Browsing by Author "Schultz, Tom"

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    A Tale of Two Reefs: Quantifying the Complexity of Artificial Reefs and Natural Reefs Utilizing Structure-from-Motion 3D Modeling
    (2018-04-26) Johnson-Sapp, Kelsey
    Anthropogenic impacts on coral reefs have stoked compounding pressures like bleaching, ocean acidification, and disease resulting in a significant global decline of coral reef cover that has weakened the resilience of adjacent coastlines to shoreline erosion. In lieu of natural defenses, coastal cities like Miami have installed artificial structures to serve as both breakwaters and refuges for coral recruitment as part of their reef mitigation initiative. However, the degree of manmade structures’ success in fulfilling these roles when compared to natural reefs is heavily debated. Photogrammetry data of three artificial and three natural reefs was collected off of the coast of Miami utilizing Structure-from-Motion methodologies to compare complexity metrics and coral coverage of each site. This approach utilizes complexity as a proxy to determine which type of habitat is more conducive to mitigating shoreline erosion and restoring coral populations. Sites were measured at geospatial scales of 1cm, 10cm, and 1m cell classes. Results revealed no significant difference between habitat types for any metric of complexity at any scale. This was an interesting finding considering the highest coral coverage was noticeably low at 30% for a natural reef, yet the low ratio of coral cover was still comparable in complexity to artificial sites. However, when artificial reefs were compared individually against the mean of combined natural reefs, a barge site indicated significant difference in complexity for all metrics on a 1cm scale, but with variable results for the other two classes depending on the metric. Coral coverage on all artificial sites was negligible, suggesting that coral recruits may exhibit site preference for natural reefs as opposed to barges or cement structures.
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    Population Genomics of Bottlenose Dolphins (Tursiops truncatus) in the Northwest Atlantic
    (2021-04-30) Shintaku, Nikki
    Bottlenose dolphins (Tursiops truncatus) are widely accepted as belonging to one of two ecotypes: offshore or inshore. These ecotypes exhibit remarkable differences in ecology, morphology, and genetic diversity. However, regional patterns of genetic differentiation and stock delineation remain poorly defined for both ecotypes. To improve our understanding of the population structures among these groups we investigated genome-wide genetic variation from 96 biopsy samples collected from bottlenose dolphins in inshore and offshore waters of the northwest Atlantic from North Carolina to Florida using restriction site associated DNA sequencing to infer population structure. Analysis of 14,783 single nucleotide polymorphisms revealed at least three genetically differentiated populations. Our results suggest an inshore population along North Carolina’s Outer Banks (n=32), an offshore population off the continental shelf break from North Carolina to Jacksonville, Florida (n= 38), and a shelf population off Jacksonville, Florida (n=26). Bayesian clustering showed significant admixture between the North Carolina and Jacksonville populations, providing potential evidence of historical or current gene flow. Most of the offshore samples were collected off Cape Hatteras, but this population also includes four individuals sampled beyond the continental shelf break off Jacksonville, FL, in close spatial proximity to shelf animals. This suggests a sharp distinction between shelf and offshore individuals structured by the shelf break itself. Such habitat heterogeneity is likely a driver in diversifying populations through influences on social behavior and foraging strategies. Our analyses provide fine-scale genetic resolution of bottlenose dolphin population differentiation in the Western North Atlantic. These results help inform conservation management and advance our understanding of processes that may drive the evolution of population genetic structure.