Posts Tagged ‘ocean acidification’

Signal from Sea Butterflies

Sunday, June 8th, 2014

Sea butterflies are in the news, stressed by ocean acidification.

What do we now know about the decline in pH of ocean waters?

Well, we know that the pH has dropped from 8.2, where it was at the start of the Industrial Revolution, to its current level of about 8.1, and that the rate of change has increased in the past several decades. This may not sound like much, but in fact it indicates a 30% increase in the concentration of H+ ions in sea water. That is plenty to stress species that depend on carbonate ions in the water to build the calcium carbonate shells and skeletons that they depend on.

pH of ocean water in 1850 was about 8.2, with lower levels occurring in a few areas of coastal upwelling (

pH of ocean water in 1850 was about 8.2, with lower levels occurring in a few areas of coastal upwelling (

At current rates of global atmospheric CO2 emissions, ocean pH will drop further to 7.8 by the end of the century.

By 2100 ocean pH will have dropped to about 7.8, with extensive coastal areas particularly affected (

By 2100 ocean pH will have dropped to about 7.8, with extensive coastal areas particularly affected (

Ocean acidification has occurred before on the planet, but this event is different: it is happening 100 times more rapidly than any previous events we know of. Geochemists are looking 300 million years into the past, and there is nothing like it.

As CO2 levels in the atmosphere have risen, about 30% has dissolved in ocean water, where pH has dropped (

As CO2 levels in the atmosphere have risen, about 30% has dissolved in ocean water, where pH has dropped (

And it matters. Anything with an exposed calcium carbonate shell or skeleton will be affected – think mollusks, corals, and shellfish like crabs, shrimp and lobsters. With more CO2 dissolved in the water, there are more more bicarbonate ions along with the greater levels of H+ ions, and as a result less carbonate is available to make calcium carbonate. The shells are vulnerable to dissolution unless the surrounding water is saturated with carbonate ions, for they then lose calcium back into the water. As the shells erode and weaken, the animals become stressed, misshapen and potentially dead.

We’ve known about the increasing threat of ocean acidification for some years, but perhaps it has seemed a more distant threat than others associated with our increased CO2 emissions. But we know there already has been an impact on shell growth of oysters and mussels, and we know that coral reefs are particularly vulnerable as pH continues to decline. We have certainly been warned.

Sea butterflies are planktonic snails abundant over the world's continental shelves (

Sea butterflies are planktonic snails abundant over the world’s continental shelves (

Now we are warned once again, this time by sea butterflies. Also known as pteropods, these actually are pea-sized snails that live in the plankton where they are predators of other plankton and the common prey of fish. They are very beautiful to us – translucent, graceful, with the snail foot modified into what look like flapping wings. The shell is much reduced, though still very present, and the shells of species living in the California Current along the west coast of the US are showing signs of unusual erosion from exposure to the lower pH.

Electron micrographs of the shell of a healthy sea butterfly on the left, and the eroded shell of one stressed by lower pH on the right (

Electron micrographs of the shell of a healthy sea butterfly on the left, and the eroded shell of one stressed by lower pH on the right (

There are several key issues here. The rate of ocean acidification is unprecedented, and we don’t really know what lies ahead. We also know that vulnerable organisms will have insufficent time to adapt even if adaptation were possible. Eliminating vulnerable species like pteropods – or brittle stars, corals, mollusks or crustacesns – from ecosystems where they play a critical role as prey or predator will change the communities in ways that may also effect the top predators we want to catch. We are not short of discouraging examples of such community restructuring.

Do poster species help? Though the looming loss of coral reefs has not galvanized us to action, effective conservation campaigns have been built on the images of a variety of mammals, from whales and polar bears to koalas and pandas.

But sea butterflies as poster species? Because of their beauty, perhaps that isn’t impossible. It can’t hurt.

Tatoosh and Ocean Acidification

Wednesday, October 31st, 2012

Long-term studies are rare – the costs in time, effort, enthusiasm, persistence and funding are all formidable. But they are as valuable as they are rare.

One such study, stretching back five decades, is the research on the intertidal community of Tatoosh island, off the northwestern-most point of Washington State, at the mouth of the Strait of Juan de Fuca. Like other long-term studies it has depended on the initial and long-term research of a particular scientist and then his graduate students, and then theirs. In this case Robert Paine started the work, Timothy Wootton and Catherine Pfister are among his graduates students, and their graduate students continue to work with them on the island.

