Another research direction focuses on molecular understanding of the composition of natural waters and how it affects both the ecological function of aquatic ecosystems, the transport and fate of nutrients and pollutants, and the development of analytical methods for natural waters. For example, one current project examines the composition, chemical reactivity, and biological utilization of the naturally-occurring organic carbon that is present in all natural waters. This material is an important component of the global carbon cycle. However, the chemical mechanisms that determine its molecular structure and its fate in the environment are not well understood. We use a suite of analytical and biochemical methods to examine this material and to study its physical, chemical, and biological transformations in the environment.