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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