Disease-hunting scientist: Dr Laurie Richardson and black band disease in coral

Just finished reading a great excerpt from a book called ‘Disease-hunting scientist’ by a Canadian author called Edward Willett. The scientist in question is Dr Laurie Richardson from Florida International University, who is well known for her work on ‘black band disease’ (see image above) on Caribbean coral reefs. I’ve never read Willett’s work before … Continue reading Disease-hunting scientist: Dr Laurie Richardson and black band disease in coral

Coral reefs and climate change: Microbes could be the key to coral death

Coral reefs could be dying out because of changes to the microbes that live in them just as much as from the direct rise in temperature caused by global warming, according to scientists speaking today (Wednesday 2 April 2008) at the Society for General Microbiology’s 162nd meeting being held this week at the Edinburgh International Conference Centre.Tropical ecosystems are currently balanced on a climate change knife edge. Corals in coral reefs, which are made up of animals called polyps that secrete hard external skeletons of calcium carbonate, are living perilously close to their upper temperature limits. This makes them very vulnerable to even small temperature rises of 1-2oC above the normal summer maximum.

“Many of the deaths we see in the coral reefs, which occur following coral bleaching events, when huge areas of reef die off like in 1998 when 17% of the world’s reefs were killed, can be put down to changes in the microbes which live in and around the reefs,” says Dr John Bythell, a biologist from Newcastle University. “These microbes can be thought of as being similar to the bacteria that normally live in our guts and help us digest our food.”

Changes in sea temperature caused by climate change and global warming affect corals, but they also affect the types of bacteria and other microflora that live with them. When the water warms up, some disease-causing bacteria are more successful and can attack the corals. The corals themselves suffer from heat, which reduces their defences. Also, some of the friendly bacteria that normally live in the corals’ guts become weakened, allowing other harmful bacteria to multiply and cause diseases or other problems.

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

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.

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