New finding provides better understanding of oceans' capacity to absorb atmospheric carbon dioxide

New finding provides better understanding of
oceans' capacity to absorb atmospheric
carbon dioxide

February 20 2023

Satellite PIC and location map. August satellite-derived Particular Inorganic
Carbon (PIC; mg CaCO3 m-3) climatology (2002-2017) and location of C-DisK-
IV stations (black crosses) and long-term sediment trap studies (orange/pink
crosses). Large black crosses show the location of Niskin bottle rosette, plankton
tow, and floating sediment trap sampling sites at C-DisK-IV stations. Small black

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crosses show sites with additional plankton tow sampling only at C-DisK-IV
stations. Note the logarithmic scale. Credit: Nature Communications (2023). DOI:
10.1038/s41467-023-36177-w

A new study demonstrates the important role of a common group of
marine calcifying phytoplankton (coccolithophores) in the regulation of
carbon dioxide (CO2) concentrations in the atmosphere.

The ocean has removed roughly a third of the CO2 released by humans
since the Industrial Revolution. It is one of the largest sinks of
anthropogenic CO2 and the largest reservoir of carbon that can easily
exchange with the atmosphere on our planet. Understanding the
processes that control the exchange of carbon between the ocean and
atmosphere is key for projecting the future effects of carbon dioxide on
climate change, ocean acidification, marine organisms, and society.

Research led by the Institute of Environmental Science and Technology
of the Universitat Autònoma de Barcelona (ICTA-UAB) in collaboration
with an international scientific team discovered that the exchange of
carbon between the atmosphere and ocean is highly modulated by a
unique group of photosynthesizing plankton called coccolithophores.

These common microscopic organisms which live in the sun-lit layer of
the world's oceans form elaborate plates of the carbon bearing mineral
calcium carbonate. These layers are visible, for example, in places like
the White Cliffs of Dover.

In the study published today in the journal Nature Communications, the
team co-led by ICREA research professor Dr. Patrizia Ziveri at the
ICTA-UAB found that coccolithophores dominate the production of
CaCO3.

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Coccolithophores are tiny algae which measure less than one hundredth
of a millimeter and form the basis of the aquatic food web and
contribute to the regulation of atmospheric CO2 levels through
calcification and photosynthesis.

The study shows coccolithophores comprise 90% of the total production
of CaCO3 in the surface ocean, indicating they play a key role in
controlling ocean chemistry and CO2. This research highlights that the
other two main planktonic calcifying groups, zooplankton (pteropods)
and foraminifera, play a secondary role in the context of atmospheric
CO2 modulation.

The study also revealed that rather than sinking into the deep ocean, a
large portion of this CaCO3 dissolves close to the surface where carbon
is more readily exchanged with the atmosphere and where sunlight
penetrates the surface (photic zone).

"This extensive shallow dissolution explains the apparent discrepancy
between previous estimates of CaCO3 production derived from satellite
observations/biogeochemical modeling versus sinking particle estimates
from shallow sediment traps," explains Ziveri, who clarifies that the
finding suggests that the processes driving shallow CaCO3 dissolution are
key to understanding the role of planktonic calcifiers in regulating
atmospheric CO2. This is important as more dissolution will increase the
ability of water to hold CO2.

Dr. William Gray, a research scientist at the Laboratoire des Sciences du
Climat et de l'Environnement who co-led the study, explains, "The
dissolution of so much CaCO3 close to the ocean's surface shows the
exchange of carbon between the ocean and atmosphere is much more
complicated than we first thought. Until we better understand the
processes driving this shallow dissolution, it will be difficult to predict
how the ocean will uptake carbon in the future."

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The study, which also involved ICTA-UAB researchers Michael
                                   Grelaud, Sven Pallacks and Griselda Anglada-Ortiz, used data obtained
                                   during a 2017 expedition to the North Pacific Ocean from Hawaii to
                                   Alaska and was produced in collaboration with an international scientific
                                   team with institutions from five countries.

                                    More information: Patrizia Ziveri et al, Pelagic calcium carbonate
                                   production and shallow dissolution in the North Pacific Ocean, Nature
                                   Communications (2023). DOI: 10.1038/s41467-023-36177-w

                                   Provided by Autonomous University of Barcelona

                                   Citation: New finding provides better understanding of oceans' capacity to absorb atmospheric
                                   carbon dioxide (2023, February 20) retrieved 6 April 2024 from
                                   https://phys.org/news/2023-02-oceans-capacity-absorb-atmospheric-carbon.html

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