Lecture 8 - Rocky Shores Flashcards

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1
Q

Are rocky shores generally high or low energy?

A

High, depending on their exposure to waves.

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2
Q

In what way are rocky shores similar to reefs?

A

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

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3
Q

What acts as food for detritivores in rocky shores?

A

Broken/rotting seaweed

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4
Q

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

A
  • High primary productivity
  • Low sediment supply
  • Stable substrate that erodes slowly
  • Diverse habitat types present (ledges, overhangs, crevices, pools etc.)
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5
Q

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

A
  • Desiccation
  • Wave action
  • Temperature fluctuation
  • Salinity fluctuations
  • Range of illumination
  • Double predation
  • Pollution
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6
Q

Give the three zonations in a rocky shore environment.

A
  • Upper shore (furthest from ocean)
  • Middle shore
  • Lower shore (edge of ocean)
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7
Q

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

A

Submergence

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8
Q

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

A

Lichens

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9
Q

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

A

The ‘splash zone’, above the upper shore.

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10
Q

Name an organism found in high water.

A

Brown algae/seaweed.

Pelvetia canaliculata

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11
Q

Name the seaweed found at low water.

A

Fucus serratus

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12
Q

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

A

Laminaria species.

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13
Q

Where on the rocky shore are limpets found?

A

At highest high tide.

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14
Q

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

A

Soft-body organisms, such as sponges.

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15
Q

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

A

Ligia italic

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16
Q

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

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

A

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

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17
Q

Name some organisms that are found in the sublittoral.

A
  • Kelps
  • Soft sponges
  • Urchins
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18
Q

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

A

Exposed to surging waves, which can remove things.

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19
Q

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

A
  • Thermal tolerance
  • Food availability
  • Competition (for space and resources)
  • Predation
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20
Q

Describe seaweed zonation in a rocky shore.

A
  • Top of shore; Helvetia
  • Upper shore; Fucus spiralis
  • Mid shore; Fucus vesiculosus and Ascophyllum.
  • Then Fucus serrates
  • Then Laminaria
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21
Q

Describe Pelvetia.

A

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.

22
Q

Describe Fucus spiralis.

A

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

23
Q

Describe Fucus vesiculosus.

A

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

24
Q

Describe Ascophyllum.

A

Flatter fronds.

Better at photosynthesis, but dries out quicker.

25
Q

Describe Fucus serratus.

A

Very flat with serrated edge.

26
Q

Describe Laminaria.

A

Requires immersion.

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

27
Q

What are upper limits of distribution determined by?

A

Desiccation tolerances

28
Q

What are lower limits of distribution determined by?

A
  • Competition for space

- Grazing invertebrates, e.g. limpets

29
Q

What are epiphytes?

A

Plants that grow on top of other plants.

30
Q

Why are seaweeds often referred to as microhabitats?

A

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

31
Q

Which grazers tend to be found in the middle shore?

A

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

32
Q

What grazer is normally found in lower shores?

A

Urchins

33
Q

Name the most common UK species of

a) Limpet
b) Sea urchins

A

a) Limpet = Patella vulgata

b) Sea urchin = Strongylocentrotus purpuratus

34
Q

How are barnacles adapted for water loss?

A

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.

35
Q

Describe an adaptation of Patella limpets for water loss.

A

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

36
Q

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

A

Their foot

37
Q

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

A

Small - tuck into nooks and crannies.

Dome structure, keeps their foot small relative to the size of their body.

38
Q

Describe the body structure of lower shore marine invertebrates.

A

Flatter.

Have bigger feet.

39
Q

Describe zonation in periwinkles.

A
  • Top of shore; small periwinkle (Melarhaphe neritoides).
  • Upper shore; Littorina saxitalis.
  • Midshore; flat periwinkle Littorina obtusa.
  • Bottom of shore; Littorina littorea (common periwinkle).
40
Q

Describe some adaptations in periwinkles.

A
  • 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.
41
Q

Describe some adaptations to wave action in

a) Molluscs
b) Mussels
c) Sea stars
d) Isopods
e) Kelps

A

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.

42
Q

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

A

Byssal threads of mussels

43
Q

Why are mussel larvae more prone to desiccation stress?

A

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

44
Q

What is the distribution of mussels driven by?

A

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

45
Q

What enhances the settlement of mussel larvae?

A

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

46
Q

What is the lower boundary of mussel distribution set by?

A

Starfish predation

47
Q

Describe Connell’s (1961) paper.

A
  • 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.
48
Q

What are the key predators for barnacles?

A

Dog whelks

49
Q

Describe a modification of dog whelks as predators.

A

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

50
Q

Describe the work of Paine (1969).

A
  • 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.