The Photophysiological Response of Nitrogen-Limited Phytoplankton to Episodic Nitrogen Supply Associated With Tropical Instability Waves in the Equatorial Atlantic
In the Equatorial Atlantic nitrogen availability is assumed to control phytoplankton dynamics. However, in situ measurements of phytoplankton physiology and productivity are surprisingly sparse in comparison with the North Atlantic. In addition to the formation of the Equatorial cold tongue in the b...
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ftdoajarticles:oai:doaj.org/article:841fe76dc1934f7a8e104e115d4f5ded 2023-05-15T17:36:16+02:00 The Photophysiological Response of Nitrogen-Limited Phytoplankton to Episodic Nitrogen Supply Associated With Tropical Instability Waves in the Equatorial Atlantic Jonathan Sherman Ajit Subramaniam Maxim Y. Gorbunov Ana Fernández-Carrera Rainer Kiko Peter Brandt Paul G. Falkowski 2022-01-01T00:00:00Z https://doi.org/10.3389/fmars.2021.814663 https://doaj.org/article/841fe76dc1934f7a8e104e115d4f5ded EN eng Frontiers Media S.A. https://www.frontiersin.org/articles/10.3389/fmars.2021.814663/full https://doaj.org/toc/2296-7745 2296-7745 doi:10.3389/fmars.2021.814663 https://doaj.org/article/841fe76dc1934f7a8e104e115d4f5ded Frontiers in Marine Science, Vol 8 (2022) phytoplankton photophysiology variable fluorescence fluorescence lifetimes Equatorial Atlantic tropical instability waves (TIWs) Science Q General. Including nature conservation geographical distribution QH1-199.5 article 2022 ftdoajarticles https://doi.org/10.3389/fmars.2021.814663 2022-12-31T08:06:37Z In the Equatorial Atlantic nitrogen availability is assumed to control phytoplankton dynamics. However, in situ measurements of phytoplankton physiology and productivity are surprisingly sparse in comparison with the North Atlantic. In addition to the formation of the Equatorial cold tongue in the boreal summer, tropical instability waves (TIWs) and related short-term processes may locally cause episodic events of enhanced nutrient supply to the euphotic layer. Here, we assess changes in phytoplankton photophysiology in response to such episodic events as well as short-term nutrient addition experiments using a pair of custom-built fluorometers that measure chlorophyll a (Chl a) variable fluorescence and fluorescence lifetimes. The fluorometers were deployed during a transatlantic cruise along the Equator in the fall of 2019. We hypothesized that the Equatorial Atlantic is nitrogen-limited, with an increasing degree of limitation to the west where the cold tongue is not prominent, and that infrequent nitrate injection by TIW related processes are the primary source alleviating this limitation. We further hypothesized phytoplankton are well acclimated to the low levels of nitrogen, and once nitrogen is supplied, they can rapidly utilize it to stimulate growth and productivity. Across three TIW events encountered, we observed increased productivity and chlorophyll a concentration concurrent with a decreased photochemical conversion efficiency and overall photophysiological competency. Moreover, the observed decrease in photosynthetic turnover rates toward the western section suggested a 70% decrease in growth rates compared to their maximum values under nutrient-replete conditions. This decrease aligned with the increased growth rates observed following 24 h incubation with added nitrate in the western section. These results support our hypotheses that nitrogen is the limiting factor in the region and that phytoplankton are in a state of balanced growth, waiting to “body surf” waves of nutrients which fuel growth ... Article in Journal/Newspaper North Atlantic Directory of Open Access Journals: DOAJ Articles Frontiers in Marine Science 8 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
phytoplankton photophysiology variable fluorescence fluorescence lifetimes Equatorial Atlantic tropical instability waves (TIWs) Science Q General. Including nature conservation geographical distribution QH1-199.5 |
spellingShingle |
phytoplankton photophysiology variable fluorescence fluorescence lifetimes Equatorial Atlantic tropical instability waves (TIWs) Science Q General. Including nature conservation geographical distribution QH1-199.5 Jonathan Sherman Ajit Subramaniam Maxim Y. Gorbunov Ana Fernández-Carrera Rainer Kiko Peter Brandt Paul G. Falkowski The Photophysiological Response of Nitrogen-Limited Phytoplankton to Episodic Nitrogen Supply Associated With Tropical Instability Waves in the Equatorial Atlantic |
