L5 Rocky shores

Question 1

How does the degree of wave exposure affect the Rocky shore?

Answer 1

If v exposed - severe pressure from wave action

• anemones clamp down to be more compact
• seaweeds adapted to be more flexible - lack lignin, and strong holdfast. Able to regenerate blades high in meristem
• mussels cluster (using bysall threads) to reduce exposure as water flows over them. But if too much clustering can become free from substrate.

Question 2

What does variable tidal amplitude

Answer 2

Variable periods of immersion and emersion, desiccation and time in light.

Question 3

Where do abiotic and biotic features have most effect on the rocky shore?

Answer 3

Highest - Supralittoral fringe - Most effect from abiotic features.
Infra littoral and at the lowest tides there is most effect from biotic features.

Question 4

What species are present in the supralittoral zone?

Answer 4

littorina saxatalis
Lichens
Ephemeral algae

Question 5

What species are present in the midlittoral zone?

Answer 5

Barnacles
Mussels
Fucoids
Limpets

Question 6

What species are present in the infralittoral zone?

Answer 6

Red algal turfs

Kelps

Question 7

What species are present in the lowest tidal zone?

Answer 7

Small red algae
Urchins
Sessile animals

Question 8

How do littorina cope with desiccation?

Answer 8

Move to moist crevice

Clamp to rock ad seal tight with operculum to reduce water loss

Question 9

What is under strong competition?

Answer 9

Space - some organisms grow on top of each other.

Question 10

On UK rocky shores, what species dominates the Littoral fringe?

Answer 10

Littorina saxatilis

Question 11

On UK rocky shores, what species 4 dominate the Eulittoral fringe?

Answer 11

Semibalanus balanoides
Pelvetia canaliculata
Fucus spiralis
Patella vulgata

Question 12

On UK rocky shores, what 2 species dominate the sublittoral fringe?

Answer 12

Fucus serratus

Laminaria digitata

Question 13

describe recolonisation of the rocky shore

Answer 13

1978 Porthleven, Cornwall, had oil spill.
First year - Enteromorpha (ulva) rapid growth as surfactant promoted growth and no grazers to control it.
Second year - Fucus grows and colonises
Decade later - Arrival of limpets which graze on macroalgae.

Question 14

what demonstrates competition between macroalgae?

Answer 14

Ususally pelvetia grown shallower than Fucus.

If Fucus removed, Pelvetia cannot grow higher as it cannot survive due to desiccation and waves bringing new Pelvetia.

Question 15

Explain the zonation of 2 barnacle species

Answer 15

Chthamalous found shallower than Semibalanus
Larvae settle - Chthamalous in shallows, and semibalanus all over. Adult semibalanus can’t survive light, temp and dessication factors so is restricted to lover regions. Small overlap.
Competition then limits Chthamalous to upper levels.

Question 16

Describe an experiment showing how dog whelk predation maintains diversity.

Answer 16

3 communities

1. Control, Nucella present - semibalanus pop high then mussels overtake. However both kept low.
2. Nucella excluded - Semibalanus rise and quickly fall, died out. Mussels rise and stay high.
3. Nucella and mussels excluded - Semibalanus rises, fucus rises.

Question 17

What can be used as an alternative to removal experiments

Answer 17

Cages

Question 18

Describe an experiment which showed starfish to be a keystone species

Answer 18

Sea stars are a predatory structuring force.
Spring 1963-summer 1968 manually removed sea stars in Mukkaw bay
Mussels colonised, replacing barnacles and dominating the shore.

Question 19

Describe how changing sea temp has causes virus spread in starfish MORE INFO

Answer 19

Legs go mushy and detach. Move elsewhere and get broken down.
Sea surface temperature changes cause stress easily to starfish.
Radius if starfish reduced. Larval recruitment will affect recovery of starfish from decline.

Question 20

What is the intermediate disturbance hypothesis?

Answer 20

When a clear patch of seashore occurs, patterns of recolonisation can be difficult to predict. Depends on the time of year, what species are initially there, which reaches the space first etc..
Used to think zones were predictable, but now see that zones aren’t fixed and species can move up and down.
Medium amount of disturbance gives greatest diversity
Suggested by Connell JH 1978, but Pfaff 2010 suggests not the case for rocky shores.