Lecture 8 - Rocky Shores

Question 1

Are rocky shores generally high or low energy?

Answer 1

High, depending on their exposure to waves.

Question 2

In what way are rocky shores similar to reefs?

Answer 2

They are autochthonous - energy is derived from the same location that it is used.

Question 3

What acts as food for detritivores in rocky shores?

Answer 3

Broken/rotting seaweed

Question 4

Name four factors that favour life in a rocky shore environment.

Answer 4

• High primary productivity
• Low sediment supply
• Stable substrate that erodes slowly
• Diverse habitat types present (ledges, overhangs, crevices, pools etc.)

Question 5

Give seven challenges faced by organisms in a rocky shore habitat.

Answer 5

• Desiccation
• Wave action
• Temperature fluctuation
• Salinity fluctuations
• Range of illumination
• Double predation
• Pollution

Question 6

Give the three zonations in a rocky shore environment.

Answer 6

• Upper shore (furthest from ocean)
• Middle shore
• Lower shore (edge of ocean)

Question 7

What is the main physical factor for marine organisms living in rocky shores?

Answer 7

Submergence

Question 8

What organisms are often present in the upper shore, supra-littoral zone?

Answer 8

Lichens

Question 9

Which zone of a rocky shore does tide never fully cover?

Answer 9

The ‘splash zone’, above the upper shore.

Question 10

Name an organism found in high water.

Answer 10

Brown algae/seaweed.

Pelvetia canaliculata

Question 11

Name the seaweed found at low water.

Answer 11

Fucus serratus

Question 12

What is the fleshy algae normally found at the bottom of rocky shores?

Answer 12

Laminaria species.

Question 13

Where on the rocky shore are limpets found?

Answer 13

At highest high tide.

Question 14

What kind of organisms are normally found at lowest tide zone?

Answer 14

Soft-body organisms, such as sponges.

Question 15

Name a species of lichen that is similar to a marine woodlouse.

Answer 15

Ligia italic

Question 16

Name an organism found in the intertidal / Eulittoral zone within the:

a) Upper littoral
b) Mid-littoral
c) Lower littoral

Answer 16

a) Upper littoral = barnacles
b) Mid-littoral = limpets
c) Lower littoral = Actinia species (anemone)

Question 17

Name some organisms that are found in the sublittoral.

Answer 17

• Kelps
• Soft sponges
• Urchins

Question 18

Why do organisms at the bottom of the shore need to be more sticky?

Answer 18

Exposed to surging waves, which can remove things.

Question 19

Name four biotic factors determining the distribution of organisms in a rocky shore habitat.

Answer 19

• Thermal tolerance
• Food availability
• Competition (for space and resources)
• Predation

Question 20

Describe seaweed zonation in a rocky shore.

Answer 20

• Top of shore; Helvetia
• Upper shore; Fucus spiralis
• Mid shore; Fucus vesiculosus and Ascophyllum.
• Then Fucus serrates
• Then Laminaria

Question 21

Describe Pelvetia.

Answer 21

Small, with waxy appearance.
Needs to be exposed.
Thick cuticle, preventing it from drying out.
Not good at photosynthesis as waxy cuticle prevents light from penetrating.

Question 22

Describe Fucus spiralis.

Answer 22

Traps moisture inside the spiral form, keeping moisture inside the fronds.

Question 23

Describe Fucus vesiculosus.

Answer 23

Has gas bubbles that enable it to float as tide comes in.

Question 24

Describe Ascophyllum.

Answer 24

Flatter fronds.

Better at photosynthesis, but dries out quicker.

Question 25

Describe Fucus serratus.

Answer 25

Very flat with serrated edge.

Question 26

Describe Laminaria.

Answer 26

Requires immersion. | Long fronds that can reach the surface when tide is in.

Question 27

What are upper limits of distribution determined by?

Answer 27

Desiccation tolerances

Question 28

What are lower limits of distribution determined by?

