Written by Danielle Salley, Four Green Steps

Did you know that regions of high phytoplankton biomass can be found using satellite imaging? You may wonder why this would be useful: long story short, this identifies regions of high primary production.  For biological oceanographers, these regions are of importance because phytoplankton (photosynthetic algae) are useful in determining areas of high nutrient levels (i.e. nitrogen, phosphorus, carbon) in an attempt to comprehend the “why’s”.

For example, areas of upwelling, like the Gulf Stream, typically experience algal blooms in the spring as nutrients get upwelled from the deep sea along the thermohaline circulation (global water movement along the ocean seafloor).  Phytoplankton act as carbon sinks as they take CO2 from the atmosphere and use it for photosynthesis, creating organic carbon for oceanic species to then use. Phytoplankton also provide half of the world’s oxygen via this same process; they undergo the same function as trees, yet on an exponentially smaller organismal scale—imagine the efficiency!

Satellites discover areas of high biomass by determining which wavelengths get either absorbed or reflected back to space.  If a given amount of sunlight hits an area and a significant amount of that radiative energy gets absorbed, one can calculate the biomass of phytoplankton. Phytoplankton absorb sunlight along the visible light spectrum (400-700nm), mainly absorbing blue (lower wavelength) and red (higher wavelength), hence giving off a green hue to an observer’s eye.  Cool, eh?

Image courtesy of Creative Commons.

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