dc.contributor.author |
Ryan-Keogh, Thomas J
|
|
dc.contributor.author |
Thomalla, Sandy J
|
|
dc.date.accessioned |
2023-04-06T12:12:15Z |
|
dc.date.available |
2023-04-06T12:12:15Z |
|
dc.date.issued |
2020-05 |
|
dc.identifier.citation |
Ryan-Keogh, T.J. & Thomalla, S.J. 2020. Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders. <i>Frontiers in Marine Science, 7.</i> http://hdl.handle.net/10204/12724 |
en_ZA |
dc.identifier.issn |
2296-7745 |
|
dc.identifier.uri |
https://doi.org/10.3389/fmars.2020.00275
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|
dc.identifier.uri |
http://hdl.handle.net/10204/12724
|
|
dc.description.abstract |
Chlorophyll fluorescence, primarily used to derive phytoplankton biomass, has long been an underutilized source of information on phytoplankton physiology. Diel fluctuations in chlorophyll fluorescence are affected by both photosynthetic efficiency and non-photochemical quenching (NPQ), where NPQ is a decrease in fluorescence through the dissipation of excess energy as heat. NPQ variability is linked to iron and light availability, and has the potential to provide important diagnostic information on phytoplankton physiology. Here we establish a relationship between NPQsv (Stern-Volmer NPQ) and indices of iron limitation from nutrient addition experiments in the sub-Antarctic zone (SAZ) of the Atlantic Southern Ocean, through the derivation of NPQmax (the maximum NPQsv value) and aNPQ (the light limited slope of NPQsv). Significant differences were found for both Fv/Fm and aNPQ for iron versus control treatments, with no significant differences for NPQmax. Similar results from CTDs indicated that changes in NPQ were driven by increasing light availability from late July to December, but by both iron and light from January to February. We propose here that variability in aNPQ, which has removed the effect of light availability, can potentially be used as a proxy for iron limitation (as shown here for the Atlantic SAZ), with higher values being associated with greater iron stress. This approach was transferred to data from a buoyancy glider deployment at the same location by utilizing the degree of fluorescence quenching as a proxy for NPQGlider, which was plotted against in situ light to determine aNPQ. Seasonal increases in aNPQ are consistent with increased light availability, shoaling of the mixed layer depth (MLD) and anticipated seasonal iron limitation. The transition from winter to summer, when positive net heat flux dominates stratification, was coincident with a 24% increase in aNPQ variability and a switch in the dominant driver from incident PAR to MLD. The dominant scales of aNPQ variability are consistent with fine scale variability in MLD and a significant positive relationship was observed between these two at a 10 day window. The results emphasize the important role of fine scale dynamics in driving iron supply, particularly in summer when this micronutrient is limiting. |
en_US |
dc.format |
Fulltext |
en_US |
dc.language.iso |
en |
en_US |
dc.relation.uri |
https://www.frontiersin.org/articles/10.3389/fmars.2020.00275/full |
en_US |
dc.source |
Frontiers in Marine Science, 7 |
en_US |
dc.subject |
Iron |
en_US |
dc.subject |
Fluorescence |
en_US |
dc.subject |
Gliders |
en_US |
dc.subject |
Chlorophyll |
en_US |
dc.subject |
Non-photochemical chlorophyll fluorescence quenching |
en_US |
dc.title |
Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders |
en_US |
dc.type |
Article |
en_US |
dc.description.pages |
13 |
en_US |
dc.description.note |
Copyright © 2020 Ryan-Keogh and Thomalla. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. |
en_US |
dc.description.cluster |
Smart Places |
en_US |
dc.description.impactarea |
Ocean Systems and Climate |
en_US |
dc.identifier.apacitation |
Ryan-Keogh, T. J., & Thomalla, S. J. (2020). Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders. <i>Frontiers in Marine Science, 7</i>, http://hdl.handle.net/10204/12724 |
en_ZA |
dc.identifier.chicagocitation |
Ryan-Keogh, Thomas J, and Sandy J Thomalla "Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders." <i>Frontiers in Marine Science, 7</i> (2020) http://hdl.handle.net/10204/12724 |
en_ZA |
dc.identifier.vancouvercitation |
Ryan-Keogh TJ, Thomalla SJ. Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders. Frontiers in Marine Science, 7. 2020; http://hdl.handle.net/10204/12724. |
en_ZA |
dc.identifier.ris |
TY - Article
AU - Ryan-Keogh, Thomas J
AU - Thomalla, Sandy J
AB - Chlorophyll fluorescence, primarily used to derive phytoplankton biomass, has long been an underutilized source of information on phytoplankton physiology. Diel fluctuations in chlorophyll fluorescence are affected by both photosynthetic efficiency and non-photochemical quenching (NPQ), where NPQ is a decrease in fluorescence through the dissipation of excess energy as heat. NPQ variability is linked to iron and light availability, and has the potential to provide important diagnostic information on phytoplankton physiology. Here we establish a relationship between NPQsv (Stern-Volmer NPQ) and indices of iron limitation from nutrient addition experiments in the sub-Antarctic zone (SAZ) of the Atlantic Southern Ocean, through the derivation of NPQmax (the maximum NPQsv value) and aNPQ (the light limited slope of NPQsv). Significant differences were found for both Fv/Fm and aNPQ for iron versus control treatments, with no significant differences for NPQmax. Similar results from CTDs indicated that changes in NPQ were driven by increasing light availability from late July to December, but by both iron and light from January to February. We propose here that variability in aNPQ, which has removed the effect of light availability, can potentially be used as a proxy for iron limitation (as shown here for the Atlantic SAZ), with higher values being associated with greater iron stress. This approach was transferred to data from a buoyancy glider deployment at the same location by utilizing the degree of fluorescence quenching as a proxy for NPQGlider, which was plotted against in situ light to determine aNPQ. Seasonal increases in aNPQ are consistent with increased light availability, shoaling of the mixed layer depth (MLD) and anticipated seasonal iron limitation. The transition from winter to summer, when positive net heat flux dominates stratification, was coincident with a 24% increase in aNPQ variability and a switch in the dominant driver from incident PAR to MLD. The dominant scales of aNPQ variability are consistent with fine scale variability in MLD and a significant positive relationship was observed between these two at a 10 day window. The results emphasize the important role of fine scale dynamics in driving iron supply, particularly in summer when this micronutrient is limiting.
DA - 2020-05
DB - ResearchSpace
DP - CSIR
J1 - Frontiers in Marine Science, 7
KW - Iron
KW - Fluorescence
KW - Gliders
KW - Chlorophyll
KW - Non-photochemical chlorophyll fluorescence quenching
LK - https://researchspace.csir.co.za
PY - 2020
SM - 2296-7745
T1 - Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders
TI - Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders
UR - http://hdl.handle.net/10204/12724
ER -
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en_ZA |
dc.identifier.worklist |
24400 |
en_US |