Investigating the effect of nickel concentration on phytoplankton growth to assess potential side-effects of ocean alkalinity enhancement
<p>Ocean alkalinity enhancement (OAE) is a proposed method for removing carbon dioxide (CO<span class="inline-formula"><sub>2</sub></span>) from the atmosphere by the accelerated weathering of (ultra-)basic minerals to increase alkalinity – the chemical capaci...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-08-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/19/3683/2022/bg-19-3683-2022.pdf |
| Summary: | <p>Ocean alkalinity enhancement (OAE) is a proposed method for
removing carbon dioxide (CO<span class="inline-formula"><sub>2</sub></span>) from the atmosphere by the accelerated
weathering of (ultra-)basic minerals to increase alkalinity – the chemical
capacity of seawater to store CO<span class="inline-formula"><sub>2</sub></span>. During the weathering of
OAE-relevant minerals relatively large amounts of trace metals will be
released and may perturb pelagic ecosystems. Nickel (Ni) is of particular
concern as it is abundant in olivine, one of the most widely considered
minerals for OAE. However, so far there is limited knowledge about the
impact of Ni on marine biota including phytoplankton. To fill this knowledge
gap, this study tested the growth and photo-physiological response of 11
marine phytoplankton species to a wide range of dissolved Ni concentrations
(from 0.07 to 50 000 nmol L<span class="inline-formula"><sup>−1</sup></span>). We found that the phytoplankton species
were not very sensitive to Ni concentrations under the culturing conditions
established in our experiments, but the responses were species-specific. The
growth rates of 6 of the 11 tested species showed generally limited but
still significant responses to changing Ni concentrations (36 % maximum
change). Photosynthetic performance, assessed by measuring the maximum
quantum yield (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>F</mi><mi mathvariant="normal">v</mi></msub><mo>/</mo><msub><mi>F</mi><mi mathvariant="normal">m</mi></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="31pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="4748c5c19bb0957c33ea1b7ddcad2005"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-3683-2022-ie00001.svg" width="31pt" height="14pt" src="bg-19-3683-2022-ie00001.png"/></svg:svg></span></span>) and the functional absorption cross-section
(<span class="inline-formula"><i>σ</i><sub>PSII</sub></span>) of photosystem II (PSII), was sensitive to changing Ni in 3
out of 11 species (35 % maximum change) and 4 out of 11 species (16 %
maximum change), respectively. The limited effect of Ni may be partly due to
the provision of nitrate as the nitrogen source for growth as previous
studies suggest higher sensitivities when urea is the nitrogen source.
Furthermore, the limited influence may be due to the relatively high
concentrations of synthetic organic ligands added to the growth media in our
experiments. These ligands are commonly added to control trace metal
bioavailability and therefore for example “free Ni<span class="inline-formula"><sup>2+</sup></span>” concentrations
by binding the majority of the dissolved Ni. Our data suggest that dissolved
Ni does not have a strong effect on phytoplankton under our experimental
conditions, but we emphasize that a deeper understanding of nitrogen
sources, ligand concentrations, and phytoplankton composition is needed when
assessing the influence of Ni release associated with OAE.</p> |
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| ISSN: | 1726-4170 1726-4189 |