Living with tides

Last week, in Step 2.4 you learned about the effect of the sun, the moon, and other factors which affect the tides on earth.“It is advisable to look from the tide pool to the stars and then back to the tide pool again”. John Steinbeck
What types of organisms are found in tidal seas?
All major types of animals (phyla, singular: phylum) are found in the intertidal zone. Sometimes a member of each phylum can be found on a single rock or boulder! Examples of such animal phyla found within the intertidal zone include:- Mollusca (e.g. limpets/snails, clams/oysters/mussels, octopus)
- Cnidaria (e.g. sea anemones)
- Arthropoda (e.g. barnacles, hermit crabs)
- Annelida (e.g. polychaete worms)
- Chordata (e.g. fish, seagulls)
- Echinodermata (e.g. sea-urchins, sea-stars)


How are animals adapted to tidal environments?
A case study: rocky shoresThe organisms living in the intertidal zone must be adapted to daily cycles of exposure to aerial (emersion) and oceanic conditions (immersion). For example, a low tide on a hot sunny day can be stressful for rocky shore animals because can cause them to dry out (desiccation) and heat up. Fortunately, many animals are well adapted to such conditions. Part of this adaptation is to simply slow/stop activity entirely and shelter until the tide comes back in.For example, limpets are able to maintain moisture within their shells by firmly clamping down on the rock during low tide. In addition, some gastropods (e.g. limpets, top shells, other types of snails) seek shelter under a cool canopy of brown algae where moisture collects and is protected from the harsh rays of the sun. Other animals higher up on the shore, where algae are less common, will find shelter within a crack in the rock where moisture collects and provides some shade. Alternatively, animals such as periwinkles and top-shells often cluster together at low tide. The increased surface area created within these clusters causes moisture to evaporate slower.


Have you ever been rockpooling? What was your favourite find?
Our purpose is to transform access to education.
We offer a diverse selection of courses from leading universities and cultural institutions from around the world. These are delivered one step at a time, and are accessible on mobile, tablet and desktop, so you can fit learning around your life.
We believe learning should be an enjoyable, social experience, so our courses offer the opportunity to discuss what you’re learning with others as you go, helping you make fresh discoveries and form new ideas.
You can unlock new opportunities with unlimited access to hundreds of online short courses for a year by subscribing to our Unlimited package. Build your knowledge with top universities and organisations.
Learn more about how FutureLearn is transforming access to education