Temporal and Spatial High-Frequency Monitoring of Phytoplankton by Automated Flow Cytometry and Pulse-Shape Analysis
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Phytoplankton were investigated with automated high frequency flow cytometry to address their patchiness and short-term variability.
To document this, we deployed a submersible flow cytometer (Cytosub, www.cytobuoy.com) in the Bay of Marseille (North Mediterranean) at 2 m depth.
This instrument involves pulse shape analysis and can analyze cells (1–1000 μm) and even chains at a flow rate of 8 mm3.s−1. During experiments, which took place in summer 2005, phytoplankton were monitored in situ every 30 min. The seven clusters (cells sharing the same optical properties of scatter and fluorescence) resolved in the size range 1–50 μm and behaved as independent entities, suggesting that they could be considered as functional groups.
The spatial heterogeneity of oceanic phytoplankton surface distribution was addressed by running the CytoSub on board a 33-m schooner (Fetia Ura, www.seanergies.com) between the Azores and French Brittany in April 2007. The flow cytometric analysis was triggered every 15 min (spatial resolution of 2.8 km). Five clusters were resolved in the pumped surface water, and specific relationships were determined between their distributions within the different water masses sampled during the cruise.
The evidenced variabilities are critical to explain the impact of intrinsic and extrinsic factors on phytoplankton spatial and temporal distributions. Automated in situ flow cytometry appears to be a powerful tool to investigate phytoplankton assemblages at high frequency and at the single cell level. Undergoing technological developments are extending this capacity to the whole microbial ecosystem and aim at real-time information of stakeholders.
KeywordsPhytoplankton Assemblage Phytoplankton Distribution Sailing Ship Dimethyl Sulphide Ship Track
We thank the captain and crew of the Fetia Ura ship as well as the teenagers and the instructors of the “Deferlante.” The work was supported by the “Cytometry In Situ” (CYMIS) contract between the Centre National de Recherche Scientifique (CNRS) and the City of Marseille, partially supported by “l’Agence de l’Eau Rhône Méditerranée Corse”, by the “Deferlante” association, and the “SEANERGIES OCEANES” company, which allocated the ship. M Thyssen benefited from a fellowship from the Region Provence Alpes Côte d’Azur.
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