OXYGEN-SATURATION TRENDS IN THE BALTIC SEA

Marine monitoring programmes are seldom planned and realized to fulfil the requirements of the statistical methods used. The shortcomings of these methods are rarely discussed in the literature. In this work tw o different methods for trend analysis are applied to a real case and attention is given to the possible violation of the underlying assumpt ions, Long-term changes in oxygen supersaturation in the Baltic Sea ar e the object of the study. Linear regression and non-parametric method s are those chosen. The linear regression gave significantly increasin g trends of oxygen saturation in Arkona, Eastern Gotland basin and in the Bothnian Sea, but the tested assumptions turned out to be violated . The corresponding non-parametric trend test only confirmed the incre asing trend in Arkona, It is suggested that non-parametric methods, li ke the one used in this work, should be favoured in the future for sim ilar types of marine environmental data.