Kelp forests

Question 1

What are the common kelp species in NZ?

Answer 1

• Ecklonia radiata
• Lessonia spp
• Carpophyllum spp
• Crystophora spp
• Sargassum spp

Question 2

What determines the distribution of kelp globally?

Answer 2

Ocean temperature (like the cold) and ocean currents -> distributed further north or south depending on the oceanic gyres direction of circulation (anti clockwise on southern hemisphere and clockwise on northern hemisphere)

Question 3

What are the three main orders of kelp in NZ?

Answer 3

• Durvilleles (bull kelp)
• Lamminariales (Ecklonia radiata)
• Frucales (Carpophyllum)

Question 4

What is the significance of Macrocystis pyrifera dispersal?

Answer 4

Male and female haploid gametophytes drop to the sea floor rapidly (8m range) where they fertilize and grow to diploid sporophyte.

The dispersal of the seaweed is happening during the adult face when the plant detaches from the substrate floating around with currents to drop gametophytes elsewhere

Question 5

What physical factors regulate seaweed productivity?

Answer 5

• Light (photosynthesis) -> turbidity in coastal water is a problem
• nutrients (need nitrate) -> can store nutrients and disperse them to adapt to different environments
• water movement (essential for maintaining nutrient supply) -> severe storms can destroy kelp beds

Question 6

What effects do kelp forests have on the community structure?

Answer 6

• Light intensity
• Reduce currents and waves
• Alter habitat complexity
• Food source
• Reduce dissolved nutrient concentration (coming from land)

Question 7

What is the fate of kelp production?

Answer 7

• DOM (15%) leaches off the plant to be consumed by bacteria -> bacteria consumed by filter feeders
• POM (70%) breaks off the plant together with DOM (15%) which is either directly consumed by filter feeders or bacteria that are then eaten by filter feeders

Question 8

How does a kelp forest tip to an alternative state due to environmental conditions?

(California)

Answer 8

behavioral change at alternative state as urchins move collectively feeding on algae as a result of lack of resources forcing them to leave their protective shelters.

-> difficult to flip back to stable state

Question 9

How does a kelp forest tip to an alternative state due to overfishing of rock lobster?

(Nova Scotia)

Answer 9

Trophic cascade due to the low abundance of apex predator (rock lobster) praying on urchins

-> a disease occurring every 20 years (hypothesis) might be responsible for wiping out urchin populations

Question 10

How does the lack of sea otters affect kelp forests?

Answer 10

• No sea otters (prey on urchins that eat kelp) -> no kelp forests
• More sea otters -> more kelp

now orcas prey on otters as salmon is depleted -> causing trophic cascade as humans did with the killing of otters