Intertidal Communities Rocky Shore Communities Sandy Bottom Communities Intertidal Communities

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

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

Spring and Neap Tides

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

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

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

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 Intertidal Communities

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

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

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

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

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

Rocky Shore Zonation Intertidal Communities

Supralittoral zone Midlittoral zone Infralittoral

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

Keystone Predators

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

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

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

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

Sandy Beach Zonation

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

Mole Crabs Intertidal Communities

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

Meiofauna Intertidal Communities