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Blue‐green algal scums: An explanation for their occurrence during freshwater blooms 1
Author(s) -
Paerl Hans W.,
Ustach Joseph F.
Publication year - 1982
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1982.27.2.0212
Subject(s) - eutrophication , photosynthesis , cyanobacteria , phytoplankton , environmental chemistry , environmental science , total inorganic carbon , carbon fixation , shading , surface water , chemistry , ecology , botany , biology , nutrient , environmental engineering , carbon dioxide , genetics , bacteria , art , visual arts
Nuisance blue‐green algal (cyanobacterial) scums are a sign of advanced eutrophication in aquatic systems. Previous workers have concluded that scums arc a sign of cyanobacterial senescence, or uncontrollable buoyancy. Our studies, however, indicate that scum formation may represent a mechanism by which the cyanobactcria can dominate surface waters. The mechanism is based on a preference for CO 2 over HCO 3 − and CO 3 2− as a photosynthetic carbon source, particularly in poorly buffered (low total inorganic carbon) waters. On calm days, when surface waters are thermally stratified, supplies of free CO 2 are depleted, resulting in an increase in ambient pH. In response to CO 2 depletion, cyanobacteria form surface scums, enabling them to use CO 2 at the air‐water interface. This also promotes optimal photosynthetic growth and N 2 fixation while simultaneously shading underlying noncyanobacterial phytoplankton.