A team of researchers has managed to record the behaviour of organisms in the face of
declining oxygen levels. They simulated dead zones on the Adriatic Sea bed with an
underwater device they developed themselves. Funded by the Austrian Science Fund
FWF, a catalogue of animal behavioural models will be published this August, which can
be used to classify the state of such threatened marine environments.

It is no secret that our seas are endangered. What is far less well-known is that a perilous
lack of oxygen in our oceans is causing mass mortalities on the sea bed at an ever-
increasing rate. Moreover, there has been a recent increase in the prevalence of so-called
dead zones – places where there is not enough oxygen in the water. This phenomenon is
promoted by polluted rivers and global warming. A total of 400 dead zones have already
been recorded across the globe and they cover an area in excess of 250,000 square
kilometres – the size of Germany. What exactly happens in such zones has been poorly
explored to date. Now, however, scientists from Vienna are the first to have successfully
simulated oxygen crises in the sea on a tiny scale. Their project will help detect such
situations at an early stage, enabling countermeasures to be taken. The key lies in the
threatened animals themselves – in their behaviour.

BEHAVIOUR IS THE YARDSTICK
When the oxygen content in the water drops, marine organisms modify their behaviour.
This knowledge forms the basis for the project conducted by a team of researchers at the
University of Vienna, as Dr. Michael Stachowitsch from the Department of Marine Biology
explains: „We are studying precisely what happens at the bottom of the Adriatic Sea when
oxygen levels drop – before, during and after they fall. We observe exactly how the various
species react to the lack of oxygen: some try to escape and make their way up to higher
water strata, while others curtail their activity or display entirely unnatural behaviour. The
goal of our project has been to compile a catalogue to describe these types of behaviour
in detail and to match them to specific oxygen concentrations in the water.“ The catalogue
of behaviours will enable experts to determine the status of the water without the need for
costly and time-consuming measurements. Dr. Stachowitsch is working together with Dr.
Bettina Riedel and Prof. Martin Zuschin to compile the catalogue, the first part of which will
be published in August.

In their project, the Vienna-based scientists are following the tradition of the highly-
respected „Vienna School of Marine Biology“. This approach means is that the research is
not performed solely on the computer or in the lab, as is common practice. The work is
conducted „in situ“, in other words at the site of the action. In the current project, this is 24
metres below sea level at the bottom of the Adriatic, two kilometres off the coast of Piran,
Slovenia. However, in order not to miss the poorly predictable oxygen deficiencies, the
research team simulates their own little dead zone, which required developing and building
an underwater apparatus.

OXYGEN CRISIS UNDER PLEXIGLAS
The EAGU (Experimental Anoxia Generating Unit), developed by the team, is a Plexiglas
chamber equipped with high-tech apparatus to supply crucial data, as Dr. Riedel explains:
„First, we move a 50 x 50 x 50 centimetre open frame into position. This allows us to
observe the events at normal oxygen concentrations for a period of 24 hours. Then we
close the cube. Within a few days the entire oxygen inside the EAGU is used up. As the
oxygen level declines, the behaviour of the mussels, sponges, snails, brittle stars,
anemones and sea squirts enclosed in the cube changes too. A time-lapse camera takes
images at six-minute intervals and sensors measure the concentration of oxygen and
hydrogen sulphide in the water, along with the pH value and the temperature.“ The
scientists are thereby able to ascribe the behaviour of the animals as recorded in the
images to the individual oxygen categories.

The resulting catalogue of behaviours, which is being supported by the FWF, can serve as
a guide for the early recognition of dead zones. As such, it could also help to ensure that
the correct political action is taken without delay in the event of an emergency – for
instance, a ban on fishing in the affected area to give the ecosystem a chance to
regenerate.

University of Vienna
Department of Marine Biology
Althanstraße 14
1090 Vienna, Austria
T +43 / 1 / 4277 57103
E stachom5@univie.ac.at

The Austrian Science Fund FWF:
Mag. Stefan Bernhardt
Haus der Forschung
Sensengasse 1
1090 Vienna, Austria
T +43 / 1 / 505 67 40 – 8111
E stefan.bernhardt@fwf.ac.at
W http://www.fwf.ac.at

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PR&D – Public Relations for Research & Development
Campus Vienna Biocenter 2
1030 Vienna, Austria
T +43 / 1 / 505 70 44
E contact@prd.at
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