Go check out these incredible photographs by National Geographic photographer Thomas Peschak of mantaray feeding frenzies in the Maldives. Apparently this swirling ‘cyclone‘ feeding behavior is rarely seen outside of the Maldives. Click here for a previous post on Climate Shifts for more details and video footage of Mantaray feeding behaviors.
Seagrass meadows have long been known to be highly productive habitats, and as a result producing oodles of oxygen in the midday sun. Anyone who’s ever snorkelled over a seagrass meadow on a sunny day will have seen seagrass leaves furiously bubbling away. This photosynthetic productivity can result in an increase in the pH of the water column (becoming less acidic). This is primarily because CO2 and, thus, its form when dissolved in seawater, carbonic acid, are withdrawn from the water as a substrate for photosynthesis. This results in the production of the bubbling O2. But what are the consequences of such a pH change?
Recent research by the Universities of Dar es Salaam, Tel Aviv and Stockholm published in the Marine Ecology Progress Series (volume 382) and conducted in tropical seagrass meadows of East Africa have investigated the impact of such pH changes. Semasi et al. revealed that this change in pH can cause localised increases in the rates of calcification and growth of calcareous algae such as Hydrolithon sp., Mesophyllum sp., and Halimeda sp., hence seagrass buffers high acidity (low pH).
As has been debated by ClimateShifts previously, there is increasing evidence that oceans have become more acidic since the start of the industrial era. Recent predictions suggest that oceans could become much more acidic over the next 100 years as a result of increasing CO2 emissions. Current predictions suggest that this will result in (amongst other things) declining reef calcification rates.
Although this study by Semesi et al. shows the effects of seagrass upon algae, the questions on the lips of many reef conservationists will be whether such findings are cross transferable to the calcification of corals. These studies in Zanzibar were small scale, carried out in seagrass mesocosms, and currently only reflect small scale patterns. Whether seagrass productivity can result in larger spatial scale changes that could buffer pH changes on nearby reefs remains to be seen. Maybe the World should be looking at seagrass meadows with greater attention?
I stumbled across this great mapping system of CO2 emmisions over at Science Daily. Whilst previous estimates of CO2 levels have been calculated per capita in the US, a new map called ‘Vulcan’ created by biogeochemists at Purdue University shows the top local and regional carbon dioxide producers in high resolution.
In the past, CO2 levels have been calculated based on population, putting the Northeast at the top of the list. Now, a new map called Vulcan reveals for the first time where the top carbon dioxide producers are in the country. The answer surprised Kevin Gurney, Ph.D., a biogeochemist at Purdue University in West Lafayette, Ind.
“There are a lot more emissions in the Southeast than we previously thought, and a lot of that is because it’s not necessarily associated with where people live directly, but actually where industry and activities are,” said Dr. Gurney.
The high-resolution map shows 100 times more detail than ever before and zooms in to show greenhouse gas sources right down to factories, power plants and even roadways. An animated version of Vulcan reveals huge amounts of greenhouse gas gets blown toward the North Atlantic region.
“We’ve never had a map with this much detail and accuracy that everyone can view online,” Dr. Gurney said. (Read more @ Science Daily)
The official website (“The Vulcan Project“) has an amazing Google Earth interface, where you can map the emissions from US power producers, residential and commercial CO2 emissions at 100km2 local scale resolution. Perhaps the most interesting contrast is the maps of residential CO2 emissions when comparing Republican vs Democrat districts. Given the difference in population density between the US and Australia, it’d be interesting to see someone scale this effort to a continental scale, allowing regional comparisons and perspectives on global carbon budgets.
In a major step to protecting the inshore reefs of the GBR, the Queensland Government have inacted fairly dramatic legislation on the use of fertilisers and pesticides on farms in the reef catchment. Under the new rules, farmers in the Mackay-Whitsunday, Burdekin Dry Tropics and Far North’s Wet Tropic catchments must keep records on fertiliser usage and apply ‘no more than the optimum amount of fertiliser to their soil’. The use of the pesticides Atrazine, Diuron, Ametryn, Hexazinone or Tebuthiuron are also subject to an array of new rules and regulations.
