Figure 1.

Map of the Iroise Sea and its hydrological conditions during our three sampling campaigns in 2015. On the map, the sampling stations (dots and names) are superimposed on the corresponding temperature (background color) and chlorophyll a (isoligns). Each map was assembled in R⁵⁰ using raster images estimated with satellite data (

source: NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Ocean Biology Processing Group. Moderate-resolution Imaging Spectroradiometer (MODIS) Aqua Ocean color Data; NASA OB. DAAC, Greenbelt, MD, USA. Accessed 2017/10/17). Vertical profiles of fluorescence (green, μg/L), temperature (black, °C), and PAR (yellow, W/m²) were measured on board with a CTD probe and a fluorescence sensor. Values of the down-cast were averaged every 5 m, variability comes from the triplicated casts. NOX (nitrate + nitrite, red, µM) were measured a posteriori from water sampled at three depths (a single time). Dashed horizontal lines represent the sampling depth for surface and, when present, DCM samples.