Formed in depressions along the shoreline of rocky coasts, tide pools are filled with seawater that gets trapped as the tide recedes. While these small basins at the ocean’s edge typically range from mere inches to a few feet deep and a few feet across, they are packed with sturdy sea life such as snails, barnacles, mussels, anemones, urchins, sea stars, crustaceans, seaweed, and small fish.
As ocean water retreats outside the tide pool during low tide, the resident marine life must endure hours exposed to the sun, low oxygen, increasing water temperature, and predators such as wading birds that specialize in dining in these shallow pools. At high tide, the pool’s plants and animals are bathed in fresh seawater, but must endure the pounding of crashing waves and foraging fish with temporary access to the shoreline.
To survive in this rugged environment, tide pool inhabitants often cling very tightly to any rock to which they can adhere. Barnacles, for example, produce a fast-curing cement that lets them stay put. This natural substance is among the most powerful glues known to exist. In fact, researchers are trying to figure out if and how it can be harvested or reproduced for commercial use.
The space in a tide pool may be limited, but the food there is plentiful. Every wave at every high tide delivers fresh nutrients and microscopic organisms, such as plankton, to support and replenish the pool’s intricate food chain. Washed in by the waves, these organisms nourish the smallest animals, which, in turn, sustain the larger ones.