A number of aquatic ecosystem responses to changing climate have been documented in Lake Washington and other lakes around the world. These responses could only have been detected and understood in the context of climate change as the result of consistent long-term monitoring of physical, chemical, and biological components of the ecosystem. Further understanding of the effects of changing climate will come from continued comprehensive routine monitoring. However, more frequent sampling (daily to sub-daily) (e.g., Staehr and Sand-Jensen 2007) coupled with modeling (e.g, Peeters et al. 2007) has begun to greatly improve the understanding of linkages between climate and lake ecosystem response. A recent re-assessment of the "Lake Washington Story" (Hampton et al. 2006), highlighted the key role played by picoplankton and cryptomonads in zooplankton growth that were previously overlooked by other researchers of Lake Washington (also see Hampton 2005, Hampton and Schindler 2005). Considering the hypothesized connection between picoplankton and lake warming trends (Fietz et al. 2005, Stockner 1998), this new twist in the Lake Washington Story deserves further attention.

The initial continuous temperature monitoring effort described in this report, demonstrated the methods and utility of frequent temperature measurement in the three major lakes routinely monitored by King County. These data match less frequent routinely collected data in long-term warming trends but adds more precise information on dates and duration of seasonal stratification and periods of maximum (and minimum) temperatures. These data also inform fish and hydrodynamic studies that historic data cannot. Also, example uses of these data – Index of Thermal Stress (ITS), thermal stability calculations, and identification of internal seiches have been provided.