Document Type

Internship Report

Publication Date

Fall 2013


Coral reefs throughout the Caribbean have declined dramatically over the past few decades due to a variety of interacting threats, including disease outbreaks, coral bleaching, ocean acidification, and poor water quality. These declines have led to the 2006 listing of the staghorn coral (Acropora cervicornis) as ‘threatened’ under the Endangered Species Act. As a result of this listing, restoration of A. cervicornis has been implemented as a mitigation strategy in many parts of the Florida Keys. In the Dry Tortugas National Park, naturally recovering populations, although rare, occur as either sparse groups of individual colonies, or as dense thickets. In this project, I tested the influence of colony density on the growth and survival of transplanted nubbins in the field. The density of corals in naturally recovering populations was measured, and patches of high and low colony density were identified. The growth of nubbins transplanted to these patches was measured, and their Symbiodinium identity and density was compared to evaluate if colony density in naturally recovering populations affected growth of transplanted nubbins. Eighty days after transplantation, I found that transplanted nubbins at the sparse sites increased in symbiont densities (measured as symbiont cells per cm2 coral tissue) and grew significantly faster than those at the dense sites, which exhibited a decrease in symbiont density and grew more slowly. Molecular assays of the Symbiodinium communities in experimental corals revealed that all colonies hosted only Symbiodinium in clade A (most likely A3), regardless of colony density. These findings may be used to improve restoration effo1ts by identifying site characteristics that promote growth and survivorship and by establishing target colony densities for restoration projects.


Department: MBF

MPS Track: TME

Location: National Oceanographic and Atmospheric Administration

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