Kelp Forest Zonation
Canopy
Understory
Algal Turf
Offshore
(Z3)
Kelp Canopy
(Z2)
Inshore
(Z1)
Phyllospadix
Egregia
Laminaria
Nereocystis
Macrocystis
A. Canopy Assemblages (isopods, tubeworms, hydrozoans and bryozoans)
B. Planktonic Assemblages (jellyfish, fish larvae, diatoms, and crustaceans).
C. Holdfast Assemblages (sea urchins, crustaceans, brittle stars, and sea anemones)
D. Horizontal Substrate Assemblages (urchins, sea stars, algae, tunicates, and bottom fish).
E. Vertical Wall Assemblages (coralline algae, anemones, cup corals, sponges, and bryozoans)
Canopy
Plankton
Holdfast Community
Vertical Wall
Horizontal Surface
Ecological Relationships in Kelp Forests
Kelp
Orca
Sea Otter
Urchins
Ecological Relationships in Kelp Forests - Aleutian Archipelago
Adak Island
Ecological Relationships in Kelp Forests - Aleutian Archipelago
Otter #
1972
1997
Ecological Relationships in Kelp Forests - Aleutian Archipelago
Otter #
Urchin
Biomass
1972
1997
Ecological Relationships in Kelp Forests - Aleutian Archipelago
Otter #
Urchin
Biomass
Grazing
Intensity
1972
1997
Ecological Relationships in Kelp Forests - Aleutian Archipelago
Otter #
Urchin
Biomass
Grazing
Intensity
Kelp
Density
1972
1997
Mortality of Kelp - Effect of El Niño event
Recovery of community (Ebeling et al., 1985)
Original situation
- Macrocystis canopy, understory kelp (Pterygophora)
- urchins S. purpuratus & S. franciscanus feed in crevices on drift kelp
Destroyed kelp (Macrocystis) canopy but left understory kelp
Storm 1
Reduction in drift kelp used by urchins
Urchins forage in open on understory kelp
Urchins destroy remaining kelp
Storm 2
Kelp settlement and mature
forest (1 year)
Kills urchins and left bare rock
Mortality of Kelp - Effect of El Niño event
Other El Niño Effects
-rip up holdfasts  no vegetative growth
-high water temperature  retards growth
-reduction in nitrogen  retards growth
General Model for Maintenance of Barrens and Kelp areas
BARRENS
High grazing activity
KELP
Low drift
abundance
Low algal recruitment
Low grazing activity
High drift
abundance
High algal recruitment
Low standing
stock of
attached
algae
Severe storms
Low nutrient
Warm temperatures
High standing
stock of
attached
algae
Benign storms
High nutrient
Low temperatures
STABLE STATES
General Model for Maintenance of Barrens and Kelp areas
Barren Ground
Kelp Forest
- created by urchin grazing
-abundant drift kelp
-little drift kelp
- urchins remain in crevices
- urchins actively forage
Recruitment of kelp
Effect of urchins due to a change in behaviour not numbers
Harold & Reed, 1985
General Model for Maintenance of Barrens and Kelp areas
Effect of urchins due to a change in behaviour not numbers
Harold & Reed, 1985
General Model for Maintenance of Barrens and Kelp areas
Harold & Reed, 1985
Kelp Forest Food Web (with otters)
Sharks
Larger fish & octopus
Sea otter
Larger crabs
Sea stars
Abalone
Smaller predatory
Fish and invertebrates
Sea urchins
Drift algae &
dead animals
Small herbivorous fish &
invertebrates
Sessile invertebrates
Planktonic invertebrates
Kelp and other algae
Planktonic algae
Kelp Forest Food Web (without otters)
Sharks
Larger fish & octopus
Sea otter
Larger crabs
Sea stars
Abalone
Smaller predatory
Fish and invertebrates
Sea urchins
Drift algae &
dead animals
Small herbivorous fish &
invertebrates
Sessile invertebrates
Planktonic invertebrates
Kelp and other algae
Planktonic algae
Kelp Forest Productivity
50
3.0
40
2.5
30 Producer
Biomass
Kg/m2
Annual Net 2.0
Production
1.5
Kg/m2/yr
Litter Mass
Kg/m2/yr
20
1.0
10
0.5
0
Tropical Tropical
Rain
Seasonal
Forest
Forest
Evergreen
Forest
Deciduous
Forest
Boreal
Forest
Kelp
Forest
0
Kelp Forest Productivity
SUSPENSION
FEEDERS
Mussel
Soft coral
Barnacle
Sea Anemone
Rock Jingle
Mysid
DETRITIVORES
Amphipod
Crab
PREDATORS
Rock greenling
Sea star
Cormorant
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Percent of Kelp Derived Carbon
Next time
Coral Reefs