Transcript Rocky Intertidal, lecture 6

Intertidal Communities
Rocky Shores
 Distance from low water is correlated with
variations in physical and biological
stresses, resulting in distinct horizontal
bands of zonation.
Intertidal Zone
The area that lies between the highest
high tides and the lowest low tides
Figure 10.22
Intertidal Communities
Rocky Shores
 The middle intertidal is more densely
populated with species more troubled by
competition for food and space than physical
limitations of the environment.
Intertidal Communities
Rocky Shores
Magnified cross-section of a lichen with algae cells
(dark spots) embedded in fungal filaments.
Snails and limpets grazing on sparsely distributed
algae growing along the edge of a tidal pool.
© Wildlife Pictures/age fotostock
Intertidal Communities
Rocky Shores
 The upper intertidal of rocky shorelines
hosts organisms that suffer with frequent
desiccation and punctuated food supplies.
Stunted acorn barnacles,
Chthamalus, survive in the
shallow depression of
carved letters.
Intertidal Communities
Rocky Shores
The aggregate sea anemone, Anthopleura elegantissima.
Exposed individuals (upper right) have retracted their tentacles
to avoid dessication.
© Danita Delimont/Alamy Images
Rocky Intertidal Communities
Close-up view of mussels, Mytilus, attached to rocks in
the middle intertidal.
Algal species exposed during low tides use
thickened cell walls to prevent water loss.
© Carsten Medom Madsen/ShutterStock, Inc.
Rocky Intertidal Communities
Tightly packed barnacles compete for space along the intertidal.
Photo by Dave Cowles, Rosario Marine Invertebrates website http://rosario.wallawalla.edu/inverts
Rocky Intertidal Communities
Sea stars, Pisaster, aggregating
near the low tide line to avoid dessication.
© Charles A. Blakeslee/age fotostock
Intertidal Communities
Rocky Shores
 The lower intertidal hosts a diversified assemblage
of plants and animals that are exposed to air for only
a short period of time each day.
Surf grass covers rocks and helps to keep intertidal
organisms moist during low tide.
© Weldon Schloneger/ShutterStock, Inc.
Rocky Intertidal Communities
The green anemone,
Anthopleura xanthogrammica.
© Weldon Schloneger/ShutterStock, Inc.
An eolid nudibranch with long finger-like
cerata projecting from its dorsal surface.
© Kerry L. Werry/ShutterStock, Inc.
Rocky Intertidal Communities
A scallop flaps its valves (shells) vigorously to jet away from a predatory
sea star.
© Marevision/age fotostock
MORE SPECIFICALLY
Rocky Intertidal Zone
Have hard rocky bottoms
On shores without much sediment
Found in New England and the west
coast
Locally here – “Montauk Bluffs” and the LI
(North Shore) coastline
Rocky Intertidal Zone
Problems of living in intertidal zone:
 Exposure to air
 Wave shock
Exposure to Air
Varies along the intertidal zone
 High intertidal zone is exposed longer
Exposure to Air
Water Loss = Dessication
Prevention:
Exposure to Air
Water Loss = Dessication
Prevention:
 Move – tide pools
 Hide – in moist areas
 Close up
Seaweed
Dessication
Figure 11.5
Figure 11.2
Exposure to Air
Water Loss = Dessication
Prevention:
 Move – tide pools
 Hide – in moist areas
 Close up
Withstand Drying out – seaweed, chitons
Exposure to Air
Temperature Fluctuations
 More extreme in air
Solutions: tolerance or hiding
Figure 11.3
Exposure to Air
Salinity Fluctuations
 Fresh water from rain
 High salinity in tide pools from evaporation
Solutions: tolerance, close up, hide or
death
Exposure to Air
Restricts Feeding
 Most sessile animals are filter feeders
 Others are busy avoiding stress
Animals in high intertidal grow slowly
(CA)
Mussel
Figure 11.4
Wave Shock
A problem even when the tide is high
varies along coastlines
Wave Shock
Adaptations to reduce the impact:
 Thicker shells
 Compact bodies
 Flexibility
Wave Shock
Many organisms must anchor themselves
 Mussels- byssal threads
 Seaweeds – holdfast
 Barnacles – glue
Others move to sheltered areas
Flexible kelp – withstands wave action
Figure 11.10
Figure 11.26
1 more
Intertidal
Organism…
Holds on!
416530
Credit: © Brandon Cole/Visuals Unlimited
Sunflower Sea Star, California.
Adaptations…
Because of all of these adaptations, you
see a distinct vertical ZONATION on
rocky shorelines.
Resultant (from competition)
Figure 11.9
Zonation in
seaweeds
Rocky Intertidal Communities
Vertical zonation patterns on a 3m-high rock on the coast of
Oregon.
Vertical Zonation
All rocky intertidal communities are
divided into distinct bands or zones
Each species is only found in one specific
vertical range
Vertical Zonation
Results from biological and physical
factors
Upper limit – physical factors
Lower limit – biological factors
Because of Zonation, there is Competition
For Space
Open space on the rock usually limits
populations
Food is plentiful
How to Win the
Competition For Space
Be the first to get there
 Good dispersal
Undercut or grow over your neighbors
 Barnacles
 “Competition example!!!”
Figure 11.14
Zonation
Zonation causes there to be very distinct
biotic communities in a rocky intertidal
zone:
Upper (Intertidal)
Middle (Intertidal)
Lower (Intertidal)
Upper Intertidal
Splash zone – above the high tide line
Lichens, cyanobacteria, periwinkles
(snails)
Mostly land predators
Middle Intertidal
May have many zones within this zone –
due to tidal differences
Barnacles
Mussels, other barnacles and rockweed
Sea stars = predators
Figure 11.18
Bands/zones between organisms on rocks
Zonation in Bonaire: Limpets
Keystone Predator
Sea stars can dramatically affect the
community structure
“Intermediate Disturbance Hypothesis” –
increases diversity
(will be in competition lecture too)
Local…
A few pictures from your local “rocky
intertidal” habitat
Long Island Sound (Bluff View)
“Rocky Intertidal” (LIS)
<-- “Wrack Line”
“Wrack” Weed (dead)
Wrack Weed (alive)
“Fucus sp.)
LONG ISLAND SOUND, LI, NY
“Sandpiper”
(Calidris)
Now
-- Our 1st “Main” Habitat
-- part of the Rocky (hard bottom)
ecosystem
-- KELP FOREST (go to new lecture)