Intertidal zone

The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide. It is part of the littoral zone within the tidal range. This special area includes many different habitats where many kinds of life live, such as sea stars, sea urchins, and many species of coral. These habitats can look very different depending on where they are in the world.

The intertidal zone can include steep rocky cliffs, sandy beaches, bogs, or wetlands like big mudflats. In some places, like Pacific islands, this area is just a narrow strip, while in other places it can stretch for many meters along the shore. The animals and plants that live here have to be very tough, because they deal with changing tides, competition from other species, and very different temperatures.

Water in the intertidal zone can change a lot, from a mix of fresh and salty water after rain to very dry and salty salt between tides. The sun can heat this area very quickly, making temperatures very different depending on where you are. Even though it can be a hard place to live, many kinds of animals and plants have special ways to survive and use the nutrients that tides bring in from the sea. The intertidal zone is an important part of the world's ecosystems, sitting right at the edge where land meets the sea.

Zonation

Marine biologists divide the intertidal region into three zones — low, middle, and high — based on how often they are exposed to air. The low intertidal zone is only exposed during very low tides and is mostly underwater. The mid intertidal zone is regularly covered by water and exposed by tides. The high intertidal zone is only covered by the highest tides and often stays dry.

On rocky shores, tide pools form in small depressions that fill with water when the tide comes in. In some places, like Morecambe Bay, quicksand can also form. The intertidal zone changes based on waves, with spray from breaking waves affecting areas further up the shore.

Low tide zone (lower littoral)

The low tide zone is mostly underwater and only shows during low tide. This area is full of life, with lots of plants like seaweeds and many animals such as abalone, sea anemones, chitons, crabs, limpets, mussels, starfish, sea urchins, snails, and sponges. These creatures usually aren’t used to being dry or feeling very hot or cold.

Because this zone stays wet most of the time, plants and animals can grow bigger here than in other tidal areas. The shallow water lets in plenty of sunlight for the plants to make food through photosynthetic processes. The water also has the right amount of salt, and the strong waves keep bigger predators like fish away.

Ecology

Main article: Intertidal ecology

See also: Intertidal fish and Tide pool

The intertidal zone is a great place to study nature because it has many different kinds of animals and plants living very close together. The changing tides create different areas where animals live, making it easier for scientists to watch how these animals change over time.

Animals that live in the intertidal zone must be able to handle both being underwater and being out in the air. Some common animals you can find there are sea urchins, sea anemones, barnacles, crabs, mussels, and starfish. These animals have special ways to survive when the tide goes out and the sun shines on them. The intertidal zone also helps protect the shore from strong waves.

Legal issues

See also: Public trust doctrine

The area where the ocean meets the land, called the foreshore, can cause debates about who owns it and how it should be used. In some places, like New Zealand, there have been big discussions about this. In the United States, rules differ by state. For example, Massachusetts uses the low-water mark to decide what belongs to the state and what to beach owners, while California uses the high-water mark.

In the United Kingdom, the foreshore is usually owned by the Crown, except in special areas called several fisheries. In Greece, laws prevent permanent buildings on the foreshore to protect the coast. Some places, like parts of Italy, lease shoreline areas to private beach clubs. In some regions, like East Africa and the West Indian Ocean, managing these areas is challenging due to limited knowledge about caring for coastal ecosystems.

Threats

Intertidal zones are special areas where land meets the sea, home to many sea creatures. These areas can be harmed by human activities such as tourism and pollution. Other dangers include overharvesting, where too many animals are taken, and habitat destruction, which happens when the natural home of these animals is damaged or lost. Climate change also poses a serious threat to these delicate ecosystems.