Finding Climate Stars to Steer By.


Bleaching as a sign we are off course

It started last month with scattered reports from Mackay in the south to Port Douglas on the north Queensland coast.  The Great Barrier Reef has begun to bleach again.  Coral polyps by the million tossing out their minute symbiotic algae under the stress of warm water, and becoming metabolically challenged as a result.  The last mass bleaching on the Great Barrier Reef occurred during the first half of 2016 and did major damage, particularly on the northern third of the reef.  North of Cairns, the bleaching was widespread and severe — about 67% of shallow-water corals eventually died.  That is the kind of damage that will require 10-20 years for reasonably complete recovery, so the news that bleaching is starting all over again is definitely bad.  A reef cannot prosper if it is bleaching severely every year or so.

Map showing the extent of coral mortality recorded in October-November 2016, 8-9 months after the mass bleaching event on the Great Barrier Reef.  Unusually cloudy weather at the time of the event appears responsible for the low mortality (and bleaching) recorded in the southern section.  Map © ARC Center of Excellence for Coral Reef Studies.

The reason for the renewed bleaching is not hard to find.  Australia has had a scorching summer with records broken here, there and everywhere.  The warmer than usual water has extended down the coast threatening corals as far south as Sydney Harbor – there are corals there, but not coral reefs– and scientists are concerned that the reefs at Lord Howe Island, about 400km offshore and slightly north of Sydney, and the most southerly coral reefs on the planet, could be up for bleaching any day now.  The renewed bleaching is alarming also because the very strong el Niño which drove the global mass bleaching event from 2014 through 2016, ended mid-2016, and the world entered a weak and brief period of ‘cooler’ la Niña conditions last September.  NOAA declared la Niña over early in February and the world may be heading back towards el Niño conditions again later this year.  That bleaching occurred during a (weak) la Niña period tells us just how much the world’s oceans are warming up.  It will not be many years before coral bleaching is a process that happens every summer.  What happens to coral reefs then?

The Great Barrier Reef and Australia are far away from Canada, but we are all experiencing unusual weather and strange events, such as the ever lower amounts of ice across the Arctic Ocean, and the crazily oscillating weather of this year’s winter in eastern North America.  We live in the Anthropocene and we continue to alter the planet in many ways.  Through the type and extent of actions that characterize our global economy, we are exceeding several of what environmental scientists term the planetary boundaries that define an acceptable space for continued functioning of the biosphere.  Our increased emissions of greenhouse gases (GHGs), and the resulting changes to climate are just one of the boundaries we are reckless about.  Some others are the concentration of ozone in the stratosphere (perhaps now being repaired), the rate of extinction (going up), nitrogen and phosphorus pollution (going up), and ocean acidification (pH going down).

The nine planetary boundaries as defined by Johan Rockström.  We need to steer the planet to keep within these boundaries if we want to ensure an environment commensurate with good quality of life for humanity, but we are already on the shoulders of the path.
© F. Pharand-Deschênes/Globaïa.

(I use the word ‘reckless’ because we are in uncharted territory.  Scientists do not know with any certainty the extent to which we can exceed planetary boundaries without destabilizing the complex system which is the biosphere, causing it to veer off into an alternative state that may or may not be amenable to our way of life.  If we can keep the planet within the boundaries, scientists expect that conditions typical of the Holocene will continue.  The Holocene, some 10,000 years long is that most recent time period within which human civilization developed and flourished.  Now, we are already exceeding some of the boundaries, and may well shift conditions on this planet to something quite different.  One definition of the Anthropocene likely to be provided by researchers in a distant future time: “that period of time when the planet sort of went to hell”.)

Most of us who understand our predicament want us to stop our reckless behavior.  As time goes on with only modest signs that we are changing our ways, the call to change grows more urgent, and we point to signs that dangerous times are approaching.  The melting of the Arctic sea ice is not just an observation about the Arctic Ocean.  Nor is the increasing frequency of bleaching an observation about the world’s coral reefs.  Both are signs that we are driving the planet’s climate away from what it has been for the last 10,000 years, and signs that the climate is changing rapidly.  We should be using these signs as ‘climate stars’ to steer by, just as we should be using other signs – ocean pH, stratospheric ozone concentration, availability of phosphates in coastal waters – as stars guiding our steering with respect to other boundaries.  Because, make no mistake about it, our activities make us a major force governing the state of our planetary environment, whether we like that or not, and we need a steadier hand on the wheel, the tiller, the joy-stick or whatever control device this crazy planet possesses.  Up till now, we have been in the driver’s seat but have not been paying too much attention.  It’s time to get real, and paying attention to coral reefs can help.

Steering towards a safe climate, or just fiddling with the joy-stick?

The trans-oceanic voyages of Hokule’a have reestablished Polynesian navigational prowess.  Now we must learn how to steer our planet using the special stars it provides to keep within environmentally safe boundaries.  Photo of navigator on board Hokule’a © Bryson Hoe, ʻŌiwi TV and the Polynesian Voyaging Society

When it comes to climate, we know what we have been doing wrong, and we know how, and how rapidly, we have been changing the nature of our atmosphere.  More than that, the governments of 197 countries have now agreed broadly on what we must do to track towards a safe Holocene-like climate amenable to life as we know it.  I’m not talking here about controlling the weather, or even about making the climate as perfect as it can be for human endeavors across this planet.  I’m talking simply about stabilizing the climate at an average temperature deemed not too much higher than at present.  To do this we have got to halt the increase in concentrations of greenhouse gases sufficiently quickly to keep their combined warming effect to one that maintains a mean global temperature no more than 1.5oC warmer than in preindustrial times (about 0.6oC greater than now).  And that means reducing anthropogenic emissions of CO2 sufficiently to stem the current rapid increase in concentration of this gas in the atmosphere, and ultimately to lock that concentration to the vicinity of 400 to 450 ppm, not much more than today.  Personally, I believe we should try to ratchet down the concentration to about 350 ppm, a concentration we last saw in the mid-1980s, but I also recognize that it is going to be extremely difficult just to achieve the 1.5o/430 ppm goal.  Obviously, if we cannot get back to 350 ppm, mass coral bleaching is unlikely to go away.

The Paris Accord, agreed to in December, 2015, and into effect the next year, sets a goal of no more than 450 ppm CO2 eq. for atmospheric greenhouse gases, and an aspirational goal of 350 ppm.  It is up to each of the 197 signatories to decide what changes to policies to implement to achieve a reduction in emissions commensurate with those goals.

Most countries’ currently announced plans are woefully inadequate to meet these goals, although many represent real changes in policy that move emissions rates lower.  The expectation is that countries will progressively ratchet up their commitments over time and reach the goals before the end of the century.  However, most countries are moving too slowly to put in place the policies they have promised, let alone moving to strengthen those promises, and with its recent change of government there is a real chance that the USA will move backwards.  The international community is going to require all its diplomatic skills to keep the world moving forward in this effort to cut GHG emissions, because persuasion and shaming are the only weapons that enforce the Paris Accord.  Time will tell whether we try harder to stop being reckless with the climate.

Despite the severe bleaching the Great Barrier Reef received last year, and the critical scrutiny given to Australia’s management of this UNESCO World Heritage area, the current Australian government has backed away from prior climate-focused decisions and is instead implementing policies that it claims will deliver jobs and a growing economy while ignoring environmental consequences.

Australia has long had a resource-based economy and at present both federal and state governments are hell bent on rapidly exploiting the enormous coal reserves of Queensland, for export to Asia.  The planned increase in mining and transport runs directly counter to improved management of the Great Barrier Reef, because the coal will be shipped from large new terminals along the Queensland coast, through the myriad channels of the Great Barrier Reef.  Not only will increased shipping create a greater risk of groundings; coal management at loading facilities will generate coal dust pollution, and the harbors will be kept navigable by repeated dredging, with its resultant siltation, especially if dredging spoil is dispersed offshore.  On top of this, that coal, which has sat storing carbon safely underground for millions of years, will be burned once it reaches its destinations, releasing CO2 into the atmosphere and adding to our global climate problem.

