Independent iron and light limitation in a low-light-adapted Prochlorococcus from the deep chlorophyll maximum
Throughout the open ocean, a minimum in dissolved iron concentration (dFe) overlaps with the deep chlorophyll maximum (DCM), which marks the lower limit of the euphotic zone. Maximizing light capture in these dim waters is expected to require upregulation of Fe-bearing photosystems, further depletin...
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Veröffentlicht in: | The ISME Journal 2021, Vol.15 (1), p.359-362 |
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Sprache: | eng |
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Zusammenfassung: | Throughout the open ocean, a minimum in dissolved iron concentration (dFe) overlaps with the deep chlorophyll maximum (DCM), which marks the lower limit of the euphotic zone. Maximizing light capture in these dim waters is expected to require upregulation of Fe-bearing photosystems, further depleting dFe and possibly leading to co-limitation by both iron and light. However, this effect has not been quantified for important phytoplankton groups like
Prochlorococcus
, which contributes most of the productivity in the oligotrophic DCM. Here, we present culture experiments with
Prochlorococcus
strain MIT1214, a member of the Low Light 1 ecotype isolated from the DCM in the North Pacific subtropical gyre. Under a matrix of iron and irradiance matching those found at the DCM, the ratio of Fe to carbon in
Prochlorococcus
MIT1214 cells ranged from 10–40 × 10
−6
mol Fe:mol C and increased with light intensity and growth rate. These results challenge theoretical models predicting highest Fe:C at lowest light intensity, and are best explained by a large photosynthetic Fe demand that is not downregulated at higher light. To sustain primary production in the DCM with the rigid Fe requirements of low-light-adapted
Prochlorococcus
, dFe must be recycled rapidly and at high efficiency. |
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ISSN: | 1751-7362 1751-7370 |
DOI: | 10.1038/s41396-020-00776-y |