Sampling, Biomass Estimation and Counts of Freshwater Algae - Freshwater Algae: Identification, Enumeration and Use as Bioindicators - page 82

Protein

Water

Carb.

Lipid

1.0

0.5

Extr.

NA

0.0

Si

A. HIGH−SI CELL

2000 1000

3000

Wavenumber (cm −1 )

4

K Ca

P S CI

Mg

2

0

B. LOW−SI CELL

-2

-4

-6

-4 -3 -2 -1 0 1 2 3

Principal component 1

Figure 2.20 FTIR resolution of phytoplankton popu-
lations.Top:FTIRspectrumfromsinglecolonyof Micro-
cystis . The absorption bands are derived from differ-
ent radicals or molecular groups in water, lipid, protein,
nucleic acid (NA) and carbohydrate (Carb) within algal
biomass. One band (Extr.) is derived from extraneous
(atmospheric) CO 2 . Bottom: Principal Component Anal-
ysis(PCA)loadingplot,separatingspectraof Microcystis
(m) and Ceratium (c) into two separate clusters. PCA was
carried out on all spectra ( n = 40) for the spectral region
1750-900 cm −1 . Adapted from Dean et al. , 2007.

C. FILTER MEMBRANE

2 4 5

1 3

X-ray energy (keV)

Figure 2.21 High-Si and low-Si subpopulations in a
colony of Microcystis. Top: Scanning electron micro-
graph of carbon-coated, freeze-dried colony of Micro-
cystis . Bottom: X-ray emission spectra from single cells
of Microcystis with high (A) and low (B) above sam-
ple levels of Si. The control spectrum (C) from a clear
area of filter membrane next to cell A does not have any
elemental peaks. Sigee and Levado, 2000.

differences between the two algae in relation to
protein and carbohydrate levels (Dean etal ., 2007).

Resolution of species sub-populations. Multivari-
ate analysis can also be applied to single-species
samples and has the potential to demonstrate