AFTER THE CORAL BLEACHING, THE WINNER IS...

The winners: Acropora corals. Credit: Albert Kok at Wikimedia Commons. 

  
After 14 years of tracking coral colonies at Sesoko Island, Okinawa, Japan, through two coral bleaching episodes—1998 and 2001—the big coral winners and losers on the reef have been announced...

• The winners: Porites, faviids, and Acropora colonies

• The losers: pocilloporids

Except it's not that simple, the authors of a new study warn. Since 14 years is hardly the long long run.

The losers: Pocillopora corals. Credit: Mila Zinkova at Wikimedia Commons.

  
In a new paper in the current issue of MEPS we get a sense of what happens in the short long run after of a big coral bleaching event. 

Background: Coral bleaching occurs when water temperatures rise, stressing the coral animals enough to expel their symbiotic partners—the zooxanthellae. These single-celled plants give corals their beautiful colors and help feed them through photosynthesis (as if we could grow rice inside our bodies). In some plant-animal partnerships, the zooxanthellae entirely feed their corals.

Zooxanthellae (yellowish streaks) cells embedded in coral polyps. Via.

 
In the past 30 years, rising sea surface temperatures have stressed and bleached corals worldwide. 

Yet few researchers have looked at what recovery looks like over time—whether the species of corals that fare better in the short term also fare better in the long term.

A partially bleached faviid coral. Credit: Nhobgood at Wikimedia Commons.

At Sesoko Island, the researchers found that although species richness recovered after 10 years, the composition of coral species on the reef had changed. The pocilloporids were nearly completely gone. Among their other findings:

• Short-term winners were generally thermally tolerant encrusting and massive corals, like Porites and faviids and small (<5 cm/2 in) Acropora colonies. 
• Ten years after the bleaching the community was still structurally different, consisting of a combination of survivors that were either:

1. Tolerant to heat stress
2. Surviving as fragments of colonies that experienced rapid regrowth 
3. Regionally persistent colonies that recruited locally

Credit: R. van Woesik, et al. MEPS. DOI:10.3354/meps09203.

  
The last point is interesting because it means that having healthy reef neighbors enabled some species to recover—thanks to seeding from nearby islands. 

Yet even the short long term winners may not survive the long long term. The authors close with these strongly cautionary words: 

The present study suggests that as the oceans warm even further, the coral assemblages will change. Reefs may soon essentially only support heat-tolerant coral species. The narrowing of genetic diversity within communities is likely to impact other dependent species such as fishes and crustaceans, especially if important reef-building branched corals, such as Acropora, Stylophora, Pocillopora, and Porites cylindrica, become rare on account of their inherent sensitivity to thermal stress. Bleaching may also become punctuated over the next several decades. In the short term, the remnant yet hardy populations may show some resistance to the higher water temperatures, and bleaching may be reduced for a decade or more if Acropora and pocilloporids are removed from local reefs. However, reduced bleaching may give false hope because once the inevitable temperature threshold of the remnant communities is surpassed, widespread coral mortality will follow. Given that even the hardiest coral genera have their limits, global temperature increases will eventually lead to an exponential rate of local, regional and global reduction of coral species. To what extent this reduction of coral species will occur will depend on how rapidly and by how much the ocean temperatures increase, which depends on the fossil-fuel-emission pathway that humans choose.

  

Coral recovery underway on a reef. Credit: Bruno de Giusti at Wikimedia Commons.

The paper:

• van Woesik R, Sakai K, Ganase A, Loya Y (2011) Revisiting the winners and the losers a decade after coral bleaching. Mar Ecol Prog Ser 434:67-76. DOI:10.3354/meps09203.

SUNDAY POETRY: "FIVE VIEWS OF CAPTAIN COOK"

FIVE VIEWS OF CAPTAIN COOK

[A fragment]

by Kenneth Slessor

Flowers turned to stone! Not all the botany   

Of Joseph Banks, hung pensive in a porthole,   

Could find the Latin for this loveliness,   

Could put the Barrier Reef in a glass box   

Tagged by the horrid Gorgon squint

Of horticulture. Stone turned to flowers   

It seemed—you’d snap a crystal twig,   

One petal even of the water-garden,

And have it dying like a cherry-bough.

They’d sailed all day outside a coral hedge,   

And half the night. Cook sailed at night,   

Let there be reefs a fathom from the keel   

And empty charts. The sailors didn’t ask,

Nor Joseph Banks. Who cared? It was the spell   

Of Cook that lulled them, bade them turn below,   

Kick off their sea-boots, puff themselves to sleep,   

Though there were more shoals outside

Than teeth in a shark’s head. Cook snored loudest himself.

(You can read this amazing poem in its entirety at the Poetry Foundation website.)

The illustration of a coral above is by Eugenius Johann Christoph Esper from his c.1798 book Die Pflanzenthiere in Abbildungen nach der Natur mit Farben erleuchtet nebst Beschreibunge.

That translates roughly to: "Images from nature of animal-plants, illuminated with color and descriptions." For more scans of Esper's work, see the digital gallery of Germany's Humboldt University.

HMS Endeavour. 1768. Thomas Luny.

Joseph Banks was the botanist/naturalist who sailed aboard HMS Endeavour on James Cook's first voyage voyage of exploration between 1768 and 1771. 

