Fixed point (time-series) observations

Cefas currently operates an integrated network of buoys in the southern North Sea primarily designed to provide information on ecosystem health and information for coastal defence, especially flooding. At one offshore location a buoy is maintained jointly by Cefas and RIKZ as part of a UK-Netherlands bilateral collaboration. For ecosystem monitoring high frequency (minutes to hours) sub-surface measurements are made of environmental control variables (e.g. temperature, salinity, turbidity, irradiance, nutrients) and key ecosystem variables (e.g. phytoplankton biomass and species composition, oxygen concentration, SPM). For coastal defence purposes surface measurements of significant wave height, wave period and direction are made. Data is returned in real-time for wave data or near (2-6 hours) real-time for ecosystem data and published to the web.

Time series of SmartBuoy (2000-2005) measurements from southern North Sea (Warp Anchorage - Thames estuary) showing (upper panel) near surface TOxN (nitrate + nitrite) measured at high frequency using a NAS in situ nutrient analyser. TOxN is also presented from lower frequency (approx. 2/week) measured on discrete water samples collected by an automated water sampler (AquaMonitor - WMS) together with silicate concentration. Ship based measurements from water bottle casts are also shown. The lower panel shows near surface chlorophyll concentration derived from fluorescence measured every 30 minutes. Strong interannual variability is seen in the data set with over-winter nutrient and chlorophyll concentrations varying by almost an order of magnitude during the time-series. Note the apparent absence of a spring bloom in 2005.