Answer 28

- Competition for space | - Grazing invertebrates, e.g. limpets

Question 29

What are epiphytes?

Answer 29

Plants that grow on top of other plants.

Question 30

Why are seaweeds often referred to as microhabitats?

Answer 30

Remain moist when tide is out, and provide habitats for - Epiphytes - Small animals Bryozoans form colonies on fucoid fronds.

Question 31

Which grazers tend to be found in the middle shore?

Answer 31

Molluscs/gastropods. Most commonly: - Limpets - Large periwinkle

Question 32

What grazer is normally found in lower shores?

Answer 32

Urchins

Question 33

Name the most common UK species of a) Limpet b) Sea urchins

Answer 33

a) Limpet = Patella vulgata | b) Sea urchin = Strongylocentrotus purpuratus

Question 34

How are barnacles adapted for water loss?

Answer 34

Have thick calcium carbonate plates that water cannot evaporate through. When pull legs back in, they trap water inside the plates, to prevent them from drying out.

Question 35

Describe an adaptation of Patella limpets for water loss.

Answer 35

Have secondary gills around the margin of the shell, and use water trapped on the rock surface around the edge of the gill.

Question 36

Where do marine invertebrates found in rocky shores mostly lose their heat from?

Answer 36

Their foot

Question 37

Describe the body structure of upper shore marine invertebrates to reduce heat exchange.

Answer 37

Small - tuck into nooks and crannies. | Dome structure, keeps their foot small relative to the size of their body.

Question 38

Describe the body structure of lower shore marine invertebrates.

Answer 38

Flatter. | Have bigger feet.

Question 39

Describe zonation in periwinkles.

Answer 39

- Top of shore; small periwinkle (Melarhaphe neritoides). - Upper shore; Littorina saxitalis. - Midshore; flat periwinkle Littorina obtusa. - Bottom of shore; Littorina littorea (common periwinkle).

Question 40

Describe some adaptations in periwinkles.

Answer 40

- Shells are light coloured, to reflect light and prevent heating - Produce uric acid rather than ammonia to prevent water loss. - High enzyme heat capacity. - Can lower metabolic rate.

Question 41

Describe some adaptations to wave action in a) Molluscs b) Mussels c) Sea stars d) Isopods e) Kelps

Answer 41

a) Molluscs = low-profile, hydrodynamic shells. b) Mussels = tethering byssal threads and glues. c) Sea stars = thousands of suctioning tube feet. d) Isopods = hook-like appendages. e) Kelps = avoid breaking in high flow locations with their strength and flexibility.

Question 42

What is stronger: the suctioning feet of sea stars, or beds threads of mussels?

Answer 42

Byssal threads of mussels

Question 43

Why are mussel larvae more prone to desiccation stress?

Answer 43

Have larvae that float in the pelagic zone and do not have an adult shell.

Question 44

What is the distribution of mussels driven by?

Answer 44

Where larvae can settle without driving out when tide goes out.

Question 45

What enhances the settlement of mussel larvae?

Answer 45

The presence of barnacles, by providing rough-tetuned surfaces.

Question 46

What is the lower boundary of mussel distribution set by?

Answer 46

Starfish predation

Question 47

Describe Connell's (1961) paper.

Answer 47

- Competition in species distribution. - C stellatus and S balanoides species of barnacles. - C stilettos better at surviving heat and desiccation upshore, but down shore there is competition between the two barnacles - S balanoides can grow faster than C stellatus.

Question 48

What are the key predators for barnacles?

Answer 48

Dog whelks

Question 49

Describe a modification of dog whelks as predators.

Answer 49

Have a modified radula that drills into shells, injecting a paralytic enzyme. Can feed on things much bigger than themselves.

Question 50

Describe the work of Paine (1969).

Answer 50

- First discovered role of starfish in maintaining diversity - Pisaster ochracceuss; predates on mussels, controls their lower limit of the shore. - Removing starfish left mussels to take over the shore, and greatly reduced community diversity.