Effects of ocean acidification, temperature and organic matter on Fe(II)
persistence in the Atlantic Ocean (ATOPFe)
The ATOPFe Project will study the effects of pH, temperature, and organic
matter (TOC) on Fe (II) oxidation kinetics and its persistence in the ocean.
Three specific regions: polar, subtropical and submarine volcanic regions, have
been selected as the fundamental basis for comparing laboratory studies and
developing a kinetic model for iron in the context of ocean acidification and
warming.
Iron is a trace element
essential for the development of organisms and has a great impact on the Carbon
cycle through its effect on planktonic communities and their productivity.
Reduced iron, Fe(II), is the bioavailable species for phytoplankton, rather
than oxidized iron, Fe(III). Fe(III) presents a low solubility and is mostly
complexed by organic ligands. Fe(II) is thermodynamically unstable due to pH,
O2 and temperature conditions in the medium and tends to become oxidised.
Acidification favours the presence of Fe(II) in the medium. Moreover, organic
matter plays an essential role in the Fe cycle in the ocean. The presence of
organic compounds may reduce Fe(III) to Fe(II) and also stabilise Fe(II) by
complexation.
The main goal of the
EACFe project is to investigate which compounds and mechanisms determine the
presence of Fe(II) in the marine environment and how the presence of organic
matter, ocean acidification and global warming affect them.
To achieve these goals,
the studies that will be carried out in the three selected regions will be
combined with laboratory studies to provide the response from a theoretical
marine physical-chemistry perspective of those mechanisms that control the
behavior of Fe (II) and explain how it may persist as such in the ocean.
The objectives of the ATOPFe project are:
1. To study the oxidation kinetics of Fe(II) (k-Fe (II) in the text) to
describe its persistence in the water masses found in different regions of the
Atlantic Ocean: submarine volcanic, polar and subtropical regions.
2. To study the chemical behavior of Fe(II) in volcanic environments by
carrying out kinetic laboratory studies considering the ionic interaction that
can occur with other components emitted by the volcano and that will affect Fe(II) speciation.
3. To study the interaction of Fe-Cu-phytoplankton by focusing on the
determination of organic compounds excreted as a consequence of the Fe-Cu
interaction and on the effect of
assimilation by phytoplankton.
4. Modeling of Fe(II).
By justifying the presence of Fe(II) in the marine environment, these
studies will shed light, from a theoretical point of view, on the results found
in other projects related to the studies of mesocosmos, ocean fertilization and
iron emissions in hydrothermal zones.