Taking a sample

Where to look and what to bring home: plant scrapings, bottom film, moss.

Open water looks empty. Most of the life sits on surfaces: stems and leaves of water plants, the brown film on stones and dead leaves, the soft top layer of mud.

What to take

• A clean jar with a lid, filled about two-thirds with water from the same place.
• A few submerged leaves or a handful of plant stems, gently squeezed into the jar.
• A spoonful of the loose top layer of sediment, not the black mud below it.
• For tardigrades and bdelloid rotifers: a pinch of dry moss from a wall or roof, soaked in rain water for a few hours, then squeezed.

At home

Leave the lid loose and keep the jar out of direct sun. Let it settle for an hour: many organisms gather near the bottom, in the plant material and at the surface on the light side. Take drops from each of these places separately.

A sample changes over days. The first day shows what was there; a week later the jar has its own community. Both are worth looking at.