MARINE PHYTOPLANKTON PIGMENTS

ALGORITHM FOR CALCULATION OF MARINE PHYTOPLANKTON PIGMENTS
NON-PACKAGED SPECTRAL ABSORPTION COEFFICIENT

Source:Woźniak B., Dera J., Ficek D., Majchrowski R., Kaczmarek S., Ostrowska M., Koblentz-Mishke O. I., 1998, Modelling the influence of photo- and chromatic - acclimation on the absorption properties of marine phytoplankton, Ocean Optics Conference, Kailua-Kona, Hawaii, USA, 10-13 November 1998.

Absorption coefficients of phytoplankton pigments are complex sums of absorption coefficients of particular photosynthetic and photoprotecting pigments The specific absorption coefficients of the component pigments unfortunately, are not uniformly determined by various authors (e.g. Bidigare et al.1990 - Ocean Optics 10 Proc. SPIE 1302, 290-302; Hoepffner and Sathyendranath1991 - Mar. Ecol. Prog. Ser., 73 (1), 11-23). We describe the specific absorption coefficients of particular groups of pigments as the sums of Gaussian bands. These results we obtained on the base of empirical data measured in various water types.

TABLE

Model characteristics of the specific absorption Gaussian bands of the major groups of the phytoplankton pigments (the mean values for all types and cases of the ocean waters):

a^*_a - chlorophylls a (A₁ ¸ A₆)

Characteristic	Gaussian bands number
Characteristic	A-1	A-2	A-3	A-4	A-5	A-6
l _max,i	381	420	437	630	675	700
s _i	33.8	8.25	6.50	89.8	8.55	101
a^_max,i*	0.0333	0.0268	0.0580	0.0005	0.0204	0.0005

a^*_b - chlorophylls b (B₁ ¸ B₆)

Characteristic	Gaussian bands number
Characteristic	B-1	B-2	B-3	B-4	B-5	B-6
l _max,i	380	442	452	470	609	655
s _i	194	7.45	5.6	10.5	16.0	18.5
a^_max,i*	0.0059	0.0145	0.0631	0.0514	0.0083	0.0257

a^*_c - chlorophylls c (C₁ ¸ C₄)

Characteristic	Gaussian bands number
Characteristic	C-1	C-2	C-3	C-4
l _max,i	408	432	460	583
s _i	16.1	7.93	14.2	32.2
a^_max,i*	0.0561	0.0234	0.0072	0.0133

a^*_PPS a^*_PPC - photosynthetic (PSC-1, PSC-2) and photo-protecting carotenoids (PPC₁ ¸ PPC₃).

Characteristic	Gaussian bands number
Characteristic	PSC-1	PSC-2	PPC-1	PPC-2	PPC-3
l _max,i	490	532	451	464	493
s _i	17.1	22.8	32.0	8.60	12.0
a^_max,i*	0.0313	0.0194	0.0632	0.0253	0.0464

Specific absorption coefficient of the j-pigments group (i.e. chlorophylls a, chlorophylls b, etc. as given in the table) can be determined by the following sum of Gaussian bands:

A graphical illustration of these coefficients for individual pigment groups compared with data by the other authors is given in Fig. 1.

Fig. 1 ‘Unpackaged’ specific absorption spectra modelled in this paper for the major pigment groups (solid lines) and postulated by other authors: Hoepffner and Sathyendranath 1991 (dashed lines), Bidigare et al. 1990 (dotted lines).

There are clearly visible differences between ours and other authors’ results, but the former give the best approximation of total mean phytoplankton absorption spectra in solvent (Fig. 2).

Fig. 2 Specific light absorption spectra (mean for all natural waters): modelled main groups of phytoplankton pigments, their sum (dashed line) and total spectum determined on the bases of the measured data sets (solid lines)