M. Debora Iglesias-Rodriguez
talks with ScienceWatch.com and answers a few
questions about this month's Fast Breaking Paper in the
field of Geosciences. The author has also sent along
images of her work.
Article Title: Phytoplankton calcification in a
MD;Halloran, PR;Rickaby, REM;Hall,
IR;Colmenero-Hidalgo, E;Gittins, JR;Green, DRH;Tyrrell,
T;Gibbs, SJ;von Dassow, P;Rehm, E;Armbrust, EV;Boessenkool,
Year: APR 18 2008
* Univ Southampton, Natl Oceanog Ctr, Waterfront
Campus,European Way, Southampton SO14 3ZH, Hants,
* Univ Southampton, Natl Oceanog Ctr, Southampton SO14 3ZH,
(addresses have been truncated)
Why do you think your paper is highly
Because recent debate about the long-term fate of increasing carbon dioxide
(CO2) in the oceans and its effect: ocean acidification has
prompted questions about how marine organisms, particularly those that
calcify, will adapt to these changes.
While most studies have dealt with either laboratory observations or the
geological record, my work combines both laboratory analysis of the effect
of ocean acidification on calcium carbonate-producing phytoplankton with
analysis of their geological record over the past 220 years, during the
Anthropocene epoch—the period of anthropogenic CO2
The model organisms that I investigate, coccolithophores (single-celled
algae, protists, and phytoplankton), are responsible for most of the
open-ocean calcification and thus, information on how these adapt to
climate change is extremely important in order to predict any alteration in
the marine carbon cycle.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
Yes, my paper describes a new finding and synthesizes information spanning
from cellular responses to long-term trends in the geological record.
Would you summarize the significance of your paper in
Increased CO2 in the Earth's atmosphere is causing some
microscopic ocean plants to produce greater amounts of calcium
carbonate—with potentially wide-ranging implications for predicting
the cycling of carbon in the oceans and global climate modeling.
This work shows that calcification by phytoplankton could increase along
with the increasing levels of CO2. This is important because the
majority of ocean calcification is carried out by coccolithophores.
When coccolithophores make plates of calcium carbonate they also release
CO2. But because these organisms photosynthesize they also
consume CO2. It is the balance between calcification—which
produces carbon dioxide—and the consumption of CO2 by
photosynthesis that will determine whether coccolithophores act as a "sink"
(absorbing CO2) or as a source of CO2 to the
Our results, based on experiments that directly replicate how the oceans
take up carbon dioxide, show that the rise in CO2 produced by
increased calcification is mitigated by its removal through increased
photosynthesis, with a net effect that is unlikely to either contribute
greatly or significantly reduce the rise in atmospheric CO2.
Our research has also revealed that, over the past 220 years,
coccolithophores have increased the mass of calcium carbonate they each
produce by around 40%. These results are in agreement with previous
observations that coccolithophores are abundant throughout past periods of
ocean acidification, such as that which occurred roughly 55 million years
ago—the Palaeocene Eocene Thermal Maximum.
How did you become involved in this research, and were
there any problems along the way?
I was testing whether different varieties of Emiliania huxleyi,
the model coccolithophore species used in my study, responded differently
to varying CO2 levels. At the time when I found my exciting
results, I also met Paul Halloran (Oxford University) who was working on
the geological record of calcifying phytoplankton. When I realized their
observations in the geological record showed that coccolithores have
adapted to decreasing pH we started a collaboration that resulted in the
Where do you see your research leading in the
My research will continue to contribute to the understanding of the
evolution of coccolithophores by answering fundamental questions in
cellular biology. A central question is why do coccolithophores calcify?
Without knowing the answer to this question we will not be able to make
much progress in our understanding of the environmental regulation of
calcification. Because understanding these controls is central to
predicting changes in the carbon cycle, I plan to work together with
modellers to further our understanding of calcification in the present-day
ocean and to make more robust predictions for the future.
Do you foresee any social or political implications for
Most definitely. Ocean acidification has a potentially dramatic impact on
ecosystems, from single-cell organisms to large predators. This could have
societal implications at different levels with potential effects on
tourism, food availability, and the economy. However, these questions are
still facing the community of scientists (from molecular biologists to
population ecologists and carbon cycle modellers), who, for the first time,
are working together to find solutions. My work represents a contribution
toward whatever future scenarios could be like for organisms which are
central to the ocean carbon pump.
Dr. M. Debora Iglesias-Rodriguez
Lecturer, Molecular Biology and Phytoplankton Physiology
National Oceanography Centre
University of Southampton
KEYWORDS: EOCENE THERMAL MAXIMUM; EMILIANIA-HUXLEYI;
ATMOSPHERIC CO2; SOUTH ATLANTIC; CARBON; SEDIMENTS; OCEAN; FEEDBACK;