Environmental Engineering Reference
In-Depth Information
surface of sand and mud (estuaries - Fig. 3.8) and
the surface waters of lakes and wetlands, attached to
macroalgae (Fig. 2.28) and higher plants (Fig. 2.29).
The techniques used for collecting non-planktonic
algae depend upon the depth of the water, the nature
of the substrate and the type of algal community.
Once these algae have been collected, the principles
of biomass and species quantitation are essentially
the same as those previously described for phyto-
plankton. The application of these quantitative tech-
niques to periphyton, including cell counts, use of
vital stains, determination of biovolumes and assay
of dry/ash-free weight is described by Eaton et al .
(2005). In this section, the techniques involved in
algal collection and analysis are considered from two
main viewpoints - deep water benthic algae and shal-
low water communities.
use of sediment traps, bulk samplers and remote sen-
sors. The use of such techniques is illustrated in rela-
tion to studies (Table 2.5) on benthic algae in lakes
(benthic-pelagic coupling) and estuaries (sediment
stability, invertebrate grazing). The algae being sam-
pled may occur below the zone of light penetration
(photic zone) and include attached biofilm organisms
as well as unattached algae that have sedimented to
the bottom of the water body or been carried there by
circulation within the water column.
2.7.1 Benthic-pelagic coupling
In temperate lakes, many algae have distinct benthic
and pelagic phases, overwintering on sediments as
resting stages before migrating into the water col-
umn (Spring/early Summer) under more favourable
conditions to form an actively growing planktonic
population. This has been studied particularly with
bloom-forming colonial blue-green algae, which are
able to dominate the surface waters of both rivers
(Baker, 1999) and lakes (Verspagen et al ., 2005) in
summer, but occur as resting benthic populations dur-
ing the rest of the year. The transition from planktonic
2.7 Deep-water benthic algae
Deep-water benthic algae may be defined as those
algae at the bottom of lakes, deep rivers and estuaries
that are relatively inaccessible and have to be sampled
ormonitoredbyremoteprocedures.Theseincludethe
Table 2.5 Some Recent Studies on Deep Water Benthic Algae.
Site
Methods
Reference
Benthic-pelagic coupling
River benthos
Measurement of planktonic and benthic (akinete)
populations of Anabaena
Baker (1999)
Eutrophic lake
Measurement of benthic populations of Microcystis and
recruitment levels into water column
Verspagen et al . (2005)
Eutrophic lake
Measurement of recruitment of Gloeotrichia into the water
column. Laboratory experiments on akinete colonies
removed from sediment.
Karlsson (2003)
Eutrophic lake: shallow and
deep waters
Measurement of benthic populations of Anabaena and
Aphanizomenon and recruitment levels into water column
Karlsson-Elfgren and
Brunberg (2004)
Sediment stability
Estuarine sediments
Correlation of algal biomass (chlorophyll- a ) and biofilm
matrix (carbohydrate level) with sediment stability
Sutherland et al . (1998)
Benthic grazing
Estuarine sediments
Measurement of algal removal by filter-feeding bivalves.
Collection of near-sediment samples and remote
fluorimeter monitoring.
Jones et al. (2009)
 
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