Biology and the Carbon Cycle
Biological communi-
ties found in sea ice
and in the upper
part of the water
column in a North
South section of the
Arctic Ocean during
summer.
Bottom ice community
Sub-ice community
Melt pools community
Planktonic community
a tenth, then enters the atmosphere. The rest is either consumed by bacteria or
broken down by sunlight to form dimethylsulfoxide (DMSO).
Algae exploit several habitats in the polar environment. In ice-free polar
seas, microscopic algae are found mainly in the upper part of the water col-
umn. They are called the planktonic algae, or phytoplankton. In ice-covered
seas, algae are found mainly:
At the surface of the ice in melt pools formed by thawing surface ice,
flooding or a combination of flooding and thawing;
In the bottom 25 cm of the ice, where they form a brownish layer; and
In the seawater immediately under the ice, where they form huge mats
and strands up to 3 m long.
These unicellular algae that grow in and on the ice are called the sea ice algae.
In the Arctic, phytoplankton and ice algae both contribute to DMS produc-
tion.
The goal of our study was to determine the contribution of planktonic and
sea ice microalgae to the production of DMSP and DMS in the western and
central Arctic Ocean during summer. Sampling was conducted on the
multi-year ice of the Arctic Ocean from 26 July to 26 August 1994, onboard
the USCGC Polar Sea. The transect began in the continental shelf of the Chuk-
chi Sea on the western side of the Arctic and terminated in the deep Nansen
Basin on eastern side of the Arctic. Along the transect the ice thickness varied
from 1 to 5 m, and ice coverage varied from 50 to 100%. Bottles specifically
designed for oceanographic research were used to collect surface water sam-
ples, while melt pools were sampled by means of a bucket. An ice corer was
used for collecting the bottom-ice samples. Finally, the sub-ice samples were
collected by U.S. Coast Guard scuba divers, using a 2-L syringe sampler called
a "slurp gun." In the laboratory, various measurements were performed on the
melted ice and water samples. Chlorophyll a concentrations, an index of algal
biomass, were determined using the fluorometric method. Particulate DMSP,
dissolved DMSP and free DMS were determined by gas chromatography.
Significant DMS concentrations were measured in all the habitats studied.
In surface water, DMS concentrations were highest on the continental shelf of
the Chukchi Sea and rapidly decreased toward the Pole. Surface DMS concen-
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