Among their many shared adventures was a near-sinking after weeks of entrapment (occasionally escaping, only to get sucked back in by winds or currents) in the maze of Australia's Great Barrier Reef. 

Eventually Endeavour was holed on a reef and Cook's men were forced to lay her ashore for seven weeks of repairs. Cook wrote with unusual feeling about his adventures in the coral shallows:

It is but a few days ago that I rejoiced at having got without the Reef, but that joy was nothing when Compared to what I now felt at being safe at Anchor within it, such is the Visissitudes attending this kind of Service & must always attend an unknown Navigation where one steers wholy in the dark without any manner of Guide whatever.

(Les Gibson. Photo by Julia Whitty.)

 

The site of Endeavour's repairs is today known as Cooktown—home then and now to the Guugu Yimithirr people, who taught Cook's men the word ganguru (kangaroo) and who kept them alive with gifts of food and natural history lessons in an unfamiliar landscape/seascape.

I wrote at some length about the Guugu Yimithirr and Cook's legacy in my Mother Jones article Listen to the Lionfish: What Invasive Species Are Trying to Tell Us. 

In the photo above, Les Gibson, a Guugu Yimithirr, is showing me how to "hunt" (fish) near the place where Endeavour limped ashore 232 years earlier.

 

James Cook. c. 1775. Nathaniel Dance.

After his sojourn with the Guugu Yimithirr, after enjoying the bounty of their vibrant world, Cook concluded:

In reality they are far more happier than we Europeans; being wholy unacquainted not only with the superfluous but the necessary conveniencies so much sought after in Europe.

CORAL CONUNDRUM

(Photograph of Acropora pulchra by Albert Kok at nl.wikipedia, courtesy Wikimedia Commons.)

I had the good fortune to meet Greta Aeby last April at her lab on Hawaii's Coconut Island—that tiny gem in Kaneohe Bay that was filmed for the show open of Gilligan's Island—now home to the Hawaii Institute of Marine Biology. 

I was planning to write about Greta's work on coral diseases for a new Mother Jones article. Then the Deepwater Horizon rearranged the known world and I never got to write that piece. 

(Coconut Island. Via HIMB.) 

Now I see that Greta is lead author of a new paper in PLoS ONE, assessing the causes of tumorlike diseases afflicting corals in the Indian and Pacific Oceans. Coral cover in those waters has declined  by about 1 percent per year for the last 20 years, increasing to 2 percent between 1997 and 2003.

So what's doing that?

This paper outlines the first broad-scale assessment of how nine "predictors of interest" correlate with tumorlike diseases. You can see the predictors in the table below.

(Image: PLoS ONE DOI: 10.1371/journal.pone.0016887)

The nine predictors fall into three broad categories:

• biological factors: population abundance of affected corals
• human factors: human population
• environmental factors: warming waters, surface ultra-violet radiation

Statistical models were used to examine the prevalence of two coral diseases—Acropora growth anomalies and Porites growth anomalies. These diseases manifest like tumors. They're easy to identify in the field and not easily confused with anything else.

(Porites growth anomaly at top, and Acropora growth anomaly at bottom. Images courtesy PLoS ONE DOI: 10.1371/journal.pone.0016887)

The team surveyed for growth anomaly diseases on 937 reefs from 13 regions across the Indo-Pacific between 2002 and 2008. They examined corals at the genus level.

The results:

• The Acropora growth anomaly was most associated with Acropora abundance—that is, the more Acropora corals, the more Acropora disease too
• The Porites growth anomaly was associated with Porites abundance, but also with nearby human populations—that is, the more people, the more disease too

Which basically means that the growth anomaly diseases are likely communicable, and the the Porites version is also likely related in some fashion to an environmental co-factor or two: pollution, eutrophication, habitat fragmentation, and/or direct introduction of novel pathogens into the ecosystems.

Might there be a similar correlation for human health?

(Survey sites. Image: PLoS ONE DOI:10.1371/journal.pone.0016887)

Meantime, the heavily populated coasts suffering the most Porites growth anomalies are also home to many of the 500 million people most immediately dependent on coral reefs. The authors note:

As human densities and environmental degradation increase globally, the prevalence of coral diseases like [Porites growth anomalies] could increase accordingly, halted only perhaps by declines in host density below thresholds required for disease establishment.

Or... halted perhaps by declines in human density below thresholds required for disease establishment? 

This is not an impossible reality beginning sometime this century if—as projected—our population peaks and then naturally falls as more women become literate wage-earners. (For more about that, see my article The Last Taboo.)

But can coral reefs—or the people dependent on them—hold out until then? It's sort of a Catch-21st century. 

Coral Beauty from Greg Rothschild on Vimeo.

Finally, for your enjoyment, an incredibly gorgeous video of captive corals. Though the porno soundtrack is a puzzler.

The paper:

Aeby, G., Williams, G., Franklin, E., Haapkyla, J., Harvell, C., Neale, S., Page, C., Raymundo, L., Vargas-Ángel, B., Willis, B., Work, T., & Davy, S. (2011). Growth Anomalies on the Coral Genera Acropora and Porites Are Strongly Associated with Host Density and Human Population Size across the Indo-Pacific PLoS ONE, 6 (2) DOI: 10.1371/journal.pone.0016887

I ♥ open access papers.