HCNSO Student Theses and Dissertations

Defense Date

12-11-2015

Document Type

Thesis

Degree Name

M.S. Marine Biology

First Advisor

Joana Figueiredo

Second Advisor

David Gilliam

Third Advisor

Bernhard Riegl

Abstract

Corals face serious worldwide population declines due to global climate change in combination with direct anthropogenic impacts. Global climate change is difficult to manage locally, but policy makers can regulate the magnitude of local stressors affecting reefs. The objective of this experiment is to investigate if reducing sedimentation will enable reef corals to better endure global climate change. It has been shown that some coral species can handle climate change stress when provided with additional energy resources. Here I tested if the capacity of corals to cope with climate change can be improved when their ability to feed and photosynthesize was not compromised by increased sedimentation. Sedimentation can impede coral feeding and their ability to photosynthesize due to direct polyp blocking and increased turbidity, which reduces light availability. To evaluate the potential of enhancing coral ability to tolerate climate change by reducing a local stressor, I examined the survival and growth of brooding coral Porites astreoides juveniles when exposed to ambient and elevated water temperatures under differing sedimentation rates. I also assessed if sediment composition has significant impacts on these results. I used sediment from a reef and sediment from a boat basin within a port to mimic natural and anthropogenic sediment types and processes (e.g. dredging). Experiments were conducted to quantitatively assess the synergistic effects of sediment concentration and composition, along with increased temperature on the survival and growth of juvenile P. astreoides. The most detrimental effects were observed with anthropogenic sediment, when both sediment concentration and water temperatures were high. However, increased natural reef sediment was found to be beneficial to juvenile corals. More interestingly, I found that corals capacity to deal with higher temperatures is improved when anthropogenic sedimentation is maintained at minimal levels and turbidity resulting from sedimentation was low. Therefore, this information will aid managers in making decisions that regulate dredging and construction activities to minimize sedimentation, which will contribute to increase coral survival under climate change.

Comments

NSU President's Faculty Research and Development Grant #335340

Permit number FKNMS-2015-007 from NOAA Office of National Marine Sanctuaries (ONMS)

NOAA permit #NA15NOS4820078

ORCID ID

orcid.org/0000-0003-1305-1627

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