Sampling, Biomass Estimation and Counts of Freshwater Algae - Freshwater Algae: Identification, Enumeration and Use as Bioindicators - page 92

Table 2.8 Mucilaginous Biofilms: Examples of Matrix and Community Analysis.

Environment/Experiment Analysis Reference

(a) Total biomass
Experimental biofilm Total carbohydrate (matrix), PLFA (organisms) and

chlorophyll- a (algae) analysis

Droppo et al . (2007)

Estuarine sediments Colloidal and bulk carbohydrate Sutherland et al . (1998)

Epilithic biofilms in
headwater streams

Total algal biomass (chlorophylls- a ,- b ,- c ) and eukaryotic
algal biomass (PLFA analysis) expressed per unit biofilm
carbon

Lyon and Ziegler (2009)

(b) Cell counts
River biofilm food web

Biofilm disrupted by sonication or shaking. Bacteria,
protozoa and algae counted by light microscopy.

Augspurger et al . (2008)

(c) Community molecular analysis
Experimental; biofilm PLFA analysis and nucleotide sequencing. Droppo et al . (2007)

River biofilm Seasonal changes in enzyme activity Romani et al . (2013)

PLFA, phospholipid fatty acid.

1 ml of 5 ml concentrated sulphuric acid and 5%
phenol were added to each sediment pellet (bulk
carbohydrate fraction) and each supernatant.

concentrations (phytoplankton) that developed in the
water column.
In addition to chlorophyll determinations, the
biomass of eukaryotic algae can be estimated by
phospholipid fatty acid (PLFA) analysis (Fig. 2.26).

Samples were shaken, allowed to stand for 1 h and
then spectrophotometrically analysed at 485 nm.
Readings were expressed in reference to a glucose
calibration curve.

Matrix biomass: carbohydrate analysis

Biofilm matrix (often taken as an index of total
biofilm biomass) is typically measured as total car-
bohydrate (units of monosaccharide) per unit area.
This can be determined as colloidal and bulk carbo-
hydrate - expressed as μg glucose cm −2 .
Sutherland et al . (1998) used a modified phenol-
sulphuric acid procedure with spectrophotometry to
monitor biofilm carbohydrate levels in estuarine sed-
iment samples as follows:
Half slices of sediment core were placed in test
tubes and washed in 10% HCl followed by rinses
in purified water.

Assessment of biofilm biomass can provide use-
ful information on the overall growth of biofilm
and the external factors that affect this. Sutherland
et al . (1998) established that stabilisation of estuar-
ine sediments was directly related to levels of sur-
face biofilm. More recently, Droppo et al . (2007)
measured biomass as carbohydrate per unit area (μg
glucose cm −2 ) to assess the impact of wave action
on biofilms under laboratory experimental condi-
tions. Exponential increase in biomass occurred over
a 15-day period under relatively undisturbed con-
ditions (Fig. 2.26), whereas erosion and biomass
loss occurred when shear forces were imposed by
increased wave action.

The test tubes were shaken thoroughly, left for
1 h (to extract colloidal carbohydrate) and then
centrifuged for 10 min at 2000 rpm.

2.9.3 Taxonomic composition

The supernatant (colloidal carbohydrate fraction)
was transferred to a clean set of test tubes.

Community composition may be defined as the
total numbers and balance of individual microbial