Australia’s GHG emissions since 2005, as reported by the government, with two most recent quarters provided by NDEVR Environmental.  The downward trend is, at best, anemic since 2011 and will not meet the government’s pledged commitment, a national commitment widely seen as inadequate.  Image © The Guardian

Australia has signed the Paris Accord, but even while its emissions commitment has been widely criticized as one of the weaker efforts made, it has been finding it difficult to reduce emissions at a rate commensurate with that commitment.  This appears to be partly due to an ideological resistance to carbon pricing entrenched within the current Liberal/Country government, which stripped away a carbon tax introduced by Labor as soon as it came into office.  Instead, there is considerable talk in government circles about the promise of clean coal – a promise that has yet to bear fruit anywhere and is seemingly far off in the future in Australia.  Meanwhile the government is stubbornly refusing to acknowledge the link between its fondness for coal, its own GHG emissions, global GHG emissions and the plight of the reef, a major earner of tourism and fishery revenues.  Because the voices speaking for the reef, the biosphere, and the need to stop recklessness are less loud in Canberra than the voices espousing quick wealth and job creation by digging and shipping, the country is adrift on carbon policy and would likely jump at the chance to follow suit if the USA pulls out of Paris.  The Aussie government is where Canada was a short year ago, and has the USA for company – the big voice of fossil fuels has drowned out the opposition for now.

Canada and Australia share much; Canada may be steering better

Canada does not have a Great Barrier Reef, although the rapidly changing Arctic should be an equivalent climate-star.  However, too many Canadians see its thawing as an opportunity for more get rich quick resource exploitation schemes, rather than as a potent sign of serious biosphere risk.  Like Australia, Canada has a long history of dig and ship and its own enormous fossil fuel reserve, the Alberta tar sands, and there are many in and out of Canadian governments who argue that we must dig and ship as fast as possible because doing so is good for economy and jobs.  Also like Australia, Canada is a net energy exporter.  Neither country needs to extract increasing amounts of fossil fuel to keep its own economic engines supplied with energy and humming happily along.  The jobs in the fossil fuel sector in both countries could be replaced by jobs creating a non-polluting energy sector and a modern, knowledge-based economy.

Hay Point Coal Terminal on the Queensland coast, and Suncor’s main site in Alberta – Canada and Australia share a lot.  Photos © (left) and David Dodge/Pembina Institute (right)

Unlike Australia, Canada’s development of its tar sands has proceeded rapidly enough that its capacity to ship the product to markets has been stretched.  Not to the breaking point, although listening to people in the industry you’d not guess that.  There is great pressure to build pipelines.  Canadian environmentalists have seen expansion of pipelines as an enabler of tar sands production, and have attempted to block new pipelines as a proxy for blocking the expansion of production.  If they can choke off the path to market, production will have to slow, or so they claim.  Putting Canadian oil into the global market is the same as putting Australian coal there.  The product will get used, GHGs will be emitted, the planet will warm, and the GBR will bleach some more, while the Arctic melts further.  So impeding the delivery of that tar sands oil makes some sense.

Unlike Australia, the election in Canada a bit over a year ago brought in a government interested in strengthening Canada’s climate policy.  Canada went to Paris in December 2015 as a reformed pariah, and got deserved credit for its constructive efforts while there.  But the Canadian Liberal government also wants a strong economy and jobs, and so the public has watched a dizzying performance of to and fro in which new climate initiatives are balanced by announcements favorable to the tar sands producers and their pipeline-building partners.  Just this week, PM Justin Trudeau was a keynote speaker at the CERAWeek oil industry conference in Houston where he described his balancing act on climate and oil.  “There is no path to prosperity in Canada that does not include a thriving, vibrant energy sector, both traditional and renewable,” he said, while reiterating his view that there will be a transition off fossil fuels and that Canada must prepare for the day “far off but inevitable, at some point, when traditional energy sources will no longer be needed.”  His is a nuanced view that his predecessor did not possess.  Elsewhere at the same conference, Alberta Premier Notley was making the case for her climate policies, including that cap on tar sands emissions of greenhouse gases, as being good for the fossil fuel industry, in part because climate policy provides cover for decisions favoring pipelines.

So how should Canadians interested in changing our global recklessness on climate respond to new governmental initiatives to put a price on carbon?  Or to proposals to expand pipeline capacity?  Or to construction of new upgrading and refining capacity within Alberta?

Helping Canada steer to the right path

I think it imperative that we strongly support efforts by provincial and federal governments to price carbon.  This is the right thing to do, and Canada has been slow to take this step.  At the same time, we must continue to advocate for higher carbon prices than those already in place and for greater efforts to ensure the cost is shared equitably – meaning helping the poorer sections of the community to bear the cost that pricing carbon pollution inevitably brings.  We must also continue to hold government feet to the fire concerning the sheer inadequacy of Canada’s existing commitments on GHG emissions.  Having been slow to start down the right path, there is no reason why Canada should not pick up the pace and become one of the leaders reaching the goal.

The old environmentalist argument against pipelines needs to change.  All pipeline investments are not environmentally bad, and obstructing pipelines as a way of forcing curtailment of expanded production from the tar sands was always a clumsy way of turning off the fossil fuel tap.  Canadians should welcome pipeline construction that expands our capacity to move oil across our country, better serving our own energy needs and reducing the need for imports.  We should not automatically oppose pipelines intended to diversify potential markets, although we must demand that pipeline construction and operation is held to the highest environmental standards.  It seems unfortunately true that people whose job it is to build pipelines have never seen a project they did not want to build, but crisscrossing our most pristine natural lands with pipelines is not a worthwhile venture in itself and can significantly degrade environmental value.  Such value is hard to rebuild once the need for pipelines has gone.  Above all, we must not be seduced by claims that current pipeline capacity is inadequate to the task of shipping current or realistically expected future production from the tar sands, nor by claims that pipeline construction creates huge numbers of jobs and great wealth.  Mammoth construction of solar or wind farms or new hydro projects would do the same for jobs and wealth as any planned pipeline construction, and current pipeline capacity is fully sufficient for all expected production if Alberta’s GHG emissions cap is going to be honored, as it must be.

Environmentalists must keep the pressure on Canadian governments to fulfill and strengthen commitments on GHG emissions if needed changes are to be achieved.  But the pressure must be more nuanced than simply opposing every pipeline.
© Canadian Centre for Policy Alternatives.

Those concerned about our need to reduce global GHG emissions need to watch the fossil fuel industry closely.  Industry spokesmen can be very convincing when they argue that Canadian pipeline capacity must be expanded, or that ramping up the tar sands production is good for economic growth.  Indeed, a pair of them provided a wonderful tale about how tar sands oil is becoming very clean, in part because of the emissions cap and carbon taxes.  They argue that by obstructing the tar sands industry, Canadian environmentalists are in danger of putting less clean oil from places like Venezuela into the marketplace instead (I put italics around ‘becoming’ because we are not there yet, and may never be).  Still, at the same time as industry spokespeople are making these claims, fossil fuel corporations are doing things that suggest they expect the market for oil to dwindle.  Reporting in the Globe and Mail at the end of January, Carl Mortished dissected BP’s annual World Energy Outlook which claims the current global glut in oil is going to last at least to 2050, meaning that cheaper oil will gobble up the available market, putting pressure on high-priced producers such as Canada – those frequently repeated claims of rapid growth in the tar sands are unlikely to happen.  Just this week Shell announced two major agreements that will permit it to further reduce its exposure to tar sands oil, part of a process it has had under way to progressively reduce its exposure to high-carbon sources, and to focus on natural gas, offshore oil, and downstream operations.  Shell is the latest European producer to reduce its investments in Alberta, following France’s Total and Norway’s Statoil.  In mid-February, pipeline builder Enbridge’s CEO stated that their recently approved Line 3 expansion plus just one other pipeline would suffice for foreseeable demand into the 2030s.  Enbridge is also diversifying.  All these corporations are preparing themselves for the downturn they know is coming.  So environmentalists should continue to keep the pressure on, but selectively and wisely.

