Phytoplankton group dynamics in the Bay of Marseilles during a 2-year survey based on analytical flow cytometry Article - Juillet 2001

Gérald Grégori, A Colosimo, Michel Denis

Gérald Grégori, A Colosimo, Michel Denis, « Phytoplankton group dynamics in the Bay of Marseilles during a 2-year survey based on analytical flow cytometry  », Cytometry, juillet 2001, pp. 247-256. ISSN 0196-4763

Abstract

Background : The Bay of Marseilles is under the influence of a large urban concentration and its maritime activities. All of them discharge compounds (hydrocarbons, excess nutrients, heavy metals, chemicals, etc.) that can alter the marine ecosystem. To investigate whether ultraphyto- plankton ( , 10 m m) could be used as biosensors for their own ecosystem, a 2-year survey was conducted in the Bay of Marseilles. Methods : Seven stations monitored water mass and po- tential anthropic effects in the bay. Seawater samples were collected monthly or bimonthly at three depths, prefiltered, fixed, and kept in liquid nitrogen until flow cytometric analysis. Results : Five categories were created : Prochlorococcus, picoeukaryotes ( , 2 m m), nanoeukaryotes I (2- 6 m m), nanoeukaryotes II (6 -10 m m), and Synechococcus ( , 1.5 m m). Artificial neural network analysis (Kohonen self-or- ganizing maps) produced the same number of clusters as cluster analysis with Winlist software (Verity Software House). Conclusions : In addition to the wide variabilities in abun- dance and biomass, there were a strong seasonal signal and sporadic events. Lessons are derived from this study for future monitoring of marine microorganisms. Cytometry 44:247-256, 2001. © 2001 Wiley-Liss, Inc.

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