Transcript Chapter_13
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
Organisms must be able to tolerate radical
changes in temperature, salinity, moisture, and
waves
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
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
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
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
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
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
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
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
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)
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 topdown factors
Effects may flow down the food chain
Nutrient
availability and recruitment are
bottom-up factors
Affect the base of food chains
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
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
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