Upper suboxic water masses confine a majority of the microbial communities that can produce up to 90 % of oceanic N<sub>2</sub>. This effective N<sub>2</sub>-yielding section encloses a suspended small-particle layer, inferred from particle backscattering (bbp) measurements. It is thus hypothesized that this layer (hereafter, the bbp-layer) is linked to N<sub>2</sub>-yielding microbial communities such as anammox and denitrifying bacteria – a hypothesis yet to be evaluated. Here, data collected by three BGC-Argo floats deployed in the Black Sea are used to investigate the origin of this bbp-layer. To this end, we evaluate how key drivers of anammox-denitrifying bacteria dynamics impact on the vertical distribution of bbp and the thickness of the bbp-layer. In conjunction with published data on N<sub>2</sub> excess, our results suggest that the bbp-layer is at least partially composed of anammox-denitrifying bacteria for three main reasons: (1) strong correlations are recorded between bbp and nitrate; (2) the top location of the bbp-layer is driven by the ventilation of oxygen-rich subsurface waters, while its thickness is modulated by the amount of nitrate available to produce N<sub>2</sub>; (3) the maxima of both bbp and N<sub>2</sub> excess coincide at the same isopycnals where denitrifying-anammox bacteria coexist. We thus advance that bbp and O<sub>2</sub> can be exploited as a combined proxy to delineate the N<sub>2</sub>-yielding section of the Black Sea. This proxy can potentially contribute to refining delineation of the effective N<sub>2</sub>-yielding section of oxygen-deficient zones via data from the growing BGC-Argo float network.