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Unformatted text preview: scientists first referred to accumulations of phytoplankton as “wasser blooms” and the name stuck Here is a closer view of a Here is a closer view of a Trichodesmium bloom The rows are 1­ 3 meters apart. Early sailors referred to these blooms as “sea sawdust” Trichodesmium cells have hollow gas Trichodesmium cells have hollow gas vesicles in their cells to provide buoyancy. This keeps colonies near the surface • Each cell may have dozens of gas vesicles There are spectacular blooms of There are spectacular blooms of cyanobacteria in the Baltic sea every summer • Sweden on left, Finland on right Nitrogen Fixation Nitrogen Fixation • N2 fixation is done only by some prokaryotes • • (eukaryotes can’t do it) such as certain species of bacteria or cyanobacteria Nitrogen gas makes up 78% of the volume of air. N is necessary to make proteins, but eukaryotes can’t use the N2 gas in air. It must be “fixed” by prokaryotes first. N2 fixation is the conversion of gaseous nitrogen (N2) into ammon...
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