AZTI Station D2 Southeastern Bay of Biscay Latitude:   43.4542     Longitude:   -1.9167 Associated Investigators: Marta Revilla , Ángel Borja ,   Almudena Fonán ,   Victoriano Valencia   Related Web Sites: [www.azti.es/en]   [www.azti.es/rim/en]   [www.uragentzia.euskadi.net]   Along the Basque coast (southeastern Bay of Biscay), the longest series on phytoplankton biomass (Chlorophyll a concentration) has been obtained at station D2 (Site 50, 43 27'N 01 55'W). This station is located 13.1 km offshore and at a water depth of 110 m. Data are collected since 1986 by AZTI Tecnalia, within the project Variaciones , funded by the Department of Environment, Territorial Planning, Agriculture and Fisheries of the Basque Government. Surveyed months and total number of surveys per year are variable (3-12). On average, eight surveys per year are conducted. Details on sampling and analytical methods are available in Revilla et al. (2010). Generally, CTD continuous vertical profiles have been obtained. Here, longterm series on chlorophyll, salinity, and temperature are presented. Additionally, phytoplankton abundance and composition, together with general environmental conditions (e.g. oxygen, nutrients, and optical properties) are shown from 2002 to 2010. This is part of the Littoral Water Quality Monitoring and Control Network of the Basque Country, conducted by AZTI-Tecnalia for the Basque Water Agency (URA). For this purpose, the station D2 is sampled every three months from February to November. Water samples for phytoplankton analyses (Utermohl, 1958) are collected at the surface with a clean bucket and immediately fixed with glutaraldehyde. Field and laboratory methods are described in detail by Garmendia et al. (2011). The offshore station D2 is considered to be unaffected by anthropogenic influence, owing to its distance from the main pollution sources on land. The main fertilization factor for the surface waters of this area is the continental run-off coming from the rivers around the southeastern Bay of Biscay (Valencia and Franco, 2004; Diaz et al., 2007; Ferrer et al., 2009). Surface salinity is 34.8 +/- 0.67 (average +/- standard deviation) from 1986 to 2008 (n = 174), which indicates a low average freshwater content (2.3%).