From Time Machine
Derived from the Aqua MODIS satellite by NASA Goddard Space Flight Center, this dataset documents chlorophyll concentrations in the oceans from June of 2002 through July of 2011.
Chlorophyll concentrations in the ocean primarily indicate algae and other types of plankton growing. Observe the seasonal shifts between summer in the northern hemisphere to summer in the southern hemisphere 6 months later.
Zoom in especially to river outlets, which can provide nutrients to algae. Sometimes the rivers provide too much -- especially fertilizer runoff from farms, and sewage, can causing too much algae to grow -- an algal "bloom". When the algae dies, bacteria feed on it, starving the water of oxygen and creating a "dead zone" in which fish and most other sea creatures cannot live.
The imagery here represents a rolling 32-day composite, meaning each frame of the animation is a composite of 32 successive days of data from the Aqua MODIS satellite.