Intertidal Zonation on Species Diversity Lab Report

Intertidal Zonation on Species Diversity Lab Report -...

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Intertidal Zonation of Species Diversity on Pier Pilings Holden Harris with Kenny Maskell April 28, 2008 Schuyler van Montfrans
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Holden Harris Page 2 Abstract Vertical zonation of organisms within rocky intertidal ecosystems has been found to be driven by a combination of factors, including predation, settlement, desiccation stresses, and intra-specific competition. The lower limits of adult prey organisms are typically attributed to predation, and the upper limits are believed to be driven by larval settlement and environmental stresses. This assessment studied the zonation of a community of five benthic organisms in five vertical plots, along five pier pilings, each one further out to sea. Density was measured by counting the abundance of each species in each plot, and this data was then used to determine diversity by the Shannon Diversity Index. We found organism density and species diversity increased significantly in the lower plots and the later (further out) pilings. This suggests that the upper limit factors – i.e. desiccation and settlement – applies a stronger control on distribution than predation. Wave-splash was attributed as the likely cause for the gradual increase and subsequent leveling off of density and diversity in the later pilings. Finally, specific species distribution was noted, with the acorn barnacles showing universal preference and the other four species exhibiting specific, vertical inhabitation zones. Introduction The vertical zonation of benthic organisms in the marine intertidal zone has been long known to marine biologists (Connell, 1972.) Historically, the ecological study of intertidal zonation has created a paradigm of predation in rocky intertidal ecosystems, which stated that the observed horizontal bands of adult prey are driven by predation by “keystone” predators (Robles & Desharnais, 2002). Newer models hold that a balance between predation and prey production
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Holden Harris Page 3 sets the intertidal boundaries of prey. Larval behavior is believed to have an important role in vertical distributions (Grosberg, 1982). Biotic settlement cues from barnacle spat have in fact been shown to cause barnacle settlement above the upper survival limits of barnacles (Raimondi, 1988). After settlement, vertical zonation determines the total amount of time sessile organisms spend submerged in water or exposed to air, and so has a strong effect on post-settlement mortality. When submerged, organisms experience relatively constant environmental variables. Vertically higher organisms are exposed to air for longer periods, and are subjugated to three
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This note was uploaded on 04/29/2008 for the course PCB 4044 taught by Professor Osenberg,mack during the Spring '08 term at University of Florida.

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Intertidal Zonation on Species Diversity Lab Report -...

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