What is an intertidal zone ecosystem and know more?

What is an Intertidal zone:

The intertidal zone is a very important area from an ecological point of view. The intertidal zone exists, where the sea or ocean meets the landmass. This area or zone becomes indented during high tides and exposed to air during low tides. It is an area in between the low tide and high tide zone rich in diverse ecosystems known as intertidal zone ecosystems.

What is an intertidal zone ecosystem?

The intertidal zone ecosystems harbor many flora and fauna species. An intertidal zone ecosystem is a physical environment, where biological communities of interacting species of flora and fauna coexist within the said zone. The zone may be steep, rocky, sloping sandy beaches or mud flats, that can extend from a few meters up to a hundred miles in some cases.

Intertidal zone/ image credit/

The inter-tidal zone ecosystem may be divided into different zones, depending on its habitations, flooding of tidewater, exposure to air, landscape, etc. such as:

  • The splash zone.
  • The upper intertidal zone.
  • The middle intertidal zone.
  • The lowest intertidal zone.
  • The subtidal zone.

The Splash zone:

The splash zone also referred to as the supralittoral zone, spray zone, or supratidal zone, is the area in the inter-tidal zone ecosystem that is periodically in and out of tidal waves. If such a surface is muddy it can harbor many species of crabs and a few fish species which can live underground for a long.

In the case of a sandy surface, we may see a few crabs and other seagrasses. Further, this zone witnesses the presence of fungi, algae, isopods, periwinkles, and other species. On the Odisha coast, of the splash zone (Dagara, Baleswar) a rare species of crabs called red carpet are seen. Earlier the entire coastline from the Budhabolang river estuary to the Subarnarekha river estuary was inhabited by the said crab species.

Image of red carpet crabs, Dagara, Baleswar, Odisha/ image

The upper intertidal zone:

The upper intertidal zone is exposed to air most of the time, except on the occasion of high tide waves. Many species of fauna can be seen in this zone including starfish, algae, barnacles, saline snails, mussels, limpets, and different crabs like shore crabs and hermit crabs, etc.

The middle intertidal zone:

The middle intertidal zone is exposed to the low tide zone but is indented by the high tide waves often. The surface remains swampy most of the time creating suitable habitats for the organisms like anemones, barnacles, algae, isopods, limpets, sea stars, sea palms, snails, sponges, mussels, etc.

Low intertidal zone:

The low intertidal zone may be exposed to air for a short duration of time at low tides keeping the organisms to stay in underwater conditions. Basically, Rockey sores shelter sea stars, snails, seaweeds, algae, crabs, barnacles, and mussels like marine species. Small fish like blenny, goby, and triple fins are commonly chipped to the rocky surface during high tide and wait for another high tide to return.

Subtidal zone:

The subtidal zone is close to shore but constantly remains underwater and the subtidal ecosystems always remain submerged due to tidal events. We find forests (mangroves), algae beds, seagrass, and coral reef in this zone. These ecosystems are normally found in shallower areas of the subtidal zone.

Coral reef/ image credit/ Pinterest

Coral reefs:

Coral reefs are some of the most diverse ecosystems of the globe coming within intertidal zone ecosystems. Coral reefs are structures made of thousands of tiny coral creatures referred to as polyps. It appears like rocks but corals are live fauna. It is an amazing fact that a polyp has no eyes, ears, nose, tongue, or brain, a nerve network keeps the creature alive.

Polyps prey on zooplankton,the floating tiny creatures. The bigger one can catch tiny fish to eat. At night polyps come out of the coral shell to catch the prey. Coral reef harbors approximately 25% of marine species.

Different fish like butterfly fish and damselfish, crabs, lobsters, seahorses, sponges, turtles, coral shrimp, urchins, sea stars, sea snakes, rays, octopus, snails, mollusks, worms, etc. found in coral reef zone. Many of these creatures work together as a team to survive, known as symbiosis. It is the tidal condition that contributes to the size of coral reefs, in any situation.

Mangrove forests:

Mangrove forests play a very crucial role in intertidal zone ecosystems. The distribution of mangrove species and growth depends on freshwater inflow, silt deposits, and most importantly tidal water inflows. In India, the Bay of Bengal coast has more mangrove species than, the Arabian coast. The river deltas have exclusive growth of mangroves across the world.

The vast Sundarbans, Niger, Orinoco, and Bhitarakanica are a few examples of river deltas, where vast extensive growth of mangroves is seen. Spalding et al(2010) in “World Atlas of Mangroves” identified 73 mangrove species out of which 38 are considered core species.

In Odisha 35 true mangrove species belongs to 29 genera, and 14 families were found out of which Bhitara Kanica contributes 33 true mangrove species, where more than 40 associate species say the story of diversified ecosystems.

Spotted deer in Sundarban/ Bangladesh/ image credit/National

Mangrove forest which is also an important member of intertidal zone ecosystems not only rich with diverse floras but also many fauna species. The animals, birds, fish, turtles, and crab species enrich these ecosystems. The royal Bengal tiger, fishing cats, monkeys, owls, dugong, mangrove red snapper, crocodiles, different species of birds like hoatzin, boat-billed heron, spoonbill, ashy tailorbird, sunbird, crabs, lobsters, and snakes of different species, say the story of biodiversity.

Further spotted deers, foxes, jackals, saurian, monitor lizards, wild cats, wild hens, fruit bats, kingfishers, falcons, frogs like giant toad-bufo Marinus, Tree frog Osteopilus Septentrionalis and varieties of fishes and insects are the home of mangrove/ intertidal zone ecosystems.


The intertidal zone is a very important area from an ecological point of view. Each and every zone has specific importance and harbors many lives. The coral reefs and mangroves in the zone enhance the ecological diversities of the zone. It is our sacred duty to preserve the ecosystems of the intertidal zone.

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