[1] Lakes within fluvial networks may affect dissolved organic matter (DOM) dynamics in streams by dampening spring DOM snowmelt flushing responses and/or by increasing summer DOM production. We assessed the temporal variability of dissolved organic carbon (DOC) concentration and DOM characteristics (specific ultraviolet absorbance (SUVA 254 ); DOC:dissolved organic nitrogen (DOC:DON)), as well as DOC export in seven paired lake inflows and outflows in the Sawtooth Mountain lake district, Idaho. We hypothesized that lakes would decrease stream DOM temporal variability and increase DOM export as a result of autotrophic production. We correlated DOM variability with landscape factors to evaluate potential drivers of DOM temporal patterns (measured as coefficient of variation). Coefficients of variation were 40-90% higher in lake inflows than outflows for DOC concentrations, characteristics, and DOC:DON. Increases in DOC concentrations on the ascending limb of the snowmelt hydrograph were greater in lake inflows than outflows, and on average mean DOC flux occurred 5.4 days earlier in the inflows than for the outflows. During base flow, mean outflow DOC concentrations were 1.7 times greater than inflows, and six outflows had higher annual export than inflows. Combined, these results illustrate that lakes alter the magnitude, timing and temporal variation of DOM concentration and characteristics exported from subalpine watersheds. This buffering effect results from a seasonal shift in the balance between hydrological versus biological controls on DOC dynamics, where lakes act as a sink during the spring when hydrologic controls dominate watershed DOM transport and act as a DOM source during summer.
Abstract:The current and future direction of aquatic ecological research leans toward addressing questions that cover multiple scales and levels of complexity. Historically, the ability to do comparative aquatic research across large spatial and temporal scales has been impeded by a lack of comparable measurements, standard methods, and a well organized data management and retrieval system. The National Ecological Observatory Network (NEON) is the first continental-scale ecological observation system designed to collect and provide freely available data on the drivers and responses of ecological change. In this paper, we describe past and present attempts to work across multiple scales in aquatic ecology, and the potential use of NEON aquatics data and infrastructure by researchers to integrate and expand ecological research programs and address novel ecological questions.
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