Abstract:To understand the spatial distribution characteristic of diatoms in Aojiang River estuary area, Fujian, surface sediment samples from 13 sites were collected in July 2019, and the relationship between distribution of diatoms and environmental factors was studied. The results showed that there were 114 species of diatoms belonging to 39 genera identified from sediment samples. The abundance of diatoms from estuarine to offshore was firstly decreased and then increased. Cluster analysis showed that the main diatom species could be divided into fresh water assemblage zone and brackish-brackish water assemblage zone. Surface water temperature and salinity were the main environmental variables that affect the distribution of diatoms by canonical correspondence analysis (CCA). The salinity in the estuary area was relatively low, freshwater diatoms, such as Achnanthes biasolettiana, A. delicatula and Aulacoseira granulata were the dominant species. The salinity of northern offshore area of Aojiang River was high, marine diatom Surirella fluminensis was dominant. However, the salinity of southern offshore area was low, the abundance of freshwater diatom Achnanthes delicatula was higher than that in northern area. In addition, it is speculated that there may be some water pollution in estuary and the southern offshore area.