Transparent exopolymer particle (TEP) and its impact on marine carbon transport along the East China Sea coast

•TEP is an important ecological indicator for marine carbon transport.•Hydrological condition is the controlling factor affecting TEP distribution.•TEP in the seawater has a longer residence time and is more easily degraded than other forms of POC. Transparent exopolymer particle (TEP) is a transparent jellylike substance characterized with high carbon concentration, playing an important role in the marine carbon cycle. Based on a survey of the East China Sea coast in summer of 2020, the distribution, controlling factors of TEP and its impact on marine carbon transportation were discussed. The results showed that the TEP in the surface decreases from northwest to southeast gradually with an average concentration of 214.90 µg Xeq./L, which is basically consistent with the distribution of POC, Chl a and NO3-N. The TEP in the water of 10 m, 20 m, and 30 m also gradually decreases from northwest to southeast horizontally, while it is high in the surface and bottom layer, and low in the middle water layer vertically. The hydrological situation of the study area is complex and is the main factor affecting the distribution of various parameters including TEP. The TEP in the seawater has the characteristics of high TEP-C/POC, low settling ratio and high degradation ratio. The TEP-C/POC in the seawater is 32.03%, which is extremely higher than that of 14.46% in the surface sediments; the settling ratio of TEP is 17.67%, which is extremely lower than that of 50.31% for POC; the degradation ratio of TEP is 82.79%, which is extremely higher than that of 49.69% for POC. These results together indicated that TEP in the seawater has a longer residence time and is more easily degraded than other forms of POC.