Dissolved silicate in coastal marine rainwaters: Comparison between the Yellow Sea and the East China Sea on the impact and potential link with primary production

Abstract

Rainwater samples are collected from islands and seagoing cruises in the Yellow Sea and the East China Sea to determine concentration and to estimate deposition flux for dissolved silicate (DSi), together with other nutrients (e.g., nitrogen) by spectrophotometry. Concentrations of dissolved silicate in rainwater show considerable variation in time and space, with 0.5–15 μM at the Yellow Sea and the East China Sea. The (NO 3 − + NH 4 + )/DSi ratio in rainwater changes over up to 2 orders of magnitude, with high levels in winter and low in autumn. Levels of DSi falls with higher rainfall, and a positive relationship can be established with amount of total particles in rainwater samples. The deposition of DSi via rainfall is 0.97 × 10 9 mol yr −1 for the Yellow Sea and 2.0 × 10 9 mol yr −1 for the East China Sea, respectively, 20–40% higher than the atmospheric dry deposition estimated by previous work but shows critical importance to the marine ecosystems at low trophic level in terms of comparison of chemical budget and new production. The extrapolation to the global ocean indicates that aeolian inputs (i.e., wet and dry depositions) of dissolved silicate can be on the order of 0.9 × 10 12 mol yr −1 , with ∼20% of this amount is distributed in the continental margin.