Perpetual atmospheric dry deposition exacerbates the unbalance of dissolved inorganic nitrogen and phosphorus in coastal waters: A case study on a mariculture site in North China

Highlights: • Dry deposition was an important source of nutrient load in seawater of the study area. • DIN and DOP were the dominant N and P species in dry deposition fluxes. • Low concentrations of DON and DSi in February were related to COVID-19 lockdown. • Bioavailable N in dry deposition could support >6% of the new production in winter. • Dry deposition could exacerbate the unbalance of DIN and DIP in coastal waters. The monthly magnitudes of dissolvable nutrients through atmospheric dry deposition (ADD) and their ecological effects to the coastal waters around the Yangma Island, North Yellow Sea, were investigated for one year. The results indicated that anthropogenic activities were the major sources of dissolvable inorganic and organic nitrogen (DIN and DON); dust events were the major sources of inorganic phosphorus (DIP) and silicate (DSi); however, organic phosphorus (DOP) could be originated from marine biological activities. The annual ADD fluxes of DIN, DON, DIP, DOP and DSi were 21.8, 2.7, 0.10, 0.30 and 0.73 mmol m⁻² yr⁻¹, respectively. Overall, the new production supported by the bioavailable nitrogen through ADD in winter was up to 9.14 mg C m⁻² d⁻¹. Notably, the annual molar ratio of DIN/DIP through ADD was 216 ± 123, which was much higher than that of the dissolved inorganic nitrogen to phosphorus in seawater and might exacerbate their unbalance in some coastal waters.