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The stream-lake interface (SLI) is a unique hydrologic environment for biogeochemical processing of nutrients. Constantz et al. [2016] identified two distinct types of SLIs, one that has been channelized to confine and focus flow and one that naturally meanders and periodically forms a barrier beach and backwater pond adjacent to the lakeshore.

In nutrient limited lakes, excessive amounts of dissolved inorganic forms of nitrogen (DIN) and phosphorous (DIP) can stimulate primary production and accelerate eutrophication, and thus management of lakes is often focused on identifying and reducing sources of DIN and DIP [Schindler, 2006; Hale et al., 2015]. Nutrient-rich groundwater discharge can provide an efficient source of nutrients for benthic algae as concentrations at the sediment interface will be higher relative to the more dilute adjoining water column [Hagerthey and Kerfoot, 1998; Rosen, 2015; Prouty et al., 2016; Anderson et al., 2002].

Direct and indirect hydraulic and thermal estimates of seepage fluxes indicated profound impacts of channelization on surface water-ground water exchanges at the SLI. Here we extend their study and analyze organic and inorganic forms of phosphorus and nitrogen, dissolved organic carbon (DOC), pH, specific conductance (SPC), and dissolved oxygen (DO) concentrations collected in these two SLI environments to better understand biogeochemical processing and the impacts of SLI geomorphology on nutrient transport to the lake-nearshore region.

Channelization appears to increase sediment mobilization at the SLI due to greater surface water velocities, as indicated by less dissolved organic nutrients in the streambed. Channelization also appears to reduce nutrient concentrations in groundwater discharging to the lake; however, this is likely balanced by a greater amount of organic nutrients entering the lake during episodic erosion of the stream mouth during high flow events

Nutrient delivery through pore water seepage at the lakebed from the natural stream-lake interfaces contributes to nearshore algal communities and produces elevated concentrations of inorganic nutrients in the benthic zone where attached algae grow.

For additional information, view the Nutrient processes at the stream-lake interface for a channelized versus unmodified stream mouth publication below.