To keep pressure on, environmentalists should articulate the value of progressively reducing GHG emissions in tar sands operations, and give credit when such reductions are achieved.  They should absolutely demand that the cap on GHG emissions announced by the Notley government should be progressively tightened, forcing either a substantial improvement in GHG emissions per barrel of product, or a reduction in production from present levels.  At present the cap is so high that it will not impede expansion of the industry for a couple of decades.

The Sturgeon Refinery, now under construction northeast of Edmonton, Alberta, will process tar sands bitumen into diesel fuel, and has carbon capture and storage capability.
© Shaughn Butts/Edmonton Journal.

The construction of the Sturgeon Refinery northeast of Edmonton is under way with the first of three planned phases nearing completion.  It has been heavily supported by the Alberta government, yet there remain serious doubts concerning its economic feasibility, particularly in a weak market, and stages 2 and 3 may never get built.  The first new refinery in Canada since 1984, Sturgeon includes a full carbon capture and storage system, and will refine bitumen to produce diesel fuel.  It is an interesting sign that the industry can reduce GHG/barrel, and produce a higher value, more easily shipped product than the conventional bitumen.  While the economics remain a serious question, we should squeeze the industry into doing more of this, so that the tar sands might provide the useful high value products that our economy will need in the future, long after the idea of burning oil to generate energy is forgotten.  On the other hand, future refineries should be built without the substantial government funding that Sturgeon has received.  If there is one thing Canada should have learned as the tar sands industry grew, it is that corporations rarely reduce profits in order to pay for the public good unless they are aware that the public and the government expect that public good to be served.  This is not a sign of venality; it is doing what they should do – maximize profits for their shareholders.  But we should have been demanding more from them all along.

Don’t be seduced by dollars

Just as Canadians (and Australians) should not be seduced by the dig and ship mantra, which has always been flawed, we should not put up with arguments based on spuriously inflated estimates of jobs created or dollars added to the GDP.  There are many ways to build wealth and create jobs.  (I recently saw a reference in an e-mail to the number of jobs that would be generated by the construction of the Sturgeon Refinery – 76,000 person-years of work!  Just for the construction.  That seemed a lot, so I went digging.  I found two references to jobs in the Globe & Mail article: “…more than 5000 workers are laboring round the clock…” followed a couple of paragraphs later by “Phase 1 employed 7,500 workers at peak construction…”, plus news that building all three phases could take a decade.  I guess the 76,000 person-years is derived as 7,500 for ten years, plus another 100 off-site over the same period.  Moral: take all such claims with the dose of salt they cry out for.)

We must embrace the need to steer our planet

Which brings me to my final and perhaps most difficult point.  If we are serious about our desire to halt our recklessness and steer the planet back towards a quasi-Holocene state, we need to tackle the relationship between humanity and our home.  During the 16th century, notably in the writings of Sir Francis Bacon, western civilization took biblical references to having dominion over nature and molded them into the idea that we were separate from, superior to, and entitled to use the rest of creation.  At that time this entitlement meant not too much.  That view pervades our global society today, but now is a time when seeing ourselves ass separate, special and entitled does mean something because we have become powerful enough to make real differences on this planet.  It is high time for a serious reexamination within and across all nations, but particularly the wealthier, more economically advanced ones, of the relationship between humanity and the wider biosphere.  A price on carbon pollution is an important step forward, but we need many more steps forward until we are acting as a part of the biosphere and ensuring that our actions minimize disruption of biosphere function, and adequately compensate, economically and environmentally, for those few disruptions that are deemed necessary for furthering our own societal well-being.

Hokule’a sailing into a western sea.  We need to find the right climate stars to steer our planet; accepting that we are a part of the biosphere will help find those stars and the will to steer.  Photo © Daniel Lin/National Geographic

Realigning our relationship to our planet may be a bigger challenge than many environmentalists want to accept, because accepting it requires a radical change in our thinking.  It will certainly be an enormous challenge to those among us who are not already sympathetic to the plight of the planet, who have grown up with a world view that says only humans have rights, and some humans have more rights than others.  And yet, if we do not change our perspective, how will we give adequate value to the actions that need to be taken to keep our pressures on this planet under control?  How will we be able to use those climate stars, and those stars defining other planetary boundaries, to steer a path forward towards a better Anthropocene?  How indeed?

Next time you hear that a reef has bleached, or that a glacier has retreated… next time you read that another frog, bird, or coral has gone extinct… next time you see video of a devastating storm, a pernicious drought, or of massed environmental refugees on a shore… ask what you can do to help us all see the need and urgency to steer this planet into a safe Anthropocene.  And think of the benefits we all would reap if we succeeded in this effort.  It’s not rocket science.  It’s probably harder than rocket science.  But it is doable, and it begins with a goal and a star, and a hand on the tiller.  There is no better time to start than right now.

Categories: Canada's environmental policies, Changing lifestyles, Climate change, Coal, Economics, In the News, Politics, Tar Sands | Comments Off on Finding Climate Stars to Steer By.

Sea and Sky – Complexity abounds, which is why climate change is so difficult to understand and project into the future.


Reclining on a tropical beach, it is easy to think of the ocean as deliciously wet, salty and refreshing, while the sky is simply a blue transparency, a near nothingness that sometimes brings a cooling breeze.  In fact, both are complex mixtures of substances that are engaged in equally complex dances as they abide by chemical and physical laws that govern how they mix, combine and change.  Nor do sea and sky keep to themselves; they interact with each other and with the other surface component of this place we call home – the land.  Many of these interactions play roles in generating our climate, and so, climate is also complex in its causation.  And herein lies a major problem for us.  We are doing things that change our climate, but we do not fully appreciate how, why, or how quickly those changes occur.  The struggle to understand the origins and control of our planet’s climate has occupied scientists from various disciplines for many years, and has been a subject of growing study over the last three decades or so.  We know vastly more about how, why and when than we used to, but there is also lots we do not yet know.  How well we manage the current effort to put climate change onto a new, milder path will depend on how well we apply the knowledge we already have to change our behavior in useful ways; it will also depend on how rapidly we expand our understanding of climate science and incorporate that new knowledge into our actions.

A mild winter with crazy polar weather

This winter has so far been uncharacteristically mild in many parts of North America, and the Arctic experienced unseasonably warm weather with temperatures 20oC warmer than usual during November.  Meanwhile, people in Siberia were experiencing record cold.  Since November, our North American weather has gone through the same sort of bitter cold/super warm cycling that occurred last year, a feature attributed to the destabilizing climatic effect of a warmer than usual Arctic.  In January, I discussed the surprising loss of Arctic sea ice last November, and I have covered the influence of a warming Arctic on weather further south in North America several times.  Fact is that both in the Arctic and Antarctic, warming is happening faster than in less polar latitudes, and we are now discovering new things about the way ice melts.  We have some learning to do.

Map of the Antarctic Peninsula showing the Larson C ice shelf (dotted line marks inshore boundary), and the rift (solid red line) that has almost cut off the outer half of it.  The shelf is about 500 m thick, and floating with about 60 m of ice above sea level.  (Small circles on rift line mark its westernmost terminus in Nov 2010, Aug 2014, June 2016, 1 Jan 2017, and about 1 Feb 2017 respectively.)  Map © New York Times & Earthstar Geographics.

