Particulate Matter Spatial, Temporal Distribution and Size Properties in the Aegean Sea

An extensive collection of light transmission/beam attenuation coefficient vertical profiles (LT/cp), particulate matter concentration (PMC) and particulate organic carbon concentration (POC), total particle volume concentration (VC), and particle median diameter (D50) vertical profiles were assembled in order to provide an overview of particulate matter dynamics in the Aegean Sea, as well as a first time assessment of suspended particle size properties. A typical beam cp vertical profile is composed of a relatively more turbid surface nepheloid layer (SNL) associated with enhanced primary productivity and atmospheric/fluvial inorganic/organic particle inputs, more transparent mid-waters with the sporadic occurrence of intermediate nepheloid layers (INL), and occasionally a more turbid bottom nepheloid layer (BNL) attributed to seabed sediment resuspension. The Aegean Sea is characterized by very low cp values, apart from river discharge coastal regions of the North Aegean Sea. In a north-south direction, cp decreases, and the water column becomes progressively more transparent, highlighting the transition from meso/oligo- to ultra-oligotrophic conditions prevailing in the Aegean Sea. There is a clear differentiation of particle abundance between “wet” and “dry” seasons, with the former showing enhanced cp, PMC, POC, and VC values. Particle size, studied within the range 1.25–250 μm, exhibits relatively small variability, with D50 varying between 81 and 105 μm, with a general increase over depth which is more pronounced in the South Aegean Sea, most likely associated with the variable abundance of Transparent Exopolymer Particles (TEP). Deep basins of the North Aegean Sea host permanent/semi-permanent INLs at mid-depths; their presence is attributed to internal wave activity. Good correlations of cp:PMC and cp:POC allow for the conversion of cp data to PMC and POC values, in support of modeling and remote sensing applications.