Multi-year High Frequency Nutrients Measurements in an Operational Data Buoy Network

Until relatively recently nutrient measurements were only possible using ship-based monitoring techniques with samples analysed on board or in the laboratory using traditional chemical methods. The Cefas SmartBuoy measures nutrients using a NAS-3X in-situ nutrient analyser and an automated water sampler. Insitu data are also compared to the results of discrete water samples which are collected during mooring service cruises. This paper presents measurements made since 2001 at sites in the SmartBuoy network (www.cefas.co.uk/monitoring) which reveal variability at a wide range of temporal and spatial scales. Nutrient enriched coastal sites exhibit up to four fold variability in TOxN over tidal cycles. Strong interannual variability is also evident as well as episodic events associated with increased rainfall. The rapid draw down of nutrients during the spring bloom is a recurrent feature of the time-series as is the increase in nutrients during the winter period.