Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders
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...
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Online Access: | http://hdl.handle.net/10204/12724 https://doi.org/10.3389/fmars.2020.00275 |
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ftcsir:oai:researchspace.csir.co.za:10204/12724 2023-05-15T13:38:27+02:00 Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders Ryan-Keogh, Thomas J Thomalla, Sandy J 2020-05 Fulltext application/pdf http://hdl.handle.net/10204/12724 https://doi.org/10.3389/fmars.2020.00275 en eng https://www.frontiersin.org/articles/10.3389/fmars.2020.00275/full Ryan-Keogh, T.J. & Thomalla, S.J. 2020. Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders. Frontiers in Marine Science, 7. http://hdl.handle.net/10204/12724 2296-7745 https://doi.org/10.3389/fmars.2020.00275 http://hdl.handle.net/10204/12724 Ryan-Keogh, T. J., & Thomalla, S. J. (2020). Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders. Frontiers in Marine Science, 7 , http://hdl.handle.net/10204/12724 Ryan-Keogh, Thomas J, and Sandy J Thomalla "Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders." Frontiers in Marine Science, 7 (2020) http://hdl.handle.net/10204/12724 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. 24400 Frontiers in Marine Science, 7 Iron Fluorescence Gliders Chlorophyll Non-photochemical chlorophyll fluorescence quenching Article 2020 ftcsir https://doi.org/10.3389/fmars.2020.00275 2023-04-11T23:50:18Z 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 ... Article in Journal/Newspaper Antarc* Antarctic Southern Ocean Council for Scientific and Industrial Research (South Africa): CSIR Research Space Antarctic Southern Ocean Frontiers in Marine Science 7 |
institution |
Open Polar |
collection |
Council for Scientific and Industrial Research (South Africa): CSIR Research Space |
op_collection_id |
ftcsir |
language |
English |
topic |
Iron Fluorescence Gliders Chlorophyll Non-photochemical chlorophyll fluorescence quenching |
spellingShingle |
Iron Fluorescence Gliders Chlorophyll Non-photochemical chlorophyll fluorescence quenching Ryan-Keogh, Thomas J Thomalla, Sandy J Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders |
topic_facet |
Iron Fluorescence Gliders Chlorophyll Non-photochemical chlorophyll fluorescence quenching |
description |
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 ... |
format |
Article in Journal/Newspaper |
author |
Ryan-Keogh, Thomas J Thomalla, Sandy J |
author_facet |
Ryan-Keogh, Thomas J Thomalla, Sandy J |
author_sort |
Ryan-Keogh, Thomas J |
title |
Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders |
title_short |
Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders |
title_full |
Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders |
title_fullStr |
Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders |
title_full_unstemmed |
Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders |
title_sort |
deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders |
publishDate |
2020 |
url |
http://hdl.handle.net/10204/12724 https://doi.org/10.3389/fmars.2020.00275 |
geographic |
Antarctic Southern Ocean |
geographic_facet |
Antarctic Southern Ocean |
genre |
Antarc* Antarctic Southern Ocean |
genre_facet |
Antarc* Antarctic Southern Ocean |
op_source |
Frontiers in Marine Science, 7 |
op_relation |
https://www.frontiersin.org/articles/10.3389/fmars.2020.00275/full Ryan-Keogh, T.J. & Thomalla, S.J. 2020. Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders. Frontiers in Marine Science, 7. http://hdl.handle.net/10204/12724 2296-7745 https://doi.org/10.3389/fmars.2020.00275 http://hdl.handle.net/10204/12724 Ryan-Keogh, T. J., & Thomalla, S. J. (2020). Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders. Frontiers in Marine Science, 7 , http://hdl.handle.net/10204/12724 Ryan-Keogh, Thomas J, and Sandy J Thomalla "Deriving a proxy for iron limitation from chlorophyll fluorescence on buoyancy gliders." Frontiers in Marine Science, 7 (2020) http://hdl.handle.net/10204/12724 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. 24400 |
op_doi |
https://doi.org/10.3389/fmars.2020.00275 |
container_title |
Frontiers in Marine Science |
container_volume |
7 |
_version_ |
1766106442976198656 |