In-stream processes can influence eulittoral zone (nearshore) productivity dynamics through modulating the timing and amount of nutrient delivery to lakes. The degree to which mountain stream processes influence nearshore lake productivity as a function of their seasonal flow regimes remains unclear. To investigate how seasonal variation in stream flow and in-stream metabolic and nitrogen uptake rates covary with nearshore lake productivity, we continuously monitored dissolved oxygen, temperature, stream specific conductance (SPC) and collected surface and pore water samples for nutrient concentrations in streams and around the outlets and the nearshore of Lake Tahoe (California‐Nevada, United States of America), in two watersheds with differing flow regimes. We found that nearshore net ecosystem production (NEP) was negatively correlated with the magnitude of daily streamflow (β_flow:  -0.618 ± 0.069, p< 0.001, r^2c = 0.112) and positively correlated daily SPC (β_SPC:  5.64 ± 0.327, p< 0.001, r^2c = 0.291). These patterns were particularly pronounced for the west shore of Lake Tahoe which has a greater amount of annual precipitation relative to the drier east shore. The positive and negative relationships between modeled nearshore NEP, SPC and streamflow, suggest that nearshore metabolism may be more related to changes in groundwater inputs relative to surface water. Observed patterns in autotrophic production indicate that precipitation accumulation in mountain watersheds can control the physical stream processes (streamflow, timing of baseflow, and water temperature) which may influence NEP immediately near stream outlets.

Primary Presenter: Kelly Loria, University of Nevada Reno (kelly.loria@nevada.unr.edu)

Authors:

Heili Lowman, University of Nevada Reno  (hlowman@unr.edu)

Jasmine Krause, University of Nevada Reno  (jasminekrause@unr.edu)

Robert Miller, University of Nevada Reno  (millerrob035@gmail.com)

Sudeep Chandra, University of Nevada Reno  (sudeep@unr.edu)

Joanna Blaszczak, University of Nevada Reno  (jblaszczak@unr.edu)