Tide pool
Shallow seawater pools on rocky shores, exposed at low tide.
A tide pool, also called a rock pool, is a shallow body of seawater that forms on the rocky intertidal shore when the tide recedes. These pools, ranging from a few inches to a few feet deep, are home to adaptable organisms that must cope with rapidly changing water levels, temperature, salinity, and oxygen content. They have drawn the attention of naturalists, marine biologists, and philosophical essayists, and are theorized as a possible environment for the origin of life on Earth.
Quick Facts
- Also known as
- rock pool
- Location
- rocky intertidal shore
- Typical depth
- a few inches to a few feet
- Typical width
- a few feet across
- Notable inhabitants
- snails
- barnacles
- mussels
- anemones
- urchins
- sea stars
- crustaceans
- octopus
- small fish
- seaweed
- Theorized significance
- possible environment for life's origin and evolution of land-walking vertebrates
Facts from the source article.
Zones
The rocky shoreline is divided into distinct zones created by tidal movements. Above the high-tide mark lies the supralittoral or splash zone, a virtually terrestrial area that receives only occasional splashes. The intertidal fringe sits around the high-tide mark, while the intertidal or littoral zone lies between the high- and low-tide marks and can be further divided into high, mid, and low intertidal zones. Below the low-tide mark is the sublittoral or subtidal zone.
Tide pools exist within the intertidal zone, which is submerged at high tides and during storms but at other times may bake in the sun or be exposed to cold winds. The high tide zone is flooded once or twice daily, forcing organisms to survive wave action, currents, and prolonged sun exposure; it is dominated by seaweed and invertebrates such as sea anemones, starfish, chitons, crabs, green algae, and mussels. The mid and low intertidal zones are constantly covered and uncovered by water, so more plants and animals live there, including anemones that close up and cover themselves with shells during low tide to retain moisture.
Marine life
Tide pool inhabitants face frequent fluctuations in water temperature, salinity, and oxygen content, as well as hazards such as waves, strong currents, midday sun, and predators. Waves can dislodge mussels, gulls drop sea urchins to break them open, and black bears sometimes feast on intertidal creatures at low tide. The sea anemone Anthopleura elegantissima reproduces by longitudinal fission, splitting along its length, while Anthopleura sola engages in territorial fights using white tentacles with stinging cells.
Some sea stars can regenerate lost arms, and most require an intact central body, though a few can regrow from a single ray. Sea urchins move with tube-like feet and use spines for protection; the spines of Toxopneustes pileolus are toxic and can deliver an extremely painful sting. The California mussel increases the supply of inorganic nitrogen and phosphorus in coastal tide pools, enhancing ecosystem productivity. Its shell is composed of aragonite and calcite, both polymorphs of calcium carbonate, and climate change and ocean acidification have decreased these compounds in California mussel shells over many years.
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