Fig. 2

Principal component analyses (PCA) of measured environmental parameters. PCA scores of the first PCA axis (a), second PCA axis (b) and third PCA axis (c) are depicted in contour plots. The horizontal axis depicts the distance (km) of sampling sites to Helgoland Island which was set to 0 km. Increasing distance to the left represents the sampling sites along the P8 transect, increasing distance to the right represents sampling sites along the Elbe transect. The vertical axis refers to the sampling date; color code reflects PCA scores of respective samples with blue colors indicating lower scores and red colors indicating higher scores. Coefficients of the environmental parameters in the linear combinations defining the respective PCA axes are given next to the contour plots. T temperature, S salinity, DO dissolved oxygen, Chl a Chlorophyll a, Turb turbidity, cDOM colored dissolved organic matter, DOC dissolved organic matter