Heterotrophic bacteria respond differently to increasing temperature and dissolved organic carbon sources in two tropical coastal systems

Christian Lønborg, Federico Baltar, Maria de Lluch Calleja Cortes, Xose Anxelu G. Moran

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Temperature and substrate availability are important variables controlling marine heterotrophic bacterial activity. However, particularly in tropical regions it remains to be determined how these variables jointly affect bacterial activity. In this study we show how bacterial carbon cycling in two tropical coastal ecosystems (the Great Barrier Reef [GBR, Australia] and the Red Sea [Saudi Arabia]) are influenced by changing temperature (using a 6°C gradient) and the addition of dissolved organic carbon (DOC) from different sources (addition of mangroves and seagrass leachates, plus natural seawater). Our study demonstrates that elevated temperatures in the GBR increased bacterial organic carbon processing, while in the Red Sea no clear effects were found. More of the added DOC was degraded in the Red Sea but this additional carbon did not increase the biomass production, due to low bacterial growth efficiencies in all treatments. In addition, increasing temperatures in the GBR resulted in lower bacterial growth efficiencies, while no clear impact were found in the Red Sea. In conclusion, this study suggests that site-specific ecosystem differences (e.g., different microbial and macrophyte community composition) may override general responses to temperature and substrate in tropical coastal waters.
Original languageEnglish (US)
JournalJournal of Geophysical Research: Biogeosciences
StatePublished - Nov 17 2022

Bibliographical note

KAUST Repository Item: Exported on 2022-12-01
Acknowledgements: The authors would like to thank the SeaSim team at AIMS and the Coastal and Marine Resources Core Lab at KAUST for the help with setting up the experiments. The study was co-financed by the KAUST baseline funding to X.A.G.M. and a AIMS visiting fellowship program to X.A.G.M. as part of the capability development fund (CDF). CL was during the writing of this manuscript supported by the Independent Research Fund Denmark Grant (1127-00033B). FB was supported by a University of Otago Research Grant. We thank the three anonymous reviewers for their comprehensive comments and valuable suggestions that sustainably helped to improve the manuscript.


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