The Intertidal Zone

Hi guys! Today my post is about the intertidal zone, an important part of our ecosystem. I am so excited to be back from my hiatus, and have so many fun posts planned. As of now, I will just be posting on Tuesdays, though I may switch back to doing posts on both Tuesday and Thursday.

The intertidal zone is the part of the ocean that bridges the land and the sea. The organisms that call it home are tough and adaptable due to the changing factors of the tides. In order to show the levels of the intertidal zone, there is a formation called vertical zonation. The intertidal zone is broken up into several parts: the upper, middle and lower intertidal. As it gets lower, the subzones get more water.  

Abiotic Factors of the Intertidal Zone 

The intertidal zone has many abiotic factors because of the ever changing tides. The salinity can increase dramatically due to evaporation, and the temperature fluctuates depending on the water level and location. The intertidal zone also receives a large quantity of light because it is very exposed and shallow. Desiccation and wave shock are large factors, because it is very easy for organisms to get dried out or smashed on the rocks or substrate. Natural disasters such as hurricanes or soil erosion can also affect the intertidal zone.


  • Periwinkle snail: The periwinkle snail, or snails in the species Littorina, are common in the upper intertidal zone. They have a cavity inside their shell that helps with their breathing and they can survive out of the water for months, which is helpful as the upper intertidal zone does not get much water. 
  • Barnacles: Barnacles, or organisms in the species Cirripedia, are great for the intertidal zone as they can filter plankton during high tide and can seal moisture inside their bodies to help them during times of dessication.
  • Anemones: Several species of anemones can survive in the intertidal zone, one being the genus Anthopleura. During low tide, when they are exposed to air, they can pull their tentacles inside themselves and cover their bodies to protect themselves. 
  • Sea stars: Sea stars are able to survive in the intertidal because they can use their suction feet to move from tide pool to tide pool as well as to grip on to rocks in a storm. Their main food is mussels, which are also in abundant supply in the intertidal zone.
  • Fiddler crab: The fiddler crab is well suited to the intertidal zone because they have protective shells and they create burrows that allow water to enter the substrate, which is helpful for other organisms as well.  

While there are many more organisms that can be found in the intertidal zone, these are some of the main ones.

Plant/Microorganism life

  • Seagrass: Seagrasses are found in the middle or lower intertidal zone and provide food for many of the small fishes and other organisms that live in that zone. 
  • Dead man’s fingers: Dead man’s fingers grow in the tide pools of the intertidal zone and are used as food for humans as well as other organisms. 
  • Sea grapes: Sea grapes, or Coccoloba uvifera, are common, multi stemmed trees that are found in the intertidal zone. They are a great habitat for birds and also provide fruit that is a popular treat for birds. 
  • Sea lettuces: Sea lettuces attach onto the rocks using their small holdfasts, but are under risk of being torn away during strong storms. They can be eaten by many organisms as well as humans. 
  • Cyanobacteria: Cyanobacteria are microorganisms that photosynthesize on folded membranes in their cell. They don’t have chloroplasts, unlike eukaryotic photosynthetic species. They like the intertidal zone as they can get plenty of sunlight for photosynthesis. Cyanobacteria are great for the intertidal zone as they are food for many organisms and thrive (sometimes too much) with the incoming nutrients. 

The rocky intertidal does not have many true plants, but is abundant with algae and kelp growth.

I hope you enjoyed this post where I dove deeper into a specific part of the ocean. Would you like to see more on other parts? Let me know in the comments!

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