tidal pool

A tide pool on Gabriola Island, British Columbia showing ochre sea stars

Tide pools (also tidal pools or rock pools) are rocky pools by oceans that are filled with seawater. Tide pools can either be small and shallow or large and deep. The small ones are usually found far back on the shore and the large ones are found nearer to the ocean. Tide pools are formed as a high tide comes in over a rocky shore. Water fills depressions in the ground, which turn into isolated pools as the tide retreats. This process, repeated twice a day, replenishes the seawater in what otherwise might be a stagnant pool.

The area that is covered by high tide and exposed by low tide is called the intertidal zone, or foreshore. This area is often further divided into different zones based on the life forms that live there.

Life in tide pools

Sea Anemone

Well camouflaged tide pool sculpin is eating a shrimp

Life is tough for plants and animals that live in tide pools. Here portions of the shoreline are regularly covered and uncovered by the advance and retreat of the tides. In order to survive, tide pool life forms must avoid being washed away by the tidal waves, keep from drying out in the sunlight of low tide, and avoid being eaten.

Organisms that have made tidepools their home must be well adapted to adjust to the drastic changes in environment that come with the changing of tides each day. Organisms living in this environment must have adaptions for both wet and dry conditions. Hazards include being smashed or carried away by rough waves. Typical inhabitants include sea anemones, barnacles, chitons, crabs, isopods, limpets, mussels, starfish, snails, sea cucumbers, sea urchins, and whelks.

The tides bring fresh oxygen and food to the pools twice a day. Between tides, some of the smaller pools become warm and begin to dry up.

In order to survive, the animals hide under rocks and seaweed. Sessile creatures such as the barnacles can seal themselves off or retract their appendages, the better to conserve water while exposed to air. Some deeper pools will not dry out completely between tides, and can even harbor small fish.

It should be noted that disturbing the animals in a tide pool can be hazardous to them. Even moving seaweed can expose small creatures underneath that can die in the direct sun, and prying loose any creatures held fast to the rocks is almost always fatal to the animal.

External links

• Tidal swimming pools in Britain
• A heritage listed tidal pool in Sydney, Australia

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