Distribution of long chain alkyl diols in the East China Sea and its eco-environmental implications

Long chain alkyl diols (LCDs) in marine environments have been found useful in reflecting source organism ecology, ambient temperature, upwelling and nutrient conditions. However, the distribution of LCDs in the western Pacific, where wide shallow continental shelves and huge freshwater input from many world-class rivers occur, has been rarely reported. In this study, we analyzed surface sediments collected from the East China Sea for LCDs to explore their eco-environmental implications. Our results showed that the fractional abundance of C32 1,15-diol (FC32 1,15-diol) was highest in the Changjiang river mouth, with FC32 1,15-diol >15% implying significant freshwater input. The C28 and C30 1,13-diols showed a similar spatial distribution to C32 1,15-diol, suggesting that the long chain diol index (LDI), a sea surface temperature (SST) proxy, may be interfered by freshwater derived diols. By eliminating the freshwater-influenced samples (i.e., FC32 1,15-diol >15%), LDI reflected best the autumn SST, yielding minimum temperature residuals (0.2 ± 1.5 ℃). The C28 and C30 1,14-diols were abundant in the mid-depth (33–69 m) offshore environment receiving slight Changjiang River plume, and decreased in both the eutrophic estuarine and oligotrophic marine environments. This distribution pattern is similar to the reported Proboscia diatom distribution in this region, suggesting Proboscia diatom might be the source organism of 1,14-diols. Relative abundances of 1,14-diols and C30 1,15-diol were reversely related, which was surmised to result from the different source organism responses to SST change.