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14 - Optical monitoring of phytoplankton bloom pigment signatures
- 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 538-606
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Summary
Introduction
The absorption of light by algal pigments determines the cellular absorption of phytoplankton and thus contributes to the in situ optical signatures of coastal and offshore waters. This is the basis of a range of bio-optical approaches used for monitoring phytoplankton distribution (taxa and biomass) and is the focus of this chapter. Details regarding bio-optical signatures of phytoplankton and their spectral absorption, scattering and fluorescence characteristics are covered in Chapter 13, this volume. Details of how phytoplankton adjust their pigments in response to variation in light climate are reviewed in Chapter 11, this volume.
Phytoplankton blooms cover spatial scales that vary from patches of 1 m2 to large blooms covering more than 1 × 106 km2 (Franks, 1997; Smyth et al., 2004; Schofield et al., 2008). Related to the spatial scale is the temporal variability of these blooms (from minutes to years), depending on the physical and biological processes at a given location. The development of techniques for monitoring phytoplankton blooms at different geographical and temporal scales has evolved rapidly in recent years (Kahru and Brown, 1997; Schofield et al., 1999; Babin et al., 2008). Because of the wide range in scale, different methods and approaches (different sensors and corresponding platforms) are needed for monitoring water masses and associated phytoplankton blooms as a function of environmental change (i.e. temperature, salinity, circulation and light regime), biogeochemical cycling, eutrophication, ocean acidification and pollution. Globally, monitoring of phytoplankton bloom dynamics is important to estimate changes in primary productivity affecting carbon and nutrient cycling in the world oceans.
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.