Although not without controversy, this is great news for the reefs on the GBR. Over 32,000 tonnes of fertiliser (worth $32 million) leaches out into the Great Barrier Reef lagoon every year through overfertilisation on farms. There is strong scientific evidence showing that elevated pesticide and nutrients from the land associated with flood waters induce coral bleaching and mortality during flood years (see here for a great post by Jon Brodie on the subject).
Strict controls on fertilisers and pesticides and close monitoring of large and high-risk farms in north Queensland will help heal the Great Barrier Reef, Climate Change and Sustainability Minister Kate Jones said today.
Ms Jones, introducing the Great Barrier Reef Protection Bill 2009 to State Parliament, said the legislation would reduce the levels of farm chemicals and sediment harming the Reef.
“The Bill will help detox the Great Barrier Reef and give it a fighting chance,” Ms Jones said.
“The Great Barrier Reef is Australia’s most treasured possession and is worth nearly $6 billion to our economy, supporting about 63,000 jobs.
“But its health has been deteriorating from a number of factors, including damaging run-off from sugar cane fields and beef cattle farms in Reef catchments.
“We must do all we can to ensure this natural wonder of the world survives long after us and that means minimising man-made harm. This Bill is good for the Reef and it makes good business sense for farmers.
“While many farmers are doing the right thing and have minimised their impact, we must go further than the voluntary approach to get the results we need faster.
“Our Reef is too precious so we have no option but to act now and act decisively.
“The Bligh Government told Queenslanders last election that we would regulate to reduce the amount of fertiliser and pesticides entering the Reef by 50 per cent in four years.
“The Bill makes good on that commitment. It’s backed by strong scientific evidence and it gives the Reef every chance of recovering from the damage inflicted by over-fertilising, toxic pesticides and soil run-off.”(Link to media release)
The paradigm of ‘coral vs algae’ has become entrenched in coral reef science over the last few decades. The classic example of this paradigm in the Caribbean was from a paper published byTerry Hughes in a 1994 article in the journal Nature, entitled “Catastrophes, Phase Shifts and Large-Scale Degradation of a Caribbean Coral Reef”. The paper documented a series of disturbances in the late 1970’s and early 1980’s, including two major hurricanes, a disease outbreak and the loss of a seaweed-grazing urchin, after which coral cover declined dramatically from ~70 percent cover to less than 10%, and macroalgal cover to rose to almost complete dominance >90% .
Temporal trends of coral and algae on Jamaican Reefs (top left, 1975 - 1995, Discovery Bay showing dramatic declines and corals and corresponding dominance of macroalgae, top right 1995 - 2004 from Dairy Bull Reef showing a rapid recovery and reversal of the macroalgal phase shifts)
Since then, reefs throughout the Caribbean have undergone dramatic declines in coral cover, leading to the regionwide collapse of the two dominant reef building corals, Acropora cervicornis and Acropora palmata. One ‘good news’ story did come out from a neighbouring reef in Jamaica called ‘Dairy Bull’ reef, where Joshua Idjadi and a team reported a doubling of live coral cover over the last decade, resetting the balance from a macroalgal dominated reef to a coral reef.
Photograph of Dairy Bull Reef in 2003 showing the recovery of the branching coral Acropora cervicornis. No macroalgae to be seen!
Since this iconic case study, a considerable quantity of scientific literature has been devoted to management principles, herbivorous grazing pressure and the reversal of macro-algal dominated reefs. However, documented examples of regional ‘phase shifts’ between coral and algae in the literature are surprisingly few and far between (asides from a few notable exceptions). John Bruno & Elizabeth Selig, two coral reef researchers who have developed a considerable dataset on coral reefs throughout the world, decided to test this assumption by randomly samply for regional trends and patterns in algal cover – much the same as an epidimiologist would determine the generality of case reports in the medical literature.
