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Lecture 9 – INTERTIDAL ZONATION BIOLOGICAL FACTORS BIOLOGICAL FACTORS grazing competition larval settlement survival reproductive mode predation 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 in Grazers excluded Grazers in Grazers excluded Normal Normal Shade Shade 1- Open Grazers in 2 - Fence Grazers excluded 3 - Roof Grazers in Normal Normal Shade No growth or recruitment Recruitment but poor growth No growth or recruitment 4 - Cage Grazers excluded Shade Recruitment and growth to nearly adult size Therefore - upper limit dictated by exposure + grazers 2. Predation Pisaster ochraceous on Mytilus californianus R. Paine 2. Predation Pisaster ochraceous on Mytilus californianus 2. Predation Pisaster ochraceous on Mytilus californianus Pisaster removal begins Pisaster removal ends 1.5 Height above chart datum 1.0 0.5 0 2 4 Time (Years) 6 8 10 3. Competition Chthalamus Semibalanus 3. Competition Millport, Isle of Cumbrae 3. Competition EHWS Chthalamus zone MTL Semibalanus zone ELWS 3. Competition Remove Semibalanus EHWS Chthalamus zone MTL Semibalanus zone ELWS 3. Competition Remove Chthalamus EHWS Chthalamus zone MTL Semibalanus zone ELWS 3. Competition 100 50 0 Lifted Smothered Source of Mortality Crushed ?? 3. Competition Chthamamus Semibalanus MHWS MHWN MTL MLWN MLWS Larval settlement Effects of physical factors Competition Distribution of Semibalanus and Chthalamus Semibalanus Chthalamus Wethey 1983. Biol.Bull. 165:330 Distribution of Semibalanus and Chthalamus Nahant, Mass. No Chthalamus Guilford & Horse Island, Conn. Semibalanus & Chthalamus coexist Wethey 1983. Biol.Bull. 165:330 Distribution of Semibalanus and Chthalamus 100 Vertical-North Percent cover by each species 50 100 Vertical-West 50 100 10º Slope-South 50 Chthalamus Semibalanus MHWN MLWN Tidal Height Wethey 1983. Biol.Bull. 165:330 Distribution of Semibalanus and Chthalamus Drip Percent cover by each species 100 50 Dry 100 50 Chthalamus Semibalanus MHWN MLWN Tidal Height Wethey 1983. Biol.Bull. 165:330 Percent cover by each species Distribution of Semibalanus and Chthalamus Chthalamus Semibalanus Increasing sun exposure MHWN MLWN Tidal Height Wethey 1983. Biol.Bull. 165:330 Distribution of Semibalanus and Chthalamus 1.0 Vertical-North Settlement density ( no./cm2 0.5 2.0 Vertical-West 1.0 1.0 10º Slope-South Chthalamus Semibalanus 0.5 MHWN MLWN Tidal Height Wethey 1983. Biol.Bull. 165:330 4. Larval Settlement Generalized life cycle for marine invertebrates Dispersing larva (planktonic) egg settle adult juvenile 4. Larval Settlement Larval settlement Final distribution pattern happens because of 1. Indiscriminate settlement and high mortality 2. Discriminate settlement and low mortality 4. Larval Settlement Distribution of Bryozoans Flustrellidra lives on Ascophyllum Hurlbut 1991. J.Exp. Mar. Biol. Ecol. 147:103 4. Larval Settlement Hurlbut ‘91 - Distribution of Bryozoans Chondrus Geukensia Alcyonidium Rock Fucus Hurlbut 1991. J.Exp. Mar. Biol. Ecol. 147:103 4. Larval Settlement Hurlbut 1991. J.Exp. Mar. Biol. Ecol. 147:103 4. Larval Settlement Hurlbut ‘91 - Distribution of Bryozoans Flustrellidra Ascophyllum Hurlbut 1991. J.Exp. Mar. Biol. Ecol. 147:103 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 1991. J.Exp. Mar. Biol. Ecol. 147:103 Summary desiccation ice temperature competition survival wave exposure grazing predation Observed distribution and abundance reproductive mode larval settlement
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