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Biological and Physical Factors Controlling the Spatial Distribution of the Intertidal Alga Gelidium Pristoides in the Eastern Cape, South Africa
Published online by Cambridge University Press: 11 May 2009
Extract
Gelidium pristoides dominates the lower and mid-eulittoral zones of rocky shores in the eastern Cape, South Africa. A disproportionately high percentage of the plants is attached to barnacle and limpet shells, or restricted to rock crevices. Our experiments at Port Alfred indicate that this distribution is caused by grazing by the limpet Patella oculus and/or strength of attachment of the plants to the different substrata. Exclusion of limpets caused an approximately four-fold increase in the cover of G. pristoides on rock, and an increase from almost 0 to 80% cover on sterilised (dead) limpet shells. Measurements showed G. pristoides to be more than 50% more strongly attached to barnacle and limpet shells than to rock. The distribution of G. pristoides on the various substrata is largely determined by limpet grazing and possibly the different strengths of attachment to the different substrata. The upper distribution limit of G. pristoides is set by physical effects of emersion and was largely unaffected by limpet exclusion. Competition with other algae is important in setting the lower limit: in the sublittoral fringe, although limpet exclusion enhanced recruitment, juveniles were later displaced by articulated corallines, and adult transplants senesced because of encrusting coralline epiphytes.
- Type
- Research Article
- Information
- Journal of the Marine Biological Association of the United Kingdom , Volume 71 , Issue 3 , August 1991 , pp. 555 - 568
- Copyright
- Copyright © Marine Biological Association of the United Kingdom 1991
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