Scientists at The University
of Manchester have helped to identify that the presence of large amounts
of seaweed in coastal areas can influence the climate.
A new international study has found that large brown seaweeds, when under stress,
release large quantities of inorganic iodine into the coastal atmosphere, where
it may contribute to cloud formation.
A scientific paper published online today (Monday 6 May 2008) in the Proceedings
of the National Academy of Science (PNAS) identifies that iodine is stored in
the form of iodide – single, negatively charged ions.
When this iodide is released it acts as the first known inorganic – and
the most simple – antioxidant in any living system.
“When kelp experience stress, for example when they are exposed to intense
light, desiccation or atmospheric ozone during low tides, they very quickly
begin to release large quantities of iodide from stores inside the tissues,”
explains lead author, Dr Frithjof Küpper from the Scottish Association
for Marine Science.
“These ions detoxify ozone and other oxidants that could otherwise damage
kelp, and, in the process, produce molecular iodine.
“Our new data provide a biological explanation why we can measure large
amounts of iodine oxide and volatile halocarbons in the atmosphere above kelp
beds and forests. These chemicals act as condensation nuclei around which clouds
The paper’s co-author, Dr Gordon McFiggans, an atmospheric scientist
from The University of Manchester’s School of Earth, Atmospheric and Environmental
Sciences (SEAES) said: “The findings are applicable to any coastal areas
where there are extensive kelp beds. In the UK, these are typically place like
the Hebrides, Robin Hood's Bay and Anglesey. The kelps need rocky intertidal
zones to prosper - sandy beaches aren't very good.
“The increase in the number of cloud condensation nuclei may lead to
‘thicker’ clouds. These are optically brighter, reflecting more
sunlight upwards and allowing less to reach the ground, and last for longer.
In such a cloud there are a higher number of small cloud droplets and rainfall
is suppressed, compared with clouds of fewer larger droplets.
“The increase in cloud condensation nuclei by kelps could lead to more
extensive, longer lasting cloud cover in the coastal region – a much moodier,
typically British coastal skyline.”
The research team also found that large amounts of iodide are released from
kelp tissues into sea water as a consequence to the oxidative stress during
a defence response against pathogen attack. They say kelps therefore play an
important role in the global biogeochemical cycle of iodine and in the removal
of ozone close to the Earth's surface.