Long-term variations and influence factors of nutrients in the western North Yellow Sea, China.

Abstract This study investigated the long-term variations and compositions of nutrients and the associated controlling factors in the western North Yellow Sea on the basis of historical data. The NO 3 -N and DIN concentrations and N/P showed continuous increases over the past two decades, which were dominantly affected by riverine inputs, such as inputs from the Yellow River, Yalujiang River and Jia River and atmospheric deposition. However, due to human activities, such as dam construction in rivers and climate change, the SiO 3 -Si concentrations and Si/P ratios decreased before the early 1990s and then gradually increased. The vertical distributions of nutrients displayed higher concentrations at the bottom than those at the surface in summer, which was attributed to the combined influence of the thermocline, the Yellow Sea Cold Water Mass, the Yellow Sea Warm Current and biological activities. Highlights • The NO 3 -N and DIN and N/P showed continuous increases over the past two decades. • The SiO 3 -Si and Si/P decreased before the early 1990s and then gradually increased. • Variations in N and N/P were affected by riverine inputs and atmospheric deposition. • Variations in SiO 3 -Si and Si/P were caused by human activities and climate change. [ABSTRACT FROM AUTHOR]