Download 02Rocky Shores

Rocky Shores
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
• 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
• 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
• 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
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?
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
• Six subzones:
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Black zone
Barnacle zone
Rockweed zone
Irish moss zone
Blue mussel zone
Kelp zone
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
Calothrix
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
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
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
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
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
• 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)
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
Chondrus crispus
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
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
Mytilus edulis
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
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
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