Influence of suspended particle concentration, composition and size on the variability of inherent optical properties of the Southern North Sea

► Suspended particles and their optical properties were studied in the Southern North Sea. ► Results permitted to divide the area into three optical zones: SCZ, MSNS and TCZ. ► Specific-IOPs variability between the regions predominates over seasonal variations. ► PSD bimodal distribution found in the MSNS during the spring phytoplankton bloom. ► Phytoplankton size peak at 7 μm results in an unexpected negative spectral cp slope.