Rocky ShoresRocky Shores

The trials and tribulations of The trials and tribulations of an intertidal organisman intertidal organism

Intertidal EcologyIntertidal Ecology

Much studiedMuch studied

Easy access Easy access Diversity of environmental factors Diversity of environmental factors Richness of diversity of flora and Richness of diversity of flora and

fauna (marine organisms; terrestrial fauna (marine organisms; terrestrial organisms)organisms)

TidesTides Duration of time organisms exposed Duration of time organisms exposed

to air important because  that's when to air important because  that's when they are exposed to greatest temp. they are exposed to greatest temp. ranges and get desiccation. ranges and get desiccation.

Most need to be and water to feed.Most need to be and water to feed. Tolerances differ which determines Tolerances differ which determines

the zonation of rocky shores.the zonation of rocky shores. Tides can determine behavior such Tides can determine behavior such

as rhythms of spawning and feeding.as rhythms of spawning and feeding.

TemperatureTemperature

Constant in the ocean, but highly Constant in the ocean, but highly variable in the intertidal.variable in the intertidal.

High temperatures when exposed High temperatures when exposed can kill outright or weaken organisms can kill outright or weaken organisms so much that they can’t recover and so much that they can’t recover and die from secondary causesdie from secondary causes

Desiccation Desiccation

Wave actionWave action

Waves have their greatest effect in Waves have their greatest effect in the intertidal.the intertidal.

Waves rip and tear. Waves rip and tear. Organisms require adaptations to Organisms require adaptations to

withstand this. Some are so attuned withstand this. Some are so attuned they cannot live anywhere else.they cannot live anywhere else.

Wave actionWave action

Extends the limits of the intertidal as Extends the limits of the intertidal as water is splashed where it would not water is splashed where it would not otherwise reach.otherwise reach.

Organisms can live higher in Organisms can live higher in windswept, wavy areas than in calm windswept, wavy areas than in calm areas, even in the same tidal range.areas, even in the same tidal range.

Waves can add oxygen to the water.Waves can add oxygen to the water.

SalinitySalinity

Heavy rains at low tide can cause Heavy rains at low tide can cause large salinity changes. Organisms large salinity changes. Organisms usually have limited tolerance and usually have limited tolerance and die.die.

Tidepools have problems at low tideTidepools have problems at low tide Can be flooded with freshwater from Can be flooded with freshwater from

heavy rains or subject to increased heavy rains or subject to increased salinity from evaporation.salinity from evaporation.

http://www.countryside-trust.org.uk/seashorecentre/sea_world/coastal_habitat.htm

Adaptations of intertidal Adaptations of intertidal organisms organisms

Resistance to water lossResistance to water loss

How does this fellow avoid the problem?How does this fellow avoid the problem? He runs away. He runs away. Crabs and other mobile organisms move Crabs and other mobile organisms move

to a suitable micro-habitat. Go where the to a suitable micro-habitat. Go where the moisture is: e.g. cracks and crevices, moisture is: e.g. cracks and crevices, under moist covering of algae. under moist covering of algae.

Resistance to water lossResistance to water loss Tolerate it.Tolerate it.

Some algae survive 60 to 70 pct. water Some algae survive 60 to 70 pct. water loss. loss.

Chitons tolerate 75 pct. loss and limpets Chitons tolerate 75 pct. loss and limpets 30-70 pct.30-70 pct.

Resistance to water lossResistance to water loss(behavioral and structural adaptations)(behavioral and structural adaptations)

Barnacles close up into impermeable Barnacles close up into impermeable shell.shell.

Resistance to water lossResistance to water loss(behavioral and structural adaptations)(behavioral and structural adaptations)

Some Some AcmaeaAcmaea species (limpets) have species (limpets) have "home scar".  Shells fit exactly and "home scar".  Shells fit exactly and return to it when tide out.  Other return to it when tide out.  Other limpets simply clamp down tight.  limpets simply clamp down tight. 

Resistance to water lossResistance to water loss(behavioral and structural adaptations)(behavioral and structural adaptations)

Periwinkles (Periwinkles (Littorina sp.Littorina sp.) have ) have opercula, which complete ly seal off opercula, which complete ly seal off aperture to shells.  Pull in, close aperture to shells.  Pull in, close aperture and wait it out. aperture and wait it out.

Littorina ziczak

Resistance to water lossResistance to water loss(behavioral and structural adaptations)(behavioral and structural adaptations)

ActiniaActinia spsp.(anemone) produces .(anemone) produces mucus. mucus.

Maintenance of heat Maintenance of heat balance balance

Most organisms can’t tolerate more Most organisms can’t tolerate more heat so need mechanisms to keep heat so need mechanisms to keep cool. cool. What are the two ways to do What are the two ways to do this?this?