John and his team trawled through an immense number of reef surveys (3,500 to be exact) from over 1,800 reefs across the globe between 1996 and 2006, and developed a ‘phase shift index’ based upon corals and macroalgae. They then tested this index in four geographic regions (Greater Caribbean, Florida Keys, Indo-Pacific and the Great Barrier Reef) to see if the severity of phase shifts altered over the decade between 1996 – 2006. Their findings were surprising, and might prove to be somewhat controversial…
A coral reef in the Caribbean dominated by macroalgal cover
Whilst phase shifts were indeed more common in the Caribbean than elsewhere, very few of the worlds reefs fell into either a stable ‘coral reef dominated’ or a ‘macroalgal dominated’ category. Furthermore, the ‘severity’ of phase shifts at a regional level was much less severe than the classic examples of macroalgal dominance, such as the Jamaican coral decline story. The data also suggested that there was no trend (>1995) towards macroalgal dominance in the Florida Keys or Indo-Pacific. Coral cover during this period (1996 – 2006) did decline (primarily due to crown of thorns starfish plagues), but their was no corresponding increase in macroalgal cover at all during this time.
Bruno et al argue that the apparent mismatch between the local scale descriptions of macroalgal dominance and regional scale patterns was caused by a gross generalisation of a relatively small number of ‘atypical’ case studies. This in itself is no small finding, and may go along way to altering the way we manage coral reefs. These findings may be somewhat controversial, it’s hard to disagree with the data. In what’s bound to throw the proverbial cat amongst the pigeons, the authors conclude:
“Since the Jamaica story was an anomaly, it makes a poor foundation for general models of reef ecology (e.g., Knowlton 1992, Bellwood et al. 2004 ). The current paradigm of reef management and ‘‘resilience’’ is based in large part on the perception that most of the world’s reefs are being overrun by seaweed (Szmant 2001, Precht and Aronson 2006, Knowlton 2008). This belief led to the argument that reef managers should focus primarily on conserving herbivores or water quality (Szmant 2002, Pandolfi et al. 2003, Bellwood et al. 2004 ). While these are clearly important objectives of management, our analysis suggests that the macroalgae problem has been exaggerated.
Overfishing and poor land use practices may trigger widespread coral to macroalgal phase shifts in the future, but to date, the principal form of coral reef degradation has been the loss of reef-building corals, with only limited and localized increases in macroalgae. Therefore, the primary goal for reef managers and policy makers should be the conservation of coral populations, without which the entire system would collapse.”
You might think that this idea sounds a little crazy but I urge you to read on. Here’s the idea: Everyone paints the roof of their house white and the rate of global warming will be radically reduced!
Insane? Well, this idea does have some sense and logic to it. I recently discussed this with my friend Ken Caldeira at Stanford University. Over some monstrously huge American sandwiches, our discussions eventually came round to the amazing impact that losing the reflectivity of Arctic summer ice would have on the rate of global warming. A few back of the envelope calculations by Ken soon convinced the people around the lunch table that changing the reflectivity of an even 1% of the Earth’s surface could have a major impact on the amount of trapped radiation solar. Flip side? Essentially, losing the albedo of the Artic sea ice is like piling massive amounts of CO2 into the atmosphere.
Back at Ken’s lab, discussions with Long Cao (one of Ken’s postdoctoral fellows) turned to whether or not one could influence this effect by manipulating the reflectivity of the earth through other means – What about doing a Christo? What about covering large areas with white chalk or mirrors? What about inventing a highly reflective plant that would spread out across arid areas and change the reflectivity of desert regions? Interestingly, the quick search of the literature revealed that this latter idea is being actively explored by scientists:
Andy Ridgwell and colleagues at the University of Bristol in England have another idea, one they call bio-geoengineering. Rather than developing infrastructure to help cool the planet, they propose using an existing one: agriculture. Their calculations, published in Current Biology, suggest that by planting crop varieties that reflect more sunlight, summertime cooling of about 2 degrees Fahrenheit could be obtained across central North America and a wide band of Europe and Asia. Plants reflect slightly different amounts of light depending on factors like how waxy the leaves are. Even differences in growth patterns between two varieties of a crop — the way leaves are arranged — can affect reflectivity. (Read More)
Now, Steven Chu, the Nobel prize-winning physicist appointed by President Obama as Energy Secretary, has proposed that we seriously explore this idea. Rather than use the rather challenging (from all aspects!) idea of engineering plants, Steven would like to whitewash the world – to initiate a global initiative to change the colour of roofs, roads and pavements so that they reflect more sun?
