GEOL 3070 Lecture 26: Primary Producers

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University of Colorado - Boulder
Geological Sciences
GEOL 3070
Thomas Marchitto

Primary Producers Thursday, April 13, 2017 10:55 AM I. Primary Production • Synthesis of organic matter (reduced C-H-O molecules) from inorganic chemicals and energy (autotrophic) • Environmental energy converted into stored chemical energy (carbohydrates) • Photosynthesis (algae, plants): energy source is sunlight A. Gross vs. Net Production • Gross Primary Production: Total amount of carbon fixed • Much of the fixed C goes into growth of the organism, but some cell maintenance requires energy • Energy is retrieved from carbohydrates by respiration • (Gross photo/chemosynthesis -- Respiration by the producers) = net primary production (creates biomass) Clicker Questions: How does the residence time of C in living marine autotroph biomass Net Production by Autotrophs compare that in living land autotroph biomass? • ~90%-96% by phytoplankton --> volume/flux = mass (total)/flux (in or out) • ~2-5% by seaweeds --> Much shorter time in the ocean • ~2-5% by chemosynthesizers • Total is ~60-75 billionmetric tons (Gt) C per year What factor best explains why the subpolar gyres are eutrophic while • Comparable to terrestrial net production the subtropical gyres are oligotrophic? • But marine autotroph biomass is 1/300 to 1/1000 of terrestrial --> Subpolar gyres are regions of Ekman divergence
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