Biogeochemical and physical controls on concentrations of polycyclic aromatic hydrocarbons in water and plankton of the Mediterranean and Black Seas

International audienceThe Mediterranean and Black Seas are unique marine environments subject toimportant anthropogenic pressures due to atmospheric and riverine inputs of organicpollutants. They include regions of different physical and trophic characteristics, whichallow the studying of the controls on pollutant occurrence and fate under differentconditions in terms of particles, plankton biomass, interactions with the atmosphere,biodegradation, and their dependence on the pollutant physical chemical properties.Polycyclic Aromatic Hydrocarbons (PAHs) have been measured in samples of seawater(dissolved and particulate phases) and plankton during two east‐west sampling cruisesin June 2006 and May 2007. The concentrations of dissolved PAHs were higher in thesouth‐western Black Sea and Eastern Mediterranean than in the Western Mediterranean,reflecting different pollutant loads, trophic conditions and cycling. Particle and planktonphase PAH concentrations were higher when lower concentrations of suspendedparticles and biomass occurred, with apparent differences due to the PAH physicalchemical properties. The surface PAH particle phase concentrations decreased when thetotal suspended particles (TSP) increased for the higher molecular weight (MW)compounds, consistent with controls due to particle settling depletion of water columncompounds and dilution. Conversely, PAH concentrations in plankton decreased at higherbiomass only for the low MW PAHs, suggesting that biodegradative processes in the watercolumn are a major driver of their occurrence in the photic zone. The results presented hereare the most extensive data set available for the Mediterranean Sea and provide clearevidence of the important physical and biological controls on PAH occurrence and cycling inoceanic regions