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A Conceptual Approach to Partitioning a Vertical Profile of Phytoplankton Biomass Into Contributions From Two Communities.

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Název: A Conceptual Approach to Partitioning a Vertical Profile of Phytoplankton Biomass Into Contributions From Two Communities.
Autoři: Brewin, Robert J. W., Dall'Olmo, Giorgio, Gittings, John, Sun, Xuerong, Lange, Priscila K., Raitsos, Dionysios E., Bouman, Heather A., Hoteit, Ibrahim, Aiken, Jim, Sathyendranath, Shubha
Zdroj: Journal of Geophysical Research. Oceans; Apr2022, Vol. 127 Issue 4, p1-20, 20p
Témata: PHYTOPLANKTON, MIXING height (Atmospheric chemistry), POWER resources, ACCLIMATIZATION, BIOMASS, MARINE ecology, PLANT phenology, COMMUNITIES
Abstrakt: We describe an approach to partition a vertical profile of chlorophyll‐a concentration into contributions from two communities of phytoplankton: one (community 1) that resides principally in the turbulent mixed‐layer of the upper ocean and is observable through satellite visible radiometry; the other (community 2) residing below the mixed‐layer, in a stably stratified environment, hidden from the eyes of the satellite. The approach is tuned to a time‐series of profiles from a Biogeochemical‐Argo float in the northern Red Sea, selected as its location transitions from a deep mixed layer in winter (characteristic of vertically well‐mixed systems) to a shallow mixed layer in the summer with a deep chlorophyll‐a maximum (characteristic of vertically stratified systems). The approach is extended to reproduce profiles of particle backscattering, by deriving the chlorophyll‐specific backscattering coefficients of the two communities and a background coefficient assumed to be dominated by non‐algal particles in the region. Analysis of the float data reveals contrasting phenology of the two communities, with community 1 blooming in winter and 2 in summer, community 1 negatively correlated with epipelagic stratification, and 2 positively correlated. We observe a dynamic chlorophyll‐specific backscattering coefficient for community 1 (stable for community 2), positively correlated with light in the mixed‐layer, suggesting seasonal changes in photoacclimation and/or taxonomic composition within community 1. The approach has the potential for monitoring vertical changes in epipelagic biogeography and for combining satellite and ocean robotic data to yield a three‐dimensional view of phytoplankton distribution. Plain Language Summary: Phytoplankton are microscopic, photosynthetic organisms that live in the sunlit layer of our ocean. They contribute to around half of planetary net primary production and supply energy to the marine ecosystem. They also help maintain the stability of the Earth's climate and are considered an essential climate variable. Monitoring phytoplankton is consequently important for understanding how our planet is changing. To do that, scientists use satellites and ocean robotic platforms. Satellites can see the surface ocean daily at global scales, but cannot see the subsurface. Ocean robotic platforms do not have the coverage of satellites but can see the subsurface. Mathematical approaches can be used to combine information from both platforms to produce synoptic, depth‐resolved fields of phytoplankton abundance. Here, we present one such approach that considers two communities of phytoplankton, one at the surface which can be seen from a satellite and an ocean robotic platform, the other below the surface layer, hidden from the satellite but seen by a robotic platform. We apply the approach to data from a Biogeochemical‐Argo float to reveal the dynamics of these two communities of phytoplankton in the northern Red Sea. The approach is useful for understanding vertical changes in phytoplankton community structure. Key Points: Gaussian and Sigmoid functions are used to partition vertical profiles of chlorophyll‐a concentration into contributions from two communitiesThe approach is extended to the modeling of particle backscattering and applied to a Biogeochemical‐Argo float in the northern Red SeaThe approach reveals contrasting phenology in the two communities of phytoplankton [ABSTRACT FROM AUTHOR]
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Databáze: Complementary Index
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Abstrakt:We describe an approach to partition a vertical profile of chlorophyll‐a concentration into contributions from two communities of phytoplankton: one (community 1) that resides principally in the turbulent mixed‐layer of the upper ocean and is observable through satellite visible radiometry; the other (community 2) residing below the mixed‐layer, in a stably stratified environment, hidden from the eyes of the satellite. The approach is tuned to a time‐series of profiles from a Biogeochemical‐Argo float in the northern Red Sea, selected as its location transitions from a deep mixed layer in winter (characteristic of vertically well‐mixed systems) to a shallow mixed layer in the summer with a deep chlorophyll‐a maximum (characteristic of vertically stratified systems). The approach is extended to reproduce profiles of particle backscattering, by deriving the chlorophyll‐specific backscattering coefficients of the two communities and a background coefficient assumed to be dominated by non‐algal particles in the region. Analysis of the float data reveals contrasting phenology of the two communities, with community 1 blooming in winter and 2 in summer, community 1 negatively correlated with epipelagic stratification, and 2 positively correlated. We observe a dynamic chlorophyll‐specific backscattering coefficient for community 1 (stable for community 2), positively correlated with light in the mixed‐layer, suggesting seasonal changes in photoacclimation and/or taxonomic composition within community 1. The approach has the potential for monitoring vertical changes in epipelagic biogeography and for combining satellite and ocean robotic data to yield a three‐dimensional view of phytoplankton distribution. Plain Language Summary: Phytoplankton are microscopic, photosynthetic organisms that live in the sunlit layer of our ocean. They contribute to around half of planetary net primary production and supply energy to the marine ecosystem. They also help maintain the stability of the Earth's climate and are considered an essential climate variable. Monitoring phytoplankton is consequently important for understanding how our planet is changing. To do that, scientists use satellites and ocean robotic platforms. Satellites can see the surface ocean daily at global scales, but cannot see the subsurface. Ocean robotic platforms do not have the coverage of satellites but can see the subsurface. Mathematical approaches can be used to combine information from both platforms to produce synoptic, depth‐resolved fields of phytoplankton abundance. Here, we present one such approach that considers two communities of phytoplankton, one at the surface which can be seen from a satellite and an ocean robotic platform, the other below the surface layer, hidden from the satellite but seen by a robotic platform. We apply the approach to data from a Biogeochemical‐Argo float to reveal the dynamics of these two communities of phytoplankton in the northern Red Sea. The approach is useful for understanding vertical changes in phytoplankton community structure. Key Points: Gaussian and Sigmoid functions are used to partition vertical profiles of chlorophyll‐a concentration into contributions from two communitiesThe approach is extended to the modeling of particle backscattering and applied to a Biogeochemical‐Argo float in the northern Red SeaThe approach reveals contrasting phenology in the two communities of phytoplankton [ABSTRACT FROM AUTHOR]
ISSN:21699275
DOI:10.1029/2021JC018195