What drives phytoplankton diversity at fine scales? Phytoplankton diversity is a key component in ocean biogeochemical services and contributes to the resilience and health of ocean ecosystems in respect to local and global stressors, including climate change. Understanding the mechanisms behind phytoplankton diversity in the open ocean is a matter of concern, especially in these years in which large Marine Protected Areas are created in international waters and an international legally binding treaty on Marine Biodiversity Beyond National Jurisdiction is under negotiation. Model studies suggest that finescale ocean dynamics are an important driver of plankton diversity and several scenarios have been suggested. In situ observations however are difficult to perform, due to the ephemeral nature of finescale features and the difficulty of tracking them from available remote sensing. This observational limit will be largely reduced by the SWOT mission, in particular during the fast sampling phase, opening new possibilities to biophysical experiments in the open ocean. The BIOSWOT-Med campaign aims at exploiting SWOT observations for unveiling the drivers of phytoplankton diversity in the Western Mediterranean. The western Mediterranean Sea is characterized by high plankton diversity, low nutrient concentration, and weak oceanic circulation. Here, finescale features, even if weak and short-lived, can strongly modulate the microbial community structure. To study the finescale biophysical coupling, and its impact of phytoplankton diversity, the BIOSWOT-Med campaign will follow the temporal evolution of eddies and filaments over the western Mediterranean SWOT crossover. The physical-biochemical coupling at the frontal zone between Atlantic Water recently entered in the Mediterranean basin and modified Atlantic Water coming from cyclonic circulation in the western Mediterranean basin will be studied through an adaptive Lagrangian sampling strategy using the software SPASSO (Software Package for an Adaptive Satellite-based Sampling for Oceanographic cruises) developed in previous research cruises. This physical information will be paired by a multi-sensor characterization of the planktonic community, including advanced molecular (meta-transcriptomics, metagenomics and meta-barcoding) techniques, and the use of autonomous and robotic platforms. Institutes involved in the campaign: AMU, LOCEAN, CEA, CNR, CNRS, CSIC, Fisheries and Ocean Canada, IFREMER, IRD, MBARI, NWRA, OGS, SHOM, Sorbonne Université, SZN, UCSD, ULCO, University of Exeter, University of Washington.

The scientific objectives of the project MAUPITI HOE are to understand the hydrodynamics of an archetypal reef-lagoon system of a high volcanic reef island. The physical functioning of the hydrosystem involves a fine coupling between water levels, waves (including wind, infragravity and VLF waves), currents and seabed structure (reef roughness). The present data focuses on the reef barrier dynamics. Citation: - Sous D., Bouchette F., Certain R., Meulé S. (2021). Maupiti Hoe 2018 [Data set]. MIO UMR 7294 CNRS, GLADYS. https://doi.org/10.34930/9DB3BEC4-0BBF-4531-8864-F100C4B8ECED

Maupiti ("the Stuck Twins'') is a diamond-shaped island located in the western part of the Society archipelago in French Polynesia. The present study focuses on the data recovered over a single cross-barrier transect located in the south-west barrier during the MAUPITI HOE field campaign, from 5 to 18 July 2018. The studied area is representative of the reef structure observed along the 4km-long southwestern barrier reef, showing an alongshore-uniform structure exposed to swell approaching with weak incident angles, a healthy reef colony. In the cross-barrier direction, the reef displays a clear partitioning of bottom roughness that ranges from low-crested compact structures at the reef crest to higher and sparser coral bommies on the backreef. The experimental setup was specifically designed to analyse and differentiate the dynamics over three roughness-contrasting sections found over the barrier reef. The scientific objectives of the project MAUPITI HOE are to understand the hydrodynamics of an archetypal reef-lagoon system of a high volcanic reef island. The physical functioning of the hydrosystem involves a fine coupling between water levels, waves (including wind, infragravity and VLF waves), currents and seabed structure (reef roughness). Four pressure sensors (OSS3, OSS4, OSS5, OSS6) have been deployed across the reef flat/ backreef, outside the surf zone. The bottom pressure is measured continuously at 10 Hz, and are converted into free surface elevation assuming hydrostaticity. An electrocurrent meter S4 provides the wave forcing while AQP1 is a velocity profiler providing the transports. The bed profile is obtained from the combination of (I) boat survey in the deeper part and (ii) high resolution GNSS RTK topography by feet. Two datasets are available: one is concerning the mean parameters linked to the reef barrier dynamics, and the second dataset is concerning the wave friction.

Maupiti ("the Stuck Twins'') is a diamond-shaped island located in the western part of the Society archipelago in French Polynesia. The present study focuses on the data recovered over a single cross-barrier transect located in the south-west barrier during the MAUPITI HOE field campaign, from 5 to 18 July 2018. The studied area is representative of the reef structure observed along the 4km-long southwestern barrier reef, showing an alongshore-uniform structure exposed to swell approaching with weak incident angles, a healthy reef colony. In the cross-barrier direction, the reef displays a clear partitioning of bottom roughness that ranges from low-crested compact structures at the reef crest to higher and sparser coral bommies on the backreef. The experimental setup was specifically designed to analyse and differentiate the dynamics over three roughness-contrasting sections found over the barrier reef. Four pressure sensors (OSS3, OSS4, OSS5, OSS6) have been deployed across the reef flat/ backreef, outside the surf zone. The bottom pressure is measured continuously at 10 Hz, and are converted into free surface elevation assuming hydrostaticity. An electrocurrent meter S4 provides the wave forcing while AQP1 is a velocity profiler providing the transports. The bed profile is obtained from the combination of (I) boat survey in the deeper part and (ii) high resolution GNSS RTK topography by feet. S4 position : -16.47109°N; -152.2782°E OSS3 position: -16.46968°N; -152.27698°E OSS4 position : -16.46931°N; -152.27676°E OSS5 position : -16.46851°N;-152.27614°E OSS6 position: -16.46706°N; -152.27504°E AQP1 position: -16.46318°N ; -152.27348°E