An intertidal zone is the area between low and high tides, which is home to a rich variety of animal and plant species. This, and many other related facts, are explained in this ScienceStruck post.
Did You Know?
The life cycle of the animals and plants living in the intertidal zone are completely dependent on the rhythm of the tides.
The intertidal zone, also called the littoral zone, foreshore or seashore, is the part of the coast that is submerged during high tide, but exposed during low tide. In other words, it is the zone lying between the high tide mark and the low tide mark.
Most of the animals that live in the intertidal zone are invertebrates, such as clams, barnacles, hermit crabs, sea snails, sea stars, and sandcastle worms, though other vertebrates such as sea gulls, seals, and otters are found too. The vertebrates found here come to feed upon the invertebrate animals and the marine flora that is washed ashore. Other animals that―though not a part of this zone―come to forage for food here include foxes, goats, bears, eagles, and of course, humans. The main challenge for the animals and plants that live here is the harsh environmental conditions.
The Intertidal Zone
The intertidal zone, rather than being a homogeneous region, is in fact an area of constant variation. It is divided into several parts, that differ from each other in almost every aspect. The depth of the zone increases as one progresses from the higher to the lower parts. This zone is commonly divided into four distinct regions by biologists.
- Spray Zone: This region, also called the supra-intertidal zone, is almost always above water. It is only submerged during very high tides or extreme storms, though it is regularly moistened by spray arising from the pounding of waves.
- Higher Intertidal Zone: This zone is submerged during high tides, especially during the peaks, and is left dry during the remainder of the day. It is a highly saline zone, making life for most aquatic plants difficult.
- Middle Intertidal Zone: This region is submerged under water most of the day, except during low tide. Due to this, the salinity level and temperature are lower than the higher zone. This allows for more aquatic plant growth. However, the wave action is harsher in this zone.
- Lower Intertidal Zone: This zone is always under water, and is rarely exposed during an exceptionally low tide. It is teeming with marine flora, which is of much larger size. Despite being submerged, large predator fish can’t come here due to the shallow depth of the water.
Intertidal Zone Animals
Intertidal Zone Plants
Important Facts About an Intertidal Zone
The flora and fauna of intertidal regions are adapted to the extremes of weather, such as bright sunlight and even freezing temperatures in colder climates.
Specialized organisms exist in this zone, due to the excess salinity caused by the evaporation of water from rock pools. Moreover, these areas are highly turbulent due to waves constantly splashing over the shore.
The lower, constantly submerged regions are more populated than the higher, intermittently submerged ones.
Animals in these zones show interesting adaptations of survival. Some sea snails bore cavities in rocks to hide when the tide goes out. When sea cucumbers are pursued by predators, they will expel their guts towards the predator, creating a distraction which allows them to escape. Hermit crabs can avoid dehydration by conserving moisture in their shells.
Plants living in this region also have to develop certain strategies for survival from the pounding waves. Some kelp species have a specialized root structure called ‘holdfast’, which helps them hold on to the rocks and avoid being swept away. Other plants like Porphyra, Enteromorpha, and Fucus can survive losing up to 60 to 90% of their water content. They become dry and brittle, but soon reabsorb water when the tide comes back in.
One of the best strategies offering protection to the animals living in higher intertidal regions is that, when the tide goes out, this part is cut off from the sea, preventing marine predators from having access to it. This is why mussels and barnacles can avoid getting eaten by sea stars, by living in the upper parts of the zone. Sea stars cannot reach this region.
An intertidal zone also serves as ‘nurseries’ to the juveniles of some fish species, which thrive in the protection offered by the growth of algae and seaweeds.
The rocky pools formed when the tides recede, leaving water in the crevices of the rocks, are by themselves an important ecological habitat for various animals and fish such as the Sculpin.
The types of organisms that inhabit these areas will vary from place to place around the world. For example, a temperate rocky intertidal region will have quite different flora and fauna when compared to a mangrove intertidal zone.
Intertidal zone animals and plants have been an important source of food for man since thousands of years.
Intertidal zones are popular because of their accessibility and rich biodiversity. A large variety of animals and plants thrive in a relatively small area in these regions, which is a one-of-a-kind occurrence. However, rapid development along coastal regions and human interference are serious threats to this fragile ecosystem.