If the Arctic has been going crazy this year, so has the Antarctic, where the latest news is of a crack in the Larson C ice shelf which has grown 27 km longer in the last two months.  The crack, which extends right through the half kilometer thickness of the ice is now close to completing its journey across the shelf.  Once that happens, the largest iceberg in memory will be set free.  While this will have a negligible effect on sea level, it is likely to lead to acceleration of flow in the glaciers feeding the shelf, and that will lead to overall break-up of the shelf and sea level rise.  This is the kind of break-up that few if any glaciologists were contemplating a decade ago.

Sea level rise – our estimates keep growing

In 1995, in its 2nd Assessment Report, the Intergovernmental Panel on Climate Change predicted that by 2100, sea level would likely rise 49 cm above its average level in 1990.  They gave a range from 20 to 86 cm.  By 2013, in their 5th Assessment Report, they were projecting sea level rise under a business-as-usual scenario (RCP8.5) of from 52 to 98 cm, although they also reported that the pace of sea level rise has been quickening from about 1.7 mm per year in the first half of the 20th century to about 3.2 mm per year during 1993-2010.  One factor for the only slightly increased estimate of sea level rise was their expectation that Antarctic ice would be increasing in extent because of enhanced snowfall.  Break-up of the Larson C ice shelf is not compatible with a growing mass of Antarctic ice, so their 2013 estimate for sea level rise, little changed from that in 1995, is certainly still too low!  Most climate scientists in 2013 expected the estimates of sea level rise would get even bigger, and studies of how glaciers melt help confirm this expectation.

In 2015, James Hansen and colleagues published a wide-ranging study including analyses of Antarctic glacial melt processes and evaluation of climate during the last interglacial period to argue that sea level was likely to rise several meters as our climate warmed, rather than the several centimeters being projected by IPCC.  (I discussed this paper on two occasions shortly after it appeared.)  Now, in an article published in Science on 20th January, Jeremy Hoffman, Oregon State University, and three colleagues have reported detailed estimates of sea surface temperature at various times during the last interglacial period 129 to 116 thousand years ago.  Their results show that sea surface temperatures were only ~ 0.5oC warmer than during 1880 to 1899, and indistinguishable from global mean temperatures between 1995 and 2014.  Sea level back then was 6 to 9 meters higher than today.  We don’t need to have any more warming than has already occurred to still melt a lot of ice!

Hoffman’s study shows that without temperatures any warmer than today, glaciers melted sufficiently to raise sea level several meters higher than today during that last interglacial.  It does not show how rapidly the melting occurred, and few climate scientists are yet talking about 6 to 9 meters before 2100.  But they are talking about a couple of meters or more before that date.  This has implications for real people, especially those living in low-lying coastal areas.

Graph showing relative sea level changes at Virginia Key, Florida, projected out to 2100, under three scenarios – average global sea level rise of +1 m, +1.5 m, and +2.5 m by 2100 – as solid lines, and “one in one hundred year” extreme high mean water levels for each scenario as dotted lines.  The dots and bars at year 2070 show the 95% confidence limits of these projections.  Graph courtesy NOAA.

Despite the policy of the Florida government among others) to not mention climate change, a quick google of Florida + sea level brings up plenty of news, and NOAA, just last month, released a comprehensive technical report detailing global and regional sea level rise scenarios for the United States.  Under most scenarios there is an alarming amount of red (meaning high risk) all along the eastern and southern coastline.  Miami may become New Venice.  In truth, the report, available here, uses color on its maps to show the relative sea level from place to place within the USA.  The full sea level rise at any location is equal to the mean sea level rise for that scenario plus the adjustment shown in color.  Thus, most of the US southeast is likely to get nearly a meter more sea level rise than the average global rise.  NOAA’s “extreme” scenario projects a 2.5 m increase in sea level globally by 2100, nearly 3.5 m in Florida.

Maps showing the relative sea level rise by 2100 for USA coastal locations under six different scenarios for global sea level rise.  To determine the actual projected increase in sea level at 2100, compared to today, add the mean value (e.g. 0.3 m for the “Low” scenario) to the amount indicated by the color.  Maps courtesy NOAA.

NOAA’s report, which uses average global sea level increases by 2100 ranging from 0.3 m to 2.5 m, draws attention to the fact that sea level is not uniform around the globe, and that sea level rise will not be uniform.  Some places will be luckier than others and experience less sea level rise than average while others, unlucky, will receive more.  For Florida… not so good.  Not only is it low lying, but it is going to receive a greater increase in sea level than average because of its location relative to the Atlantic ocean, and the way oceans behave in response to gravity.  While we think of sea level as flat, there are hills and valleys maintained by winds, by currents, by gravity.  Our world is a strange place.

Deeper warming of the upper ocean – what’s going on?

Remember the global warming hiatus so beloved by climate deniers?  There was a period at the end of the 1990s while the strong el Niño conditions of 1997-8 were abating, that global temperatures were not rising.  This was not because global warming had ceased, as the denialists crowed, because our economy kept on pumping CO2 into the atmosphere, and heat-trapping capacity continued to increase.  But the heat was not showing up in the lower atmosphere, the ocean surface, and the land where we expected it to be.  It was going somewhere else.  Climate scientists expected that it was getting stored in the deep oceans, but at first did not know why.  Why should processes that had been warming our atmosphere and land and ocean surfaces bit by bit start warming something else?  Why indeed?

Research over the last five years or so has established that the ‘missing’ heat was indeed being stored in the deep ocean.  On 9th February, in a paper published in Nature, Tim DeVries of University of California, Santa Barbara, and two colleagues, confirmed that this happened because of a weakening of the rate of what they call upper ocean overturning circulation – a process driven by systems of global-scale currents and winds that moves cooling surface waters down to the depths in places such as the north Atlantic while upwelling water in the Southern Ocean and in the subtropics.  With overturning slowing, the capacity of surface waters to absorb heat from the atmosphere slows (because the water warms up), and the ocean can even begin a net flow of heat back to the atmosphere.  With more rapid overturning, surface waters are continually being replenished by formerly deep, cooler water, and the capacity to absorb heat from the atmosphere increases.  The net result was that during the early part of this century the upper kilometer of the ocean was being warmed to a greater depth than it is now, but it was not any warmer at the surface.  In more recent years, with less overturning, the warmth is being kept closer to the ocean surface and the surface layer and the atmosphere are becoming warmer again.  It’s nice to have an explanation for what has happened.  This knowledge also permits refinements to the global models that attempt to project future changes in climate as we pump more CO2 into the atmosphere.

Methane, that other greenhouse gas

The usual emphasis, when we discuss causes of the warming climate, is on CO2 emissions driven by the global economy and its dependence on fossil fuels.  Occasionally, discussion pauses to recognize the other greenhouse gases, particularly methane, which have also been rising in concentration in the atmosphere.  Last December, in the journal Science, there was a short news item by Paul Voosen concerning the 3% increase in atmospheric concentration of methane since 2008.  This relatively large increase has puzzled scientists because most known sources, such as cattle burps and farts, have not been increasing since 2008 (the size of the global herd has not expanded), yet the extra methane has obviously come from somewhere.  Voosen reported that there are currently two competing hypotheses.

Concentration of methane in the atmosphere above Mauna Loa, Hawaii, as recorded by instruments that monitor continuously.  While methane has been increasing with the growth of the human enterprise, the rate mysteriously quickened following a slow-down in the early years of this century.  Graph courtesy NOAA.

One hypothesis holds that the global improvements in air pollution that have occurred have reduced availability of pollutants such as ozone and nitrous oxide which are precursors for the production of hydroxyl ions.  The resulting slow-down in hydroxyl generation in the atmosphere is slowing the removal of methane (which is rapidly broken down by hydroxyl).  As a result, even with no increase in the rate of delivery of methane to the atmosphere, its concentration is rising because each molecule gets to stay a bit longer.

The competing hypothesis is a bit simpler.  It holds that the changing climate is increasing precipitation over tropical wetlands, and that this is leading to increased biological activity there, particularly at a microbial level that would be more difficult to monitor.  As a result, there is increased release of methane to the atmosphere.

