intertidal communities1 rocky shore communities sandy bottom communities
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Intertidal Communities 1
Intertidal Communities
Rocky Shore CommunitiesSandy Bottom Communities
Intertidal Communities 2
The Intertidal (Littoral Zone)
The littoral zone is the area between the highest high and the lowest low tide
Organisms that live in this area undergo the greatest variations in environmental conditions
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Tidal Forces Gravitational pull on the earth by the sun
and moon combined with centrifugal force generated by the earth moon system
Spring tides Neap tides Semidiurnal tides Diurnal tides
Spring and Neap Tides
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Rocky Intertidal Community
Rocky coasts usually occur on steep coasts that lack sediment
Ft. Fisher is one of the only naturally occurring rocky outcrops in the S.E. U.S.
Epifauna Sessile
Living on the rocks animals are exposed to the environment which can be very stressful Animals exposed to air must have adaptations to
avoid desiccation
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Abiotic Factors (Physical) Desiccation (water loss) Extreme changes in temperature Changes in salinity Turbulence
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Water Loss (Desiccation) For survival the
duration of exposure to air is critical
Sessile animals have structural adaptations
Mussel Bed
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Dessication Algae - can
withstand 70 - 90% of water loss in tissues and survive
Littorina (Periwinkle) reduce area in contact with the substrate and have a light colored shell to deal with extreme heats
Algae mat at low tide
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Changes in Temperature Due to its high heat capacity water shows a
minimum change in temperature when compared with the air
If extreme temperature does not kill an organism it may severely weaken it and cause it to die of secondary causes
Extreme temperatures may hasten desiccation
Adaptations
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Drastic Fluctuations in Salinity
Salinity may change due to severe rainfall If severe enough at
low tide the entire community may experience high mortality
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Wave Action
Waves act to smash and tear organisms from the substrate
Sessile animals use cementing (barnacles), holdfasts (seaweeds) and, byssal threads (mussels)
Mobile animals have appendages for clinging and snails have an enlarged foot used for attachment
Wave action also effects the intertidal by disturbing the substrate
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Modes of Feeding Due to the lack of sediment
there are no deposit feeders! Almost all of the sessile animals
are filter or suspension feeders Heavy wave action also effects
feeding Mobile animals are usually
holed up during low tide so they are not feeding
Not being able to feed at will has effects on growth rate especially those who are higher in the intertidal
Suspension
Feeding
Barnacles
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Vertical Zonation Species settle in specific vertical bands based on their
ability to withstand exposure to air The rocky intertidal provides many microhabitats (Numerous
niches)
High species diversity Distinct banding which progress from the low tide line to the high tide line Zonation occurs due to a both physical and biological interactions
Organisms are found in a given area by their ability to compete and deal with physical factors. Most animals in the intertidal live near the upper end of their lethal limitsLower distribution is determined by competition and predation
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Rocky Shore Zonation
Supralittoral zone
Midlittoral zone
Infralittoral
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Biotic Factors Competition
Due to the limited amount of area competition for space is acute
Succession – natural progression of communities The creation of open spaces results in quick colonization by
opportunistic species. Soon replaced by slower growing competitively dominant spp.
Keystone species: a single species, which has a controlling effect on the community in which it lives
Keystone Predators
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Tide pools Animals have the
same physical factors to contend with
Closed Tide Pools
Open Tide pools
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Sandy Shoreline Community
Soft bottom communities are found in areas where sediment has accumulated
Dominate the east coast of the U.S and the gulf coast
Due to the environmental conditions most animals bury themselves in the substrate.
Ghost crab
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Environmental Conditions Wave action is the most important physical
factor and correlates directly with beach slope and grain size
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Sandy Beach Intertidal The swash zone is the area where most
animals are found and is the area of constant change
Some species burrow deep and extend siphons to the surface
Most animals have heavy shells and are extremely fast burrowers
Sandy Beach Zonation
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Fauna Composition Noticeably absent
are the plants, due to lack of stable substrate
Crustaceans, bivalves, and polychetes dominate sandy beaches
Predators? Feeding strategies?
Coquina clams
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Mole Crabs
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Locomotion Bivalves use a
muscular foot for locomotion
Mole crabs and other arthropods use appendages for burrowing
Sea cucumbers and worms both feed and burrow at the same time
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Meiofauna