Kelp Forest Zonation

Inshore(Z1)

Kelp Canopy(Z2)Offshore

(Z3)

Canopy

Understory

Algal Turf

Macrocystis

Laminaria

Egregia Nereocystis

Phyllospadix

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)

Holdfast Community

Plankton

Canopy

Vertical Wall

Horizontal Surface

Orca

Sea Otter

Kelp

Urchins

Ecological Relationships in Kelp Forests

Ecological Relationships in Kelp Forests - Aleutian Archipelago

Adak Island

Ecological Relationships in Kelp Forests - Aleutian Archipelago

1972 1997

Otter #

Ecological Relationships in Kelp Forests - Aleutian Archipelago

1972 1997

Otter #

Urchin Biomass

Ecological Relationships in Kelp Forests - Aleutian Archipelago

1972 1997

Otter #

Urchin Biomass

Grazing Intensity

Ecological Relationships in Kelp Forests - Aleutian Archipelago

1972 1997

Otter #

Urchin Biomass

Grazing Intensity

Kelp Density

Mortality of Kelp - Effect of El Niño event

Recovery of community (Ebeling et al., 1985)

Destroyed kelp (Macrocystis) canopy but left understory kelp

Original situation - Macrocystis canopy, understory kelp (Pterygophora)- urchins S. purpuratus & S. franciscanus feed in crevices on drift kelp

Reduction in drift kelp used by urchins

Urchins forage in open on understory kelp

Urchins destroy remaining kelp

Storm 1

Storm 2 Kills urchins and left bare rock

Kelp settlement and mature forest (1 year)

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

Low algal recruitment

Severe stormsLow nutrientWarm temperatures

Low driftabundance

Low standing stock of attached algae

Low grazing activity

High algal recruitment

Benign stormsHigh nutrientLow temperatures

High driftabundance

High standing stock of attached algae

KELP

STABLE STATES

General Model for Maintenance of Barrens and Kelp areas

Harold & Reed, 1985

Barren Ground

-little drift kelp

- created by urchin grazing

- urchins actively forage

Kelp Forest

-abundant drift kelp

- urchins remain in crevices

Recruitment of kelp

Effect of urchins due to a change in behaviour not numbers

General Model for Maintenance of Barrens and Kelp areas

Harold & Reed, 1985

Effect of urchins due to a change in behaviour not numbers

General Model for Maintenance of Barrens and Kelp areas

Harold & Reed, 1985

Kelp and other algae

Sea urchins

Sea stars

Sea otter

Small herbivorous fish & invertebrates

Drift algae & dead animals

Abalone

Sharks

Planktonic algae

Planktonic invertebrates

Sessile invertebrates

Smaller predatoryFish and invertebrates

Larger crabs

Larger fish & octopus

Kelp Forest Food Web (with otters)

Kelp and other algae

Sea urchins

Sea stars

Sea otter

Small herbivorous fish & invertebrates

Drift algae & dead animals

Abalone

Sharks

Planktonic algae

Planktonic invertebrates

Sessile invertebrates

Smaller predatoryFish and invertebrates

Larger crabs

Larger fish & octopus

Kelp Forest Food Web (without otters)

Kelp Forest Productivity

Tropical Rain Forest

Tropical Seasonal Forest

Evergreen Forest

Deciduous Forest

Kelp Forest

Boreal Forest

3.0

2.5

2.0

1.5

1.0

0.5

0

50

40

30

20

10

0

Producer BiomassKg/m2

Annual Net ProductionKg/m2/yr

Litter MassKg/m2/yr

Kelp Forest Productivity

SUSPENSION FEEDERS

MusselSoft coralBarnacle

Sea AnemoneRock Jingle

Mysid

DETRITIVORESAmphipod

Crab

PREDATORSRock greenling

Sea starCormorant

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

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