Since its creation in 1882, the Observatoire Océanologique de Banyuls (formerly known as Laboratoire Arago) has been constantly monitoring, surveying and recording the continental and marine environment. The data series acquired by the BOSS (Banyuls Observation Sea Service) over the last 20 years constitute one of the longest and most complete databases available in the Mediterranean Sea. The originality of this database lies in the fact that it samples a unique offshore gradient at the exit of the Gulf of Lion under the influence of continental inputs and the general circulation. BOSS is committed to long-term observation of coastal and offshore biogeochemistry in order to understand the natural variability of the ecosystem, the long-term trends that may occur as a result of climate variability and the occurrence of short-term extreme disturbances. The mission is in line with national and international programmes (SOMLIT, OSD, MOOSE, MISTRALS, GOS) that emphasise the importance of maintaining observation networks to understand the effects of climate change and is an essential activity of the Laboratory. The service is currently involved in routine sampling at three observation stations in the Gulf of Lion (Western Mediterranean Sea) along a coast-wide gradient using the Observatory at-sea facilities (R/V Néréis II):

• SOLA station (Service d'Observation du Laboratoire Arago): it is located 0.5 miles from the Observatory (42°29'300 N - 03°08'700 E), above sandy-muddy bottoms at 27m depth. This station is the SOMLIT site; it is monitored weekly since 1997; samples are taken at two depths (surface and bottom) and probe profiles are performed.
• POLA station (Plateau Observatoire Laboratoire Arago): it is located 5 miles off the Observatory (42°28'300 N - 03°15'500 E) above a bottom at about 95m depth. This station is monthly monitored since 2005.
• MOLA station (Microbial Observatory Laboratoire Arago): it is located on the northern flank of the Lacaze-Duthiers Canyon, 19 miles from the coast (42°27.200' N - 03°32.600' E) above a bottom at about 600m depth. This station, identified in the MOOSE network, is monthly monitored since 2003; samples are taken at six different depths and probe profiles are performed.

The physical and chemical parameters acquired at the different stations are: temperature, salinity, pH, dissolved oxygen, nitrate, nitrite, silicate, ammonium, phosphate, SPM, particulate organic carbon, particulate organic nitrogen, stable isotopes 13C and 15N, and chlorophyll. Biological parameters are: bacterial production (leucine incorporation), phytoplankton and bacterial abundance by flow cytometry, bacterial community structure by DNA/RNA extraction and new generation sequencing. All stations are monitored using the same analytical protocol as the SOMLIT-SOLA station Since 2008, BOSS has been designing and developing technologies for complete systems deployed in situ to create automated marine observatories that can obtain large data sets at high frequency and thus access small-scale variability in addition to traditional sampling observations. BOSS has been deploying an instrumented buoy at the SOLA site since 2010, which provides high-frequency data on surface meteorological and physico-chemical parameters every 15 minutes. This buoy is identified in the national high-frequency network COAST-HF. The BOSS service offer will soon be enriched within the framework of the development of the regional technological platform REMIMED (REseau Marin Instrumenté en MEDiterranée) to provide academic and private users with access to a high-frequency instrumented marine network via means at sea (ships, crewmen, diving service, Rosette/CTD, ROV, etc.), the service's automated oceanographic buoys and a pilot underwater cabled observation site positioned at SOMLIT-SOLA.