Chapter 2 includes a photograph taken from space of a bloom in the Benguela upwelling zone. Plankton blooms are a common phenomenon in the oceans, and they are apparent in both regional and global CZCS images. A plankton bloom is defined as a rapid and marked increase in the local population of plankton. The phenomenon can occur in a matter of days, and can disappear just as rapidly.
Blooms generally mark a convergence of factors that encourage plankton growth.
The main factors that cause blooms to occur are sunlight, nutrients, and changes in water temperature. One of the best ways to understand blooms is to examine how they occur in an isolated body of water, such as a lake or a bay. The classic pattern is a seasonal sequence of events corresponding to winter, spring, summer, and fall. We'll start in the winter. During the winter, plankton activity is at a low level due to the lesser amount of sunshine during short winter days, and lower water temperatures.