Tag Archives: Science & Politics

Coral reef fish act as “lawnmowers” in the fight against climate change

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BBC News, 20th March

A healthy fish population could be the key to ensuring coral reefs survive the impacts of climate change, pollution, overfishing and other threats. Australian scientists found that some fish act as “lawnmowers”, keeping coral free of kelp and unwanted algae. At a briefing to parliamentarians in Canberra, they said protected areas were rebuilding fish populations in some parts of the Great Barrier Reef.

Warming seas are likely to affect the reef severely within a few decades. Pollution is also a growing problem, particularly fertilisers that wash from agricultural land into water around the reef, stimulating the growth of plants that stifle the coral. The assembled experts told parliamentarians that fish able to graze on invading plants played a vital role in the health of reef ecosystems.
“The Great Barrier Reef is still a resilient system… and herbivorous fish play a critical role in that regenerative capacity, by keeping the dead coral space free of algae, so that new juvenile coral can re-establish themselves,” said Professor Terry Hughes from James Cook University in Townsville. His research group has conducted experiments which involved building cages to keep fish away from sections of reef. They found that three times as much new coral developed in areas where the fish were present as in the caged portions.

Parrotfish in particular use their serrated jaws to scrape off incipient algae and plants. More recently, his team has also identified the rabbit fish – a brown, bland-looking species – as a potentially important harvester of seaweed. “So managing fisheries can help to maintain the reef’s resilience to future climate change,” he said. In recent years, Marine Protected Areas have been set up along the Great Barrier Reef in order to provide sanctuaries where fish and other marine creatures can grow and develop.

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

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

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

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

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

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

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

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

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

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

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

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AIMS Media Release, 5th March 2008

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

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

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

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

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

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Butterfly fish ‘may face extinction’

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Wildlife Extra, 29th February 2008

Scientists have warned that a beautiful black, white and yellow butterflyfish, much admired by eco-tourists, divers and aquarium keepers alike, may be at risk of extinction.

The case of the Chevroned Butterflyfish is a stark example of how human pressure on the world’s coral reefs is confronting certain species with ‘blind alleys’ from which they may be unable to escape, says Dr Morgan Pratchett of the ARC Centre of Excellence for Coral Reef Studies and James Cook University.

 

Highly Specialized Feeding Habit
In a study published in the journal Behavioural Ecology and Sociobiology Dr Pratchett and Dr Michael Berumen of Woods Hole Oceanographic Institution (USA) warn that the highly specialized nature of the feeding habits of this particular butterflyfish – the distinctively patterned Chaetodon trifascialis – make it an extinction risk as the world’s coral reefs continue to degrade due to human over-exploitation, pollution and climate change.

‘The irony is that these butterflyfish are widespread around the world, and you’d have thought their chances of survival were pretty good,’ Dr Pratchett said today. But they only eat one sort of coral – Acropora hyacinthus – and when that runs out, the fish just disappear from the reef.’

Rather Starve Than Change Diet
The team found it hard to believe a fish would starve rather than eat a mixed diet, so they tested C. trifascialis in tank trials on a range of different corals. The fish grew well when its favourite coral was available – but when this was removed and other sorts of corals offered, it grew thin, failed to thrive and some died.

‘We call these kinds of fish obligate specialists. It means they have a very strong dietary preference for one sort of food, and when that is no longer available, they go into decline. We still don’t have a satisfactory scientific explanation for this, as it seems like rather a risky tactic in evolutionary terms – but it must confer some advantage provided enough of its preferred food is available,’ Dr Pratchett says.

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Shifting Baselines, Local Impacts, and Global Change on Coral Reefs – a note from Nancy Knowlton & Jeremy B. C. Jackson

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Healthy Reefs, Dying Reefs, and Corals in Bocas del Toro, Panama:(A) Example of a healthy reef with abundant living coral. (B) Example of a reef in which most coral has died and been replaced by macroalgae. (C) Bleached and healthy coral colonies; both are alive but the bleached colony has lost its symbiotic algae. (D) Coral suffering from disease and with encroaching macroalgae.

PLoS ONE, February 26th 2008

Nancy Knowlton & Jeremy B. C. Jackson

Imagine trying to understand the ecology of tropical rainforests by studying environmental changes and interactions among the surviving plants and animals on a vast cattle ranch in the center of a deforested Amazon, without any basic data on how the forest worked before it was cleared and burned. The soil would be baked dry or eroded away and the amount of rainfall would be greatly decreased. Most of the fantastic biodiversity would be gone. The trees would be replaced by grasses or soybeans, the major grazers would be leaf-cutter ants and cattle, and the major predators would be insects, rodents, and hawks. Ecologists could do experiments on the importance of cattle for the maintenance of plant species diversity, but the results would be meaningless for understanding the rainforest that used to be or how to restore it in the future.

Fortunately, ecologists began to carefully describe tropical forests more than a century ago, and vast areas of largely intact forests have persisted until today, so there are meaningful baselines for comparison. Networks of 50-hectare plots are monitored around the world [1], and decades of experiments have helped to elucidate ecological mechanisms in these relatively pristine forests [2]. But the situation is very different for the oceans, because degradation of entire ecosystems has been more pervasive than on land [3] and underwater observations began much more recently. Monitoring of benthic ecosystems is commonly limited to small intertidal quadrats, and there is nothing like the high-resolution global monitoring network for tropical forests for any ocean ecosystem.

