Symbiodinium Reactive Oxygen Species (ROS) Production and Migration in the Octocorals Sympodium sp. and Sarcothelia sp.
El Rahmany, Weam S., 1996--
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Climate change may be increasingly causing corals to bleach, as bleaching may be triggered by elevated temperatures and light. Corals bleach due to their symbionts’ overproduction of reactive oxygen species (ROS). This mechanism breaks down the syntrophic relationship between corals and symbionts, as the symbionts either migrate or die (Parrin et al., 2012). We primarily aimed to identify the relationship between stress, ROS production, and symbiont migration in the octocorals, Sympodium sp. and Sarcothelia sp. The experimental groups were stressed with 140 µmol photons sec-1m-2 for 4 hours (Table 1), while the control groups were kept in a culture tank with minimal light. The groups were put in finger bowls in an incubator with a probe that detects ROS for 1 hour. Through Image Pro 6.3, we were able to quantify background and colony luminance that represents ROS production. We also used the manual tag feature in the software to count the migrating and non-migrating symbionts. Our data is shown in graphs (Figs. 3-6) and paired comparisons (Tables 2-3). In general, there was a positive correlation between stress and colony luminance and moving symbionts on both Sympodium sp. and Sarcothelia sp. (Figures 3-6). There was a greater correlation between relative luminance and stress in Sympodium as compared to stressed Sarcothelia (Tables 2-3). This implies that in the presence of ROS, symbionts are more likely to exit the cells of Sarcothelia. We had good control groups for both octocorals, as there wasn’t a significant difference between nonmoving symbionts in the control and stressed groups in either (Figure 7). To form more conclusive results, we could have done more trials, while limiting our errors, on both species. Because coral bleaching is detrimental to corals and other marine organisms, many sought to find ways to prevent or alleviate it. Environmental conditions that may prevent or aid in the recovery of bleached corals include shade and deeper waters, as they lack in temperature and illumination (Grahem et al., 2015). Symbionts may avoid stress by migrating to the coenenchyme lumen, then back to the stolons of the coral tissues, once the stress ceases (Parrin et al., 2012). Parrin and his team, also found that because Sarcothelia and Sympodium had higher surface area coenenchyme than Phenganax parrini, they had more symbiont recovery. Acropora millepora increased their tolerance to stress by changing from type C symbionts to type D symbionts (Berkelmans and van Oppen, 2006). Further studies on the syntrophic associations between corals and symbionts, may help increase knowledge of the coping mechanisms that may mitigate coral bleaching.