As a weapon against global warming, it sounds so simple and low-tech that it could not possibly work. But the idea of using millions of buckets of whitewash to avert climate catastrophe has won the backing of one of the world’s most influential scientists.
Steven Chu, the Nobel prize-winning physicist appointed by President Obama as Energy Secretary, wants to paint the world white. A global initiative to change the colour of roofs, roads and pavements so that they reflect more sunlight and heat could play a big part in containing global warming, he said yesterday. By lightening paved surfaces and roofs to the colour of cement, it would be possible to cut carbon emissions by as much as taking all the world’s cars off the roads for 11 years, he said. (Read More)
Not a bad idea at all – and one that would be achievable in a short-period of time. It would work like this: basically, governments would institute the painting of the tops of roofs and buildings (traditionally black tar, slate, or grey colours) white, this would alter the albedo (surface reflectivity of the sun’s radiation), effectively reducing the amount of heat trapped by the Earth’s surface to offset projected increases from global warming.
As a weapon against global warming, this idea sounds so simple and low-tech that it just might work. It could be used to reduce warming associated risks and buy some important time as we struggle to bring emissions down. As with all of these ideas, however, we must also be cautious not to use them as an excuse for not dealing with the problem of rising atmospheric CO2. These measures will only offset part of the problem and certainly will be exceeded in time. And, clearly, reducing global temperature in this way will do nothing for problems like those assoociated with ocean acidification.
A recent study published by Tom Oliver and Stephen Palumbi from Stanford University in the journal ‘Marine Ecology Progress Series‘ seems to suggest yet another miraculous and novel mechanism by which corals will ‘escape’ the pressures of global warming. In a nutshell, the researchers found that corals from ‘warm pools’ at Ofu Island (American Samoa) hosted ‘heat tolerant’ types of symbiotic algae, whereas corals from cooler lagoons hosted more ‘heat sensitive’ types of algae. When combined with regional data, Oliver & Palumbi suggest that in regions where annual maximum temperatures reached 29 – 31C, coral ‘avoided bleaching’ by hosting higher proportions of ‘heat tolerant’ algal symbionts. Whilst these findings are interesting, the study is a long way from the suggestion in the paper and accompanying press release that coral reefs are ‘adapting’ and ‘may survive global warming’, and relies mainly on over interpreting their results. There are several issues at hand:
These points aside, the study is an interesting one in terms of exploring heat stress in corals. My main issue is that Oliver & Palumbi have massively overextended their conclusions, which is particularly apparent in the associated press release. Needless to say, these sorts of overblown claims are less than useful in the lead-up to the critically important COP15 negotiations in Copenhagen at the end of year.
Update, 25th May
And here is a classic example of why such media releases are less than useful, courtesy of the detractor Andrew Bolt:
The megamouth shark (Megachasma pelagios) is one of the worlds rarest sharks – spotted only 43 times since its discovery back in 1976 off Oahu, Hawaii. These sharks are huge and bizzare creatures, capable of growing upwards of 5m in length, with luminescent light organs surrounding the mouth to attract plankton and small fish. So rare is the megamouth shark, that apparently scientists were surprised to find the 44th megamouth shark (caught by mackeral fishers in the Phillipines) had been cooked and eaten by local villagers before anyone could take a closer look. I wonder which part of the 500 kilogram shark was considered the delicacy? Read more at the National Geographic – thanks to Brian for the tip!
An article in press at Global Biogeochemical Cycles has shown that iron fertilisation can actually decrease the amount of carbon sinking to the ocean floor due to complex ecosystem processes.The iron fertilisation hypothesis was originally proposed as a rapid solution to climate change by increasing the photosynthetic uptake of CO2 by phytoplankton otherwise limited by their source of iron. Unfortunately, one of these climate change experiments was eaten by hungry crustaceans (see “Hungry Crustaceans Eat Climate Change Experiment”).
