Rocky Shores The trials and tribulations of an intertidal organism.

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<ul><li><p>Rocky ShoresThe trials and tribulations of an intertidal organism</p></li><li><p>Intertidal Ecology</p></li><li><p>Much studiedEasy access Diversity of environmental factors Richness of diversity of flora and fauna (marine organisms; terrestrial organisms)</p></li><li><p>TidesDuration of time organisms exposed to air important because that's when they are exposed to greatest temp. ranges and get desiccation. Most need to be and water to feed.Tolerances differ which determines the zonation of rocky shores.Tides can determine behavior such as rhythms of spawning and feeding.</p></li><li><p>TemperatureConstant in the ocean, but highly variable in the intertidal.High temperatures when exposed can kill outright or weaken organisms so much that they cant recover and die from secondary causesDesiccation </p></li><li><p>Wave actionWaves have their greatest effect in the intertidal.Waves rip and tear. Organisms require adaptations to withstand this. Some are so attuned they cannot live anywhere else.</p></li><li><p>Wave actionExtends the limits of the intertidal as water is splashed where it would not otherwise reach.Organisms can live higher in windswept, wavy areas than in calm areas, even in the same tidal range.Waves can add oxygen to the water.</p></li><li><p>SalinityHeavy rains at low tide can cause large salinity changes. Organisms usually have limited tolerance and die.Tidepools have problems at low tideCan be flooded with freshwater from heavy rains or subject to increased salinity from evaporation.</p></li><li><p></p></li><li><p>Adaptations of intertidal organisms </p></li><li><p>Resistance to water lossHow does this fellow avoid the problem?He runs away. Crabs and other mobile organisms move to a suitable micro-habitat. Go where the moisture is: e.g. cracks and crevices, under moist covering of algae. </p></li><li><p>Resistance to water lossTolerate it.Some algae survive 60 to 70 pct. water loss. Chitons tolerate 75 pct. loss and limpets 30-70 pct.</p></li><li><p>Resistance to water loss(behavioral and structural adaptations)Barnacles close up into impermeable shell.</p></li><li><p>Resistance to water loss(behavioral and structural adaptations)Some Acmaea species (limpets) have "home scar". Shells fit exactly and return to it when tide out. Other limpets simply clamp down tight. </p></li><li><p>Resistance to water loss(behavioral and structural adaptations)Periwinkles (Littorina sp.) have opercula, which completely seal off aperture to shells. Pull in, close aperture and wait it out. Littorina ziczak</p></li><li><p>Resistance to water loss(behavioral and structural adaptations)Actinia sp.(anemone) produces mucus. </p></li><li><p>Maintenance of heat balance Most organisms cant tolerate more heat so need mechanisms to keep cool. What are the two ways to do this?Reduce heat gain from the environmentIncrease heat loss from the body of the animal.</p></li><li><p>Reducing heat gainLarge body size compared to similar organisms living lower in intertidal or subtidal. Check out Nerites. Why does this work?Less surface area relative to volume so less gain in heat. Also takes longer to heat up because of specific heat of water. </p></li><li><p>Reducing heat gainKeep body off the ground. Problem because of need to attach to avoid waves. Works in less wavy areas.</p></li><li><p>Increasing heat lossSculptured light snails reflect heat compared to dark smooth shells. </p></li><li><p>Increasing heat lossEvaporation of water. Why is this difficult for intertidal organisms?Intertidal organisms are in danger of desiccation so can't afford more water loss. Some solve the problem by having an extra supply of water for cooling. Some barnacles and gastropods hold water in their shells and mantle cavity.</p></li><li><p>Mechanical stress from wavesAttach to the substrate.</p></li><li><p>Mechanical stress from wavesMost intertidal mollusks have thickened smooth shells to resist waves.Crabs and other motile animals have no special mechanisms to protect them from waves so they simply hide.</p></li><li><p>RespirationMarine animals use thin gills to extract oxygen from the water efficiently, but desiccation is a problem in the air.Problem solved by enclosing gills in a cavity.</p></li><li><p>RespirationAvoiding desiccation can lead to respiratory difficulties.When animals close up or clamp down to conserve water they decrease gas exchange.Most are quiescent at low tide.Cutaneous respiration.Intertidal fishes often decrease their gills and increase blood vessels in the skin. They can obtain over half of their oxygen this way</p></li><li><p>FeedingBig problem at low tide because have to expose their bodies in order to feed.So usually dont. Instead wait for tide to come in.</p></li><li><p>Salinity stressIntertidal organisms are osmoconformers so they cant regulate their salinity.The same mechanisms used for preventing desiccation decrease salinity stress.There arent good methods for salinity control so massive die-offs result from heavy rains.These must be rare events. Why?No special mechanisms have evolved to solve the problem in estuarine species.</p></li><li><p>ReproductionMany intertidal organisms are sessile or sedentary so require free-floating or swimming gametes or larvae. Breeding cycles often are synchronized with the occurrence of particular tides, e.g. spring tides for fertilization and neap tides for spawning.</p></li><li><p>Spring tidesSpring tides are the highest tides because the moon and sun are directly aligned and combine their gravitational forces.</p></li><li><p>Neap tidesMinimum range tides because the moon and the sun are at right angles to each other.</p></li></ul>


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