The Seasonal Dynamics of Biosedimentation and Primary Production in Sevastopol Bay: Assessment of the Relationship Using 234Th and 40K

The seasonal dynamics of biogenic sedimentation in Sevastopol Bay, Black Sea, was studied using thorium-234 (234Th) as a natural radiotracer. The percentage content of biogenic particulate matter in bottom sediments was determined based on the 40K radionuclide according to the previously developed method. Two major maxima of the rate of bottom sedimentation have been recorded: in April–June and in the second half of the summer. In the former case, the peak can apparently be attributed to a more intensive flux of terrigenous particulate matter in the spring; in the latter case, it can apparently be attributed to high values of phytoplankton primary production in the late summer. The results obtained by applying this method provide a more accurate estimate of the mean annual biosedimentation rate, which is required to calculate deposition fluxes of biogenic matter and pollutants to bottom sediments of coastal waters.