“…Many factors have been shown to control sediment NO 3 − reduction rates, including NO 3 − , C, and O 2 concentrations, and gene abundance (e.g., see Lisa et al, 2015;Pina-Ochoa & Alvarez-Cobelas, 2006). While the dynamics of water movement have been recognized as a controlling factor for N attenuation in hyporheic zones of streams and rivers (Böhlke et al, 2009;Grant et al, 2018;Harvey et al, 2013;Seitzinger et al, 2006;Zarnetske et al, 2012) and subterranean estuaries (Kroeger & Charette, 2008;Michael et al, 2005;Spiteri et al, 2008;Ueda et al, 2003), this lakebed study clearly emphasizes the importance of hydrologic transport and the associated seasonal variability on the spatial pattern of groundwater N delivery to lakes and the limiting effect of electron donor availability along upgradient groundwater flow paths.…”