Sulfur is an important nutrient in freshwater systems that interacts with and controls other biogeochemical cycles such as those of iron and phosphorus. We are studying sulfur metabolism in anoxic temperate and tropical freshwater lakes to understand the roles of microbes and viruses in controlling biogeochemistry and ecosystem-level processes.
Our field sites include Lake Mendota in Wisconsin, USA (next door to us!) and Lake Tanganyika, Tanzania.
Lake Tanganyika is the second largest and deepest lake on Earth, with a maximum depth around 1400m. It is famous in the field of ecology for its rich animal biodiversity, yet little is known about the microbes of the lake. Lake Tanganyika’s water column is extremely unique, it is permanently separated (stratified) into two distinct layers, a layer of oxygenated water floating atop a layer of anoxic (no oxygen) waters. In fact, everything below ~ 100m is devoid of oxygen, making Lake Tanganyika the largest body of anoxic freshwater on Earth (besides groundwater). Yet, many bacteria and archaea are able to live in anoxic conditions, due to their diverse metabolism. Working with collaborators in the US, Germany and Tanzania, we are seeking to study the microbial ecology and functions of the microbes living in this unique lake.
Lake Mendota is located adjacent to the UW-Madison campus, and is popular location for recreational activities for Madison residents. Pressing environmental challenges are of concern to the lake’s ecosystem health.
The full cycles of oxygenation and anoxia that characterizes Lake Mendota’s dynamic water column annually is the driver of many interesting microbial ecology questions. We study the microbial processes that happen in the anoxic water column, and how that is linked to nutrient availability over various time scales. Some of the current projects include investigating how biogeochemical cycles depend on anoxic conditions (e.g. sulfur or nitrogen) are driven by bacterial and viral communities. Additionally, we are investigating how microbially-driven sulfur cycling is linked to the iron and sulfate chemistry in the water column, over a range of temporal and spatial scales.