Microbial response to coastal-of shore gradients in Taiwan Straits: community metabolism and total prokaryotic abundance as potential proxies.

Located between the South and the East China Sea, the Taiwan Straits (TWS) are a marine shelf-channel area, with unique hydrological and geomorphological features affected by rivers in-flow and with recent algal blooms with red tides events. In this ecosytem, information is still lack-ing on the structure and function of microbial community. To fill this gap, a multidisciplinary oceanographic cruise was organized by the IHB-CAS in May 2019 within the International 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 Develop-ment Program of China. This study aimed at assessing microbial distribution and function and their modulation in response to environmental gradients. Surface (0.5 m) water samples from 16 stations along six north to south transects were collected; total prokaryotic abundance by epifluo-rescence microscope and carbon substrate utilization patterns by Biolog Ecoplates were estimated. Spatially, a patchy microbial distribution was found, with the highest microbial metabolic levels and prokaryotic abundance in the TWS area between Minjiang River estuary and Pingtan Island, and progressive decreases towards offshore stations. Complex Carbon sources and carbohydrates were preferentially metabolized. This study provides a snapshot of the microbial abundance and activity in TWS as a model site of aquatic ecosystems impacted from land inputs, obtained data highlights that microbial metabolism is more sensitive than abundance to environmental changes.