According to the Marine Strategy Framework Directive (MSFD), EU Member States must establish, by July 2014, monitoring programmes for the ongoing assessment of the environmental status of their marine waters on the basis of the indicative lists of elements set out in Annex III and the list set out in Annex V, and by reference to the environmental targets established pursuant to Article 10. This means that monitoring should provide data which support suitable indicators in order to assess if Good Environmental Status (GES) has been achieved or is maintained, to measure progress towards environmental targets and evaluate the effectiveness of measures to achieve or maintain GES. These programmes have to take into account an indicative list of characteristics, pressure and impacts but also be able to detect and assess emerging issues. They need to integrate existing monitoring programmes and result in assessments that are comparable within and between marine regions and/or sub-regions. There are agreed key principles that monitoring programmes should follow. This includes that monitoring programmes should be adequate, coordinated, coherent and adaptive, they should produce interoperable data, link with assessments, take account of risk considerations, apply the precautionary principle and acknowledge differences in scientific understanding.