Nonlinear Relationships Between Particulate Absorption and Chlorophyll: Detritus or Pigment Packaging
2007
Cleveland, Joan S.
Relationships for predicting phytoplanktonic absorption at 676 and 436 nm from chlorophyll alpha concentration have been developed for distinct geographic regions defined by latitude. The forms of the predictive equations are controlled by underlying biological mechanisms and lend insight into these mechanisms. Development of these region-specific models allows prediction of phytoplanktonic absorption from more easily measured parameters such as chlorophyll alpha concentration or in situ fluorescence and increases accuracy in modelling optical properties or primary production rate using specific absorption coefficients. Temperate and tropical regions exhibited nearly identical relationships at low chlorophyll so these regions were combined and treated as one. Subpolar waters displayed a distinct pattern and were defined as a separate region. Linear relationships between phytoplanktonic absorption and chlorophyll a concentration in the subpolar region indicated that influences of pigment packaging on phytoplankton specific absorption coefficients were relatively constant and uncoupled from water column chlorophyll a concentration. Nonlinear relationships between phytoplanktonic absorption and chlorophyll a concentration for the combined temperate/tropical region suggested that pigment packing effects were important and variable. The steepness of the relationship at low chlorophyll supported the concept of low pigment packaging effects (thus high absorption per chlorophyll a) in oligotrophic, low chlorophyll a waters.
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