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Utilizing the Subfossil Record of Seagrass-Associated Mollusks to Reveal Recent Changes in Coastal Marine Environments

Feser, Kelsey M.
http://orcid.org/0000-0003-3480-806X
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439304534

Abstract Details

2015, PhD, University of Cincinnati, Arts and Sciences: Geology.
Subfossil assemblages are used increasingly as tools for understanding recent environmental change in a wide variety of marine and terrestrial settings. In the emerging field of conservation paleobiology, a main focus has been on comparing subfossils to living assemblages to determine the extent of anthropogenically-mediated faunal change. These so-called “live-dead fidelity analyses,” while powerful, are limited because the specific nature of both spatial and temporal compositional changes are poorly understood in many settings, making it a challenge to determine the drivers of compositional similarities or differences between life and death assemblages. The goal of this dissertation was to characterize, in detail, the spatial and temporal dynamicity of shallow marine, seagrass-associated molluscan death assemblages at several localities around the island of St. Croix, US Virgin Islands. In the first chapter, I quantified the actual duration of taphonomic inertia, the time lag between an environmentally-mediated change in the composition of the life assemblage and the statistical equilibration of this change in the death assemblage. For this purpose, I utilized a unique dataset consisting of repeated life and death assemblage censuses available from one locality, Smuggler’s Cove, to demonstrate that shifts in the abundances of several common species were incorporated into the death assemblage fairly rapidly, typically on decadal timescales. This rapid equilibration serves as a caution for conservation paleobiologists who use death assemblages as historical baselines, and suggests that the duration of taphonomic inertia should be assessed directly whenever possible as part of live-dead analyses. The second chapter was premised on the hypothesis that, because their root-rhizome mats inhibit bioturbation, seagrass beds are more likely to preserve stratigraphy than bare sand substrates, and might therefore provide a direct, historical record of environmentally-mediated change to subfossil assemblages. By sampling bulk sediments in discrete depth intervals beneath the sediment-water interface, I investigated directly whether death assemblages around St. Croix changed compositionally with depth. Indeed, within-locality ordinations of molluscan abundance data revealed clear evidence of compositional stratigraphy at each locality. By examining changes in the abundances of individual species among depth intervals, I determined that compositional changes were consistent among the samples collected along transects at individual localities, but tended to vary from locality to locality. The final chapter examined spatial variation in molluscan composition among localities around St. Croix in relation to variations in metal concentrations within ambient sediments. In this case, ordinations revealed that most localities were compositionally distinct from one another in terms of both their molluscan and metal compositions. Furthermore, correspondence analyses revealed that certain metals were significantly associated with particular localities and even individual species. Two localities, the island’s principal dump site and a power plant, were strongly associated with a number of metals often indicative of anthropogenic impacts, and follow-up analyses are underway that explore the sources, either natural or anthropogenic, of these metals.
Arnold Miller, Ph.D. (Committee Chair)
Michal Kowalewski, Ph.D. (Committee Member)
Carlton Brett, Ph.D. (Committee Member)
Aaron Diefendorf, Ph.D. (Committee Member)
David Meyer, Ph.D. (Committee Member)
Amy Townsend-Small, Ph.D. (Committee Member)
206 p.
Geology
conservation paleobiology; seagrass; mollusk; live dead fidelity; taphonomic inertia; stratigraphy

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Citations

  • Feser, K. M. (2015). Utilizing the Subfossil Record of Seagrass-Associated Mollusks to Reveal Recent Changes in Coastal Marine Environments [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439304534

    APA Style (7th edition)

  • Feser, Kelsey. Utilizing the Subfossil Record of Seagrass-Associated Mollusks to Reveal Recent Changes in Coastal Marine Environments. 2015. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439304534.

    MLA Style (8th edition)

  • Feser, Kelsey. "Utilizing the Subfossil Record of Seagrass-Associated Mollusks to Reveal Recent Changes in Coastal Marine Environments." Doctoral dissertation, University of Cincinnati, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439304534

    Chicago Manual of Style (17th edition)

ucin1439304534
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