Introduction to Marine
Rocky Intertidal
Habitat
Masochistic Organisms and the
Students Who Love Them
Inhabitants of the
rocky intertidal
habitat must deal
with some of the
most extreme
envirnmental
fluctuations on
earth. These
include:
• Wave action
• Substrate
• Slope
• Exposure to the sun
• Dessication
• Extremes of salinity
• Extremes of
temperature
Physical
Challenges
Organisms must
adhere to solid
rock. Examples of
such mechanism
include:
• Holdfasts
(multicellular
algae)
• Super adhesives
(barnacles)
• Suction (sea stars,
sea urchins)
Rocky
Substrate
Byssal threads (mussels)
Wave Action
Strategies for coping with
relentless battering include:
• Clinging rigidly to rock.
• Maintaining a low profile.
• Inhabiting crevices protected from waves.
• A flexible but tough tissue consistency.
Slope
The jumble of
surfaces
exposed as
rock of the
intertidal zone
weathers and
breaks up
range from
horizontal to
vertical to
inverted.
Exposure to the Sun
• Ultraviolet rays can damage tissue and
genetic material of unprotected organisms.
• Intertidal inhabitants
are marine
organisms, but
some are exposed
to air daily by the
receding tide for
hours at a time.
• To avoid
dessication, they
must be able to seal
unprotected tissues
in a watertight
surrounding in
order to survive.
Dessication
Temperature Extremes
• Throughout the year, intertidal organisms must
cope with air temperatures ranging from subfreezing to over 35oC (mid 90’s Fahrenheit).
• On a daily basis,
sudden immersion
in and withdrawal
from ocean water
can involve a
difference of
20oC or more.
• As the mid-day sun
heats tide pools, water
evaporates, but its salt
remains behind.
• Salinity can increase
dramatically before the
next flush of fresh sea
water.
• At the opposite extreme,
tide pools with a direct
influx of fresh water from
the land can have a
much lower salinity than
ocean water.
Salinity
Extremes
Zonation on Maine’s Rocky
Shore
• Physical and biological factors create regular
patterns in the ecology of the rocky littoral zone.
These effects are displayed as wide bands, each
containing certain species.
Subtidal Zone
• Not “intertidal.”
• the extreme
low margin of
shore that is
always
submerged.
Large kelps
(brown algae)
are dominant
here along the
zone's upper
edge.
• The first intertidal zone,
dominated by Irish
moss and tufted red
weed.
"In the calm world of the
deeper rock pools,
undisturbed by the tumult of
incoming waves, crabs sidle
along the walls, their claws
busily touching, feeling,
exploring for bits of food.
The pools are gardens of
color composed of the
delicate green and ocheryellow of encrusting sponge,
the pale pink of hydroids
that stand like clusters of
fragile spring flowers, the
bronze and electric-blue
gleams of the Irish moss, the
old-rose beauty of the
coralline algae."
- Rachel Carson, The Edge of the Sea
Red Algae
Zone
• Brown algae, such
as rockweeds and
knotted wrack,
dominates.
"Meadows of brown
rockweeds
appear on the
gently sloping
rocks of the shore
as the tide
imperceptibly
ebbs. Smaller
patches of green
weed, stringy as
mermaids’ hair,
begin to turn white
and crinkly where
the sun has dried
them." - Rachel
Carson, The Edge of
the Sea
Brown Algae
Zone
Mussel Zone
• Dominated by the
edible mussel,
Mytilus edulis.
• Many other
species live in the
mussel bed
attached to the
mussels' byssal
threads, or
attached to the
mussels' shells.
Barnacle
Zone
“Like drifts of old snow no longer white, the barnacles come
into view; they blanket rocks and old spars wedged into
rock crevices, and their sharp cones are sprinkled over
empty mussel shells and lobster pot buoys and the hard
stipes of deep water seaweeds, all mingled in the flotsam
of the tides.” - Rachel Carson, The Edge of the Sea
Black Zone
• Dominated by various blue-green bacteria
(Cyanobacteria) that appear as a slimy, black film
on the rock surfaces (beware! slippery when
wet!)
Lichen
Zone
• Organisms
living here are
exposed to salt
water as spray
from crashing
waves rather
than from tidal
inundation.
• lichens tolerant
of occasional
salt spray
dominate this
zone.
Common Intertidal
Residents
Sessile algae (Protista)
Hollow green
algae
(Enteromorpha
intestinalis)
Sea lettuce
(Ulva lactuca)
Green seaweed
(Spongomorpha
sp.)
Green fleece
(Codium fragile)
Irish moss
(Chondrus
crispus)
Coral weed
(Corallina
officinalis)
Tufted red weed
(Gigartina
stellata)
Dulse
(Rhodymenia
palmata)
Rockweed (Fucus sp.)
Knotted wrack
(Ascophyllum
nodosum)
Brown kelp (Laminaria sp.)
Mollusks
Blue Mussel
(Mytilus
edulis)
Common
periwinkle
(Littorina
littorea)
Dog whelk
(Thais lapillus)
Tortoiseshell
limpet
(Acmaea
testudinalis)
Arthropods
Northern Rock
Barnacle
(Semibalanus
balanoides)
Rock crab
(Cancer
irroratus)
Hermit crab
(Pagurus
longicarpus)
Scud (Gammarus
sp.)
Echinoderms
Northern Sea Star
(Asterias vulgaris)
Blood Star (Henrica sp.)
Green Sea Urchin
(Strongylocentrotus
droebachiensis)
Sponges
• Crumb-of-bread
Sponge
(Halichondria
panacea)
Tide Pool Fishes
Enough said.