes to other commercially or ecologically important species, such as lobsters, crabs, abalone, clams, mussels, or even fish, and the consequences would be far-reaching. It could be enough to "tip" an ecosystem from one state to another." However, he emphasized, more data about the response of growing acidic conditions on more species is needed before any such extrapolation can be made. Widely cited estimates show that the average level of acidity in the oceans has risen by about 25 percent in the last 150 years, since the advent of fossil fuel burning, Havenhand explained. The most recent data show that levels of ocean acidification predicted for the end of this century—about a three-fold increase over current levels—have already been measured in some coastal waters. Continue reading →

Does humanity have the foresight to save itself?

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Mark Lynas is well known for his excellent book Six Degrees: Our Future on a Hotter Planet from 2007. In a recent edition of the Guardian (June 12 2008), he reports on the outcome of the Stockholm Network think tank examining current and future responses to climate change. The think tank concluded that the present scenario, which is called “agree and ignore”, and one which is referred to as “Kyoto Plus”, will not result in emission reductions before 2030.

The consensus within the modeling community is that we will exceed 450 ppm if global emissions do not begin to decline within the next 8 years. At this point, as argued here and elsewhere, we will lose coral reefs, wet tropical rain forests and many other high biodiversity systems. We will almost certainly enter in a period of very dangerous climate change at this point. Food and water security will decrease and conflicts will escalate.

The third scenario is termed “step change” and is particularly interesting and plausible. In this scenario, major catastrophes driven by climate change over the next decade lead to robust international commitments to cap emissions. Interestingly, this is done by regulating fossil fuel heavy companies as opposed to individuals and governments. Whatever the mechanism, however, many of us believe that this type of shock maybe required before any real action begins – a result of the apparently eternally optimistic nature of humankind.

Pity it has to be this way. Why can’t we just wake now and avoid all the pain? Read Mark Lynas’s account of why this will not happen.

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Coral Calcification and Photosynthesis in a CO2-Enriched World of the Future

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I must admit, the first time I saw this article I nearly fell out of my chair. Entitled "Coral Calcification and Photosynthesis in a CO2-Enriched World of the Future", the article attempts to make sense of a recent publication by Lydie Herfort et al entitled "Biocarbonate stimulation of calcification and photosynthesis in two hermatypic corals" by providing a stereotypical ‘skeptic’ view:

"As ever more pertinent evidence accumulates, however, the true story appears to be just the opposite of what these climate alarmists continue to tell us."

Odd how that it is always the exception to the rule is the ‘true’ story – ignoring the vast quantity of peer-reviewed literature on the topic. A bit of background here: as part of the "Centre for the Study of Carbon Dioxide and Global Change", the Idso family (Craig, Keith and Sherwood) publish a pseudo-journal entitled CO2 Science (see here for their ‘interpretations’ on other recent coral publications). A little digging reveals that the Centre (of which Craig is the chairman and founder and Sherwood the president) is part funded by Exxon (amongst other sources). Not that this in itself is much of an issue (or indeed much of a surprise), as Sherwood Idso views it:

"It is self-evident, for example, that one need not know from whence a person’s or organization’s funding comes in order to evaluate the reasonableness of what they say, if – and this is a very important qualification – one carefully studies the writings of people on both sides of the issue"

The key problem here is that the Idso et al seem to have a fairly obvious agenda, which couldn’t be further from addressing both sides of the issue:

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Rising ocean acidity threatens low-lying islands – Reuters

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A woman sits atop a section of a dyke built to protect the tiny island from the ravages of the sea during a sunrise in the Maldives capital Male in this July 12, 2001 file photo.Reuters, 1st June 2008

Rising acidity in the ocean caused by seas absorbing greenhouse carbon dioxide could make low-lying island nations like Kiribati and the Maldives more vulnerable to storms as their coral reefs struggle to survive, say scientists.

Carbon dioxide in the atmosphere is at its highest level in the past 650,000 years, possible 23 million years, and half has now been dissolved into the oceans making them more acidic.

Ocean acidification, which is projected to spread extensively north from the Antarctic by 2100, makes it difficult or impossible for some animals, like coral and starfish, to produce their shells and skeletons.

“If ocean acidification weakens the structure of reef-forming corals and algae, tropical systems (islands) will be more vulnerable to physical impacts from storms and cyclones,” said a new report by some of the world’s leading marine scientists.

“By 2100, it is expected that some reefs will become marginal and reef calcification will decline,” said the report, by the Antarctic Climate & Ecosystems Cooperative Research Centre, released on Monday.

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Coral adaptation in the face of climate change – response by Hoegh-Guldberg et al

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We certainly hope that Baird and Maynard are right and that in the coming years corals will exhibit an adaptive capability that they have not yet exhibited in situ or in the laboratory. At this point, however, it appears unlikely.
As Baird and Maynard point out, the coral genera Acropora and Pocillopora have generation times that are short (several years) relative to the generation times of other corals. The majority of coral generation times, however, are still long (decades) relative to the accelerating pace of climate change, throwing doubt on the scope of most coral species for rapid adaptation (1).

