RESEARCH

My research questions focus on ecosystem responses to ecological change over broad time and spatial scales. I blend the disciplines of biogeochemistry, paleontology, ecology, and physiology using stable isotope techniques. My community encompasses a wide range of scientists, who help me navigate within and between various disciplines. For a list of my publications, click here.

ONGOING PROJECTS:

 


How does shark physiology affect the biological parameters for interpreting stable isotope data?


The vast majority of captive feeding studies use mammals, birds, or fish because they are easy to keep in captivity. However, shark physiology differs from each of these taxa because they are aquatic ectotherms, have carnivorous diets, retain urea, have cartilaginous skeletons, and use lipids for buoyancy control. These physiological traits impact the metabolic biochemistry and therefore biological parameters of discrimination factors and tissue incorporation rates. Interpretations of ecological patterns and processes requires tissue and taxa specific biological parameters, which may differ with protein quality, growth rate, and allometric scaling. Much of this work is uses specimens from a captive feeding study with leopard sharks at UC Santa Cruz. 
 
 
Shark teeth: ancient oceanographic data loggers 

Shark teeth preserve exceptionally well and their fossil record extends over 400 million years. These teeth also contain valuable biogeochemical signals related to past oceanographic conditions. Currently, shark teeth are largely overlooked in paleontological and oceanographic studies because many aspects of their biology is unknown (even in modern sharks!) I seek to establish the link between stable isotope patterns with marine ecological processes in modern sharks, then use this knowledge to interpret signals from fossil shark teeth. An important component of my work is the biological component - how can we use biology to extend our knowledge of paleoceanography? The shark fossil record is limited to teeth, but each tooth provides paleontological and biogeochemical data about ancient ecological and oceanographic conditions.
 
 
What are the vegetation and climate signals recorded in compound specific isotope analysis of leaf waxes?

Environment and climate conditions are often interpreted from compound specific isotope analysis of leaf waxes, but how do these signals differ with vegetation type, temperature change, water stress, and carbon dioxide concentration? Each of these factors affect plant physiology and perhaps lipid biosynthesis. In addition, I am also curious how lake sediments record the vegetation signal - what is the influence of surrounding terrestrial vs. aquatic and local vs. regional? This research has implications for experimental design and data interpretation of paleoclimate studies seeking to use compound specific isotope analysis of leaf waxes.
 


Subpages (2): COMMUNITY Curriculum Vitae
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