Experimental examination of the effects of atmospheric wet deposition on primary production in the Yellow Sea.

The effects of atmospheric wet deposition on primary production in the coastal Yellow Sea were examined by in situ incubation experiments in August, 1997. Phytoplankton species flourished in response to nutrient additions and chlorophyll-a (Chl-a) increased significantly when rainwater was added. Concentration of Chl-a increased 2.6 times with the addition of 10% (v/v) rainwater. In a coastal eutrophic region like Jiaozhou Bay, the impact of atmospheric wet deposition is negligible. However, the N/P ratio ranged from 22:1 to 80:1, indicating P limitation of photosynthesis in the Yellow Sea. During field observations, high N and low P rainwater was observed to be transported into the oligotrophic central Yellow Sea. Ammonium was used by phytoplankton in preference to nitrate, and Fe stimulated nutrient uptake by phytoplankton. Rainwater increased the Chl-a growth more than a single nutrient owing to the abundance of both plant and trace nutrients in the rainwater. A negative exponent relationship may exist between the impact of rainwater and total nutrient quality of the water in influencing phytoplankton growth.