Corals, like other organisms, can also modify the risk of coral bleaching over the short term through physiological acclimation (2). Acclimation, however, as with any phenotypic change, is limited. In the same vein, corals that form symbioses with more than one variety of dinoflagellate can shift their populations so that they are dominated by their more thermally tolerant dinoflagellate genotypes during thermal stress. Unfortunately, these short-lived changes have not yet resulted in the novel host-symbiont combinations that will be required for survival in the challenging temperatures and acidities of future oceans under rising atmospheric carbon dioxide.

It is important not to confuse genetic adaptation with the increased average thermal tolerance observed for some coral communities over the past 25 years, which has occurred largely because thermally sensitive species have died out, leaving robust species behind (3). Equally important is the lack of evidence that corals have the capacity to either acclimate or adapt to falling aragonite saturation states. It seems unlikely that genetic adaptation will solve the problems of global change facing corals. Indeed, paleontological evidence indicates that calcifying marine organisms including corals suffered a protracted period of absence after large and rapid changes in atmospheric carbon dioxide associated with the Permian-riassic extinction event (4, 5). It took millions of years for these organisms and ecosystems to recover.

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Coral adaptation in the face of climate change – Baird & Maynard

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cover.gifIn their Review, “Coral reefs under rapid climate change and ocean acidification” (14 December 2007, p. 1737), O. Hoegh-Guldberg et al. present future reef scenarios that range from coral-dominated communities to rapidly eroding rubble banks. Notably, none of their scenarios considers the capacity for corals to adapt. The authors dismiss adaptation because “[r]eef-building corals have relatively long generation times and low genetic diversity, making for slow rates of adaptation [relative to rates of change].” We think the possibility of adaptation deserves a second look.
Many features of coral life histories, such as extended life spans, delayed maturation, and colony fission, do result in long generation times (1) [some between 33 and 37 years (2)]. However, other corals, such as many species of Acropora and Pocillopora, mature early, grow rapidly, and suffer whole-colony mortality, as opposed to colony fission, after mechanical disturbances (3) and thermal stress (4). The life histories of these ecologically important and abundant species suggest an underappreciated capacity to adapt rapidly to changing environments.

Repeated bleaching episodes in the same coral assemblages and the increasing scale and frequency of coral bleaching have been cited as evidence that corals have exhausted their genetic capacity to adapt to rising sea surface temperatures (5). However, comparisons of the rates of mortality within populations among bleaching events are not available. Without these data, it is not possible to assess whether the adaptive response has been exhausted. Indeed, the effects of temperature and acidification on even the most basic vital rates in corals, such as growth, mortality, and fecundity, are largely unknown, as are the physiological trade-offs among these traits. Consequently, the sensitivity of population growth to climate-induced changes in vital rates remains almost completely unexplored [but see (6)]. In the absence of long-term demographic studies to detect temporal trends in life history traits, predicting rates of adaptation, and whether they will be exceeded by rates of environmental change, is pure speculation. Indeed, where such data are available for terrestrial organisms they demonstrate that contemporary evolution in response to climate change is possible (7).

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Has the Great Barrier Reef got a future?

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Once I would have thought that a ridiculous question. Yet today, if we assemble all the best science we have, the answer can at best be “maybe”.

It may seem preposterous that the greatest coral reef in the world – the biggest structure made by life on Earth – could be seriously (I mean genuinely seriously) threatened by climate change. The question itself is probably already relegated in your mind to a ‘here-we-go-again’ catch-bag of greenie diatribe about the state of our planet. This view is understandable given that even a decade ago, there were many scientists who had not yet come to grips with the full implications of climate change.

Very likely you have a feeling that dire predictions about anything almost always turn out to be exaggerations. What you really think is: OK, where there’s smoke there’s fire, so there’s probably something in this to be worried about, somewhere. But, it won’t be as bad as those doom-sayers are predicting. When I started writing “A Reef in Time”, I knew that climate change was likely to have serious consequences for coral reefs, but even I was shocked to the core by what all the best science that existed was saying. In a long phase of personal anguish I turned to specialists in many different fields of science to find anything that might suggest a fault in my own conclusions. No luck. The bottom line remains: the GBR can indeed be utterly trashed in the lifetime of today’s children. That certainty is what motivates me to broadcast this message as clearly, as accurately and, yes, as loudly, as I can.

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“Humanity’s extra CO2 could brew a new kind of sea”

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a9391_1148.jpgTerrie Klinger is starting to wonder about the future of kelp sex. It’s a delicate business in the best of times, and the 21st century is putting marine life to the acid test.

Klinger, of the University of Washington in Seattle, studies the winged and bull kelps that stretch rubbery garlands up from the seafloor off the nearby Pacific coast. These kelp fronds do no luring, touching, fusing of cells or other sexy stuff. Fronds just break out in chocolate-colored patches.

The patches release spores that swim off to settle on a surface and start the next generation. The new little kelps don’t look as if they belong to the same species, or even the same family, as their parents. The little ones just grow into strings of cells, but these are about sex.

“Those of us who have spent far too long looking at this can tell the males from the females,” says Klinger. The subtly female-shaped filaments form eggs and release kelp pheromones to call in the male filaments’ sperm.

