The deep sea covers over two-thirds of the globe and represents 95% of the ocean. Most life on Earth is suspected to live on or near the seabed. Yet, these ecosystems are the least known on Earth and are important to explore as they are home to a diverse array of species that are currently under threat because of multiple anthropogenic pressures, including warming oceans. Exploration of these systems is critical to further the understanding of species interactions, biodiversity and their overall relationship to environmental and terrain variables. Many of these variables are used in species distribution models and technological advances have enabled the collection of high-resolution bathymetric data resulting in a need to understand how species distribution models may behave under a range of bathymetric grid resolutions and ocean warming conditions.

The goal of this dissertation is to develop a comprehensive fine-scale habitat map of discharge outcrops on Ridge Flank Hydrothermal Systems, low-temperature fluid venting systems that mimic warming conditions caused by climate change. This was accomplished by integrating high-resolution acoustic survey data with ground-truth imagery and environmental data. Fusing these data identified how warming would affect biodiversity on these systems, provided a method to assess the effects of bathymetric resolution on seafloor characterization and subsequent predictive models, and facilitated predicting species distributions under warmer temperature conditions.

In chapter II, I characterized the effects of warming water on deep-sea communities and biodiversity by comparing community composition within and outside of warm venting zones and linking them with local environmental parameters. I found a difference in community composition between vent and non-vent zones. Family richness and biodiversity also differed between vent and non-vent zones and temperature was positively correlated to richness and diversity. Though there are many additional factors that influence biodiversity and community composition, results from this chapter show that warming increases richness and biodiversity, congruent with studies that have linked increases in richness to elevated temperatures. 

In chapter III, I explored the effects of varying bathymetric resolutions (1, 2, 5 and 10 meters) on geomorphon characterization and modeling of terrain variables. I then assessed how terrain and geomorphons at different resolutions alter species distribution models. I found resolution affected the modeled representation of terrain variables, geomorphon size and distribution, and apparent associations between community composition and terrain. However, resolution did not cause a consistent pattern of change in predictive model output. The impact from resolution on the representation of terrain is the likely cause of the differences in correlations between community composition and terrain across resolution and for the predictions of suitable habitat being independent of terrain resolution. Variability in the size and distribution of geomorphons across varying bathymetric resolutions is possibly driving changes in the composition of communities and richness across geomorphons. These findings emphasize the sensitivity of ecosystem interpretation to extraction methodology and highlights limitations of finer resolution to improving deep-sea predictions. 

In chapter IV, I investigated the potential impact of projected ocean warming on predictions of suitable habitat for seven families and one genus of benthic megafauna in the deep sea. I assessed how predictions of suitable habitat varied under four temperature conditions (ambient, 0.01°C, 0.1°C, and 0.5°C above ambient). In general, suitable habitat for four families and one genus of sessile families increased by as much as 10-fold or greater under elevated temperature conditions. Changes in distribution of mobile consumers was predicted to increase by only 50%. The expansion of foundational families under warming conditions suggests, along with results from chapter II, that warming will increase pockets of biodiversity in the deep sea because of species’ ability to expand and survive in neighboring areas.

This research has sought to understand the relationships between seafloor terrain and ocean warming with community composition on deep-sea Ridge Flank Hydrothermal Systems ecosystems and the impact of bathymetric resolution on species distribution models and seafloor characterization. My findings demonstrate that temperature influences community composition and species distribution. It also reveals that for deep-sea studies, predictions of habitat suitability models may not benefit from the highest resolution of terrain variables in a range between one and ten meters. Together these findings can inform strategies for efficient and effective planning of deep-sea management and exploration.