Phytoplankton blooms in the North Sea July 7, 2015 Katherine Kizilos Katherine Kizilos is a staff writer at Cosmos. By Katherine Kizilos In late spring and early summer, the North Sea becomes a fertile breeding ground for phytoplankton. This satellite image from NASA shows masses of the drifting plantlike organisms, thriving during the season when daylight hours are longer and ocean conditions are less harsh. Originally published by Cosmos as Phytoplankton blooms in the North Sea