Atmospheric Deposition of Nutrients and Trace Elements to the Coastal Oceans: A Review

Abstract

Atmospheric transport and deposition of pollutants to the coastal oceans increase dramatically due to the impacts of climate change and human activities. The paper summarizes a number of researches after 1997 on the atmospheric inputs of nutrients and trace elements to the world coastal oceans with emphasis on the eastern China seas. The atmospheric fluxes of nitrogen and phosphorus to the coastal oceans range from 13 to 73 mmol N /( m2. a) and 0. 11 to 1. 6 mmol P /( m2.a) ,respectively. North Sea appears to be influenced by relatively higher atmospheric flux of nitrogen ( 70 mmol N /( m2.a) ) compared to the eastern coast of North America ( 50 mmol N / ( m2.a) ) and eastern China seas ( 50 mmol N /( m2.a) ). Mediterranean Sea and the Gulf of Aqaba ( Red Sea) receive the lowest fluxes of nitrogen as well as phosphorus from the atmosphere. The deposition fluxes of trace elements vary significantly in both time and space with the highest flux approximately 3 orders of magnitude higher than the lowest one. The flux variations of crustal-dominated trace elements such as Al and Fe are strongly related to the dust transport and agricultural activities of adjacent land,while atmospheric fluxes of non-crustal trace elements like Cd,Zn and Pb are mainly determined by industrial and mobile emissions. Atmospheric inputs of trace elements can partly dissolve into the seawater with the solubility ranging from a few percent to 50% and that portion may become bioavailable and thereby influence the costal ecosystem. For many coastal oceans including East China Sea and Yellow Sea,atmospheric fluxes of nutrients and certain trace elements may exceed their riverine inputs. Atmospheric deposition contributes significantly to the coastal eutrophication,and its episodic nature can enhance primary productivity within a short period,which may induce a harmful algal bloom ( red tide). Trace element deposition may have toxic effects on specific phytoplankton and influence both primary productivity and ecosystem structure of the coastal area. Further studies should be conducted for accurate estimation of atmospheric fluxes of various pollutants to the coastal oceans and for understanding their roles in marine phytoplankton growth.