Continuous nutrient automated monitoring on the Mediterranean Sea using in situ flow analyser

The development of field instruments for in situ chemical analysis in seawater is essential to better understand the physico-chemical processes occurring in the ocean as well as the supervision of the anthropogenic impact on the marine ecosystem in coastal and open ocean. Temporal resolution sampling for the analysis of chemical parameters in aquatic systems is usually low (weekly or monthly), expensive and time consuming. Some important details of transient phenomenon such as night and day cycling, strong tidal currents, episodic weather events and algal blooms can be missed. One of the advantages of in situ chemical measurements is the achievement of long term data sets to better characterize the natural variability of these elements. The use of in situ chemical analyzers also minimizes the probability of chemical changes in sample, due to reactions or contamination that may occur during transfer and storage of collected samples. There is actually the need of rugged, portable, fully automated instrumentation that can operate in situ, in order to avoid collection, transport and storage of samples for laboratory analysis; the availability of such instrumentation has proven to be a difficult challenge. Recently the WIZ multiparametric in-situ probe was developed by SYSTEA, to measure sequentially up to four chemical compounds in surface and sea water. It has been tested during two weeks in the Mediterranean sea near the French coastal station of Observatoire Océanologique de Banyuls (OOB) from University Pierre et Marie Curie (UPMC, Paris VI) in Banyuls sur Mer, well known as "Laboratoire ARAGO" since its creation two centuries ago. The probe has been deployed at 2m depth on the coastal buoy developed by OOB, to be installed first in a point which is surveyed weekly since 1997 (SOLA station, 42°29'300 N-03°08'700 E) with manual sampling and laboratory analysis. This area is particularly interesting due to the oligotrophic conditions which allowed to estimate the probe sensitivity and selectivity. In the near future, the Banyuls Observatory will deploy this automated buoy at 20 miles from the coast (MOLA station), in order to make a high frequency and long term survey of the area using several sensors. This operation will be done according to the French National program for Mediterranean Sea survey network MOOSE (Mediterranean Ocean Observation multi-Sites on Environment).