This lack of a baseline for pristine marine ecosystems is particularly acute for coral reefs, the so-called rainforests of the sea, which are the most diverse marine ecosystems and among the most threatened [4–8]. Most of the world’s tropical coastal oceans are so heavily degraded locally that “pristine” reefs are essentially gone, even if one ignores changes associated with already rising temperatures and acidity [3]. Most modern (post-SCUBA) ecological studies have focused on reef ecosystems that are moderately to severely degraded, and we have a much better understanding of transitions between human-dominated and collapsed reefs than between human-dominated and quasi-pristine reefs. Even the classic studies of Caribbean reefs that began in the 1950s were based on reefs that had very high coral cover but were severely overfished, and the first systematic surveys of subtidal Australian reefs in the late 1960s began after a severe outbreak of the crown-of-thorns starfish Acanthaster planci had devastated coral populations along much of the Great Barrier Reef. We are thus left without a clear understanding of how reefs functioned in the absence of major human impacts.

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

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


1. “Warm water is good for corals”

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

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

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

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

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“Climate change could be the next subprime meltdown”

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Financial Post, 14th February 2008

Another subprime-mortgage-meltdown-sized risk could be looming for investors: global warming. That alarm was sounded Thursday at an investor summit at the United Nations headquarters, at which 480 investors, pension fund leaders and corporate executives from around the globe were warned that the vast majority of companies are ill-prepared for the Earth’s changing climate.

Many oil producers, utilities and manufacturing plants have yet to factor in the added expense if the United States – as is expected in the next few years – imposes caps on carbon-dioxide emissions. Similarly, many companies with big real-estate holdings in U.S. coastal regions haven’t calculated their exposure to increased tropical storms and rising seas.

Most of the financial institutions that lend to these companies and the insurance companies that protect them also have yet to adequately consider how they might get burned.

"It’s like subprime mortgages…one of longest kept secrets of uncalculated risk," said Mindy Lubber, president of Ceres, a coalition of investors and environmental groups, which co-hosted yesterday’s event. "By not acting on climate change…we face the same kind of [risks] with what we’re seeing in subprime."

Former U.S. vice president Al Gore, who was awarded the Nobel Peace Prize last year for bringing attention to the issue of climate change, echoed that theme as keynote speaker, urging investors to dump any assets they hold in businesses that are heavily reliant on carbon-intensive energy – or risk losing a ton of money down the road.

"You need to really scrub your investment portfolios, because I guarantee you…that if you really take a fine-tooth comb and go through your portfolios, many of you are going to find them chock-full of "subprime" carbon assets," Mr. Gore said according to an Associated Press report of the speech, which was closed to the press.

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First map of threats to marine ecosystems shows all the world’s oceans are affected

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EurekAlert, 14th February 2008

As vast and far-reaching as the world’s oceans are, every square kilometer is affected by human activities, according to a study in the journal Science by researchers at the University of North Carolina at Chapel Hill and others.

The international team of scientists integrated global data from 17 aspects of global change – from overfishing to global warming – that threaten 20 different marine ecosystems, such as coral reefs and continental shelves. Similar to an online satellite map that lets you add layers of highways, retail stores, schools, parks, etc., to find the most congested areas or the highest concentration of fast food restaurants, the global threat map highlights areas in the ocean where threats overlap.

The researchers scored the potential threats – from having very-low to very-high impacts – and found that affects were ubiquitous, and more than 40 percent of the oceans experience medium- to very high-impact threats.

“For the first time we can see where some of the most threatened marine ecosystems are and what might be degrading them,” said Elizabeth Selig, an author on the study and a doctoral student in UNC’s curriculum in ecology in the College of Arts and Sciences.

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Floodwaters ‘threatening Great Barrier Reef’

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Brisbane Times (29th Jan 2008)

Scientists from across Queensland are converging on the mouth of the Fitzroy River in Rockhampton over fears that sediment and toxic chemicals carried by floodwaters in central Queensland now reaching the ocean may damage the Great Barrier Reef.

Marine scientists from James Cook University, the Queensland Environmental Protection Agency and the Department of Natural Resources will be collecting water samples, measuring flow rates and diving on the reef to assess its condition first hand.

Dr David Haynes, acting director of water quality and the Coastal Developmental Unit of the Great Barrier Reef Marine Park Authority, said that sediment could pose a significant threat to the health of the reef.

“The main problem with sediment is one of the things it will do is settle on coral and physically smother them in high enough concentrations,” he said.

“It can also make the water highly turbid and reduce the amount of light that can penetrate through the water and corals are very dependent on light to obtain food; they use algae in their cells to manufacture food.

“If the corals are in dirty water then the coral’s food source is cut off for as long as the water is dirty.”

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Coral reefs and climate change

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A colleague of mine, Dr John Bruno forwarded me an excellent article that he wrote for The Encyclopedia of the Earth, titled “Coral Reefs and Climate Change”

“A healthy reef ecosystem literally buzzes with sounds, activity and colors and is populated by incredibly dense aggregations of fish and invertebrates. In this respect, tropical reefs are more reminiscent of the African Serengeti than of the tropical rainforest they are often compared to, where the resident birds and mammals can be secretive and difficult to see. A coral reef can contain tens of thousands of species and some of the world’s most dense and diverse communities of vertebrate animals. Unfortunately, very few remaining coral reefs resemble this pristine condition; on most, corals and fishes are much less abundant than they were only a few decades ago”

John’s expert write-up and summary of threats to coral reefs related to climate change (coral bleaching, disease, ocean acidification) provides an excellent background of the literature and current threats, and is a worthy read for scientists, managers and the general public alike.

Healthy Great Barrier Reef reefscape A recovering Jamaican coral reef Bleached corals off Puerto Rico in 2005