Exploring the effects of dissolved organic carbon (DOC) in maintaining the coral-algal symbiosis in the facultatively symbiotic coral Oculina arbuscula (2023)

Undergraduate: Meg McCartney

Faculty Advisor: Karl Castillo
Department: Department of Marine Sciences, Environment, Ecology, and Energy Program

---

This study aimed to explore the impact of dissolved organic carbon (DOC) on the coral-algal symbiosis in the facultatively symbiotic coral, Oculina arbuscula. The research focused on the effects of DOC enrichment on coral health, nitrogen-fixing bacteria proliferation, nutrient availability, and symbiotic state. The significance of this study lies in the threat coral reefs face due to climate change and anthropogenic activities. Sugar enrichment is used to simulate DOC and the anthropogenic nutrient input, which can lead to eutrophication. This study is particularly important as it focuses on the facultatively symbiotic temperate coral, O. arbuscula, which are able to survive both with and without symbiotic algae, and inhabit the North Carolina coast. The experiment consists of 12 total tanks with additions of 4 different levels of sugar enrichment. Buoyant weight and photo analysis were used to quantify coral growth rates and algal symbiont growth, respectively. The results suggest that there was no significant growth difference between treatments but a significant growth difference was found between aposymbiotic and symbiotic corals. Additionally, there was a general trend of corals turning slightly more aposymbiotic across the DOC enriched tanks over the experiment, potentially due to corals becoming stressed under higher nutrient conditions. Understanding the consequences of nutrient enrichment is essential for proper local management and conservation efforts and globally as well, especially since corals are a foundation for marine biodiversity.

Link to Poster