Effects of high-density suspended sediments on primary production at the Yangtze Estuary

Suspended sediments from the Yangtze River and re-suspended sediments caused by tidal disturbance form a high turbidity area with a transparency of lower than 3m at the Yangtze Estuary. Light limitation resulting from suspended sediments is stronger than nutrient released to the estuarine ecosystem, which makes the primary production, biodiversity and density at a lower level at the area than adjacent sea. It is estimated that the absorption and assimilation ability of phytoplankton at the Yangtze Estuary are 66400t/km²·a for N and 9220t/km²·a for P, which are only 10.5% of other coastal areas with higher bio-productivity and photosynthesis, such as California Coast Zone. Thus, the ability of absorption and assimilation for nutrients is weakened by high-density suspended sediments, which indirectly enhance the eutrophication outside the turbidity area and become a potential factor for the red tide.