Publication Date

2014-04-29

Availability

Embargoed

Embargo Period

2016-04-28

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Marine Biology and Fisheries (Marine)

Date of Defense

2013-12-18

First Committee Member

Andrew C. Baker

Second Committee Member

Douglas L. Crawford

Third Committee Member

Michael C. Schmale

Fourth Committee Member

Chris Langdon

Fifth Committee Member

Mark E. Warner

Abstract

Reef corals are mutualisms between invertebrate animals and diverse dinoflagellate algae (Symbiodinium spp.). Originally thought to be specific relationships between particular corals and Symbiodinium types, it is now accepted that many coral species can host different types of symbionts, often simultaneously. This adds complexity to the study of coral-algal symbiosis, because subtle changes in the symbiont community may result in a coral host with increased thermal tolerance or resilience. To determine how Symbiodinium community dynamics are affected by environmental stressors (abiotic factors) and exogenous sources of algal-symbionts (biotic factors), this project utilized a highly sensitive real-time PCR assay to quantify algal abundance and monitor Symbiodinium community dynamics in response to a number of experimental manipulations. Results showed that (1) elevated temperatures (and to a lesser extent, elevated pCO2) drive changes in the Symbiodinium communities of the Caribbean coral Orbicella faveolata from clade B dominated to clade D dominated, and that this switch corresponds to a decreased growth rate and reduced photosynthetic efficiency; (2) symbiont communities of healthy Montastraea cavernosa can be manipulated using transplant plugs (12mm diameter coral cores) hosting alternative Symbiodinium types; and (3) exogenous sources of symbionts drive the initial recovery from bleaching in M. cavernosa. This is contrary to the common assumption that remnant symbiont populations are solely responsible for bleaching recovery and suggests that corals may have some capacity to acquire thermotolerance from neighboring colonies. These findings have significant implications for the study of coral reefs in an era of climate change.

Keywords

Corals; Symbiodinium; Climate change; Bleaching; Resilience

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