Intertidal Zone

1. Intertidal Zone Adaptations to a harsh life

2. Definition of Intertidal Also known as the littoral zone The area between the high water mark and the low water mark Where the land meets the ocean Sometimes dry sometimes wet

3. The intertidal zone is rich with nutrients that are replenished with each tide Each wave that enter the zone carries with it more plankton that the organisms that live in this area survive on Dead animals and plants also enter this area feeding scavengers like hermit crabs and shore crabs Constantly redesigned by three forces: wind, water and rock Winds move across the rock eroding it as each wave carries more sediment away

4. High and Low Tide

5. Type of Shore Line Rocky shore Occur on steep coasts with very little sediment Occur on active margins where the land was recently uplifted Can be caused by erosion of sediment due to wave action Soft shore Areas where large amount of sediment has accumulated – more later

6. Typical Rocky Shore

7. Soft Bottom Shore

8. Water Loss The loss of water is also called desiccation Intertidal animals must avoid major desiccation and tolerate minor desiccation This is a problem because these animals only have gills to breathe and eat only other marine organisms All organisms are approximately 70 percent water and need to retain that water to live

9. Examples of Intertidal Animals A periwinkle is commonly found in the higher zones of the intertidal area It can survive days without being submerged A sea urchin is found in areas that remain wet 99 percent of the time – either in the low zones or in tide pools It would die if exposed to air for any extended period of time

10. Run and Hide Strategy Movement of animals to follow the tide Animals move to areas that remain wet when the tide goes out Some animals only live in those areas that remain wet and are shaded at all times – tide pools are depressions that hold water when the tide goes out

11. Clam – up Strategy The animals that use this type of strategy have a protective covering like a shell that they close to prevent water loss These animals clamp themselves close to the rock – sometimes even creating depressions – and seal the opening Some animals produce a mucus that they use to help prevent water loss from openings they can not close

12. Dry Out Strategy Some animals allow themselves to just dry out A chiton has the ability to loose 70 percent of its water and still survive

13. Temperature Sea water remains relatively constant but air temperatures vary dramatically All animals in the littoral zone must be able to tolerate extreme changes – including animals in the tide pools Some animals have the ability just to withstand this variance – Others….. move to areas that have water and are shade Have a lighter shell color to reflect light Have ridges to help get rid of excess heat

15. Salinity Fluctuates largely due to Rain – dilutes the water in tide pools Evaporation – increases the salinity because only pure water evaporates living the salt behind Animals often tolerate these changes by Sealing off their shells to the environment Burrowing into the environment Not tolerating it – they die in extreme cases

17. Feeding Restrictions Most of the organisms in the littoral zone are filter feeders or predators Filter feeders filter food out of the water using feeding appendages This means that they must go without food during low tide when there is not food to filter or when they have their shells closed to prevent desiccation In areas where the tide is out for long periods of time the animals grow more slowly due to the lack of food

18. Coping with Wave Shock Animals that live in an area with wave shock are usually sessile and have a means of anchoring themselves to the rock Seaweed uses holdfasts Mussels and other shell fish uses byssal threads – as the animal moves new threads are attached to the rock and the old ones are detached Limpets and chitons use their radula to suction to the rock Fish in this area lack a swim bladder which allows them to sink to the bottom

20. Wave Shock Shell shape also helps an animal survive wave shock Shells of organisms in areas where there is a lot of wave shock tend to be compact in shape and have thick shells In times of strong wave action – like during storms – mortality is high As rocks are turned over those that live on top are crushed and those that lived on the bottom often are not adapted to the exposure they face on top