Rocky shore ecosystem I

Question 1

Why does the unique structure and species distribution occur at the rocky shore?

Answer 1

• Water movement results in gradual transition between the marine and terrestrial environments
• Organisms can withstand different degrees of stress
• Universal because of emersion & immersion (tides and wave action) is the overriding factor controlling species composition and distribution

The position in the intertidal zone determines stress

Question 2

Explain how tides are generated

Answer 2

• semidiurnal variation because of moon rotating around the earth
• about 1h later every day
• variation of tides adds to stress of organisms in the intertidal zone
• moon is the main cause of tides

Question 3

What is the difference between spring and neap tide?

Answer 3

• Spring - amplitude is increased
• neap - amplitude is decreased

Question 4

Describe the tidal division at a rocky shore

Answer 4

Supralittoral (spray zone)

• influenced by salt spray
• salt tolerant lichens

Supralittoral fringe

• wave splash, covered at mean high water spring
• low diversity
• black lichens, periwinkle snails

Midlitoral

• regular immersion and emersion (mean high water - mean low water)
• subdivided
• barnacles
• oysters and/or mussels
• polychaete tube worms
• algae

Infra - or sublittoral zone

rarely uncovered

dominated by kelps

Question 5

how does wave exposure influence the zonation of the rocky shore community?

Answer 5

expansion of areas and loss of some sp.

Question 6

How can different substrate (e.g. rocks) extend the vertical zone of rocky shore organisms?

Answer 6

a lag of wave exposure causes desiccation

• > cracks in rocks can supply food where clusters of barnacles may accumulate
• > rock snails (e.g. neriata) cluster together to decrease surface area during low tide to reduce risk of drying out

Question 7

Is macroalgae a primary food source at the rocky shore?

Answer 7

No - low in nitrogen and high in carbon and fiber -> hard to digest

However, they fix a lot of carbon and provide crucial habitat

Question 8

What is the main food source at the rocky shore?

Answer 8

Microalgae - high nutritional value and high turn over rate

therefore most organisms are suspension feeders and feed on microalgae

Question 9

What are some characteristics of barnacles?

Answer 9

• crustaceans (sessile)
• filter feeders
• main food sources is phytoplankton
• occupy space (compete with algae)
• > intense competition with algae for space

Question 10

Why is it not recommended to remove a snail from a rock?

Answer 10

they have a home scar to which they return after foraging for food. their shell fits the scar and provides additional protection from desiccation and predators during low tide

Question 11

What mobile grazers can be found at the rocky shore and what is their niche?

Answer 11

• gastropods and echinoderms
• includes limpets, chitons, topshells
• adaptive radula
• require open space
• important structuring force (remove algal spores and larvae)
• compete with encrusting species

Question 12

What mobile predators can be found at the intertidal zone?

what is their niche?

Answer 12

• echinoderms and gastropods
• feed on encrusting species
• create space
• important structuring force

they are very effective predators always racing with the time due to tidal variation -> fewer predators found the further up from the littoral zone

Question 13

What are some adaptation for the aquatic organisms that live in the semi-terrestrial environment of the intertidal zone?

Answer 13

mechanical stress

• limitation in size
• shape
• attachment

salinity stress

• osmoconformers (go with water loss)
• heat balance (e.g. different sculptured and colored shells of snails)*
• water loss (can loose up to 60% water (ulva sp.) to 75% water (chiton))*