High frequency monitoring of the coastal marine environment using the MAREL buoy

Abstract

The MAREL Iroise data buoy provides physico-chemical measurements acquired in surface marine water in continuous and autonomous mode. The water is pumped 1.5 m from below the surface through a sampling pipe and flows through the measuring cell located in the floating structure. Technological innovations implemented inside the measuring cell atop the buoy allow a continuous cleaning of the sensor, while injection of chloride ions into the circuit prevents biological fouling. Specific sensors for temperature, salinity, oxygen and fluorescence investigated in this paper have been evaluated to guarantee measurement precision over a 3 month period. A bi-directional link under Internet TCP-IP protocols is used for data, alarms and remote-control transmissions with the land-based data centre. Herein, we present a 29 month record for 4 parameters measured using a MAREL buoy moored in a coastal environment (Iroise Sea, Brest, France). The accuracy of the data provided by the buoy is assessed by comparison with measurements of sea water weekly sampled at the same site as part of SOMLIT (Service d'Observation du Milieu LIToral), the French network for monitoring of the coastal environment. Some particular events (impact of intensive fresh water discharges, dynamics of a fast phytoplankton bloom) are also presented, demonstrating the worth of monitoring a highly variable environment with a high frequency continuous reliable system.

Monitoring water quality in estuarine environments: lessons from the MAGEST monitoring program in the Gironde fluvial-estuarine system

“…2) The stations were installed on previously existing floating landing stages. This choice was different from previous MAREL systems, on the Seine river (Woerther, 2002;Dur et al, 2007;Schmitt et al, 2008) and in the rade de Brest (Blain et al, 2004), based on anchored buoys away from the banks. Our main criteria were the needs for protection of the system in a highly dynamic system (river floods often carry large branches or trunks in the axis of the channel) but also an easier access in case of breakdown.…”

“…Thus, predicting response of estuarine system to global changes and local impacts is critical to protect or restore good water quality and ecosystem functioning (Johnson et al, 2009;Stevenson and Sabater, 2010). The importance of time series in aquatic system has been recognized long ago to better understand the long-term changes (Neal, 2004;Baborowski et al, 2004;Blain et al, 2004;Horowitz, 2009). …”

Do current European lake monitoring programmes reliably estimate phytoplankton community changes?

“…Such analytical tools (sensors) are available for physical and chemical water quality elements (e.g. temperature and nutrients; (Chavez et al, 1997;Tokar & Dickey, 2000;Blain et al, 2004;Skeffington et al, 2015)). Continuous lake observatories, which are often linked to the Global Lake Ecological Observatory Network (GLEON), have been implemented in the Americas, Europe, Australia, and New Zealand (Hamilton, 2014;Rose et al, 2016, and references therein).…”

Biofouling protection for marine environmental sensors

“…In deep sea conditions this maintenance is nearly impossible to realize. For coastal applications it is quite accepted that a two-month interval for maintenance is the minimum duration for economically viable in situ monitoring systems (Blain et al, 2004). Consequently, systems without efficient biofouling protection are likely to be compromised.…”