Researchers have named the Melosira
arctica, one of the major algae species in the Arctic Ocean, as Algae of
the Year.
“None of us can foresee whether the Melosira
would be a victim or beneficiary of the melting sea ice. No one knows why it is
the most productive algae in this hostile world,” said Dr Klaus Valentin, a biologist from
the Alfred Wegener Institute for Polar and Marine Research, Helmholtz Centre
for Polar and Marine Research (AWI).
A
member of the Phycology Section of the German Botanical Society (Deutsche Botanische Gesellschaft), he was among the team of researchers
who had bestowed the award to the Melosira
arctica algae.
Valentin
added that based on their latest genetic studies, the Melosira arctica was by far the most
productive algae in the Arctic Ocean. In 2013, it accounted for 45 percent of
primary production in the region.
With “cell” walls of only 30 micrometres
in thickness consisting of silica, it has a protective gelatinous jacket made
of polysaccharides. The single-celled alga links with one another to form algae
filaments that hang from the underside of ice floes. These threads can be as
long as several metres.
Polar explorers have even found this algae
in brine and meltwater pools, where they mostly grow in large quantities.
Even today, it is largely unknown how the
Melosira arctica survives the long nights and harsh frost of the Arctic winter,
and then multiply so extensively in the spring that it dominates the Arctic
Ocean.
Even though diatoms (microscopic algae)
form the foundation of the food chain and the Melosira arctica is a key
organism in the Arctic ecosystem, the researchers do not know much about how it evolves or how it is
influenced by environmental factors like light, nutrients or salinity. Hence,
the species is now the focus of a new research project at the AWI.
Systematic analysis possible for the first
time
Thus, the project – entitled “Melosira
arctica in a changing Arctic Ocean” – was launched; it was one of AWI's first
strategic projects. Different algae samples from the Arctic were collected, so
as to extract pure cultures from them. These specimens were used to answer the
biologists' many questions.
For instance, they were interested in how
the algae responded to climate change. Since satellite measurements started in
1979, the sea-ice cover in the Arctic has shrunk significantly. Some climate
models show the Arctic becoming ice-free during summertime by the second half of
this century. Valentin wants to find out what would happen to the algae which
his team found in and around the perennial ice.
Physiological reaction of the “Ice Algae”
Most algae grow better when there is more
light exposure and warmer seawater. Through photosynthesis, they get their
energy and produce oxygen.
However, this may not be the case for the Melosira
arctica. The oxygen produced can get stuck in air bubbles in the filaments
of the Melosira arctica, adding to its bouyancy. Through their research,
the scientists also want to know the temperatures at which the algae thrive and
carry out photosynthesis, as well as how they deal with the range of nutrients
that would vary with the temperatures.
In addition, they are also curious about
the type of light conditions the algae can best tolerate
This is because light incidence, together
with the dwindling ice, can inhibit microbial growth. It is within the
controlled environment of a laboratory that all these variants can be measured
easily and more accurately.
Melosira life cycle affects biomass in the
deep sea
The recent years have seen excessive
melting of the sea ice during the Arctic summer. During this time, the algae
filaments detach, falling to the sea floor below where they are eaten by sea cucumbers
and brittlestars. Due to climate change, this descent now takes place much
sooner, so that as much as 85 percent of the biomass falls to the seafloor and
is no longer available as food in the upper water column.
Mares
19th January 2016
