Cálculo del contenido celular de carbono de cuatro taxones de diatomeas: biovolumen y espectrofotometría

Background: Phytoplankton biomass is an essential parameter in aquatic ecosystems; two of the most widely used indicators for estimating phytoplankton biomass are chlorophyll-a (Chl-a) by spectrophotometry and biovolume (BV). Goals: To show how different results are when estimating phytoplankton biomass by means of the spectrophotometric and BV methods. Methods: Biomass by Chl-a and BV were estimated in four cultures of marine diatoms. For estimating BV, we used live cells and acid Lugol’s solution fixed cells. Results: Biomass values were noticeably different: the BV for Thalassiosira hispida and Skeletonema costatum underestimates [amp]#8776;41% of the biomass with respect to values obtained by spectrophotometry. In contrast, the BV for Pseudo-nitzschia sp. and Cylindrotheca closterium overestimates the biomass by 4% and 25%, respectively. In the case of estimated biovolume, the results indicate that fixer acid Lugol’s solution modified the size of the cell significantly in C. closterium and Pseudo-nitzschia sp. (p[amp]lt;0.05), but not for S. costatum and T. hispida (p[amp]gt;0.05). Two equations are provided for biomass calculation when studying live (pgC/cell = -1.5567 + 0.1428 (BV)) or acid Lugol’s solution fixed (pgC/cell = -5.0126 + 0.1644 (BV)) diatom cells. Conclusions: Although BV is useful, it can have drawbacks because it produces values above and below those estimated by spectrophotometry, in addition to the fact that acid Lugol´s solution modifies cell size. We would advise considering the available information based in Chl-a or carbon of different species.