However, in another experiment, the scientists at the University of California at Berkeley continued to monitor the phytoplankton bloom and changes over an annual cycle with “Carbon Explorers”, floats that recorded data down to depths of 800 meters after the iron fertilisation experiment. These floats were placed both near and away from the iron induced phytoplankton blooms. Initially, these researchers discovered evidence in support of the Iron Hypothesis with a phytoplankton bloom leading to movement of carbon particles to at least 100m below the surface and this was reported in Science in April 2004.
Over the longer term the Carbon Explorers observed a different pattern which may be related to complex ecosystem processes that occurred during the following annual cycle. Despite the demise of the phytoplankton bloom the following winter, there was no carbon rain to match. In fact, there was greater particulate carbon falling at the site away from the original iron fertilisation. It turns out that the zooplankton survive the winter at depths below where the phytoplankton live due mixing of the oceans. Storms that cause this mixing create a conveyer belt of phytoplankton to the deeper dwelling zooplankton.
Larvae (zoea) of the spider crab (left) and the mitten crab (right) between 1 and 10 days old form part of the zooplankton ( 'hungry crustaceans').
If the water is continually mixed to depths with low light, then the phytoplankton do recuperate and the zooplankton eventually starve. At the site away from the iron fertilisation, the ocean mixing was intermittent and the phytoplankton were able to survive at the surface. The following spring, a bloom in phytoplankton fed the hungry zooplankton and led to increased carbon rain.
It seems that creating the right conditions for increasing oceanic carbon capture is in the hands of Poseidon and not something that can be easily predicted.
(Photograph courtesy of Flickr, zoea drawings from New Quay and UCSD)
Humans have been overfishing Caribbean reefs for decades or even centuries. And you don’t have to be a scientists to have noticed. Countless reefs once dominated by vertebrate predators are now nearly devoid of large fish.
Sharks and large grouper and snapper are a rarity on most Caribbean reefs. The reason isn’t a mystery; we simply removed them for sport, profit or sustenance. But the spatio-temporal patterns of predatory fish loss-where and when it happened-and how it was related to factors like proximity to people is largely unknown.
A new study just published in PLoS One by Dr. Chris Stallings sheds some light on the issue by documenting the dissapearence and reduction in size of predatory fish across the Caribbean. The study is based on a publicly accessible, fisheries-independent database of 38,116 reef surveys conducted between 1994 and 2008. Chris examined 20 species of top-level predators, including sharks, groupers, snappers, jacks, trumpetfish and barracuda, from 22 Caribbean nations. He found that nations with more people have reefs with far fewer large fish because as the number of people increases, so does demand for seafood.
Across the region, as human population density increases, presence of large-bodied fishes declines, and fish communities become dominated by a few smaller-bodied species.
The study nicely complements another recent study on Caribbean reef fish decline (Paddack et al 2009) covered here in Climate Shifts. One of the many advances of both papers is that they describe the Caribbean-wide loss of reef fish in greater detail than previous local studies. Seeing evidence of this ecological and economic travesty played out across the entire Caribbean is truly sobering.
“Although several factors–including loss of coral reef habitats–contributed to the general patterns, careful examination of the data suggests overfishing is the most likely reason we are seeing the disappearance of large predatory fishes across the region,” says Stallings.
Species like Nassau grouper, which was once abundant throughout the Caribbean, have completely disappeared from many Caribbean nearshore areas and are endangered throughout their range.
“This study also demonstrates the power of volunteer and community research efforts by non-scientists,” – Dr. Chris Stallings
Chris used data from the Reef Environmental Education Foundation’s (REEF) online database, which contains fish sightings documented by trained volunteer SCUBA divers, including here over 38,000 surveys spanning a fifteen year period.
“Chris was completely undaunted by the lack of fisheries data and essentially adopted the ‘Audubon Christmas Bird Count’ approach in a marine system to find strong evidence for a native fisheries effect,” says Dr. Felicia Coleman, director of the Florida State University Coastal and Marine Laboratory and Stallings’ postdoctoral advisor.
2009 Fishery-Independent Data Reveal Negative Effect of Human Population Density on Caribbean Predatory Fish Communities. PLoS ONE 4(5): e5333. doi:10.1371/journal.pone.0005333
For additional information, please visit http://www.marinelab.fsu.edu/news/predators