Prokaryote Community and Physicochemical Shifts due to Storm Induced Terrestrial Runoff in Subtropical Coastal Ecosystems

Angela Ares1, Margaret Mars Brisbin2, Kirk Sato3,4, Juan Pablo Martin Diaz1, Yoshiteru Iinuma5 and Satoshi Mitarai6, (1)OIST Okinawa Institute of Science and Technology, Marine Biophysics Unit, Onna, Japan, (2)University of South Florida, College of Marine Science, Florida, United States, (3)OIST Okinawa Institute of Science and Technology, Marine Biophysics Unit, Tancha, Japan, (4)University of Washington, Friday Harbor Laboratory, United States, (5)OIST Okinawa Institute of Science and Technology, Instrumental Analysis Section, Onna, Japan, (6)OIST Okinawa Institute of Science and Technology, Marine Biophysics Unit, Onna-son, Japan
Abstract:
Climate change scenarios predict an increase of frequency and intensity of extreme rain events (e.g. tropical storms or typhoons), making it essential to better understand how coastal ecosystems respond to such events. For instance -by responding extremely quickly to environmental changes- microbial assemblages can play an essential role as bioindicators of ecosystems health. However, while effects on corals and reef fishes are well-studied, little is known about short-term microbial responses to storm-induced terrestrial runoff, mostly due to forecast unpredictabilityand safety constraints in the field. In this study, field and mesocosms observations were combined to assess prokaryotic community dynamics (DNA metabarcoding) and changes in physicochemical properties during two storm-induced runoff events at the beginning and the end of the 2018 typhoon season (i.e. June and October) in Okinawa (Japan). Storms caused large and fast influxes of freshwater and terrestrial sediment, including moderate increases of macronutrients—especially SiO2and PO4. We detected a significant influx of common soil-derived bacterial phyla (e.g. Acidobacteria, Actinobacteria, Verrucomicrobia), as well as potential corals and human pathogens (e.g. Vibrio spp., Enterobacter spp., Campylobacterspp.) that may derive from other sources. Surprisingly, the effect on microbial communities was extremely short-lived and baseline assemblages were recovered within 3 days. These results were confirmed in concurrent mesocosms experiments, where microbial communities began recovering only 4 hours after soil addition and were fully recovered after 24 hours. We also observed that the late-season typhoon appeared to cause smaller acute effects on microbial communities, despite being a larger storm. Our results demonstrate rapid and context-dependent shifts in prokaryote communities due to terrestrially derived runoff in a subtropical coastal ecosystem.
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