topic_facet |
phytoplankton photophysiology variable fluorescence fluorescence lifetimes Equatorial Atlantic tropical instability waves (TIWs) Science Q General. Including nature conservation geographical distribution QH1-199.5 |
description |
In the Equatorial Atlantic nitrogen availability is assumed to control phytoplankton dynamics. However, in situ measurements of phytoplankton physiology and productivity are surprisingly sparse in comparison with the North Atlantic. In addition to the formation of the Equatorial cold tongue in the boreal summer, tropical instability waves (TIWs) and related short-term processes may locally cause episodic events of enhanced nutrient supply to the euphotic layer. Here, we assess changes in phytoplankton photophysiology in response to such episodic events as well as short-term nutrient addition experiments using a pair of custom-built fluorometers that measure chlorophyll a (Chl a) variable fluorescence and fluorescence lifetimes. The fluorometers were deployed during a transatlantic cruise along the Equator in the fall of 2019. We hypothesized that the Equatorial Atlantic is nitrogen-limited, with an increasing degree of limitation to the west where the cold tongue is not prominent, and that infrequent nitrate injection by TIW related processes are the primary source alleviating this limitation. We further hypothesized phytoplankton are well acclimated to the low levels of nitrogen, and once nitrogen is supplied, they can rapidly utilize it to stimulate growth and productivity. Across three TIW events encountered, we observed increased productivity and chlorophyll a concentration concurrent with a decreased photochemical conversion efficiency and overall photophysiological competency. Moreover, the observed decrease in photosynthetic turnover rates toward the western section suggested a 70% decrease in growth rates compared to their maximum values under nutrient-replete conditions. This decrease aligned with the increased growth rates observed following 24 h incubation with added nitrate in the western section. These results support our hypotheses that nitrogen is the limiting factor in the region and that phytoplankton are in a state of balanced growth, waiting to “body surf” waves of nutrients which fuel growth ... |
format |
Article in Journal/Newspaper |
author |
Jonathan Sherman Ajit Subramaniam Maxim Y. Gorbunov Ana Fernández-Carrera Rainer Kiko Peter Brandt Paul G. Falkowski |
author_facet |
Jonathan Sherman Ajit Subramaniam Maxim Y. Gorbunov Ana Fernández-Carrera Rainer Kiko Peter Brandt Paul G. Falkowski |
author_sort |
Jonathan Sherman |
title |
The Photophysiological Response of Nitrogen-Limited Phytoplankton to Episodic Nitrogen Supply Associated With Tropical Instability Waves in the Equatorial Atlantic |
title_short |
The Photophysiological Response of Nitrogen-Limited Phytoplankton to Episodic Nitrogen Supply Associated With Tropical Instability Waves in the Equatorial Atlantic |
title_full |
The Photophysiological Response of Nitrogen-Limited Phytoplankton to Episodic Nitrogen Supply Associated With Tropical Instability Waves in the Equatorial Atlantic |
title_fullStr |
The Photophysiological Response of Nitrogen-Limited Phytoplankton to Episodic Nitrogen Supply Associated With Tropical Instability Waves in the Equatorial Atlantic |
title_full_unstemmed |
The Photophysiological Response of Nitrogen-Limited Phytoplankton to Episodic Nitrogen Supply Associated With Tropical Instability Waves in the Equatorial Atlantic |
title_sort |
photophysiological response of nitrogen-limited phytoplankton to episodic nitrogen supply associated with tropical instability waves in the equatorial atlantic |
publisher |
Frontiers Media S.A. |
publishDate |
2022 |
url |
https://doi.org/10.3389/fmars.2021.814663 https://doaj.org/article/841fe76dc1934f7a8e104e115d4f5ded |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Frontiers in Marine Science, Vol 8 (2022) |
op_relation |
https://www.frontiersin.org/articles/10.3389/fmars.2021.814663/full https://doaj.org/toc/2296-7745 2296-7745 doi:10.3389/fmars.2021.814663 https://doaj.org/article/841fe76dc1934f7a8e104e115d4f5ded |
op_doi |
https://doi.org/10.3389/fmars.2021.814663 |
container_title |
Frontiers in Marine Science |
container_volume |
8 |
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1766135698032689152 |