Intertidal Zone Adaptations to a harsh life

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

The intertidal zone is rich with nutrients that are replenished with each tide 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 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 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 Constantly redesigned by three forces: wind, water and rock Winds move across the rock eroding it as each wave carries more sediment away Winds move across the rock eroding it as each wave carries more sediment away

High and Low Tide Remember that tides are caused by the gravity of the sun and The moon. Approximately twice a day the ocean swells as water Is pulled away from the center of the earth due to these forces. This creates a high tide.

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

Typical Rocky Shore

Soft Bottom Shore

Water Loss The loss of water is also called desiccation The loss of water is also called desiccation Intertidal animals must avoid major desiccation and tolerate minor 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 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 All organisms are approximately 70 percent water and need to retain that water to live

Examples of Intertidal Animals A periwinkle is commonly found in the higher zones of the intertidal area A periwinkle is commonly found in the higher zones of the intertidal area It can survive days without being submerged 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 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

Run and Hide Strategy Movement of animals to follow the tide Movement of animals to follow the tide Animals move to areas that remain wet when the tide goes out 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 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

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 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 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 Some animals produce a mucus that they use to help prevent water loss from openings they can not close

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

Temperature Sea water remains relatively constant but air temperatures vary dramatically 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 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….. Some animals have the ability just to withstand this variance – Others….. move to areas that have water and are shade move to areas that have water and are shade Have a lighter shell color to reflect light Have a lighter shell color to reflect light Have ridges to help get rid of excess heat Have ridges to help get rid of excess heat

Light color reflects light Ridges allow heat to escape

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

Picture of a crab burrowing into A rock crevice

Feeding Restrictions Most of the organisms in the littoral zone are filter feeders or predators Most of the organisms in the littoral zone are filter feeders or predators Filter feeders filter food out of the water using feeding appendages 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 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 In areas where the tide is out for long periods of time the animals grow more slowly due to the lack of food

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 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 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 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 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 Fish in this area lack a swim bladder which allows them to sink to the bottom

Mussel with Byssal thread Attached to glass

Wave Shock Shell shape also helps an animal survive 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 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 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 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