Featured Research

from universities, journals, and other organizations

Chemical microgradients accelerate coral death at the Great Barrier Reef

Date:
March 27, 2012
Source:
Max-Planck-Gesellschaft
Summary:
Researchers have examined corals from the Great Barrier Reef affected by the Black Band Disease and identified the critical parameters that allow this prevalent disease to cause wide mortality of corals around the world. Corals infected with Black Band show a characteristic appearance of healthy tissue displaced by a dark front, the so called Black Band, which leaves the white limestone skeleton of the coral animal exposed. The dark front is commonly one to two centimeters broad and consists of a complex microbial community among which there are phototrophic cyanobacteria, sulfur oxidizing bacteria and sulfate reducing microorganisms.

This coral in the Great Barrier Reef is strongly affected by the Black Band Disease. In the lower region the white limestone skeleton is visible, in the upper region the coral tissue is still intact. The BBD zone appears as a black band.
Credit: Y. Sato

Researchers of the Max Planck Institute for Marine Microbiology along with Australian colleagues, have examined corals from the Great Barrier Reef affected by the Black Band Disease and identified the critical parameters that allow this prevalent disease to cause wide mortality of corals around the world. Corals infected with Black Band show a characteristic appearance of healthy tissue displaced by a dark front, the so called Black Band, which leaves the white limestone skeleton of the coral animal exposed. The dark front is commonly one to two centimetres broad and consists of a complex microbial community among which there are phototrophic cyanobacteria, sulfur oxidizing bacteria and sulfate reducing microorganisms.

Related Articles


The corals and their endosymbiotic algae are struck by three stress factors at once: toxic sulfide, anoxia, and a low pH at the boundary of the bacterial mat and the coral tissue.

The scientists investigated the tissue lesions with microsensors for oxygen, sulfide and pH. These microprobes have a tip diameter in the micrometre range and allow the scientists to measure highly resolved depth profiles in the coral tissue. They identified big differences between infected tissue and tissue in the preliminary stage of the disease: "In diseased coral tissue two zones develop: A phototrophic zone at the top in which the cyanobacteria produce oxygen and a lower anoxic zone in which the bacteria degrade the necrotic coral tissue. Sulfide is formed in the degradation process," Martin Glas of the Max Planck Institute in Bremen explains the results. "In tissue that is only slightly infected the zonation is not nearly that strong. Usually we could not detect sulfide, and oxygen penetrated deep into the bacterial mat."

At the front of the dark zone the conditions are particularly detrimental for the corals. The increased sulfide concentration around the necrosing tissue and the resulting decrease in oxygen leads to the spreading of the lesions to the surrounding, healthy tissue; a positive feedback that causes rapid migration of the Black Band Disease.

"We assume that the biogeochemical conditions at the surface of the coral tissue are responsible for the fast spreading of the disease. The higher the sulfide concentrations are and the less oxygen there is, the faster the dark front is migrating," Martin Glas describes the causes for the origin and the high virulence of the disease. So far, at least, the scientists have not identified a pathogen that could be responsible for the necrosis of the coral tissue. "Our measurements show that the Black Band Disease can migrate at one centimetre per day in the summer months. At this speed, within a very short time, whole coral colonies can die and the population size of many coral species on the reef can number of species in the reef can drastically decline," says Martin Glas.

For several years, David Bourne of the Australian Institute of Marine Science in Townsville and his colleague Yui Sato have been performing monitoring programs on the condition of coral reefs in which they also examined the coral diseases in the Great Barrier Reef. David Bourne says: „Presumably the Black Band Disease is one of the most frequently reported diseases in tropical reefs. One major cause is the seasonally high water temperature. Thus, results from this study allow us to understand at the micro-scale how the environmental conditions and the complex microbial community interact to result in the onset and progression of this coral disease."

Is there any cure for the reefs? "If the temperature decreases in winter the disease is stagnant. However, with increasing frequency the disease recurs in the next year. The bare coral skeleton can be overgrown by new polyps. But this may take many years," as Yui Sato of the James Cook University states.


Story Source:

The above story is based on materials provided by Max-Planck-Gesellschaft. Note: Materials may be edited for content and length.


Journal Reference:

  1. Martin S Glas, Yui Sato, Karin E Ulstrup, David G Bourne. Biogeochemical conditions determine virulence of black band disease in corals. The ISME Journal, 2012; DOI: 10.1038/ismej.2012.2

Cite This Page:

Max-Planck-Gesellschaft. "Chemical microgradients accelerate coral death at the Great Barrier Reef." ScienceDaily. ScienceDaily, 27 March 2012. <www.sciencedaily.com/releases/2012/03/120327124132.htm>.
Max-Planck-Gesellschaft. (2012, March 27). Chemical microgradients accelerate coral death at the Great Barrier Reef. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2012/03/120327124132.htm
Max-Planck-Gesellschaft. "Chemical microgradients accelerate coral death at the Great Barrier Reef." ScienceDaily. www.sciencedaily.com/releases/2012/03/120327124132.htm (accessed October 25, 2014).

Share This



More Earth & Climate News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

EU Gets Climate Deal, UK PM Gets Knock

EU Gets Climate Deal, UK PM Gets Knock

Reuters - Business Video Online (Oct. 24, 2014) EU leaders achieve a show of unity by striking a compromise deal on carbon emissions. But David Cameron's bid to push back EU budget contributions gets a slap in the face as the European Commission demands an extra 2bn euros. David Pollard reports. Video provided by Reuters
Powered by NewsLook.com
Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Reuters - Innovations Video Online (Oct. 24, 2014) Miniature deep sea animals discovered off the Australian coast almost three decades ago are puzzling scientists, who say the organisms have proved impossible to categorise. Academics at the Natural History of Denmark have appealed to the world scientific community for help, saying that further information on Dendrogramma enigmatica and Dendrogramma discoides could answer key evolutionary questions. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Raw: Tornado Rips Roofs in Washington State

Raw: Tornado Rips Roofs in Washington State

AP (Oct. 24, 2014) A rare tornado ripped roofs off buildings, uprooted trees and shattered windows Thursday afternoon in the southwest Washington city of Longview, but there were no reports of injuries. (Oct. 24) Video provided by AP
Powered by NewsLook.com
Fast-Moving Lava Headed For Town On Hawaii's Big Island

Fast-Moving Lava Headed For Town On Hawaii's Big Island

Newsy (Oct. 24, 2014) Lava from the Kilauea volcano on Hawaii's Big Island has accelerated as it travels toward a town called Pahoa. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins