Rocky intertidal ecosystems

Where do you find the rocky intertidal?

It is found on 2 types of continental margins:

1. Recently glaciated margins

2. Active margins

Why is recently glaciated margins where the rocky intertidal forms? What is a local example of this?

This is because glaciers are good at dragging up all the stuff that’s loose on the landscape. Cranberry Cove is one example and here the glacier pushed it out onto the continental shelf and left exposed bedrock behind

Why are active margins where the rocky intertidal forms? What is an example of this?

This is because they are often uplifting and they haven’t had much time to accumulate sediment onto them so you see rocky coast. Cape Blanco, Oregon is an example.

What do you need for the rocky intertidal to form? Why?

Energetic waters to keep the bedrock clean of sediment and other debris

What is the rocky intertidal divided into?

4 zones based on the types of organisms that live there

Describe the four zones beginning at the landward limit

1. Black lichen in zone of wave spray

2. Littorinid snails at limit of tidal range

3. Barnacles and mussels at mid-tide levels

4. Red and brown macro algae at lower tidal levels

((closest to land) Black lichen, littorinid snails, barnacles + mussels, red + brown macroalgae (furthest seaward))

Why is the black lichen at the landward limit?

This is because they don’t like to get submerged in seawater but do fine in the wave spray

What are two types of littorinid snails? Where are they found?

Dog whelks and periwinkles. Found below the black lichen

What do dog whelks and periwinkles do?

Dogs whelks are predators that drill into shells of other snails and suck their guts out. Periwinkles are grazers

How do barnacles and mussels feed?

They are suspension feeding organisms

Is the zonation typical described above?

Yes (found in northeast North America, on Alaskan fjords, and Korean Peninsula)

Describe Stephenson’s universal scheme of zonation from limit of wave spray to furthest zone from land

1. Supralittoral zone

2. Supralittoral fringe

3. Littoral zone (intertidal zone)

4. Infralittoral fringe

5. Infralittoral zone (sub-littoral zone or subtidal zone)

Where is the infra littoral zone found? What is located in this zone?

It is extends below the LLWLT (lowest low water on a large tide). Kelp is found here (macro algae)

Where else can kelp grow besides the infra littoral zone?

It can creep a bit shoreward of LLWLT because LLWLT is a low estimate for where the water is

Where is the infra littoral fringe found?

It is between limit of kelp and LLWLT.

Where is the littoral zone found? What grows here?

It is found between LLWLT and HHWLT. It starts to fill up with mussels and barnacles. However, mussels are competitively dominant on the barnacles so they flourish in this zone. Eventually it does get too hard on the mussels so it leaves barnacles behind.

Where is the supra littoral fringe found? What grows here?

It is where the barnacles give out and give way to littorinid snails. The fringe extends all the way to the upper limit of littorinid snails

Where is the supra littoral zone found?

It is found between HHWLT and limit of wave spray