Discipline: Biological Sciences
Subcategory: Cell and Molecular Biology
Michael Marty-Rivera - University of Puerto Rico Rio Piedras Campus
Co-Author(s): Guillermo Yudowski, Institute of Neurobiology, University of Puerto Rico - Medical Sciences Campus, San Juan PR Loretta Roberson, Department of Environmental Sciences, University of Puerto Rico - Rio Piedras Campus, San Juan PR
Coral reefs are amongst the richest ecosystems in the world, and they are being threatened by environmental stressors. Reactive Oxygen Species (ROS) have been suggested as a major underlying mechanism driving coral bleaching. To define if other processes are necessary for bleaching, we sought to investigate the effects of reducing ROS by using a naturally occurring antioxidant during thermally induced stress in two different species, the sea anemone Aiptasia pallida, and the scleractinian coral, Porites astreoides. ROS levels and photosynthetic capacity were analyzed at a single cell level. Treatment duration for A. pallida experiments were 4 days, while P. astreoides were incubated for 24 hours. Homogenated coral and sea anemone tissues were separated by centrifugation so we could look at individual cells. Confocal microscopy was used for ROS identification in symbiont cells, using the non-specific ROS dye, CellROX Orange, at emission wavelength 546 nm and excitation 561.5 nm. To assess photosynthetic efficiency of experimental individuals, we measured dark-adapted maximum fluorescence yield in single symbionts as a proxy for measurement of symbiosis condition. We achieved this by using a Zeiss Axio Scope.A1 (Zeiss, Göttingen) equipped with a Walz Imaging-PAM chlorophyll fluorometer (IMAG-CM; Walz Mess- und Regeltechnik, GmbH, Effeltrich). All data were analyzed using a 2-way ANOVA, with Tukey’s multiple comparison test when there was a significant difference between treatments. We found that intracellular ROS was significantly reduced in anemones and corals exposed to thermal stress (32°-33°C) by a single exposure to 5 µM antioxidant solution. Furthermore, incubation with antioxidants prevented a significant photosynthetic decay as measured by PAM fluorometry in A. pallida symbiont cells. However, symbionts from P. astreoides with a low ROS signal still exhibited a decrease in photosynthetic yield and resulted in death. This suggests a crucial difference between these species and suggests that other mechanisms beyond ROS can mediate coral bleaching. In the future we will extend the duration of experimental treatments to better understand acclimation, and will improve water flow under experimental conditions.
Funder Acknowledgement(s): This research was supported by: 1.) National Science Foundation grants HRD #1137725; 2.)National Science Foundation grant DBI #1337284.
Faculty Advisor: Guillermo Yudowski & Loretta Roberson, email@example.com
Role: I conceived and designed the study, and carried out the experiments alongside my co-authors. I wrote the abstract with guidance from my co-authors and advisers.