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55 EINBLICKE
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"Throughout the natural world on the surface of the earth is a
substance that fluoresces light bluewhenexposed toultraviolet
light.So far it has been shown to be present in the atmosphere,
in all natural water reserves: in fog, snow, rain,hoar frost,glacial
ice, in waves, streams, rivers, lakes and in both the surface and
depths of the world‘s oceans." These are the opening words
of a publication by germanmarine chemist Kurt Kalle from the
year 1963. As early as 1909 a chemist by the name of Dienert
described this phenomenon innatural waters.At the endof the
1930s Kallebegan to inves-
tigate the distribution of
fluorescent substances
in coastal waters. At the
same time he was also interested in a second component,
one that lends water its humus-like yellow colour: Kalle cal-
led it "Gelbstoff". Besides this term and its direct translation
as "yellow substance", in scientific literature the most widely
used term is "Coloured Dissolved Organic Matter" or CDOM.
Yellow substance is the coloured, or more precisely, the blue-
absorbing part of the Dissolved Organic Matter (DOM) pool.
The world‘s oceans contain an estimated 700 gigatonnes of
DOM, a quantity comparable with the biomass of vegetation
on land. In coastal areas, CDOM is primarily washed into the
sea by rivers and subsea seeps.Out at sea CDOMmainly occurs
as a degradation product of algal blooms.The CDOM content
makes it possible to track thepassage of water through the seas
for hundreds of kilometres, for instance, fromtheGerman Bight
to the Skagerrak. Yet very little research has been conducted
into this organic substance.Scientists fromthe university‘sMax
Planck Marine Geochemistry research group are now imple-
menting complex laboratory methods to work on decoding
its chemical composition.
Coloured Dissolved Organic Matter originates from the me-
tabolism and degradation products of plants and animals.
CDOM is – the absorbent properties of pure water aside – the
key factor for the distribution of light in the sea. It absorbs
ultraviolet radiation and protects marine organisms from
its negative effects. Its absorption bands in the blue-green
spectral range overlap with those of phytoplankton, which
means that it influences the algae‘s physiology and primary
production of algae. Moreover CDOM absorbs trace metals,
serves as a nutrient for microorganisms and is directly linked
to the entire pool of organic matter.
The Institute for Chemistry and Biology of the Marine Envi-
ronment (ICBM) is studying the processes that lead to the
formation, degradation and distribution of DOM on a broad
interdisciplinary basis. The scientists involved in the project
are working with state-of-the-art laboratory methods and
measurement systems that can be applied at high-resolution
over long periods of time and in situ,which in this casemeans:
in the water.As the optically active element of organic matter,
yellow substance is particularly well suited to this process
because the absorption of blue and ultraviolet light can be
assessed with sensitive and accurate measuring equipment.
Since May 2011, the Marine Sensor Systems working group
at the ICBM has been developing new sensor principles and
is working to optimize existing approaches. Since November
2011, the Federal Ministry of Economics and Technology
(BMWi) has been funding the project titled "Development
of an Online Method to Determine and Characterise Dis-
solved Organic Material (DOM
– measured as DOC or BSB5)
using Florescence Spectrosco-
py" (DOMsense) . DOMsense
is a cooperative project between Oldenburg scientists, an
international sensor manufacturer and Hamburg University.
DOMsense aims to improve sensor technology for optically
active constituents in natural waters. Aside from CDOM there
is also an interest in "sky-blue fluorescence".
In contemporary literature this fluorescence is often described
as CDOM Fluorescence in order to emphasize its absorption-
defined connection with Coloured Dissolved Organic Matter.
Although Kalle‘s research was based on the assumption that
two different substances were in play here, today we know
that yellow substances and fluorescent substances are both
components of the vast DOM pool, albeit subject to different
photochemical processes.Scientists use the termFDOMwhen
referring to the fluorescent properties of Dissolved Organic
Matter. FDOM stands for Fluorescent Dissolved Organic Mat-
ter and can be measured with great precision and above
700 giga-tons of dissolved
organic matter in the oceans
Using high-resolution
measuring technology
Zur Person
Personal Details
Prof. Dr. Oliver Zielinski, Hochschullehrer für Marine Sensorsysteme
am Institut für Chemie und Biologie des Meeres, wurde 2011 an
die Universität Oldenburg berufen. 2005 etablierte er an der Hoch-
schule Bremerhaven den Studiengang Maritime Technologien und
war dort Mitgründer und erster Direktor des Instituts für Marine
Ressourcen. Zielinski ist Vorsitzender der Deutschen Gesellschaft
für Meeresforschung.
Prof. Dr. Oliver Zielinski, professor on marine sensor systems at the
Institute for Chemistry and Biology of theMarine Environment (ICBM),
accepted a chair at Oldenburg University in 2011. In 2005 he esta-
blished the Maritime Technologies degree course at Bremerhaven
University of Applied Science and was co-founder and first director
of the Institute for Marine Resources there. Zielinski is chairman of
the German Association of Marine Research.