Paytan Biogeochemisty Lab

photos of sunsets

The Paytan Lab is constantly developing new projects and changing the direction of current projects. Please be aware that these brief descriptions may change at any time.

Links to the left lead to the Project subsections. Publications related to each project are included with the project summary.


Our group's primary research interests lie in the fields of biogeochemistry, chemical oceanography, and paleoceanography. We use both chemical and isotopic tracers in diverse environmental samples such as water, sediments, aerosol, and vegetation in order to study present and past biogeochemical processes on a wide range of temporal and spatial scales. An over-arching goal of our research is to link changes observed in the earth and ocean systems to global changes in climate and tectonics with an emphasis on human impacts.

Diagram of the biogeochemical cycles and how land, sea, and air interact.

Paleoceanography is the study of past oceanic conditions on geologic time scales. Of interest are past temperatures, salinity, movement of water masses, and biological activity of phytoplankton - algae that is at the base of the marine food chain. Because the world's oceans closely interact with the atmosphere, paleoceanography can also tell us about past atmospheric conditions. Buried in sequental layers of ocean sediments are the remains of ocean activity such microscopic fossils, minerals, and even elemental changes within minerals and fossils that reveal information about what conditions formed them. These remnants of past chemistry and biology are called proxies and include marine barite, organic carbon, and many isotope systems within these substances.

Biogeochemical cycles describe the interactions between freshwater and oceanic chemistry and the biology - algae, microorganisms, fish - that consumes them. Particularly, we are interested in the nutrients nitrate, phosphate, ammonium, and silicate - the same nutrients found in plant fertilizer - which impact the growth of organisms in the freshwater and marine environments. Trace metals are another important aspect of water chemistry that impact biological activity. The projects in this category are studies of present conditions in lakes and coastal regions, including the groundwater and airborn dust that enters into these ecosystems.

Isotopic Tracers of Biological Processes are one set of the tools we use in our research into natural systems. Isotopes are varying types of atoms of the same element that have a differnt number of neutrons which changes the mass of the atom. In nature, many processes choose one type of the atom over another leaving an isotopic signature in the end product that we can measure. For example, tiny shelled microorganisms called benthic forams use one type of oxygen in ther shells when temperatures are lower than they would if the water was warmer. By determining the oxygen isotopic signature of the forams over time we can see the changes in temperature that have occured in the geologic record.

Page last updated on January 28, 2010