Intertidal zone

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Marine habitats
The rocky shoreline of Saint-Malo, northwestern France, with a stripe of the black lichen Hydropunctaria maura at the high tide line
Coastal habitats
Littoral zone Intertidal zone Estuaries Mangrove forests Seagrass meadows Kelp forests Coral reefs Continental shelf Neritic zone
Ocean surface
Surface microlayer Epipelagic zone
Open ocean
Pelagic zone Oceanic zone
Sea floor
Seamounts Hydrothermal vents Cold seeps Demersal zone Benthic zone Marine sediment
v t e

The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various species of life, such as sea stars, sea urchins, and many species of coral with regional differences in biodiversity. Sometimes it is referred to as the littoral zone or seashore, although those can be defined as a wider region.

The intertidal zone also includes steep rocky cliffs, sandy beaches, bogs or wetlands (e.g., vast mudflats). This area can be a narrow strip, such as in Pacific islands that have only a narrow tidal range, or can include many meters of shoreline where shallow beach slopes interact with high tidal excursion. The peritidal zone is similar but somewhat wider, extending from above the highest tide level to below the lowest. Organisms in the intertidal zone are well-adapted to their environment, facing high levels of interspecific competition and the rapidly changing conditions that come with the tides.^[1] The intertidal zone is also home to several species from many different phyla (Porifera, Annelida, Coelenterata, Mollusca, Arthropoda, etc.).

The water that comes with the tides can vary from brackish waters, fresh with rain, to highly saline and dry salt, with drying between tidal inundations. Wave splash can dislodge residents from the littoral zone. With the intertidal zone's high exposure to sunlight, the temperature can range from very hot with full sunshine to near freezing in colder climates. Some microclimates in the littoral zone are moderated by local features and larger plants such as mangroves. Adaptations in the littoral zone allow the utilization of nutrients supplied in high volume on a regular basis from the sea, which is actively moved to the zone by tides. The edges of habitats, in this case the land and sea, are themselves often significant ecosystems, and the littoral zone is a prime example.

A typical rocky shore can be divided into a spray zone or splash zone (also known as the supratidal zone), which is above the spring high-tide line and is covered by water only during storms, and an intertidal zone, which lies between the high and low tidal extremes. Along most shores, the intertidal zone can be clearly separated into the following subzones: high tide zone, middle tide zone, and low tide zone. The intertidal zone is one of a number of marine biomes or habitats, including estuaries, the neritic zone, the photic zone, and deep zones.