Publication Date

Spring 2010

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Moss Landing Marine Laboratories

Advisor

Michael H. Graham

Keywords

Chlorostoma brunnea, Macrocystis pyrifera, fungi, growth optimization, overcompensation, trophic interactions

Subject Areas

Biology; Ecology

Abstract

The purpose of this study was to evaluate how one of the most abundant kelp forest herbivores in central California, the trochid snail Chlorostoma brunnea, affects the productivity and survivorship of the giant kelp Macrocystis pyrifera within central California. The effects of this turban snail species were investigated using experimental field manipulations of snail abundance on Macrocystis sporophytes and supplementary laboratory experiments. Experimental field manipulation of C. brunnea densities (0-450 snails per sporophyte) revealed an overcompensation of growth by Macrocystis in response to moderate snail densities. This finding is consistent with a terrestrial growth premise, the Grazing Optimization Hypothesis. Laboratory feeding experiments also demonstrated an overcompensatory response of Macrocystis to C. brunnea grazing. These experiments identified marine fungi growing on Macrocystis as a potential primary food source for C. brunnea. The effects of C. brunnea grazing on fungal biomass produced an inverse relationship; fungal biomass was significantly less when C. brunnea grazed at moderate densities. These results indicate that the interaction between marine fungi and C. brunnea may serve as a potential mechanism for compensatory growth in Macrocystis. As moderately abundant snails remove fungi, Macrocystis may attain a greater growth rate.

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