Nutrient turnover at the hypoxic boundary: flux measurements and model representation for the bottom water environment of the Gulf of Riga, Baltic Sea* The study was supported by the ERAF project ‘Development of a mechanistic model of the Gulf of Riga ecosystem in support of an efficient national policy to ensure the protection of the Baltic Sea and to promote the sustainable use of its ecosystem’ (Ref. Nr. 2010/0287/2DP/2.1.1.1.0/10/APIA/VIAA/040) and the state research programme ‘Impact of climate change on Latvia’s water environment – KALME’.