Subsurface chlorophyll maxima reduce the performance of non-photochemical quenching corrections in the Southern Ocean
Non-photochemical quenching (NPQ) within phytoplankton cells often causes the daytime suppression of chlorophyll fluorescence in the Southern Ocean. This is problematic and requires accurate correction when chlorophyll fluorescence is used as a proxy for chlorophyll-a concentration or phytoplankton...
Published in: | Frontiers in Marine Science |
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Frontiers Media SA
2024
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Online Access: | http://dx.doi.org/10.3389/fmars.2023.1302999 https://www.frontiersin.org/articles/10.3389/fmars.2023.1302999/full |
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crfrontiers:10.3389/fmars.2023.1302999 2024-03-31T07:55:26+00:00 Subsurface chlorophyll maxima reduce the performance of non-photochemical quenching corrections in the Southern Ocean Baldry, Kimberlee Strutton, Peter G. Hill, Nicole A. Boyd, Philip W. 2024 http://dx.doi.org/10.3389/fmars.2023.1302999 https://www.frontiersin.org/articles/10.3389/fmars.2023.1302999/full unknown Frontiers Media SA https://creativecommons.org/licenses/by/4.0/ Frontiers in Marine Science volume 10 ISSN 2296-7745 Ocean Engineering Water Science and Technology Aquatic Science Global and Planetary Change Oceanography journal-article 2024 crfrontiers https://doi.org/10.3389/fmars.2023.1302999 2024-03-05T00:17:21Z Non-photochemical quenching (NPQ) within phytoplankton cells often causes the daytime suppression of chlorophyll fluorescence in the Southern Ocean. This is problematic and requires accurate correction when chlorophyll fluorescence is used as a proxy for chlorophyll-a concentration or phytoplankton abundance. In this study, we reveal that Southern Ocean subsurface chlorophyll maxima (SCMs) are the largest source of uncertainty when correcting for NPQ of chlorophyll fluorescence profiles. A detailed assessment of NPQ correction methods supports this claim by taking advantage of coincident chlorophyll fluorescence and chlorophyll concentration profiles. The best performing NPQ correction methods are conditional methods that consider the mixed layer depth (MLD), subsurface fluorescence maximum (SFM) and depth of 20% surface light. Compared to existing methods, the conditional methods proposed halve the bias in corrected chlorophyll fluorescence profiles and improve the success of replicating a SFM relative to chlorophyll concentration profiles. Of existing methods, the X12 and P18 methods, perform best overall, even when considering methods supplemented by beam attenuation or backscatter data. The widely-used S08 method, is more varied in its performance between profiles and its application introduced on average up to 2% more surface bias. Despite the significant improvement of the conditional method, it still underperformed in the presence of an SCM due to 1) changes in optical properties at the SCM and 2) large gradients of chlorophyll fluorescence across the pycnocline. Additionally, we highlight that conditional methods are best applied when uncertainty in chlorophyll fluorescence yields is within 50%. This highlights the need to better characterize the bio-optics of SCMs and chlorophyll fluorescence yields in the Southern Ocean, so that chlorophyll fluorescence data can be accurately converted to chlorophyll concentration in the absence of in situ water sampling. Article in Journal/Newspaper Southern Ocean Frontiers (Publisher) Southern Ocean Frontiers in Marine Science 10 |
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topic |
Ocean Engineering Water Science and Technology Aquatic Science Global and Planetary Change Oceanography |
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Ocean Engineering Water Science and Technology Aquatic Science Global and Planetary Change Oceanography Baldry, Kimberlee Strutton, Peter G. Hill, Nicole A. Boyd, Philip W. Subsurface chlorophyll maxima reduce the performance of non-photochemical quenching corrections in the Southern Ocean |
topic_facet |
Ocean Engineering Water Science and Technology Aquatic Science Global and Planetary Change Oceanography |
description |
Non-photochemical quenching (NPQ) within phytoplankton cells often causes the daytime suppression of chlorophyll fluorescence in the Southern Ocean. This is problematic and requires accurate correction when chlorophyll fluorescence is used as a proxy for chlorophyll-a concentration or phytoplankton abundance. In this study, we reveal that Southern Ocean subsurface chlorophyll maxima (SCMs) are the largest source of uncertainty when correcting for NPQ of chlorophyll fluorescence profiles. A detailed assessment of NPQ correction methods supports this claim by taking advantage of coincident chlorophyll fluorescence and chlorophyll concentration profiles. The best performing NPQ correction methods are conditional methods that consider the mixed layer depth (MLD), subsurface fluorescence maximum (SFM) and depth of 20% surface light. Compared to existing methods, the conditional methods proposed halve the bias in corrected chlorophyll fluorescence profiles and improve the success of replicating a SFM relative to chlorophyll concentration profiles. Of existing methods, the X12 and P18 methods, perform best overall, even when considering methods supplemented by beam attenuation or backscatter data. The widely-used S08 method, is more varied in its performance between profiles and its application introduced on average up to 2% more surface bias. Despite the significant improvement of the conditional method, it still underperformed in the presence of an SCM due to 1) changes in optical properties at the SCM and 2) large gradients of chlorophyll fluorescence across the pycnocline. Additionally, we highlight that conditional methods are best applied when uncertainty in chlorophyll fluorescence yields is within 50%. This highlights the need to better characterize the bio-optics of SCMs and chlorophyll fluorescence yields in the Southern Ocean, so that chlorophyll fluorescence data can be accurately converted to chlorophyll concentration in the absence of in situ water sampling. |
format |
Article in Journal/Newspaper |
author |
Baldry, Kimberlee Strutton, Peter G. Hill, Nicole A. Boyd, Philip W. |
author_facet |
Baldry, Kimberlee Strutton, Peter G. Hill, Nicole A. Boyd, Philip W. |
author_sort |
Baldry, Kimberlee |
title |
Subsurface chlorophyll maxima reduce the performance of non-photochemical quenching corrections in the Southern Ocean |
title_short |
Subsurface chlorophyll maxima reduce the performance of non-photochemical quenching corrections in the Southern Ocean |
title_full |
Subsurface chlorophyll maxima reduce the performance of non-photochemical quenching corrections in the Southern Ocean |
title_fullStr |
Subsurface chlorophyll maxima reduce the performance of non-photochemical quenching corrections in the Southern Ocean |
title_full_unstemmed |
Subsurface chlorophyll maxima reduce the performance of non-photochemical quenching corrections in the Southern Ocean |
title_sort |
subsurface chlorophyll maxima reduce the performance of non-photochemical quenching corrections in the southern ocean |
publisher |
Frontiers Media SA |
publishDate |
2024 |
url |
http://dx.doi.org/10.3389/fmars.2023.1302999 https://www.frontiersin.org/articles/10.3389/fmars.2023.1302999/full |
geographic |
Southern Ocean |
geographic_facet |
Southern Ocean |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_source |
Frontiers in Marine Science volume 10 ISSN 2296-7745 |
op_rights |
https://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.3389/fmars.2023.1302999 |
container_title |
Frontiers in Marine Science |
container_volume |
10 |
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1795037294667759616 |