The mystery of the presence of photolyzed diiodo-methane in high concentrations in the ocean surface layer where the light is reflected
concentrations are increasing in surface seawater, as observed every
year from May onwards in Funka Bay.
underlying reason is a complete mystery.
The diiodo-methane concentration was
also high near the seabed of the Arctic Ocean. Hence, assuming the presence of
a source of the generation of diiodo-methane at the seabed, we collected marine
sediments and measured iodine gas.
Results showed that only iodoethane
(C2H5I) was present in high concentrations in the sediment, and the
expected phenomenon of high diiodo-methane concentrations failed to
As observed with the vertical distribution
of the seawater analysis at Funka Bay,diiodo-methane
appears to be generated near the surface layer.
Existence of diiodo-methane near the surface layer is
also a complete mystery.
Diiodo-methane is easily decomposed
by the blue-wavelength light of the sunlight. Hence, itis a mystery why diiodo-methane is constantly present in
the ocean layer where light can reach.
It was initially believed that
diiodo-methane accumulated in the subsurface layer where the light was weak and
reached the surface layer via vertical mixing. Subsequently, it maintained the
surface layer concentration.
Therefore, we decided to confirm this
by simultaneously investigating three aspects: “turbulence measurements”
evaluating vertical mixing in detail, “light observations” analyzing the depth
of light penetration, and diiodo-methane measurements.
(We worked on this as an open call for
participants for the establishment of marine mixing studies (representative:
Professor Yasuda Ichiro) and cooperated with Professor Yasuda’s group and
Professor Hirawake’s group)
Results showed that vertical mixing cannot maintain the diiodomethane concentration
in the ocean surface layer. Hence, we formulated various hypotheses
and begun verifying them. As shown below, currently we hypothesize that iodine
is retained in the body of the phytoplankton (or the acidic polysaccharides on
their surfaces), and we are attempting to verify this.
Considering that diiodo-methane is
generated from living phytoplankton, we started culturing dinoflagellates,
which dominate Funka Bay in the summer.
（Under the guidance of Professor
Matsuno of the School of Fisheries Sciences, the fourth-year student Kawanishi
is attempting mass culturing. Good luck Kawanishi!）
（Kasai-kun, "For phytoplankton culture,
it is important to properly direct light, let them rest at night (for cell
division), control the temperature, add nutrients, vitamins, and sodium
hydrogen carbonate properly so as not to let them be carbon rate-determining." You need to be careful during plankton culture. Note: these are
used for gas measurements. Hence, the complete sealing results are obtained
after carbon control）.