Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists uncover the key to adaptation limits of ocean dwellers

01.07.2014

The simpler, the more heat-resistant: The simpler a marine life form is built, the better it is suited for survival during climate change. Scientists of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) discovered this in a new meta-study, which has been published in the research journal Global Change Biology.

For the first time biologists studied the relationship between the complexity of life forms and the limits of their adaptation to a warmer climate. While unicellular bacteria and archaea are able to live even in hot, oxygen-deficient water, marine inhabitants with a more complex structure, such as animals and plants, reach their growth limits at the latest at a water temperature of 41 degrees Celsius. This temperature threshold seems to represent an insurmountable obstacle for their highly developed metabolic systems.


Coral reefs are very sensitive towards increasing temperatures. Thus many tropical coral species already live close to their temperature maximum. Photo: Gertraud M. Schmidt / Alfred Wegener Institute

The current IPCC Assessment Report shows that marine life forms respond very differently to the increasing water temperature and the decreasing oxygen content of the ocean. “We now asked ourselves why this is so. Why do bacteria, for example, still grow at temperatures of up to 90 degrees Celsius, while animals and plants reach their limits at the latest at a temperature of 41 degrees Celsius,” says Dr. Daniela Storch, biologist in the Ecophysiology Department at the Alfred Wegener Institute (AWI) and lead author of the current study.

Since years Storch and her colleagues have been investigating the processes that result in animals having a certain temperature threshold up to which they can develop and reproduce. The scientists found that the reason for this is their cardiovascular system. They were able to show in laboratory experiments that this transport system is the first to fail in warmer water.

Heart, blood and circulation supply all cells and organs of a living organism with oxygen, but can only do so up to a certain maximum temperature. Beyond this threshold, the transport capacity of this system is no longer sufficient; the animal can then only survive for a short time. Based on this, the biologists had suspected at an early date that there is a relationship between the complex structure of an organism and its limited ability to continue to function in increasingly warm water.

“In our study, therefore, we examined the hypothesis that the complexity could be the key that determines the adaptability of diverse life forms, from archaea to animals, to different living conditions in the course of evolutionary history. That means: the simpler the structure of an oceanic inhabitant, the more resistant it should be,” explains the biologist. If this assumption is true, life forms consisting of a single simply structured cell would be much more resistant to high temperatures than life forms whose cell is very complex, such as algae, or whose bodies consist of millions of cells. Hence, the tolerance and adaptability thresholds of an organism would always be found at its highest level of complexity. Among the smallest organisms, unicellular algae are the least resistant because they have highly complex cell organelles such as chloroplasts for photosynthesis. Unicellular animals also have cell organelles, but they are simpler in their structure. Bacteria and archaea entirely lack these organelles.

To test this assumption, the scientists evaluated over 1000 studies on the adaptability of marine life forms. Starting with simple archaea lacking a nucleus, bacteria and unicellular algae right through to animals and plants, they found the species in each case with the highest temperature tolerance within their group and determined their complexity. In the end, it became apparent that the assumed functional principle seems to apply: the simpler the structure, the more heat-tolerant the species.

But: “The adaptation limit of an organism is not only dependent on its upper temperature threshold, but also on its ability to cope with small amounts of oxygen. While many of the bacteria and archaea can survive at low oxygen concentrations or even without oxygen, most animals and plants require a higher minimum concentration,” explains Dr. Daniela Storch. The majority of the studies examined show that if the oxygen concentration in the water drops below a certain value, the oxygen supply for cells and tissues collapses after a short time.

The new research results also provide evidence that the body size of an organism plays a decisive role concerning adaptation limits. Smaller animal species or smaller individuals of an animal species can survive at lower oxygen concentration levels and higher temperatures than larger animals.

“We observe in fish in the North Sea that larger individuals of a species are affected first at extreme temperatures. In connection with Earth warming, there is generally a trend that smaller species replace larger species in a region. Today, however, plants and animals in the warmest marine environments already live at their tolerance limit and will probably not be able to adapt. If warming continues, they will migrate to cooler areas and there are no other tolerant animal and plant species that could repopulate the deserted habitats,” says Prof. Dr. Hans-Otto Pörtner of the Alfred Wegener Institute. The biologist initiated the current study and is the coordinating lead author of the chapter “Ocean systems” in the Fifth Assessment Report.