Reduce heat gain from the Reduce heat gain from the environmentenvironment

Increase heat loss from the body of Increase heat loss from the body of the animal.the animal.

Reducing heat gainReducing heat gain Large body size compared to similar Large body size compared to similar

organisms  living lower in intertidal organisms  living lower in intertidal or subtidal. Check out Nerites. or subtidal. Check out Nerites. Why Why does this work?does this work?

Less surface area relative to volume Less surface area relative to volume so less gain in heat.  so less gain in heat. 

Also takes longer to heat up because Also takes longer to heat up because of specific heat of water. of specific heat of water.

Reducing heat gainReducing heat gain Keep body off the ground. Keep body off the ground.

Problem because of need to attach to Problem because of need to attach to avoid waves. avoid waves.

Works in less wavy areas.Works in less wavy areas.

Increasing heat lossIncreasing heat loss

Sculptured light snails reflect heat Sculptured light snails reflect heat compared to dark smooth shells. compared to dark smooth shells.

Increasing heat lossIncreasing heat loss

Evaporation of water. Evaporation of water. Why is this difficult for intertidal organisms?Why is this difficult for intertidal organisms? Intertidal organisms are in danger of Intertidal organisms are in danger of

desiccation so can't afford more water loss. desiccation so can't afford more water loss. Some solve the problem by having an extra Some solve the problem by having an extra

supply of water for cooling. Some barnacles supply of water for cooling. Some barnacles and gastropod’s hold water in their shells and and gastropod’s hold water in their shells and mantle cavity.mantle cavity.

Mechanical stress from Mechanical stress from waveswaves

Attach to the substrate.Attach to the substrate.

Mechanical stress from Mechanical stress from waveswaves

Most intertidal mollusks have Most intertidal mollusks have thickened smooth shells to resist thickened smooth shells to resist waves.waves.

Crabs and other motile animals have Crabs and other motile animals have no special mechanisms to protect no special mechanisms to protect them from waves so they simply them from waves so they simply hide.hide.

RespirationRespiration Marine animals use thin gills to Marine animals use thin gills to

extract oxygen from the water extract oxygen from the water efficiently, but desiccation is a efficiently, but desiccation is a problem in the air.problem in the air.Problem solved by enclosing gills in a Problem solved by enclosing gills in a

cavity.cavity.

RespirationRespiration Avoiding desiccation can lead to Avoiding desiccation can lead to

respiratory difficulties.respiratory difficulties. When animals close up or clamp down When animals close up or clamp down

to conserve water they decrease gas to conserve water they decrease gas exchange.exchange.

Most are quiescent at low tide.Most are quiescent at low tide. Cutaneous respiration.ICutaneous respiration.I

ntertidal fishes often decrease their gills ntertidal fishes often decrease their gills and increase blood vessels in the skin. and increase blood vessels in the skin. They can obtain over half of their oxygen They can obtain over half of their oxygen this waythis way

FeedingFeeding

Big problem at low tide because have Big problem at low tide because have to expose their bodies in order to to expose their bodies in order to feed.feed.

So usually don’t. Instead wait for So usually don’t. Instead wait for tide to come in.tide to come in.

Salinity stressSalinity stress Intertidal organisms are osmoconformers Intertidal organisms are osmoconformers

so they can’t regulate their salinity.so they can’t regulate their salinity. The same mechanisms used for The same mechanisms used for

preventing desiccation decrease salinity preventing desiccation decrease salinity stress.stress.

There aren’t good methods for salinity There aren’t good methods for salinity control so massive die-offs result from control so massive die-offs result from heavy rains.heavy rains.

These must be rare events. Why?These must be rare events. Why? No special mechanisms have evolved to No special mechanisms have evolved to

solve the problem in estuarine species.solve the problem in estuarine species.

ReproductionReproduction

Many intertidal organisms are sessile Many intertidal organisms are sessile or sedentary so require free-floating or sedentary so require free-floating or swimming gametes or larvae. or swimming gametes or larvae.

Breeding cycles often are Breeding cycles often are synchronized with the occurrence of synchronized with the occurrence of particular tides, e.g. spring tides for particular tides, e.g. spring tides for fertilization and neap tides for fertilization and neap tides for spawning.spawning.

Spring tidesSpring tides Spring tides are the highest tides Spring tides are the highest tides

because the moon and sun are because the moon and sun are directly aligned and combine their directly aligned and combine their gravitational forces.gravitational forces.

Neap tidesNeap tides Minimum range tides because the Minimum range tides because the

moon and the sun are at right angles moon and the sun are at right angles to each other.to each other.