HCNSO Student Theses and Dissertations

Copyright Statement

All rights reserved. This publication is intended for use solely by faculty, students, and staff of Nova Southeastern University. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, now known or later developed, including but not limited to photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author or the publisher.

Defense Date


Document Type

Thesis - NSU Access Only

Degree Name

M.S. Marine Biology


Oceanographic Center

First Advisor

Patricia Blackwelder

Second Advisor

Jose Lopez

Third Advisor

Sarah Edge

Fourth Advisor

Esther C. Peters


Coral reef biodiversity is threatened by rapidly changing anthropogenic activities and natural perturbations, leading to massive ecological and economic consequences ranging from the loss of fisheries to coastal erosion. It is necessary to understand corals responses to environmental changes in order to determine management programs on appropriate spatial and temporal scales to address these issues. Coral larvae are the product of sexual reproduction, have the potential to recruit to new areas, and are fundamental in maintaining genetic diversity. These larvae are subjected to variations in local environmental conditions until they settle, inducing specific larval molecular response patterns. One factor that influences coral health is salinity. Low salinities can alter cell homeostasis creating stress in cells. In the natural environment larvae may be exposed to low salinities due to heavy rainfall or run-off. This study investigated larvae responses to low salinity and characterized gene expression in the reef-building coral Porites astreoides using a coral stress-focused microarray. Nine batches of 250+ larvae from three different colonies were collected and immediately exposed in an acute hyposalinity experiment. Samples from two treatments of 25 and 30 ppt, and a control at 35 ppt were used in this study. After experimental exposure these samples were stored in RNAlater® and molecular analysis was performed. The RNA from the samples was extracted, purified and hybridized to a coral stress-focused microarray. Statistical analysis indicates 72 genes were differentially expressed across treatments (p<0.003, analysis of variance). The hierarchical cluster analysis groups together the larvae exposed to salinities of 30 and 35 ppt indicating both treatments induced similar patterns of gene expression. Larvae responses to 30 ppt are minimal, suggesting larvae can tolerate acute exposures to 30 ppt salinity levels. In contrast, the lower salinity (25 ppt) induced a strong response in both the coral and zooxanthellae. The coral larvae up-regulated stress response genes and down-regulated genes associated with normal cell functioning. Additionally, the zooxanthellae down-regulated genes associated with photosynthesis. These results suggest larvae may be vulnerable to bleaching, which may affect the ability of larvae to successfully undergo metamorphosis and survive at low salinities. However, this has yet to be confirmed with complementary techniques. Long-term studies are recommended to examine the effects of hyposalinity on larvae at different time scales and life history stages.

To access this thesis/dissertation you must have a valid nova.edu OR mynsu.nova.edu email address and create an account for NSUWorks.

Free My Thesis

If you are the author of this work and would like to grant permission to make it openly accessible to all, please click the Free My Thesis button.

  Link to NovaCat