Stable isotope analysis is potentially one of the most exciting techniques that has emerged in recent years. While the use of stable isotopes in ecology and the need for such studies have expanded rapidly, stable isotope ratio measurements require complex and costly equipment. However, the use of stable isotopes in animal and plant physiological ecology and ecosystem ecology are among the few areas in ecology where the rate of progress has been limited by the availability of instrumentation. The full extent to which stable isotope analyses will be used to solve problems in ecological research is yet to be determined. In this proposal, we are requesting funds to purchase an isotope ration mass spectrometer and the necessary preparation devices to process biological tissues and fluids. As a part of recent facility developments, Boston University has designed space for a stable isotope laboratory in its new (under construction) Biology Research Laboratories. This facility is conceived as a multi-user isotopes of particular interest to animal and plant physiological ecologists, and ecosystem ecologists.