The Effects of Temperature on the Zooxanthellae Density of Sarcothelia edmondsoni in Lanikai, Hawaiʻi

Abstract

Coral bleaching events have increased in frequency and severity across the world, causing decreases in coral species and diversity of reef ecosystems, along with other environmental impacts. To help protect and conserve coral reefs around the world, it is crucial to study this phenomenon. The purpose of this study was to better understand the adaptations and traits of S. edmondsoni, in order to better study the native and endemic Hawaiian species. Sarcothelia edmondsoni is a species of Hawaiian octocoral that has not been observed to bleach during warming events, as many other species of corals do. It was hypothesized that this species is more resistant to thermal stressors, which has important biological implications. To observe the effects of changing temperature on small colonies of S. edmondsoni, samples were placed in aquariums with small heaters that were used to manually and steadily increase the temperature of the surrounding water. The density of these zooxanthellae in individual polyps was measured and recorded weekly, along with observational photo-documentation, in order to determine whether or not Sarcothelia edmondsoni appeared to expel their symbionts. By the end of the experiment, husbandry conditions proved to be insufficient to maintain the specimens, even in control tanks, and the data were inconclusive. More research is still needed to further identify the thermal resistance of this species.