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