GARIBOTTI irene Adriana
congresos y reuniones científicas
Composition and biomass of the phytoplanktonic community studied by HPLC and microscopy in the Southern Ocean: a comparison of methods
Amsterdam, Holanda
Simposio; VIII SCAR (Scientific Committee for Antarctic Research) International Biology Symposium; 2001
Institución organizadora:
Scientific Committee for Antarctic Research
Composition and biomass of mixed phytoplankton populations have been usually determined by microscopical analysis or by high performance liquid chromatography (HPLC) analysis of the concentration of accessory  pigments. In this work we present preliminary results of the study of the phytoplankton community from the west Antarctic Peninsula coast using both techniques. The study area is large and highly variable, thus the microscopic and HPLC results were compared in order to assess the concordance between these techniques, and when discrepancies were found the special circumstances that generated them were evaluated. To calculate the biomass of the microalgae phytoplankton classes from pigment signatures it is necessary the accurate estimation of pigment ratios. We used multiple linear regression of pigment data to estimate these ratios (Gieskes et al., 1988), but the exploratory analysis of the results showed model deficiencies that might result on loose or misinterpretation of ecological relevant information. The diversity of the community was masked, vast regions were poorly resolved, and localized regions were over- or under-predicted. Whereas some authors fitted a suite of regressions to different hydrographic regions (Gieskes te al., 1988; Prezelin et al., 2000), we found that to overcame the problems previously described it is more relevant to consider the biological variability within the area. The discrimination of three regions according to their water column chl a concentration allowed to obtain robust and representative pigment ratios, and improved phytoplankton characterization and the estimation of its biomass. Moreover, we found that within these regions environmental conditions were homogeneous and pigment changes due to depth were minor, thus the pigment ratios estimated for each region were used in further biomass calculations. The chl a biomass estimated from pigment signatures and the carbon biomass estimated under the microscope were closely related and had a linear relationship, indicating high concordance between these techniques. However, in samples where some pigments dominated, HPLC failed in the determination of the phytoplankton diversity and underestimated the microalgae with very low diagnostic pigment concentration.