Atmospheric input of inorganic nitrogen species to the Kiel Bight

Abstract

The atmospheric input of inorganic nitrogen species to the Kiel Bight (south-west Baltic Sea) is characterized. This characterization is based on marine precipitation samples collected at Kiel Lighthouse in weekly intervals during a whole year, using wet-only and bulk-sample methods. The temporal patterns of nitrate and ammonium concentrations are highly variable, with less variability during summer. Maximum concentrations were found in winter. The annual precipitation weighted mean concentrations are 124 μmol·dm−3 for nitrate and 172 μmol·dm−3 for ammonium. Nitrite concentrations were low, its contribution to wet deposition being thus negligible (on average only 0.3% of the wet deposition of nitrate plus ammonium). Dry deposition represents approximately one third of the total input of airborne nitrogen species. Wet and dry deposition represent an annual input of around 5000 tons of nitrogen to the Kiel Bight (2571 km2), being a significant contribution to its total nitrogen content (5900 tons in winter). The hypothesis of a triggering effect of intense nitrogen wet deposition pulses for summer phytoplankton blooms is raised and a possible relationship of phytoplankton patchiness with these deposition patterns to the sea is suggested.