One Fish, Two Fish: Measuring Patterns of Reef Fish Biodiversity in Bermuda Using Environmental DNA Metabarcoding

Abstract

Monitoring reef fish biodiversity is essential in setting both marine conservation priorities and measuring their success. Bermuda’s reef fish are threatened by anthropogenic pressures and current conservation strategies are not adequately protecting them. As the Northern-most reefs in the Atlantic, Bermuda’s reefs are unique as they persist in the outer limits of survivable environmental conditions. Bermuda’s colder environment provides an opportunity to study the impact of environmental conditions on reef ecosystems, however, it also slows the reef fishes’ reproductive rate, making them more vulnerable to threats form exploitation. Thus, effective conservation strategies are essential to protect Bermuda’s reef fish stocks and biomonitoring efforts must accompany these strategies to measure shifts in biodiversity. In this thesis, I use environmental DNA metabarcoding to measure biodiversity at various sites across Bermuda’s platform to inform conservation decisions Through analysis, I examine the effect of various environmental variables, such as site type and tide predictions, on the biodiversity patterns. The results indicate that site type and sample date are significant predictors of variation in community composition. From principal component analysis, seagrass beds were distinctly different from the other site types, which could be explained by their importance as a habitat for recruitment for many reef fish species. Throughout the platform, the results found low levels of piscivorous taxa, which suggests that these commercially important species are struggling to recover from historic and continued overexploitation from fisheries. Thus, the results of this thesis indicate that improved protection of seagrass beds and piscivorous fish taxa should be conservation priorities in Bermuda.