Nitrogen loss in Saanich Inlet
We sampled a station at the mouth of Saanich Inlet, a fjord in British Columbia, during nine one-day cruises in 2008 and 2009. We observed the progression of NO3- consumption by denitrifiers in an expanding suboxic zone following major bottom water renewal events in fall 2008. We found a correlation between renewal events and tidal mixing, and derived high rates of N-loss from biologically produced N2 (from O2/N2/Ar ratios). Coupled NO3 isotopic composition suggested atmospheric N input in surface waters and NO3 regeneration in bottom waters. NO3 isotope effects in anoxic bottom waters were lower (as low as ~11‰) than the ~25‰ value for water column denitrification reported in previous studies, suggesting that ~50% of the total denitrification occurs, with a highly suppressed isotope effect, in the sediments of the Inlet.
Bourbonnais, A., M. F. Lehmann, R. C. Hamme, C. C. Manning, S. K. Juniper (2013), Nitrate elimination and regeneration as evidenced by dissolved inorganic nitrogen isotopes in Saanich Inlet, a seasonally anoxic fjord, Marine Chemistry, 157, 194–207.
Manning, C. C, R. C. Hamme, and A. Bourbonnais (2010), Impact of deep-water renewal events on fixed nitrogen loss from seasonally-anoxic Saanich Inlet, Marine Chemistry, 122(1-4), 1–10, doi:10.1016/j.marchem.2010.08.002.