Intertidal Glory

Christen Foehring

11/12/09

Area of the shore between mean high water and mean low water Also known as the littoral zone

What is intertidal zonation?

• Banding of organisms in the intertidal zone

• Zones are not absolute• Sorted out by ability to

cope with stresses• Also called vertical

zonation

Pacific Northwest Rocky Intertidal Zones

A Dynamic Environment

• Temperature

• Light

• Moisture/Desiccation

• Wave Shock/Energy

• Dissolved Oxygen

• Food Supply

Rocky shores

• Zonation of rocky shores:– Splash/ Spray zone (rarely covered by water)– Upper intertidal zone– Middle intertidal zone– Lower intertidal zone (rarely exposed)

• Upper zones have mostly shelled organisms• Lower zones have many soft-bodied

organisms and algae

Rocky shores: Intertidal zonation and organisms

Different Stresses for Different Zones

Upper Zones• Exposure (air &

weather)• Heat• Predation by birds

and land animals• Wave turbulence

Lower Zones• Competition (food &

space)• Predation by aquatic

animals

General Rule of Thumb…

• Its lower limit is determined by biological factors (i.e. predation, competition)

• The lower an organism goes, the more capable it must be of withstanding competition pressures for space and resources and avoiding predation.

• An organism’s upper limit is determined by physical factors (i.e.desiccation,temperature).

• The higher an organism lives, the more capable it must be of tolerating exposure to air and sun.

Splash Zone

• Above high-tide level

• Seldom submerged• High air exposure

Splash Zone

• Periwinkles dominate

• Limpets• Lichens• Encrusting algae• Shore crabs

http://www.elkhornslough.org

http://2.bp.blogspot.com

Pickleweed a.k.a

Sea Asparagus

Upper Intertidal Zone

• Submerged regularly (once or twice a day)

• Affected by desiccation, competition, & predation

Upper Intertidal Zone

Barnacles dominate

Photo Credit: Trina (Fish 351)

Middle Intertidal Zone

• Lower limit of barnacles is set by competition with mussels in this zone

• Mussels are more prone to drying out than barnacles

• Lower limit of mussels is set by seastars

Middle Intertidal Zone

• Mussels

• Barnacles

• Seaweeds

Keystone Species:Pisaster !

• Voracious predators• How do seastars ingest

their prey?• Often found in

middle/lower intertidal (prone to drying out)

• What happens when humans remove the seastars?

Lower Intertidal Zone

• Submerged most of the time

• Good place for predators and seaweeds

• Compete for light & space

Lower Intertidal Zone

• Seaweed• Surfgrass• Anemones• Seastars

• Green Algae– Absorb short & long

wavelengths– Ex. Sea lettuce (Ulva spp.)

• Brown Algae– Capable of absorbing

shorter wavelengths– Ex. Rockweed (Fucus

gardneri)

• Red Algae– Absorb short blue-green

light – Ex. Encrusting coralline

algae (Lithothamnion spp.)

http://lh4.ggpht.com

http://plantphys.info

Which zone? How can you tell?

What determines the limits of these species’ intertidal

ranges?

What would happen if you removed the seastars from

this tidepool?

• Mini Quadrats• Piling Zonation aka

“personal piling”– Intertidal Zonation– Compare/Contrast

Species– Art

• Perspective writing (intertidal organism)

• Periwinkle Observation Activity

• Common PNW marine intertidal organisms– Answers to the questions kids ask most

often (what is it, what does it eat, who eats it, can I eat it, where does it live, is it like a ___?)

• Tidepool Explorations - boots & flashlights required!

Come see her at Benaroya HallWednesday, November 18,2009

7 PM - $25

http://www.sundancechannel.com/greenporno