Sediments and Phytoplankton in Black Sea – June 12th, 201243.3N 30.9E
The Black Sea is still aglow with color as the phytoplankton bloom in its waters continues (click here for previous images). Here, the darker colors near the coast are likely due to the influx of freshwater and sediments from rivers. However, sediments and fertilizes from these rivers do contribute to the bloom: the salty water, provided only via the narrow Bosporus Strait, is denser than the fresh water from the rivers, and so it sinks to the bottom. This leaves a layer of relatively fresh water on top, which remains there due to the density barrier between salt and fresh water being great enough so that the two layers do not mix. For this reason, when fresh water enters the sea from rivers, it only mixes with the relatively fresh water in the top 150 meters of the sea. As such, fertilizers and runoff carried in by the rivers remain concentrated in the top of the sea where they nourish the phytoplankton.