Graduation Year

2026

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Marine Science

Major Professor

Steven A. Murawski, Ph.D.

Committee Member

David F. Naar, Ph.D.

Committee Member

Joshua P. Kilborn, Ph.D.

Committee Member

Theodore S. Switzer, Ph.D.

Committee Member

Vincent Lecours, Ph.D.

Keywords

Backscatter, Bathymetry, Fish Community Ecology, Hardbottom, Multiscale

Abstract

In this dissertation, I examine the role of spatial scale in deriving seafloor terrain attributes, modeling benthic habitat, and analyzing ecological patterns of the demersal reef fish communities on the West Florida Shelf (WFS), with implications for improving predictive habitat mapping and understanding fish-environment relationships. Spatial scale plays a central role in benthic habitat mapping and ecological inference, influencing how terrain attributes are derived, how habitats are modeled, and how ecological responses are manifested. This work integrates multiscale terrain analysis, acoustic remote sensing, and community ecology to evaluate how spatial scale influences both physical habitat representation and ecological analysis.

Chapter Two describes the MultiscaleDTM R package, an open-source tool designed to facilitate multiscale topographic analysis. The package computes terrain attributes across five major thematic groups: slope, aspect, curvature, relative position, and roughness. It also includes a novel roughness metric based on the standard deviation of residuals from a fitted plane, which decouples roughness from slope. This metric is shown to perform effectively in simulations and provides an interpretable measure of structural complexity.

Chapters Three and Four utilize data collected as part of the Continental-Shelf Characterization Assessment and Mapping Project (C-SCAMP) at the University of South Florida (USF). These data include multibeam echosounder surveys and towed underwater video transects conducted across multiple study sites on the WFS from 2015–2019. In Chapter Three, I develop models to predict seafloor induration (hardbottom vs. softbottom) using predictors derived from multibeam bathymetry and backscatter, including multiscale terrain attributes computed with MultiscaleDTM. Ground-truth observations from towed video surveys are used as the response variable. My results demonstrate that incorporating both multiscale and backscatter-based predictors improves model performance, reduces along-track artifacts, and reduces false positive and false negative classifications of hardbottom.

Chapter Four examines the demersal reef fish communities of the WFS using the same towed video dataset collected by C-SCAMP. The analyses identify significant groupings of co-occurring species, as well as spatial and temporal differences in community composition, and the taxa driving those patterns. Spatially explicit, multiscale regression models are used to relate fish communities to environmental drivers, including oceanographic conditions and substrate characteristics. Results indicate that fish-environment relationships are both scale- and taxa-dependent, with water depth acting as the dominant driver of community structure at broad spatial scales, and substrate-based predictors, including percent hardbottom, roughness, and measures of vertical relief, becoming more important at finer scales.

Together, these findings demonstrate that explicitly accounting for spatial scale improves both habitat mapping accuracy and allows for richer ecological inference. The integration of multiscale terrain analysis, facilitated by tools such as MultiscaleDTM, with acoustic data and underwater video observations, along with spatially explicit ecological modeling, highlights the value of multiscale approaches for predictive habitat modeling and understanding fish-environment relationships. These methods and findings demonstrate the importance of explicitly considering multiple spatial scales in habitat characterization and ecological inference, with important implications for marine resource management and marine spatial planning.

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