In:
Biogeosciences, Copernicus GmbH, Vol. 17, No. 9 ( 2020-05-07), p. 2453-2471
Abstract:
Abstract. The reaction between ozone and iodide at the sea surface is now
known to be an important part of atmospheric ozone cycling, causing ozone
deposition and the release of ozone-depleting reactive iodine to the
atmosphere. The importance of this reaction is reflected by its inclusion in
chemical transport models (CTMs). Such models depend on accurate sea surface
iodide fields, but measurements are spatially and temporally limited. Hence,
the ability to predict current and future sea surface iodide fields, i.e. sea surface iodide concentration on a narrow global grid, requires the
development of process-based models. These models require a thorough
understanding of the key processes that control sea surface iodide. The aim
of this study was to explore if there are common features of iodate-to-iodide reduction amongst diverse marine phytoplankton in order to develop
models that focus on sea surface iodine and iodine release to the
troposphere. In order to achieve this, rates and patterns of changes in
inorganic iodine speciation were determined in 10 phytoplankton cultures
grown at ambient iodate concentrations. Where possible these data were
analysed alongside results from previous studies. Iodate loss and some
iodide production were observed in all cultures studied, confirming that
this is a widespread feature amongst marine phytoplankton. We found no
significant difference in log-phase, cell-normalised iodide production rates
between key phytoplankton groups (diatoms, prymnesiophytes including
coccolithophores and phaeocystales), suggesting that a phytoplankton
functional type (PFT) approach would not be appropriate for building an
ocean iodine cycling model. Iodate loss was greater than iodide formation in
the majority of the cultures studied, indicating the presence of an as-yet-unidentified “missing iodine” fraction. Iodide yield at the end of the
experiment was significantly greater in cultures that had reached a later
senescence stage. This suggests that models should incorporate a lag between
peak phytoplankton biomass and maximum iodide production and that cell
mortality terms in biogeochemical models could be used to parameterise
iodide production.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-17-2453-2020
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2020
detail.hit.zdb_id:
2158181-2
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