In vivo absorption characteristics in 10 classes of bloom-forming phytoplankton: taxonomic characteristics and responses to photoadaptation by means of discriminant and HPLC analysis

Abstract

The spectral light absorption characteristics (400 to 700 nm) of 10 main classes, covering 31 species, of bloom-forming phytoplankton (diatoms, dinoflagellates, prymnesiophytes, euglenophytes, prasinophytes, raphidophytes, cryptophytes, chlorophytes, chrysophytes and cyanobacteria) have been examined. The survey is based on in vivo chlorophyll (chl) a-specific light absorption spectra ["a&), 400 to 700 nm] of low-and high-light adapted monocultures grown in the laboratory. Pigments were isolated by means of high-performance liquid chromatography (HPLC) to obtain visible spectra of isolated pigments to identify peaks and shoulders of the in vivo absorption spectra. A total of 217 "a&) spectra were log-transformed and normalized at 675 nm [a,,,(h)] to minimize photoadaptational effects on the spectral characteristics due to differences in pigment composition and the package effect. These alog(h) spectra were analyzed by stepwise discriminant analysis to determine sets of optimum wavelengths for classification. Discrimination and classification were most effective when lowand high-light adapted phytoplankton were grouped separately. A set of only 3 wavelengths (481,535, 649 nm) chosen on the basis of discriminant analysis classified, according to the jackknife technique, 93% of the a,,,(h) spectra. By using combinations of 4 (481, 535, 586, 649 nm) or 5 (481, 535, 586, 628, 649 nm) chosen wavelengths, 97 to 99% of the spectra were classified correctly. For pooled data (lowand high-light adapted cells), 60 to 86% of the spectra were correctly identified using a combination of 3 to 5 selected wavelengths, indicating that variations due to photoadaptation were not entirely removed by log-transforming and scaling of the spectra at 675 nm. By using the above combination of 3 wavelengths, 4 main groups of phytoplankton were clearly separated, depending mainly on their accessory chlorophylls, i.e. chl b (prasinophytes, euglenophytes, chlorophytes), chl c , and/or c;?(diatoms, dinoflagellates, prymnesiophytes, chrysophytes, raphidophytes, cryptophytes), chl c3 (toxic prymnesiophytes and dinoflagellates) and no accessory chlorophylls (cyanobacteria). The wavelengths employed here correspond to the peaks and shoulders of the in vivo absorption spectra. We conclude that different phytoplankton classes may be identified during blooms on the basis of in situ bio-optical measurements at 3 to 5 appropriately chosen wavelengths.

Space station image captures a red tide ciliate bloom at high spectral and spatial resolution

“…M. rubrum contains a suite of photosynthetic pigments from the enslaved cryptophytes, including phycoerythrin and Chl c 2 (23). A cryptophyte absorption spectrum shows the spectral regions where the ancillary pigments are known to absorb in vivo (1,24) (Fig. 2C).…”

Absorption coefficient of phytoplankton:regional variations in the North Atlantic

“…The maln carotenoid in all samples from this group was fucoxanthin, which suggests that the phytoplankton communities were dominated by diatoms. However, fucoxanthin is also found in prymnesiophytes, chrysophytes a.nd raphidophytes (Rowan 1989, Johnsen et al 1994a, therefore the presence of any of these groups cannot be ruled out.…”

“…1979, SooHoo et al 1986, Sathyendranath et al 1987, Takahashi et al 1989, Bidigare et al 1990, Sosik & Mitchell 1991, Johnsen et al 1994a. On the whole, regional differences in optical characteristics of phytoplankton, though small, contain useful information, and could be used to improve remote-sensing algorithms.…”

“…Isochrysis galbana). This affects the absorption characteristics of the algae (Johnsen et al 1994a), but a distinction as fine as this was not attempted in this study. Group C also contained samples from oligotrophic waters, but these samples were characterized by high concentrations of zeaxanthin along with 19'-hexanoyloxyfucoxanthin.…”

Determination of phytoplankton composition using absorption spectra

“…For example, Johnsen et al [5] used discriminant analysis to classify the absorption spectrum amongst 31 bloomformers (which represent the four main groups of phytoplankton with respect to accessory chlorophylls, for example Cl b, Cl c 1 and/or Cl c 2 , Cl c 3 and nonaccessory chlorophylls), thereby distinguishing dinoflagellates and toxic prymnesiophytes which contain Cl c 3 from taxons that do not have this pigment.…”