Sex filaments have kept kelp species going for millennia, but Klinger says she wants to know what’s happening now that carbon emissions are changing seawater chemistry. The intricate reproductive cycle of kelp is an example of a delicate system that can experience big effects from seemingly small changes in ocean chemistry.

This chemistry is already shifting, powered by the increased concentration of carbon dioxide in the atmosphere from human activity. Not all the carbon dioxide from burning fossil fuels stays in the air. The oceans have absorbed about half of the CO2 released from burning fossil fuels since the beginning of the industrial age, says Richard Feely of the National Oceanic and Atmospheric Administration in Seattle. The ocean takes in about 22 million tons of CO2 a day, he says.

The influx causes what scientists call ocean acidification. It’s a term of convenience. The ocean isn’t acid now, nor do Feely and other ocean chemists expect that seawater will become acid in the foreseeable future. However, the extra CO2 is driving the oceans closer to the acidic side of the pH scale. By the end of this century, Feely says, the upper 100 meters or so of ocean water will be more acidic than at any time during the past 20 million years.

Klinger is just one of the biologists trying to figure out what a shift in seawater chemistry will do to seaweed, corals, fish, and other marine life. The filaments of both bull and winged kelps grow noticeably slower in acidic seawater, she reported last week at the 2008 Ocean Sciences Meeting in Orlando, Fla.

Biologists are discussing what the chemistry change will do to marine creatures: It looks like bad news for calcium users and a new dawn for slimy rocks. It could begin an age of simplification for ocean ecosystems. Either way, there’s a rising consensus that, by changing the oceans’ chemistry and biology, burning fossil fuels is essentially making new oceans.

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“Alarm bells as evidence of slowed coral growth on the GBR emerges”

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AIMS Media Release, 5th March 2008

Worrying signs that warmer seawater combined with a possible change in the ocean’s acid balance may be curtailing the growth of an important reef-building coral species have been documented by a research team from AIMS in Townsville.

The paper, published in the journal Global Change Biology*, points to a 21 per cent decline in the rate at which Porites corals in two regions of the northern Great Barrier Reef (GBR) have added to their calcium carbonate skeletons over the past 16 years.

The AIMS research team analysed a total of 38 Porites colonies from the two regions. Porites are a common massive coral with a striking spherical appearance. They are long-lived and distributed widely around the Indian and Pacific oceans.

The researchers speculate that their results may be an early signal that the corals, as well as being subjected to warmer water, are being affected by a phenomenon known as ocean acidification. This is a predicted consequence of climate change, in which large quantities of carbon dioxide from the atmosphere dissolve in the oceans, causing their alkaline/acid balance (their “pH”) to shift towards acidic.

AIMS climate change team leader, Dr Janice Lough, a co-author of the paper, said that much more needs to be done to understand all the implications of the increase in carbon dioxide entering the oceans and to put these preliminary coral growth data into context.

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Are the impacts of climate change on coral reefs exaggerated? Questions and Answers (Part 1)

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For a long time the New Scientist has waged an ongoing battle with the climate change “skeptics”, and have produced some thorough articles such as “Climate change: a guide for the perplexed“, a round-up of the 26 most common climate myths and misconceptions. Time and time again I see people use similar myths and misconceptions regarding corals and coral reefs that are used as an argument as to why global warming is clearly a hoax, how warm water is good for corals (and the list goes on). In response to recent debates, below is the first part of a series called “Are the impacts of climate change on coral reefs exaggerated? Questions and Answers” in which I hope to address these misconceptions following the scientific evidence. Over the coming weeks I will aim to add more in the series: please feel free to add or ask any further questions in the comments below or email me at climateshifts @ gmail.com


1. “Warm water is good for corals”

Corals are locally adapted to the water temperature that they live in. This has taken many hundreds if not thousands of years to occur. It does not happen over decades, which would be the requirement if corals were to tolerate and survive the very rapid changes in sea temperature that we are currently facing.

The statements that “corals calcify faster in warmer waters” and “hotspots of coral diversity are found in warm waters close to the equator” are indeed true, but these conditions are only good for those corals that have adapted to these warmer conditions. For example, if you take corals from the southern end of the Great Barrier Reef and put them at the northern end of the Great Barrier Reef, these corals will suffer from being exposed to warmer than normal conditions and will die.

Although corals thrive within the upper limits of their thermal tolerance (within 1-2ºC), coral bleaching occurs when this tolerance is exceeded, resulting in loss of photosynthetic function, expulsion of symbiotic algae, and ultimately death of the coral. Clearly warm water is beneficial to those corals that are adapted to these warmer temperatures, although exceeding these thresholds results in mortality – a precarious balance.

With respect to the statement “corals in Moreton Bay are regularly stressed as the water is too cold” – it is well-known that corals in Moreton Bay (and other high latitude regions) where conditions that drop below 18°C in the winter lead to coral death. Just like they are sensitive to being too hot, they are also sensitive to becoming too cold. This is called the physiological range or tolerance of species. Conditions at places like Moreton Bay are marginal and therefore an outlier in global coral reefs and are restricted by their latitudes by cold winters.

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