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Lecture 9 – INTERTIDAL ZONATION BIOLOGICAL FACTORS
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BIOLOGICAL FACTORS grazing competition larval settlement survival
reproductive mode predation
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1. Grazing -growth of Laminaria - zone ends abruptly Why?
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1. Grazing Experiment done in New South Wales, Australia
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Underwood (1980 Oecologia 46:201)
Used exclusion cages 1- Open 2 - Fence 3 - Roof 4 - Cage Grazers in Grazers excluded Grazers in Grazers excluded Normal Normal Shade Shade
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Therefore - upper limit dictated by exposure + grazers
1- Open 2 - Fence 3 - Roof 4 - Cage Grazers in Grazers excluded Grazers in Grazers excluded Normal Normal Shade Shade No growth or recruitment Recruitment but poor growth No growth or recruitment Recruitment and growth to nearly adult size Therefore - upper limit dictated by exposure + grazers
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2. Predation Pisaster ochraceous on Mytilus californianus R. Paine
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2. Predation Pisaster ochraceous on Mytilus californianus
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2. Predation Pisaster ochraceous on Mytilus californianus
Pisaster removal begins Pisaster removal ends 1.5 Height above chart datum 1.0 0.5 Time (Years)
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3. Competition Chthalamus Semibalanus
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3. Competition Millport, Isle of Cumbrae
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3. Competition EHWS Chthalamus zone MTL Semibalanus zone ELWS
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3. Competition Remove Semibalanus EHWS Chthalamus zone MTL
Semibalanus zone ELWS
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3. Competition Remove Chthalamus EHWS Chthalamus zone MTL
Semibalanus zone ELWS
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3. Competition 100 50 Lifted Smothered Crushed ?? Source of Mortality
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3. Competition Chthamamus Semibalanus MHWS MHWN MTL MLWN MLWS
Larval settlement Effects of physical factors Competition
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Semibalanus Chthalamus Distribution of Semibalanus and Chthalamus
Wethey Biol.Bull. 165:330
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Distribution of Semibalanus and Chthalamus
Nahant, Mass. No Chthalamus Guilford & Horse Island, Conn. Semibalanus & Chthalamus coexist Wethey Biol.Bull. 165:330
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Distribution of Semibalanus and Chthalamus
100 50 Vertical-North 100 50 Vertical-West Percent cover by each species 100 50 10º Slope-South Chthalamus Semibalanus MHWN MLWN Tidal Height Wethey Biol.Bull. 165:330
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Distribution of Semibalanus and Chthalamus
100 50 Drip Percent cover by each species 100 50 Dry Chthalamus Semibalanus MHWN MLWN Tidal Height Wethey Biol.Bull. 165:330
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Distribution of Semibalanus and Chthalamus
Increasing sun exposure Percent cover by each species Chthalamus Semibalanus MHWN MLWN Tidal Height Wethey Biol.Bull. 165:330
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Distribution of Semibalanus and Chthalamus
1.0 0.5 Vertical-North 2.0 1.0 Settlement density ( no./cm2 Vertical-West 1.0 0.5 10º Slope-South Chthalamus Semibalanus MHWN MLWN Tidal Height Wethey Biol.Bull. 165:330
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Generalized life cycle for marine invertebrates
4. Larval Settlement Generalized life cycle for marine invertebrates Dispersing larva (planktonic) egg settle juvenile adult
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4. Larval Settlement Larval settlement Final distribution pattern
happens because of 1. Indiscriminate settlement and high mortality 2. Discriminate settlement and low mortality
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4. Larval Settlement Distribution of Bryozoans
Flustrellidra lives on Ascophyllum Hurlbut J.Exp. Mar. Biol. Ecol. 147:103
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4. Larval Settlement Hurlbut ‘91 - Distribution of Bryozoans Chondrus
Geukensia Alcyonidium Rock Fucus Hurlbut J.Exp. Mar. Biol. Ecol. 147:103
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4. Larval Settlement Hurlbut J.Exp. Mar. Biol. Ecol. 147:103
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4. Larval Settlement Hurlbut ‘91 - Distribution of Bryozoans
Flustrellidra Ascophyllum Hurlbut J.Exp. Mar. Biol. Ecol. 147:103
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larvae selectively settle on Ascophyllum
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 Hurlbut J.Exp. Mar. Biol. Ecol. 147:103
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Observed distribution and
Summary desiccation ice temperature wave exposure reproductive mode grazing competition larval settlement survival predation Observed distribution and abundance
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