ECOLOGICAL COMMUNITIES IN THE LITTORAL ZONE
INB Page 71
EQ: Explain how environmental factors influence the formation of ecological communities in the littoral zone, including mangrove, sandy shore & rocky shore.
HOW DO MANGROVES FORM ECOLOGICAL COMMUNITIES?
• Mangroves• Tropical & subtropical; found between 25°N & 25°S latitude• Form woodland or shrubland habitat in estuarine or coastal conditions where silts accumulate
• Habitat is referred to as: • Mangrove swamp• Mangrove forest• Mangrove
World map of the mangrove distribution zones and the number of mangrove species along each region. (Credit: Deltares)
HOW DO MANGROVES FORM ECOLOGICAL COMMUNITIES?
• Mangrove adaptations help survival in wide range of salinity & low oxygen concentrations in sediment• Pneumatophores
• Root-like structures
• Obtain oxygen directly from air
• Extensive root systems
• Traps particles suspended in water
• Reduces water flow � increases deposition of sediment
• Root system + added sediments = habitats for many organisms
• Crabs, barnacles, asst. crustaceans
• Algae •Oysters
• Sponges •Fish
• Also help dissipate wave energy
• Protects coastal areas from erosion
HOW DO SEA SHORES FORM ECOLOGICAL COMMUNITIES?
• Sandy Shore• Sand is relatively unstable:
• Fine mineral particles are easily moved by winds & tides
• Sand is not suitable substrate for attachment of sea weeds
• Provides no shelter for epifauna (organisms living on surface)
• Infauna (burrowing organisms) do well• Ghost crabs
• Bivalve molluscs
• Annelid worms
• Ragworms
• Lungworms
• Where sand mixes with muddy deposits: more stable• Supports wider range of organisms
HOW DO SEA SHORES FORM ECOLOGICAL COMMUNITIES?
• Rocky Shores
• Relatively stable substrate
• Large rocks & stones provide firm surface for attachment of algae and animals (molluscs & sea anemones)
• Rock pools hold water when tide goes out, supporting range of species
• Environmental factors influencing communities on rocky shore include:
• Aspect (geological positioning)
• Desiccation
• temperature
• Wave action
• light intensity
• Slope
• nature of substrate
HOW DO SEA SHORES FORM ECOLOGICAL COMMUNITIES?
• Rocky Shores• Often show clear zonation patterns of different species
• Appear as distinct bands along the shore & rocks
• Bands associated with resistance to desiccation
• Species near top of shore exposed to air for longer periods of time when tide is out
• Have adaptations for survival
• Includes behavior and morphology
• Species near water line spend less time exposed to air, fewer adaptations
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