The Rocky Intertidal

A rocky intertidal "moment"

Biologist researching distribution patterns in the rocky intertidal

Organisms in the rocky intertidal face many challenges to their survival in their daily routine. They are submerged underwater as the tide comes in and exposed to air as the tide rolls out. The habitat is made up of varying gradients of wave exposure and the length of time an organism is exposed to water is dependent upon vertical placement in the intertidal. The rocky intertidal is also characterized by extremely uneven surfaces which can create tide pools and a multitude of vertical and horizontal surfaces of varying degrees. Ecologists studying the rocky intertidal have noticed patterns in the vertical placement of organisms, most commonly a zonation pattern in which certain species dominate certain heights of the intertidal. The height at which a certain species tends to be found is determined by its upper limit, the highest height it can survive, and a lower limit, the lowest height it can survive. Generally biologists have found that the upper limit of organisms is set by the species physical limitations. The higher you move up in the intertidal, the more exposed you are to the air, and whatever its weather conditions (sunny, snowy, etc.) for longer periods of time and to survive you must have a some defense against desiccation, but also have a good strategy for obtaining nourishment. The lower limit is generally thought to be set by biological limitations, which include competition for space and predation. Space is very limiting in the intertidal, especially in the lower, more water exposed part and each neighbor has some strategy for occupying as much space as possible. Also, since conditions are a little less drastic in the lower intertidal, more predators are able to survive and move around in search of food.  A good example of this zonation pattern is the blue mussel, to find out more click here.

This paper examines two rocky intertidal habitats, both on the Atlantic Ocean: Nahant, Massachusetts and a rocky section of the Bermuda shoreline.

2002 Laura Brentner, for educational purposes only

The rocky intertidal at the Northeastern Marine Science Center in Nahant, MA