1. Carbon and phosphorus cycling at the sediment-water boundary in a deep lacustrine basin
James McManus, College of Oceanic and Atmospheric Sciences, Oregon State University
Our group is interested in the cycling of elements in aquatic sedimentary systems. We are particularly interested in the relationships among oxygen, carbon, the major nutrients, and a variety of trace metal and trace metal isotopes. Our focus for this project has been on Lake Malawi (Lake Nyasa), and the relationships among phosphorus and various elements that are sensitive to sedimentary reducing conditions. Phosphorus concentrations in Lake Malawi sediment vary by more than a factor of three. Concentration maxima are generally found in the upper 10 cm of sediment, with concentrations generally showing a decrease with depth. Although there is some indication that there are lower phosphorus concentrations with increasing abundance of metals associated with reducing conditions, this relationship is not uniform within the data set, implying that other factors aside from sedimentary redox are influencing sedimentary P burial.
We are currently extending our project to include Lake Tanganyika, and this work will include analyses of trace metal stable isotopes. Like Malawi, Tanganyika has a deep oxic/anoxic boundary and sampling above and below this zone allows for an improved understanding of the relationship between aquatic system reducing character and element burial.
Map showing location of Lake Malawi Modified from Wikipedia ( which is taken from the CIA’s World Factbook.