Rocky Shore Notes
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Rocky Shore Notes

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    Rocky Shore Notes Rocky Shore Notes Presentation Transcript

    • Chapter 11 Between the Tides Intertidal Zone = Littoral Zone
    • Rocky Shore Communities Rocky shores occur on steep coasts without much sediment. Formed by uplift or when waves and currents carry sediments away leaving the rocks. Common on West Coast and on the East Coast north of Cape Cod, MA
    • EXPOSURE AT LOW TIDE These periwinkles get through low tide by clustering in a moist, shady crevice. They also seal against the rock to retain moisture.
    • The ocean stays in small tide pools at low tide. Life is tough in tide pools because of drastic changes in salinity, oxygen, and temperature.
    • Mussels form dense clumps that retain moisture. This can help protect the mussels themselves and provides habitat for a variety of smaller organisms.
    • Seaweeds grow only on moist rocks, not on ones that dry out.
    • The shell ridges on this tropical snail help it stay cool by radiating heat. The white color also reflects sunlight.
    • Intertidal areas have extreme temperatures and salinity more than any other marine environment. How do they survive this hostile place?
      • Avoid Dessication
      • Huddle in moist shady cavities
      • Tide pools
      • Seal off shell opening with an operculum
      • Some dry out 75% of tissue water = Chitons
      • Some seaweed – rockweed – can lose 90% of water and live when water comes back.
      • Some intertidal organisms avoid drying out by…
      • Moving to or living in wet spots
      • Close a shell to retain water
      • Some dry out and then recover after the tide returns
    • Incoming waves refract or bend from the shelf Power of the Sea
    • Wave impact is stronger at headlands and less in bays
      • Coping with Wave Shock
      • Seaweeds use holdfasts
      • Mussels hold on with byssal threads – strong fibers made of protein.
      • Limpets and chiton use foot like a suction cup.
      • Intertidal fish tend to lack swim bladder so they sink to stay on bottom.
      • Thicker shells and compact shapes reduce impact of waves.
      • Live in colonies
      • Flexible bodies to “go with the flow”
    • WAVE SHOCK: Shock to animal from the waves The giant green sea anemone lives low in the intertidal zone. a) In sheltered locations it grows tall b) In heavy wave action they are shorter to reduce drag
    • Organisms like this brown alga (kelp) withstand waves by being flexible. They are streamlined to reduce water resistance.
    • Intertidal animals get some protection from wave shock by growing in dense groups. Waves slide over much of them forming eddies. This also traps plankton near them.
    • A general food web on a rocky shore.
    •  
    • Vertical Zonation
    • Patterns of zonation on temperate shores
    •  
    • Intertidal organisms live attached to the rocks. Space gets used up.
    • The sea palm uses waves to compete for space. Adults “drip” spores on competitors and get pulled from rocks. This clears the way for new sporelings.
    • Intertidal organisms form distinct bands or zones.
      • Intertidal Zone
      • Physical factors determine how high in the zone they live
        • Sun, Heat, Desiccation= drying out, salt
      • Biological factors
      • Competition and Predation
      • How can you tell why a species is found only in a particular zone, not higher or lower?
    • Keystone Species A key predators whose effects on their communities are greater than their abundance Example: Sea Otter Otters eat sea urchins and other invertebrate kelp grazers. No otters = no kelp forest = few animals that live there. Kelp protects shoreline from wave erosion.
    • Sediments are classified by the size of particles. Sand is relatively coarse. Clay is fine. Silt and Clay together are mud.
    • Fine Sediments are found in calm areas such as bays and lagoons. Coarser sediments are found in areas affected by waves and currents.
    • Interstitial Water Water between the grains of sand. New water between grains brings oxygen. Only the top few centimeters of mud has oxygen. Anoxic – No oxygen Hydrogen Sulfide – “rotten egg” noxious gas produced by anaerobic bacteria w/o oxygen.
    • Figure 11.28a
    • Figure 11.28b
    • Figure 11.28c
    • Burrowing of a clam The foot does all the work. Foot gets pushed down and expands to anchor the clam. Clam gets pulled by the foot. Is this infauna or epifauna? Epifauna – Lives on the Sediment Infauna – Lives in the Sediment
    • Transplantation, Removal and Caging Experiments
    • Caging Experiment: Mussels grow in cage because lobsters could not get in to eat them. Mussels out-compete the sea weed.
    •  
    •  
    • Ecological Succession
      • Ecological Succession
      • Ecological Succession follows the clearing of a patch in a mussel bed.
      • The pathway taken and the end result depend on…
        • the size of the patch
        • when it opens up
        • just plain luck
    •  
      • Diversity
      • The number of species depends on how often disturbances occur.
      • Predation on the dominant competitors counts as a disturbance.
      • When disturbance is rare the dominant competitors take over and exclude others.
      • Intermediate levels of disturbance prevent this and give other species a chance
      • High disturbance means most species cannot get a foothold and the number of species drops.
    • Biological Interactions determine the type of seaweed that predominates
    • Green Sea Anemone catches small prey with tentacles but also gets nutrition from zooxanthellae, a symbiotic algae in its tissues
    • Getting Around Clams use their foot – Sea Cucumbers use an inchworm style. They digest organic material and leave the rest behind.
    • Food Web on Sandy Beach
    • Zonation pattern on Sandy Beaches