FN Archimer Export Format PT J TI Assessing spatial and temporal variability of phytoplankton communities' composition in the Iroise Sea ecosystem (Brittany, France): A 3D modeling approach. Part 1: Biophysical control over plankton functional types succession and distribution BT AF CADIER, Mathilde GORGUES, Thomas SOURISSEAU, Marc EDWARDS, Christopher A. AUMONT, Olivier MARIE, Louis MEMERY, Laurent AS 1:1;2:2;3:3;4:4;5:5;6:2;7:1; FF 1:;2:;3:PDG-ODE-DYNECO-PELAGOS;4:;5:;6:PDG-ODE-LOPS-OC;7:; C1 UMR CNRS IFREMER IRD UBO 6539, Lab Sci Environm Marin LEMAR, F-29280 Plouzane, France. Univ Brest, Lab Oceanog Phys & Spatiale, CNRS, IRD,Ifremer,IUEM, F-29280 Plouzane, France. IFREMER, Ctr Brest, Dept Dynam Environm Cotier DYNECO PELAGOS, F-29280 Plouzane, France. Univ Calif Santa Cruz, Inst Marine Sci, Santa Cruz, CA 95064 USA. Lab Oceanog & Climat Experimentat & Approches Num, F-75005 Paris, France. C2 UBO, FRANCE IFREMER, FRANCE IFREMER, FRANCE UNIV CALIF SANTA CRUZ, USA LOCEAN, FRANCE SI BREST SE PDG-ODE-DYNECO-PELAGOS PDG-ODE-LOPS-OC UM LOPS LEMAR IN WOS Ifremer jusqu'en 2018 copubli-france copubli-univ-france copubli-int-hors-europe IF 2.506 TC 13 UR https://archimer.ifremer.fr/doc/00352/46367/45986.pdf https://archimer.ifremer.fr/doc/00352/46367/46029.pdf https://archimer.ifremer.fr/doc/00352/46367/46030.csv LA English DT Article CR FROMVAR DE ;Iroise Sea;Tidal mixing front;Biogeochemical modeling;Phytoplankton;Functional groups;Seasonal cycle AB Understanding the dynamic interplay between physical, biogeochemical and biological processes represents a key challenge in oceanography, particularly in shelf seas where complex hydrodynamics are likely to drive nutrient distribution and niche partitioning of phytoplankton communities. The Iroise Sea includes a tidal front called the ‘Ushant Front’ that undergoes a pronounced seasonal cycle, with a marked signal during the summer. These characteristics as well as relatively good observational sampling make it a region of choice to study processes impacting phytoplankton dynamics. This innovative modeling study employs a phytoplankton-diversity model, coupled to a regional circulation model to explore mechanisms that alter biogeography of phytoplankton in this highly dynamic environment. Phytoplankton assemblages are mainly influenced by the depth of the mixed layer on a seasonal time scale. Indeed, solar incident irradiance is a limiting resource for phototrophic growth and small phytoplankton cells are advantaged over larger cells. This phenomenon is particularly relevant when vertical mixing is intense, such as during winter and early spring. Relaxation of wind-induced mixing in April causes an improvement of irradiance experienced by cells across the whole study area. This leads, in late spring, to a competitive advantage of larger functional groups such as diatoms as long as the nutrient supply is sufficient. This dominance of large, fast-growing autotrophic cells is also maintained during summer in the productive tidally-mixed shelf waters. In the oligotrophic surface layer of the western part of the Iroise Sea, small cells coexist in a greater proportion with large, nutrient limited cells. The productive Ushant tidal front's region (1800 mgC.m− 2.d− 1 between August and September) is also characterized by a high degree of coexistence between three functional groups (diatoms, micro/nano-flagellates and small eukaryotes/cyanobacteria). Consistent with previous studies, the biogeography of phytoplankton functional types at the Ushant front during summer displays an intermediate community composition between contrasted sub-regions on either side of the front. Strong mixing conditions within the frontal sub-region result in a short residence time of water masses, not allowing speciation or long term adaptation to occur. PY 2017 PD JAN SO Journal Of Marine Systems SN 0924-7963 PU Elsevier Science Bv VL 165 UT 000390737500005 BP 47 EP 68 DI 10.1016/j.jmarsys.2016.09.009 ID 46367 ER EF