Sampling, Biomass Estimation and Counts of Freshwater Algae - Freshwater Algae: Identification, Enumeration and Use as Bioindicators - page 43

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Sampling, Biomass Estimation and
Counts of Freshwater Algae

tat and the location of the algae within the water
body. Some indications of the ecological diversity of
freshwater algae are shown in Fig. 2.1, where algae
within the water column (plankton) are in dynamic
equilibrium with both attached and unattached forms
associated with plant surfaces and sediments at the
bottom of the water column. Techniques for sam-
pling and enumeration can be conveniently sepa-
rated in relation to these two main groups of algae -
planktonic and non-planktonic (substrate-associated)
organisms.

This chapter concentrates on techniques of collec-
tion, biomass estimation and numerical assessment
(microscope counts) of freshwater algae. Aspects
of algal identification are dealt with in Chapter 1
(brief account of molecular analysis) and Chapter
4 (algal key based on morphological identification).
The reader is also referred to other texts on limnolog-
ical analyses, including works by Wetzel and Likens
(1991) and Eaton et al. (2005).
Algal populations can be sampled in a number of
different ways, depending on the nature of the habi-

A. PLANKTONIC ALGAE

Lake and river phytoplankton include all those pho-
tosynthetic free-floating organisms that are present
within the main water body, and which generate
oxygen by photosynthesis. This includes prokaryotic
blue-green algae but excludes photosynthetic bac-
teria - which do not evolve oxygen and which do
not normally make a major contribution to overall
biomass formation.
The schedule for sampling and assessment of phy-
toplankton involves a sequence of stages (Fig. 2.2),
which are essentially the same for lakes and rivers.
These involve protocol for collection, mode of col-
lection and laboratory analysis of the sample. It is

essential to clarify the purpose of the study and
exactly what information is required before planning
the fieldwork, sampling and algal analysis.

2.1 Protocol for collection

As an initial step, information should be obtained on
the morphology and hydrological characteristics of
the water body to be studied. For standing waters,
these include surface area, mean/maximum depths,
water retention time plus inflow/outflow rates and for
rivers - width, transverse depth profiles, flow rates