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Intertidal Communities

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

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Intertidal Communities

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  1. Intertidal Communities

  2. Lies between the highest high tide and the lowest low tide • Stressful environment  constant environmental changes

  3. Characteristics of the Intertidal Zone • Experience daily fluctuations in their environment • Organisms must be able to tolerate radical changes in temperature, salinity, moisture, and waves

  4. High tide • When organisms are most active • Foraging for food, finding mates, and reproducing • Water contains food for filter feeders and oxygen for organisms with gills • Low tide • Organisms exposed to air • Gilled animals must protect respiratory structures from drying out and collapsing • Filter feeders withdraw into protective coverings

  5. Rocky Shores • Formed from lava flows or highly eroded areas where sediments have been removed by wind and waves • Rocky shore zonation: • Separation of organisms into definite horizontal bands • Rocks provide a stable surface for organisms to attach and provide a hiding place • Zones were established based on limits of organism distribution • Width varies depending on the amount of exposure, slope of the shore, and tidal conditions

  6. Supralittoral Fringe (called splash zone) • Uppermost area • Covered only by the highest tides • Receive very little moisture • Supports only a few organisms (ex: limpets, isopods, periwinkles) • Supralittoral (maritime zone) • Above high water • May extend several miles inland

  7. Midlittoral (true intertidal) zone • Below the supralittoral fringe • Regularly exposed to low tides and covered during high tides • Organisms must withstand force of waves during low tide (called wave shock) • Upper zone: acorn and rock barnacles • Middle and low zone: oysters, mussels, limpets, and periwinkles • Brown algae called rockweed

  8. Tide pools • Depressions in the rocks that retain water • Prevent organisms within them from being exposed to air • Can lose oxygen as it heats in the sun and increases in salinity • Salinity can decrease as heavy rains dilute seawater • Organisms: algae, sea stars, anemones, tube worms, hermit crabs, and molluscs • Most are filter feeders

  9. Infralittoral Fringe • Extends from the lowest of low tides to the upper limit reached by large kelps • Subtidal zone • Region of shore covered by water even during low tide

  10. Tropical Rocky Shores • Supralittoral fringe divided into 3 zones • White zone: border between land and the sea • Gray zone: farthest zone from the low tide line where macroscopic marine algae grow • Black zone: immersed only at the highest spring tides

  11. Midlittoral zone • True intertidal zone • Divided into 2 zones • Yellow zone: yellow or green depending on algae covering its surface • Pink zone: characterized by encrustation of coralline algae • Infralittoral fringe (surf zone) • Includes edge of the lower rocky platform and parts of the reef • Subtidal zone • Relatively barren • Small red algae

  12. Intertidal Fishes • True residents • Ex: clingfishes, blennies, gobies, sculpins, and rock eels • 20-67% of inhabitants of tide pools • Usually 8-12 inches long • Scales absent, reduced, or very firmly attached • Body shape compressed and elongated or depressed • Temporary inhabitants • Tidal visitors (to feed), seasonal visitors (to breed), and accidental visitors (trapped by storms)

  13. Ecology of the Rocky Shore • Life influenced by level of primary production, recruitment (larval settling), herbivory (grazing), predation, and competition • Competition, herbivory, and predation are top-down factors • Effects may flow down the food chain • Nutrient availability and recruitment are bottom-up factors • Affect the base of food chains

  14. Sandy Shores • Role of waves and sediments: • Heavy wave action carries off much of the finer sediment • Fine sandy beaches have very little wave action • Greater water retention • Good for burrowing • Course sandy beaches • Drain well • Dry out quickly • Support fewer organisms

  15. Comparison to rocky shores • Lack distinct pattern of zonation • Appear barren and devoid of life • Sandy shore zonation: • Less defined • 3 zones • Supralittoral • From high tide line to where terrestrial vegetation begins • Midlittoral zone • Most inhabitants are burrowers • Subtidal zone • Exposed only during lowest spring tides

  16. Meiofauna • Microscopic organisms • Inhabit spaces between sediment particles of midlittoral and subtidal zones • Entirely aquatic • Require water within spaces of sand to survive • Greatest in number in beaches protected from wave action

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