Tatoosh Island from the air – an old lighthouse, some steep cliffs, a few trees, and an extensive and accessible intertidal studied intensely since the 1960s (

The research on Tatoosh has given us insights into how predation and competition structure a community of species, including the concept of keystone species. Recently it has also provided critical evidence of current ocean acidification and correlated changes in the intertidal community.

Because the community has been so well studied for so long, changes in distribution, occurrence and sizes of individuals within populations are possible to recognize when they occur. For more than a decade now Pfister and Wootton have also measured ocean pH levels in great detail. What they are seeing is very troubling.

The intertidal of Tatoosh Island. Cape Flaherty on the Washington mainland is in the background (

Concerning ocean pH, they have found that there is considerable diurnal and seasonal variation, a result of variation in sunlight (photosynthesis), darkness (respiration), temperature, phytoplankton abundance, and upwelling of the coastal waters, all of which modify CO2 levels, and hence pH, of the water. This in itself is really interesting, for the extent of the variation is certainly unexpected.

But they also have found a declining trend in ocean pH levels over the eight years of the initial study – 2000-2007. Allowing for the various sources of CO2 variation, and applying some sophisticated statistical tests, they have concluded that the decline in pH is correlated only with increased levels of atmospheric CO2.

In fact, pH dropped 0.045 units over the 8 years, 2.5 times faster than simulation models had predicted. Not good news, but good data, and the first of its kind outside of the tropics.

Species with calcareous shells or skeletons are particularly vulnerable to erosion as ocean pH drops. Over the same time period, several well-studied intertidal species with calcareous shells or skeletons – two species of mussels, and goose barnacles – declined in abundance and mean size, while non-calcareous algae increased in abundance.

Blue mussels Mytilus californianus have declined in abundance and size in the past decade, correlated with the decline in ocean pH (

Why the drop in pH is so great remains unexplained, but further research has addressed the question of whether such a drop in pH is just natural variation, or whether it is new. Mussel shells can last a long time after the animal inside dies, and their age can be determined. They also carry in them a record of the pH of the water they formed in. They provide an extraordinary record to compare with the present changes, dating back not just to the 1960s but as much as 1340 years ago to the middens left by the Makah who fished from the island in summer.

Shells of the intertidal shield limpet, Lottia pelta, though more difficult to analyse, confirm what the mussel shells have shown (

And the conclusions? For the past decade the ocean waters around Tatoosh are acidifying at a rate faster than predicted. Nothing like this has occurred in the past 1300 years. We clearly don’t know enough yet about the causes, but the only strong correlation is with increased atmospheric CO2.

With the long-term studies of Tatoosh, we have a chance to detect such changes in water chemistry and community structure, and predict their occurrence elsewhere. That’s good science.

Meanwhile, we are warned once again. The emerging new world is going to look a lot different.

Populations of sea birds – murres and gulls – nesting on the cliffs of Tatoosh have also declined by 50% over the past decade (

The Acidification of Oysters

Monday, April 23rd, 2012

Maybe you read about this recently. It seems to me to be quite amazing.

A die-off of oyster larvae at the Whiskey Creek Shellfish Hatchery on the Oregon coast has been correlated with – and almost certainly caused by – a small increase in the acidity of the sea water the larvae were exposed to in their first 24 hrs.

Oyster larvae need critical levels of CaCO3 for their shells to develop, and these levels drop as CO2 levels in the water increase.

Oyster larvae (

The report was published in April in the journal Limnology and Oceanography by three scientists (Richard Feely, Alan Barton and Burke Hales). Then Jeff Barnard, Environmental Writer for the Associated Press, published a summary of the study, and pretty well everyone took notice. When I Googled ‘oyster larvae dying’, most of the first 300 hits were copies of his article republished by American and global news websites.

Oyster life cycle (

All the reports, not just AP’s, emphasize that this is some of the first solid evidence of the potential impact of ocean acidification on a valuable fishery, though in fact oyster growers have been concerned about the threat of acidification for some years.

Anything that has a calcareous skeleton is sensitive to increased acidity (

The event is worrisome, of course, for ocean acidification will continue for many decades, even once (or if?) we stop the increase in atmospheric CO2. Now we know that a very small change in ocean acidity can have a large impact on a sensitive species.

As atmospheric levels of CO2 increase, so do levels in the ocean, resulting in increasing ocean acidity (

But what’s unexpected is the attention the journal publication and its AP description have received. It should signal to our political leaders in North America that in fact people really are worried about the accelerating effects of global warming.

How much evidence is needed? The death of some oyster larvae won’t change the beliefs of most of the US Congress, but it ought to.

