Lecture 4 Flashcards
What factors strongly affect the nature of rocky shores?
- Particle size
- Degree of wave exposure
When are tides largest?
At the new moon and full moon, as there is gravitational pull in the same direction from both the moon and the sun at these times - greatest tidal amplitude
Tide terminology
Supralittoral / littoral fringe / splash zone = extreme high water of spring tides
Intertidal / eulittoral / midlittoral = mean tide level
Sublittoral = Extreme low water of spring tides
Abiotic constraints of rocky shores
- Variable periods of immersion and emersion
- Variable periods of desiccation
- Variable periods of time to feed when tide is in or photosynthesis effectively
- Waves may cause damage
- Larval stages vulnerable
- Competition for space on rocks
How does a periwinkle cope with desiccation?
- Move to moist crevice
- Clamp to rock and seal shell with operculum
What rockweeds are exposed at low tide?
Spiral rockweed and sea rockweed
What are methods used to cope with wave action?
Motile organisms shelter or clamp down from wave action
Sessile organisms can adapt in ways such as having a more compact shape to reduce the area exposed to wave action (sea anemone)
Adaptations to wave action in kelp
- Flexible stipe
- Streamlined shape
- Strong holdfast
- Meristem at base so won’t be lost to wave action
Adaptations of mussels to wave action
- Bysall threads attach them to rocks
- Group formation for protection due to reduced exposure so water flows over - risky as too much strain on those attacked to rock
What is the Intermediate Disturbance Hypothesis?
Shore zones are not fixed in position and species can migrate up and down
When a clear patch occurs, patterns of recolonisation and regrowth (or succession) can be difficult to predict
What regrows depends on what reaches the space first, the time of year, size of space, etc.
What is the significance of green algae in the marine environment?
Primary producers
Calcareous algae are important sources of calcareous deposits in coral reefs
What is the significance of brown algae in the marine environment?
Primary producers
Dominant components of kelp forests
What is the significance of red algae in the marine environment?
Primary producers
Coralline algae important sources of calcareous deposits in coral reefs
What is the significance of flowering plants in the marine environment?
Dominant primary producers in seagrass beds, salt marshes and mangrove forests
Nursery grounds for many species
Help stabilise soft sediment
Protect coast from turbulence
