Carbon substrate utilization and total prokaryotic abundance as proxies of microbial response to coastal-offshore gradients in Taiwan Strait

Located between the South and the East China Sea, Taiwan Strait (TWS) is a shelf-channel, with unique hydrological and geomorphological features affected by rivers inflow. In recent years, frequent algal blooms with red tides have occurred in this area, but information is still lacking on the structure and function of the microbial community inhabiting the TWS. To fill this gap, a multidisciplinary oceanographic cruise was organized by the IHB-CAS in May 2019 within the International research program Mechanisms of red tides and hypoxia as ecological marine disasters and technologies for its early warning along the Belt and Road Countries, funded by the National Key Research and Development Program of China (grant 2016YFE0202100). The aim of our study was to assess microbial distribution and function and their modulation in response to environmental gradients. Surface (0.5 m) water samples from 16 stations located along several north to south transects were collected; total prokaryotic abundance by epifluorescence microscope and carbon substrate utilization patterns by Biolog Ecoplates were estimated. Decreasing levels of community metabolism towards offshore stations was observed, with prevalence of complex Carbon sources and carbohydrates; prokaryotic abundances followed a patchy microbial distribution. This study provides a snapshot of the microbial abundance and activity in TWS as a model site of aquatic ecosystems impacted from land inputs, the obtained results highlight that microbial metabolism is more sensitive than abundance to environmental changes.