Neither hypothesis leads easily to actions to mitigate this growing methane concentration, and regardless of the cause the increase in atmospheric methane will lead to more warming than would have occurred if the methane concentration had remained stable.  We need to understand what and why if we are to correctly anticipate the likely trend in methane concentration in the future.  Stay tuned.

Dissolved oxygen in our oceans

While Science and Nature are independent, competing publishers of peer-reviewed science, they occasionally publish articles that mesh rather well together to cover a developing understanding.  That happened at the start of this year with respect to the amount of oxygen dissolved in the global ocean.

We might think simplistically that the ocean, in contact with the atmosphere, would absorb oxygen (and other gases) at its surface, keeping the surface layer in equilibrium with the atmosphere in terms of gas concentrations.  We might also expect that mixing and overturning would move surface water deeper, carrying these gases, so that deeper parts of the ocean would also contain dissolved gases.  We might also expect that biological activity – respiration, photosynthesis – might alter concentrations of the dissolved gases over time so that deeper waters would have different concentrations of each gas relative to surface waters.  That is more or less correct, simplistically.  The details are less simple as two papers by different research groups revealed.

In the 23rd December 2016 issue of Science, Andrew Watson, University of Exeter, published a short ‘perspective’ on dissolved oxygen in the ocean.  He drew attention to the fact that despite a relatively high concentration of oxygen in our atmosphere (currently 20%) over the last several hundred million years, the oceans, taken as a whole, hold remarkably little dissolved oxygen except in their surface layers, and that on a number of occasions in the deep past, the oceans have plunged into anoxia, with consequent severe reductions of biological activity.  Such large-scale anoxic events can be recognized by the deposition of dark sediments rich in organic compounds due to the demise, and relatively ineffective subsequent decomposition, of plants and animals.  Such major anoxic events are associated with many of the mass extinction events that litter our prehistory.  They seem to be promoted by warmer climates and to be associated with major environmental crises, particularly ones that alter the carbon cycle.

In recent years of human history, our agriculture and industry have transported considerable organic material to coastal waters, leading to the formation of quite large, but not global, anoxic regions – the 400 or so dead zones that cover 100’s of km2 of our coastal waters.  Our climate is also warming.  How close are we to another episode of major ocean anoxia?  Understanding the phenomenon of anoxia in the global ocean seems particularly important at the present time.

Every ocean basin contains an oxygen minimum zone a few hundred meters deep, at which the rates of respiration by organisms and decomposition of organic matter are sufficiently fast to reduce dissolved oxygen concentrations in the water sharply.  Below this depth, with relatively little in the way of organisms or organic debris remaining (most animals and plants are living in the surface layers), the consumption of oxygen is less rapid and oxygen concentrations tend to be higher again.  Watson reports that oxygen concentrations are falling in many ocean basins, and are already close to or at zero in the oxygen minimum zones of the equatorial Pacific and the Indian Ocean.

Basing his report on results from a workshop organized by the Royal Society (UK), Watson relates the availability of oxygen in ocean water to the availability of phosphate, a nutrient that is limiting to phytoplankton and other microbial growth in marine systems.  The downward movement of water which delivers oxygen to deeper layers of the ocean is compensated by upwelling of deep water that brings phosphate to surface layers stimulating phytoplanktonic activity.  That activity generates the organic material that consumes oxygen as it settles to deeper layers, resulting in the oxygen minimum zone and determining the concentration of oxygen in deeper waters.  A complicated feedback process is in place.  As Watson describes it, “demand [for oxygen] is governed by the amount of phosphate in the deep ocean, whereas the supply is set by the amount of atmospheric oxygen that dissolves in surface water.  A little more phosphate, and much more of the ocean would be hypoxic (low in oxygen).  Doubling ocean phosphate would be sufficient to bring on a full-scale ocean anoxic event.”  Watson then points to the importance of major volcanism in increasing the availability of oceanic phosphates in past times, and to anthropogenic activities, notably agriculture, forestry and some industry, that increase the transport of phosphate from the land to the ocean at the present time.  Might we be at risk of promoting the formation of an anoxic ocean today, and are observed reductions in oxygen content in recent years a sign that this is now under way?

Watson stresses that the process of turning the ocean anoxic is quite slow (timescales of 100,000 years), but also notes that once the oceans become anoxic there are positive feedbacks that can make it difficult to move back towards a more oxygenated state.  His essay shows the complexity of oxygenation in the ocean, while also suggesting that we might do well to watch our farming and other practices to limit our aid to the process of deoxygenation.

Just as readers were digesting Watson’s message, Sunke Schmidtko and two colleagues from the Helmholz Center for Ocean Research in Kiel, Germany, published their paper in Nature on 16th February.  Their concern is the decline in dissolved oxygen in the oceans over the last 50 years.  They report having performed “a quantitative assessment of the entire ocean oxygen inventory by analyzing dissolved oxygen and supporting data for the complete oceanic water column over the past 50 years.  We find that the global oceanic oxygen content of 227.4 ± 1.1 petamoles (1015 mol) has decreased by more than two per cent (4.8 ± 2.1 petamoles) since 1960, with large variations in oxygen loss in different ocean basins and at different depths.”  Translating their words from science-speak, the oceans hold about 3.6 quadrillion kilograms of oxygen, almost 77 trillion kilograms less than in 1960.  No matter how you say it, that is lots of oxygen, but distributed through the many km3 of ocean waters it is a pretty low concentration.

Schmidtko and colleagues attribute the decrease to several factors.  Warming of upper layers of the ocean has reduced the solubility of oxygen, lessening the amount that will fully saturate surface waters.  Warming also enhances metabolic processes, and thus the rate of consumption of oxygen in upper layers increases.  This in turn further reduces concentrations.  In deeper waters, reduced concentrations are likely due to slowed overturning circulation (slower rate of downward transport of oxygenated water) as well as biological activity in the deep ocean.  However, their study also reveals clearly that different ocean basins are behaving differently and rates of decline differ among depths and among basins.  This means that the factors responsible for the decline in dissolved oxygen over the past 50 years still require further investigation.  Overall, the message from Watson and from Schmidtko is that our oceans appear to be moving towards an anoxic state.  Schmidtko suggests the total reduction by 2100 could amount to about 128 trillion kilograms of oxygen, or around 3.5% of the current amount dissolved.  Not a large change, but not a desirable one given how much of the ocean is already close to anoxic.

We need more science, not less, and more use of that science in our models of the future

I started by suggesting that, from the perspective of a tropical sandy beach, the sea and the sky were rather simple and pleasant.  When you delve more deeply, it’s clear that a lot goes on in each, that there are complicated interactions and feedbacks among the processes, and that there are changes taking place at present that could pose problems for the functioning of biological systems in the future.  Some of those changes are due to our activities.

What to do?  If you are sitting on that tropical beach, enjoy being there.  But also, be aware of three things.  Nothing on this planet is a simple as it seems at first.  We need more science concerning the atmosphere and the ocean if we are going to be able to adequately understand the consequences of our planetary impacts.  And, our world is being changed, seldom for the better, in many complex ways by our activities.

If you have a house on that beach, you might also do well to think about the impossibility of holding back a rising sea.

Categories: Arctic, Changing Oceans, Climate change, In the News | Comments Off on Sea and Sky – Complexity abounds, which is why climate change is so difficult to understand and project into the future.

The many forms of cooperation on coral reefs


At a time when the political world seems overfilled with evidence of human greed, selfishness, destructive competitiveness, and utter immorality, I found myself reading Tim Flannery’s 2011 book, Here on Earth: A natural history of the planet.  It’s not perfect, but it is a good read.  It lifted my spirits.

