My research investigates physical processes in lakes and the coastal zone and their biogeochemical and ecological consequences. Studies are ongoing in Arctic and Subarctic lakes, Mono Lake, CA, tropical lakes in East Africa and the Amazon Basin, and the waters of coastal California. Our recent limnological research has illustrated the importance of instabilities of non-linear internal waves for turbulence production in the thermocline near the boundaries of lakes and resulting nutrient and gas fluxes. We have also quantified turbulence at the air-water interface due to changes in rates of heating and cooling and differences in wind speed. With this information we are developing new models of the gas transfer coefficient as needed for accurate estimates of regional and global carbon fluxes. Our goal is to extend our understandings of physical-biological coupling in individual lakes to the landscape scale using dmensionless indices and by establishing links to larger scale climate.