Using BRUVS to Characterize the Community of Sandy Shoal Habitats of the Mid-Atlantic Bight

Abstract

This study explores the biodiversity and community structure of two sandy shoal habitats on the East Atlantic coast of the United States: Sandbridge (Virginia) and Hens and Chickens (Delaware). Two different methodologies were used to characterize the communities: Baited Remote Underwater Video Surveillance/Systems (BRUVS) and longlines. We assess species relative abundance (MaxN) and diversity, evenness, and richness using Shannon’s Diversity Index, Simpson’s Diversity Index, Pielou’s Evenness, and species richness metrics. We then examine environmental covariates such as water temperature, brightness, depth, distance from shore, proximity to the closest estuary, and tidal stage at both sites to determine if the environment drives differences in community composition. Generally, species diversity and richness were greater at Sandbridge. However, we observed no significant differences in biodiversity indices between the two locations, most likely due to a small sample size of videos. Our findings also reveal significant differences in environmental variables between the two shoals, particularly in brightness and the distances from shore and the closest estuary. Brightness exhibited a positive linear relationship with diversity indices and richness, suggesting that less turbid habitats may support more complex communities. Distance to the closest estuary presented a negative linear relationship with evenness, indicating that further proximity to the estuary may maintain a more balanced distribution of species. These trends also highlight that BRUVs are dependent on clear water conditions to effectively record data. This study also touches on the significance of using multiple sampling techniques to better assess marine compositions and diversity. Long-lining and BRUVS yielded distinct species captures with minimal overlap, indicating different viii biases and strengths of each method. Water turbidity (brightness) limited species detection and identification, particularly at Hens and Chickens, highlighting a limitation of BRUVS in turbid waters. This study also suggests further research into temporal variations, additional environmental factors, and enhancements to sampling methods to improve biodiversity assessments.