SOMLIT (Service d'Observation en Milieu Littoral) time series (French Research Infrastructure ILICO): long-term core parameter monitoring of French coasts

SOMLIT (Service d'Observation en Milieur Littoral) : a French Coastal Monitoring Network

Coastal zones are where land, ocean and atmosphere interact. They are important for the exchange of matter and energy, and play a key role in (biogeo)chemical cycles at global scale. These environments are characterised by significant spatial and temporal variability of their physico-chemical and biological parameters due to local and seasonal meteorological drivers which are exacerbated by large-scale climate drivers (e.g. global warming, modification of the wind regime) and local-scale anthropogenic drivers (e.g. nutrient cycle changes linked to the use of fertilisers or the construction of large installations such as dams). These driving mechanisms are often interconnected. In the context of global warming (due to­­ climate and human-induced changes), the identification and understanding of their impact on coastal marine and littoral ecosystems is essential.

The scientific objective of SOMLIT is to 1) characterise the multi-decadal evolution of coastal marine and littoral ecosystems, and 2) determine the climatic and anthropogenic drivers.

In order to meet this objective, a nationally coordinated multi-site monitoring system was set up in the mid-1990s. The observation strategy is the same for each of the 12 monitored ecosystems with fortnightly sampling and/or measurements, at high tide (for sites subject to tides): 1) in surface-water for a range of 15 parameters (temperature, salinity, dissolved oxygen, pH, nitrate, nitrite, ammonium, phosphate, silicate, suspended particulate matter, chlorophyll a, particulate organic carbon and nitrogen and stable isotopes of particulate organic carbon and nitrogen), 2) in surface-water for a range of 26 parameters of numbering and optical characteristics of pico- and nanoplankton), and 3) along the water column for temperature, salinity, fluorescence and PAR (vertical profiles of multi-parameter probes).

SOMLIT’s activities are carried out under a quality assurance / quality control process based on the ISO 17025 standard.

SOMLIT’s service provision objectives are to provide data and logistical support for research and other observation activities.

SOMLIT has been officially accredited since 1996 as one of the CNRS (French National Centre for Scientific Research) National Observation Services (SNO). SOMLIT’s coordination is hosted by the Observatoire Aquitain des Sciences de l'Univers (University of Bordeaux / CNRS) and the service relies on strong partnerships with nine other institutions (University of Lille, University of the Littoral Opal Coast, University of Caen Normandy, Sorbonne University, University of Western Brittany, La Rochelle University, University of Montpellier, Aix Marseille University, National Museum of Natural History). SOMLIT is one of the nine networks that compose France’s Coastal Research Infrastructure (ILICO).  SOMLIT has strong ties with ILICO’s other networks such as the SNOs MOOSE (Mediterranean Ocean Observing System on Environment), PHYTOBS (microphytoplankton monitoring) and COAST-HF (Coastal Ocean Observing System - High Frequency).


Cross-discipline, Environment, Physical oceanography, Biological oceanography, Chemical oceanography


Environmental time series, Hydrological and biogeochemical data, Coastal system trends and trajectories, Climate impact, Coastal ecology, English Channel, Bay of Seine, Ria of Rance, Bay of Brest, Atlantic Ocean, Bay of Biscay, Gironde Estuary, Arcachon Lagoon, Mditerranean Sea, Bay of Banuyls, Gulf of Lion, Bay of Marseille, Bay of Villefranche, ILICO


51.5N, 41.25S, 10E, -6W


SBE-19-V2 and SBE-19-V2+ profilers are used for CTDPAR and fluorescence measurements. To guarantee best performances, the sensors return to the constructor every two years for calibration.


SOMLIT CTD-profile time series 1997-2023
5 MoCSVQuality controlled data
SOMLIT-Hydro-biogeochemical time series 1997-2023
3 MoCSVQuality controlled data
SOMLIT-Pico-nanoplankton time series 1997-2023
1 MoCSVQuality controlled data
How to cite
Savoye Nicolas, Lizon Fabrice, Breton Elsa, Claquin Pascal, Joly Orianne, Sultan Emmanuelle, Jung Jean-Luc, Bozec Yann, Boulart Cédric, Rimmelin-Maury Peggy, Leynaert Aude, Agogué Hélène, Pineau Philippe, Del amo Yolanda, Conan Pascal, Mostajir Behzad, Grégori Gérald, Mousseau Laure, Mendès Fabrice (2024). SOMLIT (Service d'Observation en Milieu Littoral) time series (French Research Infrastructure ILICO): long-term core parameter monitoring of French coasts. SEANOE.

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