UNF Digital Commons UNF Graduate Theses and Dissertations Student Scholarship 2013 The ffecE ts of Multiple Abiotic Stressors on the Susceptibility of the Seagrass Thalassia Testudinum to Labyrinthula sp., the Causative Agent of Wasting Disease Nichole Danielle Bishop University of North Florida Suggested Citation Bishop, Nichole Danielle, "The Effects of Multiple Abiotic Stressors on the Susceptibility of the Seagrass Thalassia Testudinum to Labyrinthula sp., the Causative Agent of Wasting Disease" (2013). UNF Graduate Theses and Dissertations. 471. https://digitalcommons.unf.edu/etd/471 This Master's Thesis is brought to you for free and open access by the Student Scholarship at UNF Digital Commons. It has been accepted for inclusion in UNF Graduate Theses and Dissertations by an authorized administrator of UNF Digital Commons. For more information, please contact Digital Projects. © 2013 All Rights Reserved THE EFFECTS OF MULTIPLE ABIOTIC STRESSORS ON THE SUSCEPTIBILITY OF THE SEAGRASS THALASSIA TESTUDINUM TO LABYRINTHULA SP., THE CAUSATIVE AGENT OF WASTING DISEASE By Nichole Bishop A thesis submitted to the Department of Biology in partial fulfillment of the requirements for the degree of Master‟s of Science in Biology UNIVERSITY OF NORTH FLORIDA COLLEGE OF ARTS AND SCIENCES December, 2013 1 Certificate of Approval The thesis of Nichole Bishop is approved: (Date) Dr. Cliff Ross Dr. Eric Johnson Dr. Dan Moon Accepted for the Biology Department: Dr. Dan Moon Chair Accepted for the College of Arts and Sciences: Dr. Barbara Hetrick Accepted for the University: Dr. Len Roberson Dean of The Graduate School ii Dedication In memory of my grandmother, Iola Bishop (1912-2002), who always believed “education was something that could never be taken away” iii Table of Contents 1 Introduction ................................................................................................................................... 1 1.1 Evolution, Taxonomy, Distribution and Adaptations ............................................................ 1 1.2 Ecological and Economical Importance of Seagrass Beds .................................................... 3 1.3 Seagrass Decline .................................................................................................................... 6 1.4 Wasting Disease ..................................................................................................................... 9 1.5 Labyrinthula spp. ................................................................................................................. 15 1.6 Environmental Stressors ...................................................................................................... 18 1.7 Objectives and Hypotheses .................................................................................................. 25 2 Effects of multiple abiotic stressors on the health and susceptibility of Thalassia testudinum to wasting disease when exposed to Labyrinthula spp. ..................................................................... 27 2.1 Introduction .......................................................................................................................... 27 2.2 Materials and Methods ......................................................................................................... 31 2.3 Results .................................................................................................................................. 44 2.4 Discussion ............................................................................................................................ 76 2.5 Conclusion ........................................................................................................................... 81 Reference Materials ....................................................................................................................... 83 iv List of Tables Table 1. Experimental conditions to test host-pathogen interactions between T. testudinum v List of Figures Figure 1. History of wasting disease outbreaks among temperate and tropical seagrasses 2. Necrotic lesion on T. testudinum caused by infection from Labyrinthula spp. 3. In situ localization of spindle-shaped Labyrinthula cells inside epidermal cells of the seagrass T. testudinum 4. Experimental microcosm with root chamber containing seawater treated with sodium sulfide 5. Thalassia testudinum blades infected with Labyrinthula sp. under ambient salinity groups had significantly larger lesions on average than groups incubated under high salinity conditions. There was no significant difference in lesion size due to temperature. 6. Post-infection EQY values between the high salinity + high temperature groups exposed to Labyrinthula sp. and the control group (no Labyrinthula sp.) exposed to the same stressors were not significantly different 7. Pre-infection EQY values for the groups formed by ambient and high salinity and ambient and high temperature were significantly different from their corresponding post-infection EQY values. However, there were no significant differences in main effects among post-infection EQY values. vi 8. Lesion size for salinity and temperature under a recovery simulation. There were no differences in lesion size due to either main effect. 9. Post-infection EQY values between the control group (no Labyrinthula sp.) and the group exposed to the same stressors under a recovery simulation were not significantly different 10. Comparison of pre- and post-infection EQY for salinity and temperature under a recovery simulation. All main effects had significantly lower EQY values after infection with Labyrinthula sp. All main effects also had mean post-infection EQY values below 0.700. However, here were no statistically significant differences in post-infection EQY values for the groups formed by either salinity or temperature. 11. Comparison of mean lesion size between the sustained stress condition and the recovery simulation. Lesions were significantly smaller in the experiment where stressors were maintained throughout 12. Comparison of lesion size due to the effects of sulfide and oxygen. Seagrasses exposed to 6mM of sulfide had significantly larger lesions than groups not exposed to sulfide. There were no statistically significant differences in lesion size due to hypoxia. 13. Comparison of post-infection EQY values between the control group (no Labyrinthula sp.) and the group exposed to similar stressors. There were no significant differences between the groups. vii 14. Pre- vs post-infection EQY values for the effects of oxygen and sulfide. There were no significant differences between pre- and post-infection EQY values among sulfide treatments. However, hypoxic groups possessed significantly (p = .011) lower post-infection EQY values when compared to pre-infection EQY values. There were no differences in post-infection EQY values among the groups formed by sulfide or oxygen treatments. 15. Comparison of lesion size for temperature groups when seagrasses were exposed to a combination of salinity, temperature, sulfide and oxygen. Stressors were sustained throughout the experiment. Ambient temperature groups had significantly larger lesions than high temperature groups. 16. An interaction between salinity and sulfide indicated that at ambient salinity, high sulfide results in larger lesions 17. Post-infection EQY values for the control (no Labyrinthula sp.) and the group exposed to similar stressors. There was no significant difference between the groups 18. Comparison of pre- and post-infection EQY values for the effects of salinity, temperature, sulfide and oxygen under sustained stress conditions. There were significant differences between pre- and post-infection EQY values for ambient salinity, ambient temperature, 0 mM sulfide and hypoxia. The only significant difference between post-infection EQY values was found among temperature groups, with elevated temperatures resulting in lower post-infection EQY values. viii 19. Comparison of salinity, temperature and sulfide due to the interaction of all main effects under a recovery simulation. Seagrasses in ambient salinity groups had significantly larger lesions regardless of temperature or sulfide. 20. Comparison of salinity, temperature and oxygen due to the interaction of all main effects under a recovery simulation. Seagrasses in ambient salinity groups had significantly larger lesions regardless of temperature or sulfide. 21. Comparison of salinity, sulfide and oxygen due to the interaction of all main effects under a recovery simulation. Seagrasses in ambient salinity groups had significantly larger lesions regardless of temperature or sulfide. 22. Comparison of temperature, sulfide and oxygen due to the interaction of all main effects under a recovery simulation. There was no significance for any of these effects. 23. Post-infection EQY values for the control and stress group under a recovery simulation. There were no statistically significant differences between the control (no Labyrinthula sp.) and the group with similar stressors. 24. Comparison of the pre- and post-infection EQY values for the effects of salinity, temperature, sulfide and oxygen under a recovery simulation. There were significant differences between pre- and post-infection EQY values for all main effects at all levels. However, the only significant difference among post- infection EQY values between the salinity groups with ambient salinity resulting in lower post-infection EQY values.