In it, Flannery contrasts the Medea and the Gaia hypotheses.  The Medea hypothesis, developed by Peter Ward, holds that natural selection drives a perpetual arms race among species that ultimately leads to system collapse.  The Gaia hypothesis, coined by James Lovelock, argues that the Earth system continually evolves to become more and more strongly interconnected as a self-organizing complex system with considerable resilience.  Flannery comes down in favor of Gaia, contending that natural selection is just as powerful in shaping affiliative, cooperative interactions and relationships within and among species, as it is in shaping competitive, predatory and other destructive interactions.  Let’s think of these as the win-win (Gaia) and the win-lose (Medea) interactions that characterize all interactions among living beings.  While I remain unconvinced that the planet is in the process of becoming some sort of living super-organism as James Lovelock proposed, I am persuaded by Flannery that we and all other species naturally have the capacity to develop increasingly strong affiliative responses, just as we naturally are capable of developing ever more savage destructive tendencies.

Two hypotheses about our relationship to Earth, Gaia and Medea, as visualized by Sarah Howell.  Image © Sarah Howell/

Because humanity changes through a combination of natural selection and cultural selection, our rates of change, in both positive and negative directions, are blindingly fast compared to those of our pre-civilized forebears, or those of other creatures.  This speed carries great risk because we have become a potent force for planetary-scale change, and change in bad directions (towards less well-integrated, less resilient, less effectively connected ecologies) can have substantial consequences before we are even aware of what is happening.  Flannery likens us to newborn infants still learning to function in our world; an apt metaphor that helps me understand why so many of us still do not appreciate the immense impacts of humanity on the planet over the last century or so, nor the urgency of the need to change course if we want to get to a ‘good future’ without going through hell to get there.

Evolution of cooperation

The easiest affiliative responses to understand are those within a social group of (usually) closely related individuals.  Quite simple genetics can explain the evolution of parental behavior, and the seemingly altruistic behavior directed towards one’s parents or siblings.  In these cases, actions that favor the survival of the relative can be selected for even when they lead to some risk or disadvantage to the actor.  Parents do risk their own lives to save their children, and siblings also behave altruistically to save one another; while we consider such self-sacrificing acts as noble, brave, loyal, they are also readily explained as a consequence of natural selection – taking a risk to help an immediate relative helps ensure the survival of copies of a substantial proportion of your own genes, and evolution is all about getting copies of your own genes to survive.

Extending such altruism to more distantly related members of your social group, or to random strangers, requires more complex genetic reasoning.  One argument made is that groups which contain at least some altruistic members will enjoy enhanced survivorship overall, relative to other groups comprising more completely selfish members.  Extending affiliative responses to other species requires even more genetic gymnastics, but the gymnastics are plausible and cross-species affiliative behavior definitely exists on our planet.  There are wonderful examples on coral reefs, and these are my topic today.  They are one more example of how coral reefs are magnificent, and why we should care more about their continued presence on this planet than we currently do.

Cooperation on coral reefs

Coral reefs are species-rich ecosystems.  Individuals live in close proximity to many others, of their own and other species, so opportunities for interaction are frequent.  Some of these associations among neighbors are symbiotic (literally ‘living together’), as mutualisms, commensalisms, or parasitisms.  Of these, only the parasitic ones are examples of win-lose interactions.  Symbiosis is a common occurrence on reefs, and many people have claimed the high frequency of symbiosis is a unique attribute of reef ecosystems, making them different to other marine systems.  I doubt there is anything ‘special’ about coral reefs in this regard.  So far as I know, nobody has yet demonstrated that symbiotic relationships on reefs are more common than they are in other ecosystems, once one adjusts for the very large number of species typically present there.  To put it bluntly, there are few examples of symbiosis on the tundra because that is an ecosystem comprised of few species, and the reverse is true for coral reefs.

Never mind symbioses for a moment.  A coral reef consists of a number of neighborhoods, each occupied by numerous individuals of many species.  Most of these individuals are quite circumscribed in their movements from day to day; they are resident in their neighborhoods.  Setting aside the sessile creatures such as corals, gorgonians and sponges, it does not take many visits, by snorkel or scuba, to recognize that each neighborhood has its own resident fish, crabs, sea urchins and so on that are reliably present day after day.  The fishes have neighbors that they recognize as individuals whether of their own or of other species.  I suspect the crustaceans are fully as aware; the worms, molluscs, echinoderms likely far less so.  Affiliative interactions do not require such awareness, but its presence enhances the possibilities.

A coral reef, such as this one in the Red Sea, is made up of neighborhoods, each with its own residents of various species.  Plenty of opportunities for interactions, affiliative or not.
© Vladimir Levantovsky.

Cooperative damsels

The thousands of damselfishes of the world can be roughly divided into the small, colorful, planktivorous ones (that help explain why the group was called damselfishes in the first place), and the larger, stockier, more drably colored and downright belligerent herbivores.  People whose experience is primarily in the Caribbean think of damselfishes as these belligerent beasts because they comprise over half the species present.  Those whose experience is primarily Indo-Pacific think of damselfishes as those delicate, colorful damsels hovering in vast shoals over every available coral-covered spur or slope, picking plankton one by one as the water streams past.  For them, the relatively far fewer belligerent ones are atypical of what damselfishes really are.

Lemon damsels (Pomacentrus moluccensis) and humbugs (Dascyllus aruanus) feeding on plankton above branching Acropora.  Not wandering, they are at home.
Photo © Luciano Napolitano.

When we see a shoal of the bright yellow damsel, Pomacentrus moluccensis, hundreds of individuals hovering 50cm to a meter or so above branching Acropora, we tend to assume they are rather boring little creatures with zero individuality.  Some of us simply classify them as ‘minnows’ or ‘fish food’.  Such creatures have not received the detailed attention from behavioral ecologists they might deserve, and I think we’d be surprised if some such attention was paid.  I say this because a long time ago a graduate student of mine, Bruce Mapstone, did pay attention to P. moluccensis, and while his focus was primarily demographic ecology, he tagged a few with subcutaneous latex paint marks, and discovered that the same individuals took up position over the same patch of coral day after day, that they hovered to the left and the right, above and below the same other tagged fish, and despite being ‘silly little fish’ could live a decade or more.  Now Bruce, in his wisdom, wandered away without ever publishing his results, got into more ‘important’ reef ecology, and eventually wandered clear out of the tropics to a career in Tasmania.  But think about the fish.  Day after day, the same fishes, in the same spatial relationship to one another, hovering over branching coral, feeding on plankton.  I’d never have believed that, and I would not be surprised if somebody one day discovers that their social behavior is a bit richer than just foraging beside their buddies!

The belligerent herbivorous damselfishes have received far more attention from behavioral scientists.  What is quickly obvious is that while individuals each tirelessly defend their own small territories from nearly every creature that comes by, they live in groups with contiguous territories, and spend lots of time arguing with each other across the shared borders.  In some cases, the local groups may exist because the habitat is patchy, and they have filled a patch of suitable habitat.  But in other cases, the habitat is not obviously patchy in this way, and these belligerent little fish still persist in living side by side.  Some of my earliest research once I arrived in Australia involved tracking real estate transactions among groups of territorial damselfishes occupying small patches of rubble habitat on the reef slope.  As new young juveniles arrived, as individuals grew, expanding the size of their territories, and as individuals disappeared, presumably because something ate them, space in the rubble patch would get reassigned, borders would be redrawn, and I would see that some individuals were gaining whilst others lost.  What made this particularly interesting to me was that there were three different species of damselfish in my rubble patches.  Their competition did not seem to be leading to clear winner and loser species over time, despite the fact that individuals were arriving and departing and a simple ecologist might be forgiven for expecting that over time the ‘superior’ species would come to hold all the territory.  But that is a whole other story.

