Rocky Shores

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Rocky Shores
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Abiotic Factors and Zonation

• All ocean shores are exposed to tides
• Intertidal zone or littoral zone zone between
  high and low tide marks
• Conditions are always changing
• When the tide is high, it is covered in water
• When the tide is low, it is moist and salty

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• Those that are in the upper region experience the
  sun and drying wind the longest time
• The littoral zone has several zones within it
• Rocky shores show the greatest variation, so they
  have the widest variety of habitats for algae to
  live and animals can feed

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• Rocky shores have three main zones
• Intertidal zone covered and exposed by water,
  throughout the day
• Spray zone is above it
• Below it is the sublittoral zone or ocean ocean
• The zones are quite similar throughout the world

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• Rocky shores can have steep cliffs or be flat
• May have crevices and gullies
• Waves erode rocky shores
• Tide pools are water-filled depressions that are
  present on rocky shores when the tide recedes

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Section Review

• What is the intertidal or littoral zone?
• Which organisms in the intertidal zone experience
  the greatest changes in abiotic factors? Why?
• What causes the zonation within the littoral
  zone?
• What is a tide pool?
• What are the three main zones of a rocky shore?

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Zonation

• Conditions are always changing
• Exposed to sunlight, rain, wind, and temperature
  changes
• Tides and waves bring changes in salinity,
  temperature, and light
• Dessication is a loss of moisture and is a big
  problem some bury themselves, some move with
  the tide, and others have adapted to prevent
  dessication

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• Six subzones
• Black zone
• Barnacle zone
• Rockweed zone
• Irish moss zone
• Blue mussel zone
• Kelp zone

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Black Zone

• Calothrix is often present

• Upper most of the zones
• Every two weeks the spring tides cover this zone
• Also gets wet from waves and spray
• Blue-green algae and lichens live here, and give
  the rocks their black colour

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Calothrix
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Black Zone

• Calothrix
• Consists of filaments of microscopic cells
• Filaments are surrounded by sticky gelatinous
  sheath
• This allows it to stick to the surface, protects
  it from drying out, and protects it from changing
  salt levels
• fixes nitrogen so lack of nutrients is not a
  problem

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Black Zone

• Rough periwinkle
• Main herbivore
• Eats Calothrix for its nitrogen content
• Shell is thick and has a small opening to prevent
  water loss
• Can seal itself to a rock with mucus if it gets
  too dry

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Barnacle Zone

• Covered and uncovered daily by the tides
• Barnacles are crustaceans
• Live stuck to the rocks and depend on tides for
  food
• Barnacles open up during high tide and sweep
  microscopic organisms such as diatoms and
  dinoflagellates into it

• They close during low tide to prevent water loss

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Barnacle Zone

• Limpets, dog whelks, periwinkles, and blue
  mussels may be found here
• Limpets scrape algae from rocks
• Dog whelks eat barnacles, mussels, and
  periwinkles
• Blue mussels will be small, and are filter
  feeders

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Rockweed Zone

• Brown algae called rockweeds live here
• Usually 30-40cm long
• Bladder rockweed is very common on the east coast
• Thick cell walls to prevent water loss
• Air bladders help it float
• It sticks to a rocky surface with a holdfast

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• Smooth periwinkle is a characteristic animal of
  this zone
• Graze on rockweeds
• Move under the rockweeds when the tide is out to
  retain moisture
• Limpets are found here as well, feeding on the
  rockweed

• (Limpets are like a snail)

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Irish Moss Zone

• Chondrus crispus is a red algae (known as Irish
  Moss)
• With Gigartina stellata form a spongy carpet
• Zone can be purple, or green and yellow
• Out of the water for a few hours a day
• Not tolerant of temperature extremes or dryness
• Algae retain their water at low tide

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Chondrus crispus
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Irish Moss Zone

• Isopods, amphipods and decapods live here
• Irish moss contains carrageenin which forms a
  gel used in ice cream, toothpaste, chocolate
  milk, evaporated milk, and body lotions

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Blue Mussel Zone

• May overlap the Irish moss zone
• May sometimes go up to the bottom of the barnacle
  zone
• Can be tightly packed
• Attach to rocks with threads made of protein
• Mytilus edulis is very common

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Mytilus edulis
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Blue Mussel Zone

• Underwater most of the time, or waves will be
  covering it
• Mussels are filter feeders their respiration
  passes water over the gills, the gills filter out
  food particles (phytoplankton, bacteria,
  detritus)
• Main predators are whelks, starfish, and humans
• Whelks bore through their shells and removes the
  interior of the mussel
• Starfish pry open the shell, and releases its
  stomach through its mouth and into the mussel,
  then takes its stomach back

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Kelp Zone

• Lowest zone
• Brown algae, Laminaria
• May be uncovered once every two weeks during
  spring tide, but waves may keep it covered
• Kelp provides food and habitat
• Limpets, mussels, isopods, amphipods, crabs, and
  starfish live here
• Starfish move from kelp beds to mussel zone
  during high tide

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Kelp Zone

• Kelp and other brown algae are collected for food
• Used to provide iodine
• High protein and vitamin content
• Feed for domestic animals
• Ground to make fertilizer
• Alginic acid is used as a stablilizer in ice
  cream and some paint and found in some
  antibiotics