Chlorophylls and their Degradation in Nature - Photobiogeochemistry of Organic Matter - page 691

Fig. 2 Changes in the ( a )
mean concentrations of total
pigment, chlorophyll a and
Phaeophytin- a ( P a); and
( b ) phytoplankton pigment
absorption at the Chl a
absorption maxima at 440
and 675 nm and CDOM
absorption at 355 nm during
the degradation experiment
period (0-33 days). Error
bar indicates the means and
standard deviations (n = 3).
Data source Zhang et al.
( 2009 )

(a)

(b)

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et al. 2001 ; Pérez et al. 2007 ). For Chl a , peaks that are often used are those at
412-425, 435-455, 618-623 and 662-675 nm, respectively (Zhang et al. 2009 ;
Goedheer 1970 ; Prezelin 1981 ; Aguirre-Gomez et al. 2001 ; Pérez et al. 2007 ).
The in vivo absorption spectra of the brown alga Laminaria digitata have Chl a
peaks at 418, 437, 618 and 673 nm. Moreover, absorption peaks of Glenodinium
sp. occur at 419, 437, 618 and 675 nm, and absorption peaks (average) of three
different groups of algae are located at 412, 435, 623 and 675 nm (Goedheer 1970 ;
Prezelin 1981 ; Hoepffner and Sathyendranath 1991 ). The structural configuration
of PSI and PSII in the reaction center shows that they may have two wavelength
positions: uncoupled Chls can absorb at 670 nm (close to their site energy), and
electronically coupled chlorins (the central cofactors) or Chl dimers can absorb
between 676 and 684 nm (see also chapter “ Photosynthesis in Nature: A New
Look ” ) (Telfer et al. 1990 ; Durrant et al. 1995 ; Renger and Marcus 2002 ).
Microbial degradation experiments show that absorbance of Chl a in the shorter
wavelength region (~440 nm) disappears relatively faster compared to the longer
wavelength region (~675 nm). Therefore, only the 675 nm absorption peak remains
visible in the suspension if degradation time is long enough (Fig. 2 ; see also chap-
ter “ Colored and Chromophoric Dissolved Organic Matter (CDOM) in Natural
Waters ” ) (Zhang et al. 2009 ). Absorption peaks in the shorter wavelength region