Explore microorganisms on a Moss Safari

By Andy Chandler-Grevatt

Now that the days are longer and the weather is warmer, getting out and about the school grounds offers interesting opportunities for science investigations. One often overlooked organism that survives in most places, including urban environments, is moss. Not only has moss itself got some fascinating adaptations, it is a habitat itself that contains a host of wonderful organisms that can be observed using a school microscope on a Moss Safari.

Doing a Moss Safari

Moss Safari is an approach to making the microscopic world accessible to the microorganisms that live in moss. The Big Five focuses on the five most common multicellular microorganisms that you will find in moss samples: nematodes, mites, tardigrades, rotifers and gastrotrichs.

All you need is a microscope, microscope cavity slides, microscope cover slips, Pasteur pipettes, filter papers, a pencil and a container to soak the moss in.

• Collecting moss is easy as you only need a small sample, no bigger than a small finger nail ( 1 cm³). Note where it was found.
• Soak the sample in water (rain water or mineral water). If the sample is dry then soak it for at least an hour, but ideally 24 hours.
• Agitate the surface of the moss with a mounted needle or pencil, then squeeze out the water into a small container or use a Pasteur pipette to suck up some of the solution.
• Place 2-3 drops of the solution into the well of a concave glass slide, put on a cover slip.
• Then view at the lowest magnification (x40 is best), increasing the magnification (x100) to observe anything interesting more closely.

Investigations

There are a number of investigations that can be carried out in school grounds. Here are three ideas that could be done by individual students or by a whole class and collating the results.

The questions in each investigation can be answered by comparing the presence and abundance of each of the Big Five.

• How many of the Big Five are present?
• How many of each of the Big Five are present?
• How many different ‘types’ of the Big Five are present? e.g. for tardigrades there are often two types: for simplicity they can be called ‘unarmoured’ (Eutardigradia) and ‘armoured’ (Heterotardigradia). The armoured ones are more resistant to drying out.

Sampling method

Keeping the counting method, similar to that of quadrats, the same for each sample.

• Add 2 cm³ of mineral water to each sample, soak for the same length of time, keep in the same conditions while soaking (i.e. light and temperature).
• Extract the solution from the moss in the same way. Agitate the surface and suck it up or do a moss squeeze.
• Use the same observation and counting method. Use a timed sweep of a slide e.g. two minute search, a methodical ‘transect’ across the slide or zig zag over the sample.

Questions to investigate

Is there a difference in the organisms that live in moss from a North facing roof compared to a South facing roof?

Many building roofs have moss growing on them. Often moss cushions are knocked down by birds, the wind or the rain. These cushions can be collected and studied. One simple comparison to make is the organisms that are present in moss that is growing on different sides of the building.

Consider what the environmental conditions are for moss growing on the North compared to the South facing roof.

Is there a difference in the organisms that live in moss growing in different locations (wall moss, tree moss, grass moss)?

Different mosses grow in different places such as on walls, on trees, in grass. The presence and abundance of each type of moss organism in each location can be counted and compared.

Moss can be difficult to identify without some expertise, but there is moss identification guidance here. Noting the moss habitat and naming it after its location is sufficient for this investigation. 

Does pollution impact the organisms that live in moss?

Pollution is known to affect the abundance distribution of microorganisms in moss. Taking samples of moss from pavements near roads and comparing it to moss from pavements in less polluted school grounds may reveal differences in organisms.

Safety

Precautions should be taken when collecting, soaking and using moss. Cuts on hands should be covered and hands should be washed after handling moss samples. Moss should only be collected from safely accessible places.

Learning Outcomes

Not only does the Moss Safari method make moss dwelling organisms accessible to students, it can be applied to Working Scientifically, where students can consider how to control variables, use systematic approaches to data collection and test predictions.

Top Tips

You may occasionally come across springtails (collembola) which are also bioindicators.

Other organisms that are found in moss and can be bioindicators are diatoms and testate amoebae.

About the author

Andy Chandler-Grevatt is a senior lecturer in science education at the University of Brighton and does Moss Safari as a hobby. Follow Moss Safari on Twitter or visit the Moss Safari website for more information and resources.