Iron deficiency inhibits marine microbes

by   Profile Herbert   When 26th May 2017
Two crew members take water samples using an oceanographic measuring device. (c) M. Visbeck, GEOMAR
The deep blue colour of the tropical Atlantic, as seen from the METEOR. The colour shows that not many nutrients are present in the water. (c) M. Visbeck, GEOMAR

Scientists discover important process in nutrient cycle in tropical North Atlantic

Iron has been identified as an important nutrient for algae and the
nitrogen cycle in the oceans.

Now, researchers have discovered that
marine microorganisms such as bacteria also need iron to process

Scientists regard the tropical oceans as a “blue desert” because of the
limited growth of algae there, compared to other oceanic regions. To
grow, algae depends on nutrients like nitrogen and phosphorus. However,
in the tropics, these nutrients are available in smaller quantities or
are sometimes not available. This affects the entire ecosystem, as
these "ocean plants" form the basis for many marine habitats.

Actually, nitrogen and phosphorus can be found in the tropical ocean.
However, these nutrients are often incorporated into dead plants and
animals, which subsequently sink to the sea floor.

"Microbes can get to these hidden
nutrients by recycling the dead matter with the help of enzymes. As a
result, nutrients like phosphorus can be made available again for
algae. A crucial element for this process is iron. Enzymes need this
trace metal to work properly,” explained Dr Thomas Browning from
GEOMAR Helmholtz Center for Ocean Research Kiel.

As lead author, Dr
Browning and some of his colleagues from GEOMAR and the University of
Southampton recently published a paper on this in the international
scientific journal Nature Communications.

“If you look at the nutrient distributions in the oceans on a global scale, you can see regional differences,” said Dr Browning. “Interestingly,
we know from previous observations that for regions where nutrients are
limiting the growth of marine algae, not all available pools of
nutrients are being used. But why?”

The research team looked into this question during a research cruise
within the framework of the Collaborative Research Centre 754 “Climate
– Biogeochemistry Interactions in the Tropical Ocean. Field experiments
were conducted in which iron was added to seawater and the microbial
enzyme activity measured.

Dr Browning observed that the activity of a
widely distributed group of microbial enzymes was affected by the iron
content in the seawater.
The team used the results of their research to confirm a hypothesis
made in a previous study by fellow researchers at University of Oxford.

“They demonstrated by laboratory
experiments, that microbial enzymes need iron to process phosphorus,
and suggested this could also be important in the ocean. We have
confirmed for the first time that this is indeed the case,” Dr Browning explained.

Where nitrogen and phosphorus are concerned, nitrogen is regarded as
the main limiting factor for the growth of algae in the ocean. However,
this relationship could change with the additional supply of nitrogen
into global oceans caused by human activity. The limitation of
phosphorus may become more common, while the presence of iron may play
a major role. Such changes could exert an impact on the oxygen
production of algae and their intake of carbon dioxide from the

Link to the study:

ocean, research,
Written by
Profile Herbert
When 26th May 2017
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