Rocky Shores

Question 1

Ideal habitat for study

Answer 1

Higher taxonomic diversity
Easy access for ecological study
Global habitat type
One of the oldest habitat types
Many groups well represented in Natural History Museums.
Good study system to assess human impacts

Question 2

Macrofauna/flora

Answer 2

What we can see with the naked eye.
228 animal species and 155 algae species.
>1mm

Question 3

Meiofauna

Answer 3

<1mm, as many as 1 million animas per metre squared.
Ostracods, amphipods, gastropods, forams.
Especially diverse in turf forming algae

Question 4

Primary producers

Answer 4

Diatoms:
- Microalgae
-First things to colonize a rocky habitat
Filamentous algae
Foliose algae
Macrophytes
Leathery macrophytes
Articulated calcareous algae
Crustose coralline algae

Question 5

Sea weeds

Answer 5

Grouped by their colour.
- Chlorophyta, green.
- Rhodophyta, red.
- Phaeophyta, brown.

Question 6

Grazers

Answer 6

Limpets, periwinkles, urchins, top shells.

Question 7

Filter feeders

Answer 7

Barnacles, sponges, sea squirts, mussels.
Wave impacted areas of rocky shores.

Question 8

Predators

Answer 8

Shore crab, sea star, birds, dogwhelks.
Predation pressure can affect the distribution and abundance of organisms on the rocky shore, top down impacts.
Predation pressure can also affect the morphology of their prey, predator induced defenses.
Phenotypic response or evolutionary change.

Question 9

Zonation classification scheme

Answer 9

High intertidal, lichens, periwinkles, barnacles, isopods.
Mid intertidal, barnacles, limpets, mussels
Low intertidal, sea stars, kelp, macroalgae.
Littoral zone across all 3

Question 10

Exposed and sheltered shores

Answer 10

Exposed, a lot of filter feeders, lots of water movement and water action.
Sheltered, lots of algae and grazers.

Question 11

Zonation causes

Answer 11

Larval settlements/recruitment and adult preference
Physiological tolerance to environment variables
Biological interactions:
- Interspecific competition.
- Predation

Question 12

Influence of recruitment supply on zonation

Answer 12

Higher recruitment = high larval development.
Higher competition for space, lower limits are set by presence of a dominant competitor.
Low recruitment, the distinct zonation breaks down since space is not limiting and competition for space doesn’t occur.

Question 13

Physiological tolerance to emersion

Answer 13

Low tide causes desiccation and heat stress problems.
Upper distribution of organisms broadly reflects their thermal limit.
Distribution can be modified by moving into crevices, rock pools, SA:V, limiting water loss, living in dense groups.

Question 14

Rock temperatures under canopies

Answer 14

Seaweed canopies and rock crevices help buffer organisms from both heat and desiccation stress associated with tidal emersion.
Distributions can extend up shore in the presence of seaweeds.

Question 15

Biological interactions

Answer 15

Predator-prey
When the predatory sea star was removed, the mussels and stalked barnacles moved down shore.

Question 16

Vertical distribution of rocky intertidal species

Answer 16

Rocky intertidal species are distributed vertically, according to their capability to cope physiologically with changes in physical factors and response to biological interactions.

Question 17

Larval ecology

Answer 17

70% of benthic invertebrates have planktonic larvae.
Settlement of larvae is not a random process, chemical and physical cues.

Question 18

Types of larvae

Answer 18

Direct developing:
- Juveniles hatch from eggs and “crawl away”
Lecithotrophic:
- Larvae are planktonic using a yolk-sac for nourishment
Planktotrophic
- Larvae are free-swimming and feeding.

Question 19

Direct developers

Answer 19

Dogwhelks.
Advantages:
- Predictable food source.
- No water column predators.
- Suitable habitat ready when hatched.
Disadvantages:
- Large reproductive cost for mothers.
- Few eggs.
- Poor dispersal.
- Benthic predators.

Question 20

Lecithotrophic

Answer 20

Limpets
Advantages:
- Own food supply.
- Less time for predation.
- close to suitable habitat.
Disadvantages:
- Fewer larvae produced.
- Lower dispersal distances.

Question 21

Planktotrophic:

Answer 21

Barnacles
Advantages:
- Large numbers are produced.
- Capable of staying in the water column for a long time, increasing dispersal distances.
Disadvantages:
- Unpredictable food sources
- Long exposure to predators.
- Last development stage needs to be timed when suitable habitat is found for settlement.

Question 22

Why have a pelagic larval phase

Answer 22

Larvae decreases competition between life stages
Disperse long distances, colonization of new regions.
Long pelagic phases can break parasite life cycles.
Pelagic larvae do not have benthic predators.

Question 23

Interactions with other species

Answer 23

Giant Kelp:
- Just offshore rocky coasts.
- Kelp forest slow current speeds.
- Helps larvae of rocky shore species to stay close to suitable habitat.
Mussel beds:
- Juveniles live within mussels and then move to bare rock as they grow into adults.

Question 24

Role of competition

Answer 24

Important when resources are limiting.
Types:
- Exploitative: ability to harvest limiting food resources.
- Pre-emptive: competitor recruits to and dominates space.
- Interference: competitors physically contest resources.
Large size and rapid growth translate into competitive dominance in many organisms.
Competition can occur with species or between them.

Question 25

Role of grazers

Answer 25

Limpet can defend a territory.
Physically push mussels off.

Question 26

Hume range scaling

Answer 26

Large limpet needs a larger territory.
Less grazing space means a shift in space occupancy.
Less area available for limpet to grow and feed, harder to increase home range size.

Question 27

Role of predators

Answer 27

Role of dogwhelks where seaweed fucus was removed.
Control, nucella ate many barnacles and mussels.
No nucella, mussels dominated.
No nucella and mussels, fucus resettled.
Oystercatcher birds not common in dog walking areas, in sheltered areas eat lots of limpets.

Question 28

Indirect effects of predation

Answer 28

Starfish play important role in maintained species diversity and community structure through indirect and direct effects.

Question 29

Community interactions:

Answer 29

Recruitment success
Resources
Growth rates and body size/shape
Competitive ability
Biodiversity
Predatory effects
Disturbance

Question 30

Biogeographic range limits

Answer 30

Affected by life history, population, genetics, abundance distribution, spatial availability of habitat, atmospheric factors or a combination.

Question 31

Biogeography of S Africa rocky shores

Answer 31

West coast:
- extensive kelp beds, v high production.
- many sea birds.
- kelps, brown and green algae, limpets, littorinids.
East coast:
- Subtropical community.
- low production
- greater diversity.
- Corals, coralline algae, barnacles, tube worms, oysters, whelks.

Question 32

Habitat Gaps

Answer 32

Sand beach between rocky shores can create a gap in range limits.
Larvae can’t make it across the sand to new rocky area.

Question 33

Climate change

Answer 33

Warmest sea-surface temperatures recorded in history.
Many southern warm species are moving North

Question 34

Artificial rocky substrates

Answer 34

Biodiversity is like natural substrate.
Seawalls, jetties, groynes, piers, riprap.

Question 35

Artifical coastal habitat can

Answer 35

Increase overall size of geographic rangers.
Increase genetic connectivity between populations.
be used as stepping stones for the spread of invasive species or range expansion of native species.

Question 36

Harvesting

Answer 36

Size-selective
Major food source for 125000+ years