I raise territorial damsels here because they do live in social groups, even groups comprised of more than one species.  Why do they do this, given that there seems to be enough available space in most cases for them to spread out and have more tranquil lives?  The late George Barlow of UC Berkeley, and one of the greats of behavioral biology, coined the term ‘dear enemy effect’ to describe the tendency of territorial species to live beside one another, and to behave less aggressively to known neighbors than to strangers.  This is certainly the case for territorial damselfishes.  But that does not explain why they cluster together.  Nor does the need for accessible mates – they could space themselves apart and still come together to breed with two or three quick flicks of their tails.  We have to broaden the frame of reference and remember that these fish are defending their territories from myriad species of fish and some invertebrates – any herbivore or potential egg predator gets particular attention.  And when we do, we find a wonderful example in which group living by territory holders improves their ability to defend their homes, while group foraging by roving herbivores increases their capacity to invade and feed within those same homes.

Cooperative grazers – using win-win to succeed at win-lose

While there are many solitary herbivores, many species of parrotfish and surgeonfish tend to travel in groups, of one or several species.  These are not the highly-organized schools of herring, sardine or anchovy, maintaining rigid spacing one from another as they perform intricate group gymnastics rivalling those of flocks of birds and swarms of insects, while leaving human synchronized swimmers far behind in their dust.  The herbivore schools are more like herds of cattle or sheep as they spill across the reef, munching algae as they go.  When such a group moves over the territory of a damselfish the defender’s capacity to defend is swamped, and plenty of herbivores get to feed within the territory.  Work by Susan Foster in Panama in the mid-1980s demonstrated how damselfishes were more successful at defending their algal mats when in larger groups, and that surgeonfishes were not successful at all in entering damsel territories when alone, but could enter and feed when in groups.  She showed that the feeding rate of blue tang within damsel territories was directly related to the size of the foraging group.  What we have here is pugnacious territorial damsels banding together as a group because the group of contiguous territories is better defended when they act together than individual territories could be, and roving herbivorous parrot- and surgeonfishes banding together as an effective way of managing to get some feeding done within damsel territories – two win-win affiliative responses creating two opposing groups of allies engaged in a win-lose war for access to food.

A school of Manini, Acanthurus triostegus, foraging across a reef at Hanauma Bay, Hawaii.
© Hanauma Bay Snorkel Tours.

Cooperative hunting

It’s not only reef herbivores that sometimes band together in feeding.  In a post in July 2015, I described a study showing how the coral trout, an important serranid piscivore on the Great Barrier Reef, solicits the help of a moray eel when foraging for fish in complex reef habitats.  Many reef scientists have observed predators of different species apparently teaming up to hunt for prey from time to time, but the particular study that caught my eye was an experimental one, which asked the intriguing question, “Will a coral trout solicit the help of an eel when the prey would be otherwise inaccessible to it, but not share the hunt with an eel if the prey is more accessible?  The short answer is ‘yes’ (read the post if you want more), revealing that not only do reef fish cooperate across species in hunting, but that they decide, depending on the particular circumstances, whether to seek out potential partners or not.  This is surely learned behavior of an advanced kind, and I’d love to know whether young coral trout (and eels) learn to cooperate by watching more experienced members of their species, or if these rather solitary creatures have to learn this by trial and error.  I’d also like to know how general a trait this is both within locations and across reef regions.

Just like a small cantina

To those of us who remember the first screenings of Star Wars, episode IV, in 1977, two or three scenes stand out clearly.  The Mos Eisley cantina on Tatooine is invariably one of these.  An amazing collection of very different species, all gathered together, mostly though not entirely peacefully, enjoying their favorite libations while the bar tender served and the band played on.  There is tension in the air; brief savage fights break out, but there is also laughter at shared jokes.  Creatures that would not be friends at other times or places, come together in the cantina for enjoyment and deal-making.  For me, a cleaning station is the coral reef version of this cantina, particularly when it is busy and fish of many species are queuing up waiting their turn to be serviced.

Chalmun’s Cantina in Mos Eisley, Tatooine.  A little like a cleaning station with fish of many species lining up to be serviced?  Photo © Lucasfilm.

 As anyone with a rudimentary knowledge of coral reefs knows, certain reef fishes set up cleaning stations which are visited by a wide range of species of fish (the cleanees) seeking to have parasites removed.  As is often the case, this phenomenon is better (or more extravagantly) developed in the Indo-Pacific than in the Caribbean.  In the Indo-Pacific, the most prominent cleaning stations are maintained by species of the genus Labroides, a medium-sized wrasse reaching about 10cm in length.  Labroides is an obligate cleaner, in the sense that it feeds on ectoparasites throughout its life, so long as other species of fish are available to be cleaned.  A number of other species of wrasses, gobies and other fish, and a number of shrimps clean in both the Indo-Pacific and the Caribbean.  For most fish other than Labroides, this is a juvenile occupation, although it’s a whole life career for some gobies.  Cleaning stations in the Caribbean, which lacks Labroides, are a far less dramatic engagement than what takes place at Indo-Pacific sites, where large fish of many species can be seen lining up awaiting their turn to be cleaned.

Given that cleaning requires that a small, nutritious morsel – the cleaner – must approach a larger, often piscivorous, fish with big teeth, all the while dancing seductively, and then cruise about close to its surface, touching it intimately, and even wandering into the mouth and gill chamber in search of pesky parasites, the existence of cleaning behavior is an amazing example of why reefs are wondrous places.  Cleaning is not a close association between two individuals of different species who might have learned to recognize each other and recognize the benefits of helping each other.  This is an example where one small species of fish has set up shop offering a personal grooming service that any other species of fish is welcome to request (or other large creature, because Labroides will clean turtles and divers just as willingly as large fishes).  These are creatures like Winnie the Pooh; they are ‘of little brain’.  A single misstep means one fewer cleaner exists.  How do cleaners know that it is safe to approach a cleanee?  How do cleanees know that a cleaner is offering a service?  Why don’t potential cleanees ever decide to enjoy a cheap meal at a cleaner’s cost, and then go to a rival station to be cleaned?  Put another way, cleaner fishes put themselves at far more immediate risk of death than any street prostitute ever does, no matter how bad the section of town she/he patrols.  Their clients are often many times bigger than they are, they are expected to put themselves very much in harm’s way, and their interactions are always cross-species.  People often have difficulty training their dogs to behave!  Who tells the naïve young coral trout that visiting a cleaning station is fun, but there are certain unspoken rules you must obey?

A wrasse, Novaculiththys taeniourus, being serviced by two Labroides phthirophagus at a cleaning station on a Hawaiian reef near Kona.  Photo © Mila Zinkova.

A new review of cleaning symbioses by David Vaughn of James Cook University, Australia, and three colleagues, to appear shortly in Fish and Fisheries, makes clear that the cleaning phenomenon is geographically widespread in marine and freshwater environments.  It is particularly apparent on coral reefs but that may partly reflect differing levels of researcher attention.  They list 208 fish species and 51 shrimp species as reported to engage in cleaning behavior, but many of these are facultative cleaners performing only occasionally or only during juvenile life.  They also report that cheating by both cleaners and cleanees has been documented; indeed, cheating may be quite common in the cleaner wrasses, Labroides which frequently ingests mucus and scales while ostensibly removing parasites.  Indeed, George Losey, who did much of the pioneering work on cleaner behavior maintained that Labroides was an inveterate cheat, really out to seduce other species by giving them all the tactile stimuli they want, in order to get a meal of mucus or scales, or parasites if any were present.  Cheating by cleanees, by eating cleaners, appears to be a lot less common but still occurs, and my wonder at how cleaning symbioses evolved and how they are maintained remains.

Cooperation with corals

Until now I have avoided the corals and other sessile creatures.  I tend to think of them as part of the habitat, the backdrop to an exciting play involving the more mobile creatures.  Yet they too are reef creatures, and they are important in many cross-species interactions.  Many reef scientists would begin, and perhaps end, a discussion of symbiosis with the relationship between corals and their algal symbionts, the zooxanthellae.  Given the importance of coral bleaching these days, and the fact that bleaching is the breakdown of this very close relationship, I should not ignore it.  The coral-symbiont relationship is a crucial factor in permitting the existence of coral reefs.  But that is all I will say – I prefer cooperative associations in which behavioral decisions (rather than physiological or chemical ones) are more obviously in play.

