Marc Tedetti

Plankton constitutes the primary entry point of contaminants into pelagic food webs, yet the role of plankton size structure in governing hydrocarbon fate remains poorly understood due to methodological limitations. Here, polycyclic aromatic (PAHs) and aliphatic (AHs) hydrocarbons were investigated across seven plankton size fractions (0.7 μm to >500 μm) collected in coastal waters of the northwestern Mediterranean Sea using a locally designed online sequential filtration system. Biochemical, isotopic, and molecular marker analyses were combined to characterize plankton composition, hydrocarbon sources, and PAH bioaccumulation patterns across size fractions. Molecular markers confirmed the transition from phytoplankton-dominated signatures in the smallest fractions to increasing zooplanktonic contributions in larger fractions. The 0.7–2.7 and 2.7–20 μm fractions, dominated by pico- and nanoplankton, accounted for the highest particulate organic carbon and hydrocarbon concentrations (3.0–3.4 μg g–1 dw for Σ26-PAHs) while zooplankton fractions (>60 μm) displayed lower values (0.09–0.69 μg g–1 dw). The passive uptake of low-molecular-weight (LMW) PAHs dominated across all size fractions but decreased with increasing plankton size. In contrast, high-molecular-weight (HMW) PAHs showed preferential accumulation in nanoplankton. These results demonstrate that plankton size structure and biomass dependent processes strongly influence PAH bioaccumulation and trophic transfer in marine pelagic food webs.

Model simulations and remote sensing observations show that ocean dynamics at fine scales (1–100 km in space, day–weeks in time) strongly influence the distribution of phytoplankton. However, only a few in situ-based studies at fine scales have been performed, and most of them concern western boundary currents which may not be representative of less energetic regions. The PROTEVSMED-SWOT cruise took place in the moderately energetic waters of the western Mediterranean Sea (WMS), in the region south of the Balearic Islands. Taking advantage of near-real-time satellite information, we defined a sampling strategy in order to cross a frontal zone separating different water masses. Multi-parametric in situ sensors mounted on the research vessel, on a towed vehicle and on an ocean glider were used to sample physical and biogeochemical variables at a high spatial resolution. Particular attention was given to adapting the sampling route in order to estimate the vertical velocities in the frontal area also. This strategy was successful in sampling quasi-synoptically an oceanic area characterized by the presence of a narrow front with an associated vertical circulation. A multiparametric statistical analysis of the collected data identifies two water masses characterized by different abundances of several phytoplankton cytometric functional groups, as well as different concentrations of chlorophyll a and O₂. Here, we focus on moderately energetic fronts induced by fine-scale circulation. Moreover, we explore physical–biological coupling in an oligotrophic region. Our results show that the fronts induced by the fine-scale circulation, even if weaker than the fronts occurring in energetic and nutrient-rich boundary current systems, maintain nevertheless a strong structuring effect on the phytoplankton community by segregating different groups at the surface. Since oligotrophic and moderately energetic regions are representative of a very large part of the world ocean, our results may have global significance when extrapolated.

Model simulations and remote sensing observations show that ocean dynamics at fine scales (1–100 km in space, day–weeks in time) strongly influence the distribution of phytoplankton. However, only few in situ samplings have been performed and most of them in boundary currents which may not be representative of less energetic regions. The PROTEVSMED-SWOT cruise took place in the moderately energetic waters of the western Mediterranean Sea, in the southern region of the Balearic Islands. Taking advantage of near-real time satellite information, a sampling strategy was defined in order to cross a frontal zone separating different water masses. Multi-parametric in situ sensors mounted on the vessel, on a towed fish and on an ocean glider were used to sample at high spatial resolution both physical and biogeochemical variables. A particular attention was put in adapting the sampling route, in order to also estimate the vertical velocities in the frontal area. Such a strategy was successful in sampling quasi-synoptically an oceanic area characterized by the presence of a narrow front with an associated vertical circulation. A multiparametric statistical analysis of the collected data identifies two water masses characterized by different abundances of several phytoplankton cytometric functional groups, as well as different contents in chlorophyll a and O₂. Our study shows that the Lagrangian fronts induced by the fine-scale circulation, even if much weaker than the fronts occurring in boundary current systems, maintain a strong structuring effect on phytoplankton community by segregating different taxa at the surface.

Model simulations and remote sensing observations show that ocean dynamics at fine scales (1–100 km in space, day–weeks in time) strongly influence the distribution of phytoplankton. However, only few in situ samplings have been performed and most of them in boundary currents which may not be representative of less energetic regions. The PROTEVSMED-SWOT cruise took place in the moderately energetic waters of the western Mediterranean Sea, in the southern region of the Balearic Islands. Taking advantage of near-real time satellite information, a sampling strategy was defined in order to cross a frontal zone separating different water masses. Multi-parametric in situ sensors mounted on the vessel, on a towed fish and on an ocean glider were used to sample at high spatial resolution both physical and biogeochemical variables. A particular attention was put in adapting the sampling route, in order to also estimate the vertical velocities in the frontal area. Such a strategy was successful in sampling quasi-synoptically an oceanic area characterized by the presence of a narrow front with an associated vertical circulation. A multiparametric statistical analysis of the collected data identifies two water masses characterized by different abundances of several phytoplankton cytometric functional groups, as well as different contents in chlorophyll a and O₂. Our study shows that the Lagrangian fronts induced by the fine-scale circulation, even if much weaker than the fronts occurring in boundary current systems, maintain a strong structuring effect on phytoplankton community by segregating different taxa at the surface.

Model simulations and remote sensing observations show that ocean dynamics at fine scales (1–100 km in space, day–weeks in time) strongly influence the distribution of phytoplankton. However, only few in situ samplings have been performed and most of them in boundary currents which may not be representative of less energetic regions. The PROTEVSMED-SWOT cruise took place in the moderately energetic waters of the western Mediterranean Sea, in the southern region of the Balearic Islands. Taking advantage of near-real time satellite information, a sampling strategy was defined in order to cross a frontal zone separating different water masses. Multi-parametric in situ sensors mounted on the vessel, on a towed fish and on an ocean glider were used to sample at high spatial resolution both physical and biogeochemical variables. A particular attention was put in adapting the sampling route, in order to also estimate the vertical velocities in the frontal area. Such a strategy was successful in sampling quasi-synoptically an oceanic area characterized by the presence of a narrow front with an associated vertical circulation. A multiparametric statistical analysis of the collected data identifies two water masses characterized by different abundances of several phytoplankton cytometric functional groups, as well as different contents in chlorophyll a and O₂. Our study shows that the Lagrangian fronts induced by the fine-scale circulation, even if much weaker than the fronts occurring in boundary current systems, maintain a strong structuring effect on phytoplankton community by segregating different taxa at the surface.