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Appendix A - Update on filtration, storage and extraction solvents
- Edited by Suzanne Roy, Carole A. Llewellyn, Plymouth Marine Laboratory, Einar Skarstad Egeland, Geir Johnsen, Norwegian University of Science and Technology, Trondheim
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- Book:
- Phytoplankton Pigments
- Published online:
- 05 March 2012
- Print publication:
- 27 October 2011, pp 627-635
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- Chapter
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Summary
Filtration
In Chapter 10 of Jeffrey et al. (1997), Whatman GF/F (or equivalent) filters (0.7 μm nominal pore size) were recommended for sample filtration. With the exception of targeted studies, GF/F filters remain the most commonly used media for routine filtration and accompanying in vitro analyses by HPLC, fluorometry and spectrophotometry. As indicated in the above-mentioned Chapter 10 (p. 284–287), many studies have compared the effectiveness of different filter types and highlighted their advantages/disadvantages. Of particular note are three relatively recent papers highlighting the limitations of GF/F filters. Knefelkamp et al. (2007) compared six different filter types and concluded that Whatman nylon membranes (0.2 μm pore size, 47 mm diameter) provided the most consistent results with respect to chlorophyll a analyses. Nucleopore filters (0.2 μm) have been reported to retain as much as four times the amount of chlorophyll a as GF/F filters in open ocean samples (Dickson and Wheeler, 1993). Furthermore, Lee et al. (1995) reported that GF/F filters retained only 13–51% of small bacterioplankton (< 0.8 μm diameter) in natural samples. In contrast, recent comparisons of filter types have reported no differences in pigment concentrations obtained using GF/F and membrane filters in a variety of aquatic habitats (Chavez et al., 1995; Morán et al., 1999). The choice of filter type, whether glass-fibre or membrane, should be determined by the individual investigator for their particular application. However, once a filter type is selected, it should be used uniformly for sample filtrations to insure consistency between samples.
In estuarine and coastal waters, particulate matter (seston) may result in rapid saturation and ‘clogging’ of filters. Continued vacuum filtration of ‘clogged’ filters may promote mechanical stress and induce cell lysis, potentially resulting in underestimation of the actual pigment concentrations in the sample (Goldman and Dennett, 1985; Taguchi and Laws, 1988; Richardson and Pinckney, 2004). The total time for sample filtration should not exceed 5–10 min to minimize filter saturation (Wasmund et al., 2006). Filters should be removed as soon as the passage of water through the filter is undetectable and the vacuum should never exceed 50 kPa. Although not commonly used, positive pressure filtration (7–14 kPa) reportedly allows the filtration of larger volumes of water with reduced filtration times (Gibb et al., 2001; Bidigare et al., 2002). Regardless of the filtration method used, multiple filters can be pooled to achieve the biomass necessary for HPLC analyses. After filtration, filters should be folded in half, blotted on absorbent paper to remove excess water, and immediately flash frozen and stored in liquid nitrogen or at −80 °C (Wright and Jeffrey, 2006).
Using absorbance and fluorescence spectra to discriminate microalgae
- DAVID F. MILLIE, OSCAR M. E. SCHOFIELD, GARY J. KIRKPATRICK, GEIR JOHNSEN, TERENCE J. EVENS
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- Journal:
- European Journal of Phycology / Volume 37 / Issue 3 / August 2002
- Published online by Cambridge University Press:
- 08 October 2002, pp. 313-322
- Print publication:
- August 2002
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The utility of absorbance and fluorescence-emission spectra for discriminating among microalgal phylogenetic groups, selected species, and phycobilin- and non-phycobilin-containing algae was examined using laboratory cultures. A similarity index algorithm, in conjunction with fourth-derivative transformation of absorbance spectra, provided discrimination among the chlorophyll [Chl] a/phycobilin (cyanobacteria), Chl a/Chl c/phycobilin (cryptophytes), Chl a/Chl b (chlorophytes, euglenophytes, prasinophytes), Chl a/Chl c/fucoxanthin (diatoms, chrysophytes, raphidophytes) and Chl a/Chl c/peridinin (dinoflagellates) spectral classes, and often between/among closely related phylogenetic groups within a class. Spectra for phylogenetic groups within the Chl a/Chl c/fucoxanthin, Chl a/Chl c/peridinin, Chl a/phycobilins and Chl a/Chl c/phycobilin classes were most distinguishable from spectra for groups within the Chl a/Chl b spectral class. Chrysophytes/diatoms/raphidophytes and dinoflagellates (groups within the comparable spectral classes, Chl a/Chl c/fucoxanthin and Chl a/Chl c/peridinin, respectively) displayed the greatest similarity between/among groups. Spectra for phylogenetic groups within the Chl a/Chl c classes displayed limited similarity with spectra for groups within the Chl/phycobilin classes. Among the cyanobacteria and chlorophytes surveyed, absorbance spectra of species possessing dissimilar cell morphologies were discriminated, with the greatest range of differentiation occurring among cyanobacteria. Among the cyanobacteria, spectra for selected problematic species were easily discriminated from spectra from each other and from other cyanobacteria. Fluorescence-emission spectra were distinct among spectral classes and the similarity comparisons involving fourth-derivative transformation of spectra discriminated the increasing contribution of distinct cyanobacterial species and between phycobilin- and non-phycobilin-containing species within a hypothetical mixed assemblage. These results were used to elucidate the application for in situ moored instrumentation incorporating such approaches in water quality monitoring programmes, particularly those targeting problematic cyanobacterial blooms.