ARTHUR – AQUATIC RESOURCE TOOL FOR HIGH-FREQUENCY UNDERWATER RESEARCH: ASSESSING SENTINEL RESPONSES OF LAKES TO CLIMATE CHANGE

Automated sensor platforms are becoming increasingly valuable tools to understand the sentinel responses of lakes to climate change. Based on the recent development of a novel, small, portable buoy, we designed a profiling buoy that can be deployed in the smaller lakes that dominate the distribution of lakes worldwide. A new winch system, which uses a single lay wheel, relies on wireless technology to allow a suite of sensors to collect high frequency data at multiple depths without requiring an additional electric cable. The instrument array includes sensors capable of capturing phytoplankton community indicators, dissolved organic carbon dynamics, changes in transparency, mixing processes, and oxygen depletion, as well as sensors aiding in the calculation of heat fluxes and water budgets. This unique integration of different sensors advances the field by seeking to use the latest technology to study some of the many interconnected processes that occur in lakes.

During the summer and fall of 2012, ARTHUR, the profiling buoy, was deployed in Lake Lacawac, a moderately dystrophic lake in northeastern Pennsylvania. Preliminary data show the advantage of night profiles to avoid non-photochemical quenching, often an issue when using fluorescence sensors. In addition, manual samples of dissolved organic carbon (DOC) collected over the summer were compared with CDOM sensor data from the profiling buoy to investigate seasonal changes in DOC optical quality. A climate forcing optical index was developed that allows for seasonal and inter-annual comparison of extreme events, in the form of severe droughts or intense precipitation events. The automated profiling also allows for storm event monitoring where manual sampling is unable to capture the effects of extreme events on lakes at high-frequency. Advanced sensor technologies that enable full vertical profiling are necessary to fully characterize the response of lakes to climate change and other natural or human disturbances.