It also won’t effect the politics and business of oil that dominates the Canadian economy, but it should.

They say we get the leaders that we deserve, but we don’t deserve this.

The die-off of the oyster larvae cannot be shrugged off as irrelevant or insignificant.

So we are warned.

State of the Oceans

Thursday, September 8th, 2011

Well, this is grim reading.

The International Program on the State of the Ocean – IPSO – has published a summary report of a meeting of late June. Twenty seven fisheries and ocean scientists and other experts from 8 organizations and 6 countries assessed the current state of the oceans. A lot of global expertize resides in this group of people. The ‘long’ summary includes a list of 100 references published in peer reviewed journals, a lot of them from 2010 and 2011 – the report is evidence based, to say the least.

And the evidence indicates that the oceans are well along the way of the worst case scenarios published in the IPCC report of 2007. Ice is melting faster in the Arctic Ocean, Greenland, and Antarctica; ocean surface temperatures are rising; sea levels are rising; increase in ocean acidification is measurable; methane trapped in sediments is beginning to be released; changes are occurring in the distribution and diversity of marine species, in primary production and in harmful algal blooms; and food webs continue to simplify, with jellyfish too often becoming the top predator in the ecosystem.

Sea surface temperatures, measured globally by satellite, are rising. (

The lead-off statement of the summary is clear enough: The biggest threat to our ocean’s health is climate change, with its rising sea temperatures and acidification. Because this has become so difficult to resolve, we must at least reduce the other main stressors on the ocean to give it the best chance of dealing with climate change.

What are the other stresses whose impact we could reduce? They are too familiar: overfishing, habitat destruction, extraction pollution, and alien species introductions.

Negative synergy of these stresses will certainly drive any resilience to climate change ever lower. For example, global coral reefs, coping with rising temperatures and acidification, along with the other stresses, have little chance of surviving this century.

Those parts of the Great Barrier Reef that are most protected appear to be the healthiest, the most resilient (

The IPSO report does have some strong recommendations.
– Reduce CO2 emissions immediately.
– Restore the structure and function of marine ecosystems.
– Reduce and close fisheries, and develop a holistic approach to sustainable fisheries management.
– Establish far more marine protected areas.
– Reduce pollution from agricultural runoff and from resource extraction.
– Apply the precautionary principle that everyone seems to agree with and then ignores.
– Promote effective governance of the high seas through the UN.

And then some stark conclusions:
– Current consumer values coupled with current rates of population increase are not sustainable.
– Timelines are shrinking rapidly – and the longer we wait to act, the greater the cost.
– Core values of human society and its relation to the natural world and the resources on which we all rely must be re-evaluated.

What do you think? In the face of the world’s growing economic and social problems, are we capable of changing our core values? Are we capable of finding the global resolve to meet any of the recommendations before we run out of time, and extreme and irreversible change is upon us?

Opportunities still exist. The IPSO report should be read as an opening salvo, leading up to the next UN Conference on Sustainable Development in Rio in June, 2012. Rio+20, as it also calls itself, apparently without any intended irony.

All the right things get said leading up to Earth Summits.

Reefs at Risk

Saturday, February 26th, 2011

Cyclone Yasi, as big as Katrina, and one of the strongest cyclones in a century, swept across the Great Barrier Reef and on into Queensland on Feb 2. A coral reef has little defense against such a storm.

Crossing the unusually warm Coral Sea before it got to the reef, it grew in strength to Category 5 – just as Katrina grew to Category 5 when it blew across the warm Gulf of Mexico. The Coral Sea has in fact never been warmer, a product of the impact of the current La Nina and the long-term warming of the ocean.

Cyclone Yasi, Category 5, about to hit Queensland on Feb 2 (

Because of the warmer surface waters, this has been another bad year of global coral bleaching on reefs from the Indian Ocean, Thailand, the Maldives, and the Caribbean, probably as bad as 1998, certainly worse than 2002 or 2005. Global bleaching events such as these used to occur every hundred or a thousand years. No longer.

Coral bleaching occurs when water temperatures get too warm and symbiotic algae called zooxanthellae are expelled (

Corals live very close to their upper lethal temperature limits, and a rise in surface temperatures of just 1-2 degrees centigrade is enough to cause extensive coral bleaching. Following the global bleaching of 1998, about 15% of corals failed to recover. We’ll see soon enough how much recovery occurs from the global bleaching of this last year.

