Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Rapid Coral Death

23.05.2012
Soil Erosion in Tropical Coastal Areas Accelerates Coral Death

Most people are fascinated by the colorful and exotic coral reefs, which form habitats with probably the largest biodiversity. But human civilisation is the top danger to these fragile ecosystems through climate change, oxygen depletion and ocean acidification. Industrialisation, deforestation and intensive farming in coastal areas are changing dramatically the conditions for life in the oceans.


Miriam Weber measures the oxygen concentration with hair-fine microsensors in a sediment layer, where the sediment was accumulated. If the organic load is increased in the two millimeter layer of sediments, the killing process will start. Blocked off from the light the algae will stop producing oxygen, microorganisms will start to decompose the organic matter, hydrogen sulfide is produced and kills the remaining cells.
C. Lott/HYDRA Institute/Max Planck Institute for Marine Microbiology, Bremen, c.lott@hydra-institute.com

Now Max Planck Scientists from Bremen together with their colleagues published their findings in the Proceedings of the National Academy of Sciences.PNAS 10.1073/pnas.1100715109

Reef forming stone corals inhabitat the light-flooded tropical shallow coastal regions 30 degree south and north of the equator. Coral polyps build the carbonate skeletons that form the extensive reefs over hundreds to thousands of years. Photosynthesis of the symbiotic algae inside the polyps produces oxygen and carbohydrates from carbon dioxide and water, thereby feeding the polyps.

Coral Bleaching, the slow demise
Since the 1980s the process of coral bleaching is under study: elevated temperatures of 1 to 3 degrees induce the algae to produce toxins. The polyps react by expelling the algae and the coral reef loses its color as if it was bleached. Without its symbionts the coral can survive only several weeks.
Rapid death in less than 24 hours
In coastal areas with excessive soil erosion where rivers flush nutrients, organics and sediments to the sea, corals can die quickly when exposed to sedimentation. Miriam Weber, scientist at the Max Planck Institute for Marine Microbiology in Bremen, explains the scientific approach.“Our idea was that a combination of enhanced deposition of sediments with elevated organic matter load and naturally occuring microorganisms can cause the sudden coral death. To get a handle on the diverse physical, chemical and biological parameters we performed our experiments at the Australian Institute for Marine Science (AIMS) in Townsville under controlled conditions in large containers (mesocosms), mimicking the natural habitat.“

The team of researchers found out the crucial steps:

Phase 1: When a two millimeter layer of sediment enriched with organic compounds covers the corals, the algae will stop photosynthesis, as the light is blocked.

Phase 2: If the sediments are organically enriched, then digestion of the organic material by microbial activity reduces oxygen concentrations underneath the sediment film to zero. Other microbes take over digesting larger carbon compounds via fermentation and hydrolysis thereby lowering the pH.

Phase 3: Lack of oxygen and acidic conditions harm small areas of coral tissue irreversibly. The dead material is digested by microbes producing hydrogen sulfide, a compound that is highly toxic for the remaining corals. The process gains momentum and the remainder of the sediment-covered coral surface is killed in less than 24 hours.

Miriam Weber: „First we thought that the toxic hydrogen sulfide is the first killer, but after intensive studies in the lab and mathematical modeling we could demonstrate that the organic enrichment is the proximal cause, as it leads to lack of oxygen and acidification, kicking the corals out of their natural balance. Hydrogen sulfide just speeds up the spreading of the damage. We were amazed that a mere 1% organic matter in the sediments is enough to trigger this process. The extreme effect of the combination of oxygen depletion and acidifation are of importance, keeping in mind the increasing acidification of the oceans. If we want to stop this destruction we need some political sanctions to protect coral reefs.“

Katharina Fabricius from the AIMS adds:“ This study has documented for the first time the mechanisms why those sediments that are enriched with nutrients and organic matter will damage coral reefs, while nutrient-poor sediments that are resuspended from the seafloor by winds and waves have little effect on reef health. Better land management practices are needed to minimise the loss of top soil and nutrients from the land where they are beneficial, and are not being washed into the coastal sea where they can cause so much damage to inshore coral reefs.“

Manfred Schloesser

For more information please contact

Dr. Miriam Weber, HYDRA Field Station/Centro Marino Elba, office +39 0565 988 027, Mobil +39 338 937 56 77, m.weber@hydra-institute.com

Dr. Dirk de Beer, Max Planck Institute for Marine Microbiology, office +49 421 2028 802, dbeer@mpi-bremen.de

Dr. Katharina Fabricius, AIMS Principal Research Scientist, k.fabricius@aims.gov.au

or the press officers of the Max Planck Institute for Marine Microbiology

Dr. Manfred Schloesser, +49 421 2028704, mschloes@mpi-bremen.de
Dr. Rita Dunker, +49 421 2028856, rdunker@mpi-bremen.de
Original article
Mechanisms of damage to corals exposed to sedimentation
Miriam Weber, Dirk de Beer, Christian Lott, Lubos Polerecky, Katharina Kohls, Raeid M. M. Abed, Timothy G. Ferdelman, and Katharina E. Fabricius. PNAS 10.1073/pnas.1100715109 PNAS May 21, 2012

http://www.pnas.org/content/early/2012/05/18/1100715109.abstract

Scientific Institutes

Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany

HYDRA Institute for Marine Sciences, Elba Field Station, 57034 Campo nell’Elba,
Italy;
Australian Institute of Marine Science, Townsville, Queensland 4810, Australia
Biology Department, College of Science, Sultan Qaboos University, Muscat 123, Sultanate of Oman

Dr. Manfred Schloesser | Max-Planck-Institut
Further information:
http://www.mpi-bremen.de/

More articles from Ecology, The Environment and Conservation:

nachricht How fires are changing the tundra’s face
12.12.2017 | Gesellschaft für Ökologie e.V.

nachricht Using drones to estimate crop damage by wild boars
12.12.2017 | Gesellschaft für Ökologie e.V.

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Long-lived storage of a photonic qubit for worldwide teleportation

12.12.2017 | Physics and Astronomy

Multi-year submarine-canyon study challenges textbook theories about turbidity currents

12.12.2017 | Earth Sciences

Electromagnetic water cloak eliminates drag and wake

12.12.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>