The world map of anthropogenic atmospheric nitrogen deposition and its effects on natural ecosystems is not described with equal precision everywhere. In this paper, we report atmospheric nutrient, sulphate and spheroidal carbonaceous particles (SCPs) deposition rates, based on snowpack analyses, of a formerly unexplored Siberian mountain region. Then, we discuss their potential effects on lake phytoplankton biomass limitation.

We estimate that the nutrient depositions observed in the late season snowpack (40±16 mg NO-N×m and 0.58±0.13 mg TP-P·m) would correspond to yearly depositions lower than 119±71 mg NO-N·m·y and higher than 1.71±0.91 mg TP-P·m·y. These yearly deposition estimates would approximately fit the predictions of global deposition models and correspond to the very low nutrient deposition range although they are still higher than world background values.

In spite of the fact that such low atmospheric nitrogen deposition rate would be enough to induce nitrogen limitation in unproductive mountain lakes, the extremely low phosphorus deposition would have made the bioavailable N:P deposition ratio to be frankly high. In the end, lake phytoplankton appeared to be hanging on the fence between phosphorus and nitrogen limitation, with a trend towards nitrogen limitation. We conclude that slight imbalances in the nutrient deposition might have important effects on the ecology of these lakes under the expected scenario of climate warming, increased winter precipitation, enhanced forest fires and shifts in anthropogenic nitrogen emissions.