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Welcome to the intertidal

The intertidal is a unique ecosystem - it's where the land meets the sea and because of that experiences both terrestrial and marine conditions. These harsh conditions are what make it so interesting to study!

Intertidal ecosystems are exposed to the air during low tide, and organisms that live here have adapted to deal with extreme shifts in temperature, food availability, desiccation stress, salinity, pH, and a number of other environmental conditions. There are also biological conditions that change with the tides, such as predation and competition. These conditions interact to define the intertidal community - and this is what Nyssa and I are studying (more on each of our individual projects later).

The intertidal at Asilomar State Beach

The intertidal is typically divided into three biological regions, classified as low, mid, and high. The low zone is exposed to the air for the least amount of time and primarily contains algae, sea stars, abalone, and other species that do not tolerate desiccation well. The low intertidal is also often exposed to the subtidal environment, meaning the biological interactions that occur here are very interesting.

The mid zone is primarily defined by the presence of mussels, which are considered a foundation species because they play an important role in community structure by allowing other species to settle. You can often find snails, limpets, chitons, whelks, and rock weed algae in this area as well.

The high zone is exposed to the air more than any other zones, and because of this organisms that live here must be well adapted to the stresses of desiccation. This is generally considered the barnacle zone and small litorine snails, limpets, and chitons are also common here.

Next time you're at the beach, try and see if you can determine where the different zones are!

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