Course notes / Unit 1

Tide pools

A rocky shore is covered and uncovered by the sea every day. Animals living there must survive both the water and the air.

Four bands of the shore

Typical zones of a rocky shore, from land to sea

Zone	Underwater	Typical residents
Splash zone	Almost never	Small periwinkle snails, lichens
High shore	Only at high tides	Barnacles, limpets
Mid shore	Roughly half the day	Mussels, dog whelks, rockweed
Low shore	Most of the time	Sea anemones, sea stars, kelp

Surviving the gap between tides

Barnacles close their plates and keep a drop of water inside. Limpets clamp to one spot on the rock to avoid drying out. Mussels shut their shells and gather in dense groups, which holds moisture and breaks up the force of waves.

A pool left behind by the tide changes quickly. In sunshine, evaporation makes the water saltier and warmer; in rain it becomes fresher. Animals in the highest pools have to tolerate the biggest swings.

Visiting kindly

• Walk on bare rock rather than on seaweed or animals.
• If you turn a stone over, put it back the way it was.
• Look, sketch and photograph. Leave every animal where you found it.

Field exercise

Choose a pool and sit beside it for ten minutes. Write down every animal that moves, and note how its behaviour changes when your shadow falls across the water.