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. 

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Relevant publications:

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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.

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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.

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