Botanic Gardens Trust, Sydney, Australia

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Collecting freshwater algae

Collection methods

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. Search all habitats in the waterbody including the edge of stones in fast-flowing water, aquatic plants, dam walls, and any floating debris.

In running or slightly turbid waters, a simple viewing box made from transparent perspex enables attached algae to be more easily observed. A hand lens is often useful to determine if material is reproductive (essential for species determination in some genera and helpful for generic placement).

Microscopic floating algae (the phytoplankton) can be collected with a mesh net (e.g. with 25-30 µm pores) or, if in sufficient quantity (i.e. colouring the water), by simply scooping a jar through the water. Water samples can be left overnight allowing the algae to settle and concentrate on the bottom of the container. Squeezing Sphagnum and other mosses, or some aquatic flowering plants such as Utricularia is a good way to collect a large number of species.

Microscope slides suspended in a waterbody for c. 2-4 weeks will reveal many species. The slides should be kept submerged until ready to examine under the microscope. One side can be wiped clean and a coverslip placed over the other.

Algae growing on soil are difficult to collect and study, many requiring culturing before sufficient and suitable material is available for identification.

 

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Lucy Nairn collecting algal
specimens from an ephemeral
pool

Collection information

The collector's name and a collecting number should be pencilled onto the herbarium sheet (and later replaced with a full label) or onto a collecting tag inserted into the solution. The accompanying notes should include standard information such as the locality, date of collection, and the collector's name and collection number, and as many of the following features as possible: whether the water is saline, brackish or fresh; whether the collection site is terrestrial, or a river, stream or 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 colour, texture and size of the alga.

Collecting equipment
Collecting book, vials and labels