I am a marine scientist who uses both modern organisms and the fossil record to study the ways in which marine calcifiers record and respond to climate variability in coastal environments. My work uses the shells of marine molluscs to gauge their responses to changing climates through time to contextualize modern changes. I use a combination of fieldwork, meta-analyses, and sclerochronological tools.
|
Read my recent publication on spatio-temporal controls on shell growth features in the California mussel.
Below are a few conference presentations from my dissertation work.
1. Investigating growth band patterns in the California mussel shell
Given its history as an archaeologically significant species, the California mussel (Mytilus californianus) presents a unique opportunity to examine and compare environmental and biological changes recorded in its shell at various sites along the California coast through time. Using a suite of modern and archival shells from both sites collected over different seasons from 1996-2020, I investigate average growth band thickness, average number of dark-light couplets, season of collection, and most recent band color. Relationships established here will help to 1) determine the timing and resolution of a growth band (and constrain species- and site-specific ‘growing windows’), 2) identify distinct growth trends between northern vs. southern California mussels over the past two decades, and 3) utilize dark (slow growth) bands as a physiological proxy for periods of anaerobiosis, or non-ideal growing conditions.
Presentation: Padilla Vriesman, V., Carlson, S.J., Hill, T.M., Garcia, L. Interpreting growth band patterns in the California mussel for use as an environmental and biological archive. GSA Connects Online, 2020. Funding: Cordell Durrell Grant from UCD Earth and Planetary Sciences Department and GSA Grad Student Research Grant |
2. Synthesizing Holocene stable isotope data from California mussels
We synthesized oxygen and carbon isotope data generated from Mytilus californianus specimens from 13 archaeological sites south of Point Conception (~35°N) spanning the mid to late Holocene (8800 BP through 500 BP). We compare both average values and extreme values through time and across locations in order to identify site-specific changes to M. californianus shell chemistry. Mussel shells from 8800 BP through 2000 BP are chemically different from shells collected in the past 500 years (p < 0.05, ANOVA and Tukey HSD). We established a range of “normal variability” and found only two points where average ocygen isotope values extends beyond the range: once at ~2000 BP and once in modern shells.
Presentations: (1) Padilla Vriesman, V., Palmer, H.M., Bean, J.R., Banker, R.M.W, Carlson, S.J., Hill, T.M. Evaluating chemical changes in a culturally significant intertidal marine calcifier throughout the Holocene, SACNAS Conference, 2020. (2) Padilla Vriesman, V., Palmer, H.M., Banker, R.M.W., Bean, J.R. Synthesizing geochemical data from archaeological shells to construct long-term, seasonal archives of nearshore environments. AGU Fall Meeting, 2019. Funding: Mildred Mathias Graduate Research Fellowship |
3. Examining growth rate and shell chemistry of the California mussel
We analyzed and compared trace elemental ratios (Mg/Ca, Ba/Ca) and microstructural features in modern Mytilus californianus (mussel) shells from Bodega Bay, CA. We found that Mg/Ca records relative changes in sea surface temperature, although it is strongly mediated by growth rate. We also found that ontogenetic Ba/Ca profiles are characterized by low background variability (~ 0.4 mmol/mol) with extreme peaks. Interpreted SST extrema and rainfall events can be corroborated by the instrumental records, and these paired geochemical-microstructural proxies can then be applied to archaeological and fossil shells to more accurately track changes in nearshore sea surface conditions (e.g. warm-cool oscillations, upwelling intensity) and identify "extreme" events (storms, heatwaves, ENSO, etc.).
Presentation: Padilla Vriesman, V., Hill, T.M., Carlson, S.J. Exploring the paleoceanographic utility of intertidal mussels using paired geochemical and microstructural proxies, Ocean Sciences Meeting, 2020. Funding: National Sciences Foundation Graduate Research Fellowship |