14 Apr 2022
14 Apr 2022
Status: a revised version of this preprint is currently under review for the journal BG.

Interannual variability of the initiation of the phytoplankton growing period in two French coastal ecosystems

Coline Poppeschi1, Guillaume Charria1, Anne Daniel2, Romaric Verney3, Peggy Rimmelin-Maury4, Michaël Retho5, Eric Goberville6, Emilie Grossteffan4, and Martin Plus2 Coline Poppeschi et al.
  • 1Ifremer, Univ. Brest, CNRS, IRD, Laboratory for Ocean Physics and Satellite remote sensing (LOPS), IUEM, 29280 Brest, France
  • 2Ifremer, DYNECO, Pelagic Ecology Laboratory (PELAGOS), 29280 Brest, France
  • 3Ifremer, DYNECO, Hydrosedimentary Dynamics Laboratory (DHYSED), 29280 Brest, France
  • 4OSU-European University Institute of the Sea (IUEM), UMS3113, 29280 Plouzané, France
  • 5Ifremer, Morbihan-Pays de Loire Environment Resources Laboratory (LERMPL), 56100 Lorient, France
  • 6Unité Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), Muséum National d’Histoire Naturelle, CNRS, IRD, Sorbonne Université, Université de Caen Normandie, Université des Antilles, Paris, France

Abstract. Abstract. Decadal time series of chlorophyll-a concentrations sampled at high and low frequencies are explored to study climate-induced changes on the processes inducing interannual variations in the Initiation of the Phytoplankton Growing Period (IPGP) in early spring. In this study, we specifically detail the IPGP in two contrasting French coastal ecosystems: the Bay of Brest and the Bay of Vilaine. A large interannual variability in the IPGP is observed in both ecosystems in connection with variations of environmental drivers (solar radiation, sea temperature, wind direction and intensity, precipitation, river flow, sea level, currents and turbidity). We show that the IPGP is delayed by around 30 days in 2019 in comparison with 2010. The use of a one-dimensional vertical model coupling hydrodynamics, biogeochemistry and sediment dynamics shows that the IPGP is generally dependent on the interaction between several drivers. Interannual changes are therefore not associated with a unique driver (such as increasing sea surface temperature). Extreme events also impact the IPGP. In both bays, IPGP is sensitive to cold spells and flood events. The interannual variability of the IPGP is significant and strongly conditioned, at the local scale, by a combination of several environmental parameters, with a larger sensitivity to sea temperature and light conditions, linked to the turbidity of the system. While both bays are hydrodynamically contrasted, the processes that modulate IPGP are similar. Keywords Phytoplankton biomass, Long-term in situ observations, Coastal ecosystems, Extreme events, Climate change.

Coline Poppeschi et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-86', Anonymous Referee #1, 02 Jun 2022
  • RC2: 'Comment on bg-2022-86', Anonymous Referee #2, 05 Jun 2022

Coline Poppeschi et al.

Coline Poppeschi et al.


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Short summary
This manuscript aims to understand interannual changes in the Initiation of the Phytoplankton Growing Period (IPGP) in the current context of global climate changes over the last 20 years. An important variability in the timing of the IPGP is observed with a trend towards a later IPGP during this last decade. The role and the impact of extreme events (cold spells, floods, and wind burst) on IPGP is also detailed.