Abstract's details
Evidence and likely mechanisms underlying the existence of fine-Scale frontal phytoplankton communities in the SWOT era
Event: 2025 SWOT Science Team Meeting
Session: Oceanography: Regional Validation
Presentation type: Poster
Phytoplankton communities, composed of diverse species, exhibit significant variability across the global ocean. Their composition plays a key role in the marine carbon cycle and ecosystem functioning. As drifting organisms, phytoplankton are carried by ocean currents, and several numerical studies have highlighted the key role of fine-scale physical structures (1-100km, day-weeks) in shaping their distribution and influencing their behavior. However, fine-scale in situ studies have long been limited due to the difficulty of observing at sufficiently high resolution the physical environment in which phytoplankton is living. In particular, studying front-phytoplankton interactions remains challenging because of the complexity in simultaneously tracking fronts and their phytoplankton response in space and time. The few available in situ studies concerning front-phytoplankton interactions have been conducted in highly energetic and productive regions, whereas low energetic and oligotrophic regions, constituting the majority of the ocean and expanding with global warming, remain poorly explored.
The launch of the SWOT satellite in 2022 opened the doors to the "SWOT era," in which the fine-scale component of ocean dynamics is now observable. These new observations provide essential insights for designing adapted oceanographic cruises and for gaining a more comprehensive understanding of the physical environment that shapes phytoplankton communities, even in oligotrophic and low energetic regions.
In 2023, the BioSWOT-Med cruise (doi: 10.17600/18002392) took advantage of the SWOT Cal/Val phase by integrating daily SWOT images into an adaptive, multidisciplinary Lagrangian sampling strategy aimed at accurately targeting and sampling fine-scale physical structures in the oligotrophic Mediterranean Sea. In particular, we carried out, for the first time, high-resolution spatial and temporal sampling across and within the North Balearic Front identified thanks to SWOT imagery. We discovered a specific frontal phytoplankton community, characterized by a higher contribution of non-dominant phytoplankton types and a lower contribution of dominant phytoplankton types. We suggest that this community results from the specific interplay between frontal physical and biological processes.
To investigate this hypothesis, we combined a Lagrangian physical model, to evaluate passive transport by currents, with an NPZ (nutrient–phytoplankton–zooplankton) model, to assess the effect of nutrient supply and zooplankton grazing on phytoplankton. The horizontal velocity fields derived from SWOT were used as input of the Lagrangian model to resolve the North Balearic Front at fine-scale. We show that passive advection of a water mass hosting the frontal community largely explains its presence at the front. However, the age of this advected water mass within the front is shorter than that of the frontal community, suggesting that additional processes contribute to its persistence. We propose a framework where the dynamic synergy between passive transport, nutrient supply, and predation at fine-scale explains the sustained existence of the frontal phytoplankton community.
Findings from the BioSWOT-Med cruise and the coupled Lagrangian-NPZ modeling supported by the new fine-scale ocean overview of the SWOT era, provide evidence for a mechanistic understanding of the subtle and complex dynamics governing phytoplankton community in an oligotrophic and physically heterogeneous region. These results represent a key step toward a more comprehensive understanding of the global ecological implications of fine-scale ocean structuring.
Back to the list of abstractThe launch of the SWOT satellite in 2022 opened the doors to the "SWOT era," in which the fine-scale component of ocean dynamics is now observable. These new observations provide essential insights for designing adapted oceanographic cruises and for gaining a more comprehensive understanding of the physical environment that shapes phytoplankton communities, even in oligotrophic and low energetic regions.
In 2023, the BioSWOT-Med cruise (doi: 10.17600/18002392) took advantage of the SWOT Cal/Val phase by integrating daily SWOT images into an adaptive, multidisciplinary Lagrangian sampling strategy aimed at accurately targeting and sampling fine-scale physical structures in the oligotrophic Mediterranean Sea. In particular, we carried out, for the first time, high-resolution spatial and temporal sampling across and within the North Balearic Front identified thanks to SWOT imagery. We discovered a specific frontal phytoplankton community, characterized by a higher contribution of non-dominant phytoplankton types and a lower contribution of dominant phytoplankton types. We suggest that this community results from the specific interplay between frontal physical and biological processes.
To investigate this hypothesis, we combined a Lagrangian physical model, to evaluate passive transport by currents, with an NPZ (nutrient–phytoplankton–zooplankton) model, to assess the effect of nutrient supply and zooplankton grazing on phytoplankton. The horizontal velocity fields derived from SWOT were used as input of the Lagrangian model to resolve the North Balearic Front at fine-scale. We show that passive advection of a water mass hosting the frontal community largely explains its presence at the front. However, the age of this advected water mass within the front is shorter than that of the frontal community, suggesting that additional processes contribute to its persistence. We propose a framework where the dynamic synergy between passive transport, nutrient supply, and predation at fine-scale explains the sustained existence of the frontal phytoplankton community.
Findings from the BioSWOT-Med cruise and the coupled Lagrangian-NPZ modeling supported by the new fine-scale ocean overview of the SWOT era, provide evidence for a mechanistic understanding of the subtle and complex dynamics governing phytoplankton community in an oligotrophic and physically heterogeneous region. These results represent a key step toward a more comprehensive understanding of the global ecological implications of fine-scale ocean structuring.