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Intertidal Communities. Lies between the highest high tide and the lowest low tide Stressful environment  constant environmental changes. Characteristics of the Intertidal Zone. Experience daily fluctuations in their environment - PowerPoint PPT Presentation

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Intertidal Communities

Lies between the highest high tide and the lowest low tideStressful environment constant environmental changes

Characteristics of the Intertidal ZoneExperience daily fluctuations in their environmentOrganisms must be able to tolerate radical changes in temperature, salinity, moisture, and waves

High tideWhen organisms are most activeForaging for food, finding mates, and reproducingWater contains food for filter feeders and oxygen for organisms with gills

Low tideOrganisms exposed to airGilled animals must protect respiratory structures from drying out and collapsingFilter feeders withdraw into protective coverings

Rocky ShoresFormed from lava flows or highly eroded areas where sediments have been removed by wind and wavesRocky shore zonation:Separation of organisms into definite horizontal bands Rocks provide a stable surface for organisms to attach and provide a hiding placeZones were established based on limits of organism distributionWidth varies depending on the amount of exposure, slope of the shore, and tidal conditions

Supralittoral Fringe (called splash zone)Uppermost areaCovered only by the highest tidesReceive very little moistureSupports only a few organisms (ex: limpets, isopods, periwinkles)Supralittoral (maritime zone)Above high waterMay extend several miles inland

Midlittoral (true intertidal) zoneBelow the supralittoral fringeRegularly exposed to low tides and covered during high tidesOrganisms must withstand force of waves during low tide (called wave shock)Upper zone: acorn and rock barnaclesMiddle and low zone: oysters, mussels, limpets, and periwinklesBrown algae called rockweed

Tide poolsDepressions in the rocks that retain waterPrevent organisms within them from being exposed to airCan lose oxygen as it heats in the sun and increases in salinitySalinity can decrease as heavy rains dilute seawaterOrganisms: algae, sea stars, anemones, tube worms, hermit crabs, and molluscsMost are filter feeders

Infralittoral FringeExtends from the lowest of low tides to the upper limit reached by large kelpsSubtidal zoneRegion of shore covered by water even during low tide

Tropical Rocky ShoresSupralittoral fringe divided into 3 zonesWhite zone: border between land and the seaGray zone: farthest zone from the low tide line where macroscopic marine algae growBlack zone: immersed only at the highest spring tides

Midlittoral zoneTrue intertidal zoneDivided into 2 zonesYellow zone: yellow or green depending on algae covering its surfacePink zone: characterized by encrustation of coralline algaeInfralittoral fringe (surf zone)Includes edge of the lower rocky platform and parts of the reefSubtidal zoneRelatively barrenSmall red algae

Intertidal FishesTrue residentsEx: clingfishes, blennies, gobies, sculpins, and rock eels20-67% of inhabitants of tide poolsUsually 8-12 inches longScales absent, reduced, or very firmly attachedBody shape compressed and elongated or depressed

Temporary inhabitantsTidal visitors (to feed), seasonal visitors (to breed), and accidental visitors (trapped by storms)

Ecology of the Rocky ShoreLife influenced by level of primary production, recruitment (larval settling), herbivory (grazing), predation, and competitionCompetition, herbivory, and predation are top-down factorsEffects may flow down the food chainNutrient availability and recruitment are bottom-up factorsAffect the base of food chainsSandy ShoresRole of waves and sediments:Heavy wave action carries off much of the finer sedimentFine sandy beaches have very little wave actionGreater water retentionGood for burrowingCourse sandy beachesDrain wellDry out quicklySupport fewer organisms

Comparison to rocky shoresLack distinct pattern of zonationAppear barren and devoid of lifeSandy shore zonation:Less defined3 zonesSupralittoralFrom high tide line to where terrestrial vegetation beginsMidlittoral zoneMost inhabitants are burrowersSubtidal zoneExposed only during lowest spring tides

MeiofaunaMicroscopic organismsInhabit spaces between sediment particles of midlittoral and subtidal zonesEntirely aquaticRequire water within spaces of sand to surviveGreatest in number in beaches protected from wave action

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