The simple linear relation based on the calculated average value of ap* is shown by a thin solid line. Average values ap* ± SD are plotted for the reference (the two thin dashed www.selleckchem.com/products/epz015666.html lines). We also calculated the best-fit power function between

ap(440) and SPM. The equation coefficients and statistical parameters describing the quality of this fit are given in the first row of Table 3. The fit itself is also plotted in Figure 5a as a thick solid line: this best-fit power function shows that there is a deviation from linearity in the relation between ap(440) and SPM (as the power in the fit equation is 0.703, which is much less than 1). If the particle absorption coefficient ap  (λ) is normalized to Chl a   (giving the chlorophyll-specific absorption coefficients of particles ap*(chla)(λ)), the corresponding variability is smaller at some wavelengths (400, 440 and 500 nm) and higher at others (350, 550, 600 and 675 nm) when compared to the variability in ap  *(λ) (see the data in the second row of Table 2). In the case of the chlorophyll-specific coefficient, the 440 nm band also has the smallest variability across the whole spectrum, and the corresponding CV value is 59% (which is smaller than in the case of ap  * (440)). The relation between ap  (440) and Chl selleck chemicals a   is presented in Figure 5b. The average value of ap*(Chla)(440) is about 0.073 m2 mg−1. For the

best power function fit we get an equation of ap(440) = 0.104 (Chl a)0.690 (plotted as a thick Methane monooxygenase solid line in Figure 5b; the statistical parameters of the equation are given in Table 3), which indicates a significant deviation from linearity in the relation between

ap(440) and Chl a. This particular best-fit equation is directly comparable with the similar average equation, obtained by Bricaud et al. (1998), describing the coefficient of light absorption by suspended particles in oceanic (case I) waters as a function of Chl a: ap(440) = 0.052 (Chl a)0.635 (for reference, shown as a thick dashed line in Figure 5b). As can be seen, our results obtained for southern Baltic waters suggest that the average efficiency of absorption by suspended particles measured per unit of Chl a is about twice as high as the average absorption for oceanic particles reported by Bricaud et al. (1998). At this point, let us stress that in theory such a difference in particle absorption properties may be generated by differences in both particle size distributions (PSDs) (influencing the so-called package effect) and the composition of suspended matter (of both pigmented and non-pigmented matter) (see e.g. Morel & Bricaud 1981, Bohren & Huffman 1983, Jonasz & Fournier 2007). Regardless of the fact that we estimated different major biogeochemical parameters characterizing populations of suspended particles, in our series of field experiments we were unfortunately not able to measure PSDs (to be precise, Bricaud et al. (1998) did not provide size distribution data in their work either).