WHOI PO

UnravelingFine-Scale Variability of Phytoplankton Communities in the WesternMediterranean Using Automated Flow Cytometry on a Voluntary Observing Ship

 Fine-scale physical structuresand ocean dynamics play a key role in shaping phytoplankton communitycomposition and regulating biogeochemical and ecological processes. Theseprocesses are difficult to characterize due to their transient nature. Couplinghigh-frequency in situ observations of physical, biogeochemical, and biologicalproperties offers new insights into the environmental drivers of fine-scalephytoplankton variability. Drawing on results from a pilot cruise (OSCAHR) inthe Mediterranean Sea and from high-frequency measurements collected by theFerryBox system aboard the CTN Le Carthage ferry, this work highlightsthe importance of integrating physical and biogeochemical observations toresolve phytoplankton dynamics at unprecedented resolution. The adaptivesampling strategy employed during OSCAHR, combining multidisciplinary in situ measurements,remote sensing, and model simulations, enabled a refined understanding offine-sale biogeochemical and phytoplankton community dynamics. Meanwhile, FerryBoxobservations during fall and winter provided critical information onphytoplankton community dynamics across the Western Mediterranean at highspatial and temporal resolution. These observations revealed how an extremeflooding event triggered a small phytoplankton bloom in the Bonifacio cyclonicgyre, offering key insights into the impacts of extreme events—which areexpected to become increasingly frequent—on the Mediterranean Sea. Theintegration of high-throughput single-cell analyses using automated flowcytometry with high-resolution physical and biogeochemical observations provedessential for advancing our understanding of the mechanisms driving marinebiogeochemical fine-scale dynamics at the base of the food web.