Seaweed Ecology

Question 1

• What is periphyton?

Answer 1

a complex mixture of microalgae, bacteria and fungi often held together in a mucilaginous matrix and attached to substrates

Question 2

Describe in a diagram the fate of macroalgal primary production in a food web.

Question 3

• What factors can affect vertical zonation in macroalgae?

Answer 3

Wave action
Light Availability
Type of substratum
Resistance to dessication
Grazing
Competition

Question 4

• Name 3 effects of exposure to air on seaweeds.

Answer 4

Lose source of exposed nutrients
May become desiccated
May receive damaging levels of solar radiation

Question 5

• What are the 3 nearly-universal intertidal zones?

Answer 5

An uppermost black strip of highly desiccation-tolerant cyanobacteria, marine lichen and snails

Intermediate zone of seaweeds, together with limpets, and barnacles

A lowermost zone inhabited by laminarialean, brown algae or corals

Question 6

• In regards to seaweeds, what is a boundary layer and under what conditions (of water movement) is it better established?

Answer 6

The layer around seaweed where there is a barrier to the diffusion of nutrients
Under low water movement the boundary layer is maintained

Question 7

• Describe the pros and cons of water movement for seaweed.

Answer 7

Pros:
Reduce self-shading
Constant supply of inorganic nutrients
Increase nutrient exchange
Spore dispersal
Remove sessile grazers

Cons:
Cause damage

Question 8

What are the 4 main components of macroalgal adaptation that dissipate the effect of drag forces?

Answer 8

Elasticity in tension (stretchiness)
Elasticity in bending (flexibility)
Torsion (twisting)
Breaking strain (strength)

Question 9

Describe the blade adaptations of the sublittoral kelp Nereocystis living in sheltered and energetic (moving water) environments

Answer 9

Moving Water
Narrow smooth blades that reduce drag

Slow Water
Wide ruffled blades that create turbulence and reduce boundary layer

Question 10

What are some seaweed adaptations to irradiance in the intertidal and subtidal?

Answer 10

UV-absorbing compounds like beta-carotene and aromatic amino acids
increase the number of inactive photosynthetic reaction centers

Question 11

• What is photoinhibition?

Answer 11

When high levels of light cause the depression of photosynthetic activity and photo-oxidation

Question 12

What are the effects of decreasing and increasing salinity and air exposure on seaweeds?

Answer 12

Air Exposure:
Dehydration
Increase cellular solute concentrations
lose the ability to take up dissolved nutrients

Question 13

• What factors influence nutrient uptake in macroalgae and why?

Answer 13

Water Motion: Still-water increases the boundary layer making a nutrient exchange difficult.

Frond Arrangement: Bundled fronds do not uptake nutrients as well

Air Exposure: Reduces ability to uptake nutrients

Temperature/Irradiance: Also play a role

Age

Question 14

Briefly describe the main physical and biological factors that affect kelp communities.

Answer 14

Disturbance: Such as storms and other weather events that can destroy kelp

Behavioural changes in herbivores: Structured by the herbivore community

Competition for Light

Grazing pressure

Question 15

Where are kelp forests most commonly found in the world’s oceans?

Answer 15

West coast of North America (non-equatorial)
West coast of South America (non-equatorial)
South Africa and South Austrialia
East coast New Zealand

Question 16

Explain how storms can influence kelp-sea urchin interactions, and favor the development of barren areas within kelp forests.

Answer 16

When storms rip out most of the kelp in a system the urchins graze any new recruits that try and recolonize and maintain the turf environments

Question 17

Describe with labeled diagrams the effects of changes in carnivores and herbivores (the effects of trophic cascades) on kelp forest density over time.