The beauty in small things revealed
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, S-234 Frear Building, University Park, PA 16802
Oxygenic photosynthesis accounts for nearly all the primary biochemical production of organic matter on Earth. The byproduct of this process, oxygen, facilitated the evolution of complex eukaryotes and supports their/our continuing existence. Because macroscopic plants are responsible for most terrestrial photosynthesis, it is relatively easy to appreciate the importance of photosynthesis on land when one views the lush green diversity of grasslands or forests. However, Earth is the “blue planet,” and oceans cover nearly 75% of its surface. All life on Earth equally depends on the photosynthesis that occurs in Earth's oceans.
A rich diversity of marine phytoplankton, found in the upper 100 m of oceans, accounts only for ≈1% of the total photosynthetic biomass, but this virtually invisible forest accounts for nearly 50% of the net primary productivity of the biosphere (1). Moreover, the importance of these organisms in the biological pump, which traps CO2 from the atmosphere and stores it in the deep sea, is increasingly recognized as a major component of the global geochemical carbon cycle (2). It seems obvious that it is as important to understand marine photosynthesis as terrestrial photosynthesis, but the contribution of marine photosynthesis to the global carbon cycle was grossly underestimated until recently. Satellite-based remote sensing (e.g., NASA sea-wide field sensor) has allowed more reliable determinations of oceanic photosynthetic productivity to be made (refs. 1 and 2; see Fig. 1).
Depiction of the amount of chlorophyll present in the oceans and the amount of vegetation on land. Purple and blue represent low levels of chlorophyll, and green, yellow, and red indicate progressively higher concentrations. Brown pixels show areas with little vegetation on land, and blue-green pixels represent areas of densest vegetation. [Image provided by ORBIMAGE (Copyright 2003, Orbital Imaging Corporation) and processing by NASA Goddard Space Flight Center.]
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