Page 226 - Algae

6 Algal Culturing

COLLECTION, STORAGE, AND PRESERVATION
As already pointed out in the previous chapters, algae grow in almost every habitat in every part of
the world. They can be found on very different natural substrates, from animals (snails, crabs,
sloths, and turtles are algal hosts) to plants (tree trunks, branches and leaves, water plants, and
macroalgae), from springs and rivers to hypersaline lagoons and salt lakes. They also colonize
artificial habitats, such as dams and reservoirs, fountains and pools, but cans, bottles, plant pots,
or dishes allow algae to extend their natural range. The ubiquity of these organisms together
with the plasticity of their metabolic requirements make many algal species easily available for
investigation, collection, or simple observation.
Floating microalgae can be collected with a mesh net (e.g., with 25–30 mm pores) or, if in
sufficient quantity (i.e., coloring the water), by simply scooping a jar through the water. A small
amount of the bottom sediments will also provide many of the algal species that live in or on
these sediments. Some algae live attached to other types of substrate, such as dead leaves, twigs,
and any underwater plants, which may be growing in the water. Macroalgae and the attached
microalgae can be collected by hand or with a knife, including part or all of the substrate (rock,
plant, wood, etc.) if possible. Algae growing on soil are difficult to collect and study, many requir-
ing culturing before sufficient and suitable material is available for identification.
Any sample should be labeled with standard information such as the locality, date of collection,
and as many of the following features as possible: whether the water is saline, brackish or fresh;
whether the collection site is terrestrial, a river, a stream, or a lake; whether the alga is submerged
during water level fluctuations or floods; whether the water is muddy or polluted; whether the alga
is free floating or attached, and if the latter, the type of substrate to which it is attached; and the
color, texture and size of the alga. Algae can be stored initially in a glass jar, plastic bottle or
bag, or in a vial with some water from the collecting site. The container should be left open
or only half filled with liquid and wide shallow containers are better than narrow deep jars. If
refrigerated or kept on ice soon after collecting most algae can be kept alive for short periods
(a day or two). If relatively sparse in the sample, some algae can continue to grow in an open
dish stored in a cool place with reduced light. For long-term storage, specimens can be preserved
in liquid, dried, or made into a permanent microscope mount. Even with ideal preservation,
examination of fresh material is sometimes essential for an accurate determination. Motile algae
particularly must be examined while flagella and other delicate structures remain intact, because
any kind of preservation procedure causes the detachment of the flagella.
Commercial formalin (40% formaldehyde in water), diluted between 1/10 and 1/20 with the
collecting solution, is the most commonly used fixative. As formaldehyde is considered carcino-
genic, any contact with skin, eyes, and air passages should be avoided. This compound mixed
with other chemicals such as glacial acetic acid and alcohol (FAA 1:1:8 by volume: 40% formal-
dehyde 1:glacial acetic acid 1:95% alcohol 8) gives better preservation results for some of the more
fragile algae, whereas the standard alcohol and water mix (e.g., 70% ethyl alcohol) will ruin all but
the larger algae. However, FAA may cause thin-walled cells to burst. Color is an important
taxonomic characteristic, especially for cyanobacteria, and formalin is a good preservative for
green algae, cyanobacteria and dinoflagellates because cell color remains intact if samples are
stored in the dark. Algae can be kept in diluted formalin for a number of years, but the solution
is usually replaced by 70% ethyl alcohol with 5% glycerin (the latter to prevent accidental
drying out).

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