Sampling, Biomass Estimation and Counts of Freshwater Algae - Freshwater Algae: Identification, Enumeration and Use as Bioindicators - page 99

rinsing of macrophyte leaves with tap water was
not effective in epiphyte removal from Myriophyl-
lum (Jones, 1984), and a laborious shaking technique
was adopted. Other researchers have adopted a man-
ual approach to removing algae. Asaeda etal . (2004),
for example, scraped epiphytic algae off Potamoge-
ton leaves using a soft toothbrush, prior to analysing
leaf growth (in the absence of algae) and epiphyte
biomass per unit leaf area. Algal removal without
damage to leaf tissues was confirmed by microscopic
observation. In a study on moss epiphytes, Sahin and
Ozdemir (2008) scraped algae from the surface of
small pieces of host material with a needle under a
binocular microscope.

Algal biomass can be determined as dry weight
or, chlorophyll- a , normalised to leaf surface area.
Chlorophyll- a is a better index of algal standing
crop since it does not include other microbes and
detritus also associated with leaf surfaces (Jones,
1984).
Physiological studies on epiphytic algae should
be carried out in situ rather than on separated sus-
pensions, to avoid artefacts caused by the separa-
tion procedure. The radioactive tracer experiments of
Sheldon and Boylen (1975), for example, were car-
riedoutonintact Potamogeton /epiphytepreparations.
Thiswasfollowedbyalgalremovalandseparateanal-
ysis of host/algal incorporated carbon (net photosyn-
thetic rates).
The ecological impact of epiphytic algae has been
examined particularly in the seagrass meadows of
brackishandmarineenvironments.StudiesbyKitting
et al . (1984), for example, have shown that epiphytic
algae are the primary basis of the food web in the Gulf
of Mexico, with algae having a higher productivity
than the seagrass and being preferentially ingested by
invertebrate herbivores.

Experimental and taxonomic studies Once
epiphytic algae have been removed from their host
plant, they can then be identified and enumerated in
a similar way to planktonic organisms. As with phy-
toplankton, taxonomic studies are best carried out
on fresh unfixed samples (to avoid colour change),
though diatom identification may require the use of
cleaned material.