1. Intertidal Communities
Rocky Shore Communities
Sandy 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
Intertidal Communities

3. 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
Intertidal Communities

4. Spring and Neap Tides

5. 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
Intertidal Communities

6. Abiotic Factors (Physical)
Desiccation (water loss)
Extreme changes in temperature
Changes in salinity
Turbulence
Intertidal Communities

7. Water Loss (Desiccation)
For survival the duration of exposure to air is critical
Sessile animals have structural adaptations
Intertidal Communities
Mussel Bed

8. Dessication
Algae - can withstand % 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
Intertidal Communities

9. 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
Intertidal Communities

10. Drastic Fluctuations in Salinity
Salinity may change due to severe rainfall
If severe enough at low tide the entire community may experience high mortality
Intertidal Communities

11. 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
Intertidal Communities

12. 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
Intertidal Communities

13. 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 limits
Lower distribution is determined by competition and predation
Intertidal Communities

14. Rocky Shore Zonation
Intertidal Communities

15. Supralittoral zone
Midlittoral zone
Infralittoral

16. 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
Intertidal Communities

17. Keystone Predators

18. Tide pools Animals have the same physical factors to contend with
Closed Tide Pools
Open Tide pools
Intertidal Communities

19. 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
Intertidal Communities

20. Environmental Conditions
Wave action is the most important physical factor and correlates directly with beach slope and grain size
Intertidal Communities

21. 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
Intertidal Communities

22. Sandy Beach Zonation

23. 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
Intertidal Communities

24. Mole Crabs
Intertidal Communities

25. 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
Intertidal Communities

26. Meiofauna
Intertidal Communities