INTERTIDAL ZONATIONBIOLOGICAL FACTORS

1. Grazing

-growth of Laminaria- zone ends abruptly

Why?

1. Grazing

Experiment done in New South Wales, Australia

Underwood (1980 Oecologia 46:201)

Used exclusion cages

1- Open 2 - Fence 3 - Roof 4 - Cage

Grazers excluded Grazers excludedGrazers inGrazers in

Normal ShadeShadeNormal

1- Open 2 - Fence 3 - Roof 4 - Cage

Grazers excluded Grazers excludedGrazers inGrazers in

Normal ShadeShadeNormal

No growth or recruitment

Recruitment but poor growth

No growth or recruitment

Recruitment and growth to nearly adult size

Therefore - upper limit dictated by grazers

2. PredationPisaster ochraceous on Mytilus californianus

2. PredationPisaster ochraceous on Mytilus californianus

2. PredationPisaster ochraceous on Mytilus californianus

Time (Years)

0 2 4 6 8 10

Height above chart datum

1.5

1.0

0.5

Pisaster removal begins Pisaster removal ends

3. Competition

Chthalamus Semibalanus

3. Competition

EHWS

MTL

ELWS

Chthalamus zone

Semibalanus zone

3. Competition

EHWS

MTL

ELWS

Chthalamus zone

Semibalanus zone

Remove Semibalanus

3. Competition

EHWS

MTL

ELWS

Chthalamus zone

Semibalanus zone

Remove Chthalamus

3. Competition

Lifted Smothered Crushed ??

100

50

0

Source of Mortality

3. Competition

MHWS

MTL

MHWN

MLWN

MLWS

Larval settlement Effects of physical factors Competition

Chthamamus

Semibalanus

4. Larval Settlement

Generalized life cycle for marine invertebrates

Dispersing larva (planktonic)

settle

juvenileadult

egg

4. Larval Settlement

Larval settlement Final distribution pattern

4. Larval Settlement

Larval settlement Final distribution pattern

happens because of

1. Indiscriminate settlementand high mortality

4. Larval Settlement

Larval settlement Final distribution pattern

happens because of

1. Indiscriminate settlementand high mortality

2. Discriminate settlementand low mortality

4. Larval Settlement

Flustrellidra lives on Ascophyllum

Hurlbut ‘91 - Distribution of Bryozoans

4. Larval Settlement

Hurlbut ‘91 - Distribution of Bryozoans

Alcyonidium

Chondrus

FucusRock

Geukensia

4. Larval Settlement

Hurlbut ‘91 - Distribution of Bryozoans

FlustrellidraAscophyllum

4. Larval Settlement

4. Larval Settlement

Results

Flustrellidra

- larvae selectively settle on Ascophyllum- greater survivorship on Ascophyllum

Alcyonidium

-larvae show preferential settlement on Fucus and Chondrus - most adult colonies occur on rock

Summary

Observed distribution andabundance

temperaturedesiccation ice

wave exposure

reproductive modecompetition

larval settlementpredationsurvival

grazing