As a community paleoecologist, I use the record of shallow seagrass-dwelling mollusks to infer change in marine environments.Click the button below to hear me talk about my research on this EcoTalk Podcast from 2013.
|
As hubs of anthropogenic activity, coastal environments have long been subjected to many types of stressors. Ecologists seek to mitigate the impacts of such stressors on environments but struggle to define pre-disturbance ecological baselines, particularly in areas that have been affected by human activity for centuries (or more). Conservation paleobiology is a relatively newly-developed field that seeks to apply paleontological tools and techniques to modern day ecological issues. It is within this scientific framework that my research interests lie.
|
Mixing it up in seagrass beds
In most shallow marine environments, sand accumulates very slowly (a fraction of a millimeter per year) and is subjected to repeated mixing through the action of waves and burrowing organisms. In seagrass beds, this mixing effect is lessened because the dense seagrass root-rhizome mat stabilizes the sediments and discourages burrowers from living there. Thus, there is the potential that the mollusks that comprise the death assemblage may be preserved in their original stratigraphic positions within the sediments. If this is the case, then it might shed light on when and why we see compositional variation in mollusks through time with a resolution that is not normally possible in shallow marine settings.
Based on compositional changes alone, it appears that there are differences in the molluscan death assemblage with depth in the cores we have collected. Further, the life assemblage is most similar to the shallowest death assemblage, supporting the possibility that the sediments have not been entirely homogenized through mixing. We are currently in the process of dating shells from shallower and deeper layers to determine if ages increase with depth, further supporting our hypothesis. Click here to read more about that process.
Based on compositional changes alone, it appears that there are differences in the molluscan death assemblage with depth in the cores we have collected. Further, the life assemblage is most similar to the shallowest death assemblage, supporting the possibility that the sediments have not been entirely homogenized through mixing. We are currently in the process of dating shells from shallower and deeper layers to determine if ages increase with depth, further supporting our hypothesis. Click here to read more about that process.
Collecting sediment samples in St. Croix, USVI.On the conservation paleobiological side of my research, I am interested in how humans impact their environment. To that end, one of the indicators that I have been studying is the concentration of an array of metals in marine and terrestrial sediments. Looking at the marine sediments associated with each death assemblage, there is clear variation in metal abundances among localities. So, in 2014, we went back and collected terrestrial sediments from stream beds all around the island to try and determine the source of metals that end up in coastal sediments.
Using XRF (x-ray fluorescence), I can detect ~25 metals, some of which are strong indicators of anthropogenic activity (e.g. mercury). This project is currently underway and will also soon incorporate analyses of metals in individual mollusk shells as a direct indicator of what metals are being taken up by different taxa at different locations. |