Tropical coral reefs are the most biodiverse habitats on the planet. They are also highly productive, although the regions of the oceans they live in have extremely low levels of nutrients. Until now, this so-called “reef paradox” has baffled scientists. In an international journal publication, Bremen Marine researchers have now put forward a plausible explanation for this puzzling contradiction.
A team of international researchers led by Prof. Dr. Christian Wild from University of Bremen’s faculty of Biology & Chemistry recently made the following surprising discovery: It transpires that the conversion of nitrogen, or nitrogen fixation, by micro-organisms that are associated with corals clearly in turn supports the conversion of carbon, or carbon fixation, by the micro-algae in the coral tissue. This is one of the main findings of the Bremen study that has now been published in the renowned journal “Proceedings of the Royal Society”.
One of the investigated coral colonies (species: Stylophora pistillata) with erected polyp tentacles at night
Foto: Dr. Ulisse Cardini
Although corals are animals, so-called cnidarians, they host such a lot of micro-algae and other micro-organisms like bacteria in their tissue that they develop their own micro-ecosystems and are classified as holobionts. With the aid of their tiny co-inhabitants, coral holobionts are capable of carrying out processes thoroughly untypical of animals.
Carbon fixation by means of the photosynthesis of micro-algae is especially important for the productivity of corals: What happens is that carbon dioxide is converted into organic material with the aid of light energy. Thanks to this process, corals are able to grow at extremely fast rates, creating not only new habitats, but also nourishment for other organisms. Coral holobionts carry out carbon fixation with extraordinary intensity – and they do this although they dispose of almost no nitrogen with which to produce biomass.
How does the paradox come about?
Could parallel processes, especially nitrogen fixation by bacteria and carbon fixation by micro-algae, possibly be playing a role here? This is the unorthodox hypothesis that has engaged the attention of Bremen marine researcher Professor Christian Wild for a very long time.
Funded by the German Research Foundation, he and his team of PhD students – in particular the Italian early-career researcher and lead author of the study, Ulisse Cardini – and other colleagues set out to research the interrelation between carbon and nitrogen fixation by corals.
The team examined these processes in all the dominant hard corals found on a coral reef in the northern region of the Red Sea in Jordan. They carried out their research during several lengthy expeditions in all four seasons of the year 2013. They chose this location for their research because of its high seasonality: That is the pronounced natural fluctuation in nutrient concentrations contained in the water across the seasons.
Somewhat to their surprise, they discovered that carbon fixation was highly constant for all corals throughout the whole year. This was true even in the summer months when nutrient concentrations are especially low. The key to answering this puzzle, they found, clearly lies in the process of nitrogen fixation by micro-organisms that inhabit the coral. The large number of measurements they took showed that in summer this process was about tenfold more intense than at other times of the year.
A major finding of the study is that the process of nitrogen fixation by micro-organisms compensates for the extreme nitrogen limitation of the summer months. Thus, processes by bacteria support the processes by micro-algae in the coral tissue so that in the end there is a beneficial effect not only for the coral but also for the whole reef. The study showed that corals are good examples of animals, humans included, where beneficial internal microbes fulfill roles important for the health of the host organisms.
The article by Cardini et al. breaks new scientific ground in several respects. It is now clear how the individual processes carried out by the different coral inhabitants are intertwined. And it furthermore reveals that the important role micro-organisms play in these interrelations has until now been underestimated. The international research team around University of Bremen Professor Christian Wild and his research associate Dr. Ulisse Cardini have delivered an important new explanation for the Darwinian reef paradox.
You can obtain more information on this topic by contacting:
University of Bremen
Faculty Biology / Chemistry
Prof. Dr. Christian Wild
Phone. 0421 218 63387
Dr. Ulisse Cardini
Division of Microbial Ecology
Department of Microbiology and Ecosystem Science
Research Network "Chemistry meets Microbiology"
University of Vienna, Althanstr. 14, 1090 Vienna (AT)
Telefon: +43 677 61633148
Eberhard Scholz | idw - Informationsdienst Wissenschaft
Closing the carbon loop
08.12.2016 | University of Pittsburgh
Newly discovered bacteria-binding protein in the intestine
08.12.2016 | University of Gothenburg
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
08.12.2016 | Life Sciences
08.12.2016 | Physics and Astronomy
08.12.2016 | Materials Sciences