The new meta-study shows that their complex structure sets tighter limits for multicellular organisms, i.e. animals and plants, within which they can adapt to new living conditions. Individual animal species can reduce their body size, reduce their metabolism or generate more haemoglobin in order to survive in warmer, oxygen-deficient water. However, animals and plants are fundamentally not able to survive in conditions exceeding the temperature threshold of 41 degrees Celsius.

On the other hand, simple unicellular organisms like bacteria benefit from warmer sea water. They reproduce and spread. “Communities of species in the ocean change as a result of these new living conditions. In the future animals and plants will have problems to survive in the warmest marine regions and archaea, bacteria as well as unicellular animal organisms will spread in these areas. There are already studies showing that unicellular algae will be replaced by other unicellular organisms in the warmest regions of the ocean,” says Prof. Dr. Hans-Otto Pörtner. The next step for the authors is the question regarding the role the complexity of species plays for tolerance and adaptation to the third climatic factor in the ocean, i.e. acidification, which is caused by rising carbon dioxide emissions and deposition of greenhouse gas in seawater.

Glossary:

Living at the limit

For generations ocean dwellers have adapted to the conditions in their home waters: to the prevailing temperature, the oxygen concentration and the degree of water acidity. They grow best and live longest under these living conditions. However, not all creatures that live together in an ecosystem have the same preferences. The Antarctic eelpout, for instance, lives at its lower temperature limit and has to remain in warmer water layers of the Southern Ocean. If it enters cold water, the temperature quickly becomes too cold for it. The Atlantic cod in the North Sea, by contrast, would enjoy colder water as large specimens do not feel comfortable in temperatures over ten degrees Celsius. At such threshold values scientists refer to a temperature window: every poikilothermic ocean dweller has an upper and lower temperature limit at which it can live and grow. These “windows” vary in scope. Species in temperate zones like the North Sea generally have a broader temperature window. This is due to the extensively pronounced seasons in these regions. That means the animals have to withstand both warm summers and cold winters.

The temperature window of living creatures in the tropics or polar regions, in comparison, is two to four times smaller than that of North Sea dwellers. On the other hand, they have adjusted to extreme living conditions. Antarctic icefish species, for example, can live in water as cold as minus 1.8 degrees Celsius. Their blood contains antifreeze proteins. In addition, they can do without haemoglobin because their metabolism is low and a surplus of oxygen is available. For this reason their blood is thinner and the fish need less energy to pump it through the body – a perfect survival strategy. But: icefish live at the limit. If the temperature rises by a few degrees Celsius, the animals quickly reach their limits.

Notes for Editors:

The paper with the title “Climate sensitivity across marine domains of life: Limits to evolutionary adaptation shape species interaction“ was published 26th June in Global Change Biology. DOI: 10.1111/gcb.12645.

Please find printable images on http://www.awi.de/en/news/press_releases/.

Your contact persons are Dr. Daniela Storch (tel.: +49 471 4831-1934, e-mail: Daniela.Storch(at)awi.de), as well as Kristina Baer, Dept. of Communications and Media Relations (tel.: +49 471 4831-2139; e-mail: medien(at)awi.de).

Follow the Alfred Wegener Institute on https://twitter.com/AWI_Media and http://www.facebook.com/AlfredWegenerInstitute. In this way you will receive all current news as well as information on brief everyday stories about life at the institute.

The Alfred Wegener Institute conducts research in the Arctic, Antarctic and oceans of the high and mid-latitudes. It coordinates polar research in Germany and provides major infrastructure to the international scientific community, such as the research icebreaker Polarstern and stations in the Arctic and Antarctica. The Alfred Wegener Institute is one of the 18 research centres of the Helmholtz Association, the largest scientific organisation in Germany.

Ralf Röchert | idw - Informationsdienst Wissenschaft

More articles from Ecology, The Environment and Conservation:

nachricht Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

nachricht A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde

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: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>