Many reef creatures, such as the lemon damsels I began with, use corals as shelter sites.  In many cases, including the lemon damsel, living coral is so strongly preferred that these fish will leave a coral after it has been killed, running the risk of not finding another suitable refuge.  One should call these associations with living coral a cross-species affiliative response, but they are not terribly interesting ones.  Except in cases where they are.

Gobies of the genus Gobiodon are tiny obligate occupants of branching corals of the genus Acropora.  They are widely distributed through the Indo-Pacific, and show evident preferences for particular host species.  They settle from the plankton into living Acropora colonies and are relatively long-lived (four years) for small gobies.  They spend their entire lives among the branches of their home colony, feeding partly on coral mucus, but also on small invertebrates and algal cells.  They usually are found in pairs.  In a series of papers beginning in 1997, Phil Munday of James Cook University, Australia, and colleagues mapped out the use of corals by the eight species of Gobiodon present on the central Great Barrier Reef.  Each species is associated with from 3 to 10 species of Acropora, but shows evident preferences for certain species.  Gobiodon species overlap in the species of coral occupied, and there is evidence of competition for host colonies.  Apart from the fact that the gobies only occupy living corals, there is little about this relationship to suggest it is an affiliative response between fish and coral.  But in 2012, the story changed.

Gobiodon histrio, nestled among the branches of its Acropora host with some fronds of Chlorodesmis fustigiata to the right.  Photo © Danielle Dixson.

Danielle Dixson and Mark Hay, of the Georgia Institute of Technology, reported their studies of gobies and corals in Fiji in an article published in 2012 in Science.  They had done a series of field and laboratory experiments using Gobiodon histrio and Paragobiodon echinocephalus, a second coral-dwelling genus, the coral Acropora nasuta, and a seaweed, Chlorodesmis fastigiata.  Both gobies are common in A. nasuta colonies at Fiji.  Chlorodesmis is toxic, and coral surfaces in contact with its brilliant green fronds are damaged or killed.

Corals that were empty or housing only crabs suffered substantial impairment when Chlorodesmis fronds were placed in contact with their tissues.  Those housing either species of goby were scarcely affected by the alga.  Algal mimics of nylon threads placed in contact with the coral also had no effect on coral performance.  Image © D. Dixson & Science.

Dixson and Hay demonstrated that rather than just being a case of gobies choosing to live among the branches of live coral, like so many squatters in an abandoned building, both species of goby were actively protecting their home coral from contact with the alga.  And the coral, when it came into contact with the alga, was releasing chemicals which served to summon the fish to its defense.  Their series of simple, yet convincing experiments showed:

  • that corals were damaged when fronds of Chlorodesmis were brought into contact,
  • that corals occupied by Gobiodon or Paragobiodon, but not by two other species of common coral-sheltering fishes, were protected from contact with the alga, because Gobiodon ate the offending alga while Paragobiodon bit off fronds and removed them from the vicinity of the coral,
  • that chemicals released by coral tissue in contact with Chlorodesmis attract Gobiodon, while Chlorodesmis alone does not, and
  • that when the toxic hydrophobic chemical is extracted from Chlorodesmis, and applied to a nylon twine mimic of the alga placed in contact with a coral, it still attracts Gobiodon.

Naturally, Dixson and Hay described these results using verbs like ‘signal’ and ‘respond’, even referring in a press release to Gobiodon as ‘coming to the aid of’ its host coral.  The study got plenty of press at the time.  Still, it is a surprisingly intimate association between very different kinds of creatures, acting in ways that provide benefits to both.  Personally, I find the unanswered question about Paragobiodon one of the most interesting.  Gobiodon, when alerted chemically attacks the alga and eats it.  It gets some food, and perhaps bolsters its own chemical defenses (it is toxic itself).  One can easily imagine it learning to associate the particular chemical as a sign that there is food nearby.  But Paragobiodon does not eat the toxic Chlorodesmis.  It responds just as strongly to the chemical signal from the coral, but then bites off fronds and carries them away.  Why?  Is it just a neat freak?  Or is it altruistically caring for its coral home?

I admit to being biased against corals and other sessile creatures.  I have focused almost entirely on fishes.  I’ve managed to avoid any mention of Nemo and his anemone home, but I want to finish with an example involving another anemone and a crab.  My attention was drawn to it just this month, when Laurie Richardson of Florida International University told coral list about a new paper.  (Not the best way for a scientist to keep up with the literature perhaps, but, hey, I am retired!)

Pom-pom or boxer crabs are tiny members of the genus Lybia, one of the many small crabs that occur on coral reefs.   They occur across the vast Indo-Pacific from the Red Sea to the shores of Hawaii.  Lybia leptochelis is a Red Sea species; like all members of the genus, it carries a small anemone in each claw which is otherwise weak and not suited for defense.  The anemones provide defense and they also catch food some of which the crab steals for its own use.  In the Red Sea, L. leptochelis carries anemones belonging to an as yet unnamed species of Alicia.  Even the smallest, recently hatched Lybia have minute anemones in their claws, although immediately on hatching they are unarmed.  The Alicia species has only been found on Lybia claws.

The boxer crab, Lybia leptochelis with its two Alicia anemones, one in each claw.
© Yisrael Schnytzer, PeerJ.

Now, what kind of relationship is this?  The crab clearly benefits from carrying the anemones around, and the anemone perhaps benefits by being carried to new sources of food.  That the anemone is very rare if present at all away from the crabs suggests strongly that this is an obligate partnership for both partners.  The article that caught my eye was published by Yisrael Schnytzer, of Bar-Ilan University, Israel, and three colleagues in the journal PeerJ at the end of January.  By means of a combination of field observations, aquarium experiments and genetic analyses, Schnytzer established that crabs deprived of one anemone will usually split the remaining anemone in two longitudinally, thus mimicking or facilitating normal asexual reproduction via fission.  They do this by holding the body of the anemone with both claws and slowly stretching it apart over a period of 15 min to two hours.  The authors have a neat video of this in the supplemental materials accessible from the article.

Crabs that lack anemones will fight with crabs possessing anemones and will usually succeed in taking one of the anemones away.  In such cases, both crabs cause the fission of their single anemones over the next few hours or day, so that each then has two.  In some instances, fighting results in only part of one anemone being ‘captured’.  When this happens the crab with the partial anemone will attempt to split the part to provide one small anemone for each claw.  Genetic analysis revealed very little genetic variation among anemones collected from crabs within the Red Sea study location, and showed that every crab sampled carried a pair of genetically identical clones.

Putting these results with earlier results obtained by this team, it appears that Lybia leptochelis is an obligate carrier of the Alicia anemone, despite the fact that Triactis producta, an anemone commonly carried by other Lybia species is commonly present living freely in the environment.  Further, Lybia, by regulating the food available to its anemones practices a sort of bonsai, limiting anemone growth; anemones are closely sized to the size of the host crab.  When you add in the newly reported forced reproduction of the anemone, this relationship is looking a lot more like farming than a mutualism in which the partners gain almost equal benefits.  Does the crab view the anemone as a partner?  Well, even if the crab were capable of such thoughts, I doubt it would.  This is crustacean animal husbandry pure and simple, but it is still a great example of the complexity that is possible in the positive, affiliative interactions among creatures on a coral reef.  Win-win relationships, sometimes bizarre ones, are common on this planet.  Think about that next time you see a tweet from the Oval Office.  It IS possible to see things differently to the current view from there.  Even for little, orange crabs with weak hands.  Think of that next time you see the current occupant of the Oval Office.

Categories: animal behavior, coral reef science, Stories from a Coral Reef | 2 Comments