Decadal phytoplankton biomass variability in two contrasted French coastal ecosystems in a climate change context
|Author(s)||Poppeschi Coline1, Charria Guillaume1, Daniel Anne2, Rimmelin-Maury Peggy3, Verney Romaric4, Goberville Eric5, Retho Michael6|
|Affiliation(s)||1 : Ifremer, Univ. Brest, CNRS, IRD, Laboratoire d'Océanographie Physique et SpaSale (LOPS), IUEM, Brest, France
2 : Ifremer, Laboratoire d’Ecologie Pélagique (PELAGOS), 29280 Brest, France
3 : OSU-InsStut Universitaire Européen de la Mer (IUEM), UMS3113, Plouzaneì, France.
4 : Ifremer, Laboratoire de Dynamique Hydrosédimentaire (DHYSED), 29280 Brest, France.
5 : Muséum NaSonal d’Histoire Naturelle, 8067 BOREA, Sorbonne Universiteì, CNRS, UCN, UA, IRD, Paris, France.
6 : Ifremer, Laboratoire Environnement Ressources Morbihan-Pays de Loire (LERMPL), 56100 Lorient, France
|Meeting||ECSA 58 - EMECS 13 "Estuaries and coastal seas in the Anthropocene. Structure, functions, services and management". 6-9 September 2021, Online Live and On-demand|
|Keyword(s)||Phytoplankton biomass, Time series, Sea surface temperature evolution, Coastal eutrophic ecosystems, Extreme events, Climate Change.|
Coastal environments are highly impacted by the combined influence of anthropogenic climate change and the occurrence of persistent episodes of extreme meteorological events: warming of sea waters and changes in nutrient inputs due to the modification of precipitation patterns and consequently on river flows. Here, we study the impact of climate driven changes on phytoplankton biomass dynamics by analyzing high and low frequency of phytoplankton fluorescence and chlorophyll measurements in two French eutrophic ecosystems (Bay of Brest 2000-2019 and Bay of Vilaine 2011-2019). While the frequency and intensity of blooms in the Bay of Vilaine is driven by the supply of nutrients from rivers, no clear relationship is detected in the Bay of Brest where the residence time of water masses is short and the nutrient limitations infrequent. Long-term changes in phytoplankton biomass in these two contrasted ecosystems revealed a strong interannual variability in the timing, intensity and magnitude of blooms that occurred during the growing period (mid-March to mid-September). We observed that the first spring bloom is initiated in 2019 about 30 days earlier than 20 years ago in the Bay of Brest while it is delayed by 20 days in a decade in the Bay of Vilaine. These modifications in the timing of the phytoplankton bloom are related to a “shift” in sea surface temperature and changes in solar irradiance, as originating from the influence of large-scale hydro- climatological processes.