At the same time, as atmospheric carbon levels continue to rise, the oceans are becoming more acidic. This is the greatest threat of all: at some point calcareous skeletons of corals will no longer form and the reefs will crumble. Only a reduction in atmospheric levels of CO2 will prevent this, and we all know now how unlikely that is.

As atmospheric CO2 rises, so does the amount of CO2 dissolved in sea water, and the pH gradually drops, making sea water more acidic (

Coral reef scientists around the globe have been warning us for some years that coral reefs are not going to survive global warming. The warnings have now escalated. The World Resources Institute, along with the Nature Conservancy and a diversity of coral reef monitoring organizations, has just published “Reefs at Risk Revisited”, updating its last report of 1998. Local and global stresses now threaten 75% of reefs. Without action on our part, by 2030 that will be 90%, and by 2050, all of them.

Of course, efforts to protect the reefs from overfishing, destructive fishing, pollution, and coastal development are all worthwhile, allowing the corals to be as resistant as possible to the serious global stresses of warming temperatures, coral bleaching, and ocean acidification. But there probably isn’t a single coral reef scientist left who thinks there will still be reefs in existence for our grandchildren to see.

What will the world look like without reefs? This isn’t hard to imagine – we need only go to many parts of the Caribbean and snorkel or dive around reefs that now are dead and crumbling rubble, covered with macroalgae.

A Caribbean coral reef reduced to rubble, abandoned by most fish and all scuba divers (

The costs are huge. A coral reef dies, and those who depend on it leave or die with it – reef fish and their prey and predators, scuba diving operations, recreational visitors, community fishermen, everything is lost. Vulnerable tropical countries, most of them island nations, are now advised to reduce their dependence on coral reefs, and ‘build adaptive capacity’.

We don’t know if life is abundant or rare in the universe, but we can make some reasonable guesses. With 100 billion galaxies, each with its trillion or so stars, life is probably not unusual. But it is probably bacteria-like rather than multicellular, for after all that’s what life on our own very benign planet looked like for a couple of billion years or more.

Stromatolites are mounds of cyanobacteria and look like rocks. They dominated life on Earth for about two billion years. Life on other planets may be no more complex. (

Complex ecosystems like those we find on Earth may be extraordinarily unusual across the universe. And even if complex life has evolved elsewhere, it will be different, contingent on the interacting pressures and planetary events of their own systems. Coral reefs evolved here, on Earth, and probably nowhere else.

Other ecosystems may survive these perilous times through adaptation, resilience, and migration to different latitudes. But not coral reefs. We’ve become familiar, even comfortable, with the extinction of particular species. But the extinction of an ecosystem? That is something very different.

There are no words that I know of to express the depth of such a loss. It is a loss to our universe.

Great Barrier Reef. See it while it's still there. (

Sick Seas

Friday, October 9th, 2009

(Michael Berrill,

“Sea Sick” is a recent addition to the list of valuable books describing just how seriously we are threatening the planet’s current living systems. The author, Alanna Mitchell, is an experienced journalist who travelled the world for a couple of years, getting an education about the state of the oceans from the very best scientists working on the various problems, and she shares this well.

Gradual acidification of the oceans is occurring as atmospheric concentrations of CO2 continue to climb, and coral reefs are therefore vulnerable to extinction. Altering wind and current patterns have profound and global effects on ocean productivity and terrestrial climates. Huge economies such as China’s drive too much of change. Overfishing persists everywhere. Rivers dump such huge nutrient loads into coastal waters that dead zones continue to grow in size and number every year.

It is all very bleak.

Actually, throughout her book, she includes descriptions of efforts to alleviate the stresses, from new aquaculture initiatives to the green policies emerging in China, yet at end of it all she has clearly lost hope. A dozen pages before the end of the book the bleakness has overwhelmed her “I’ve begun to think that the ocean is in palliative care and I mute witness to its death rattle”, and “I’m out of hope, mired firmly in the desolate present”.

And then she takes a final trip, this time down in a submersible to 900 meters off the edge of Florida’s continental shelf, and she has what she calls an epiphany, and finds hope. She recognizes the relation of hope to faith, but senses there is foundation to it – that all is not necessarily lost. She ends by calling us to action, seeking a new and global wisdom, now, before it is too late.

I was left thinking about hope. We use the word in so many ways all the time that defining it seems impossible.

Still, I think that if we place our hope in a sea change in human wisdom, then time is certainly our enemy. But if we nourish and share the changes that individuals, communities, NGOs and even governments have initiated around the planet – well, then perhaps we may be able to buy the time we need to find that wisdom. Is that what hope is?