Microbial planktonic communities are critical components of marine biogeochemical pathways. Despite this, there is still limited knowledge on the dynamics of this group in warm and oligotrophic waters. We used high-throughput sequencing to characterise the bacterial (16S rRNA) and eukaryotic (18S rRNA) microbial plankton communities in two regions under the influence of anthropogenic impacts (a port and sewage outflow) and a coastal region with no direct anthropogenic disturbances in the central Red Sea. Overall, bacterial and eukaryotic components responded in a similar way to the environmental conditions. Community composition and structure were more sensitive than alpha diversity measures to environmental impacts. With the exception of eukaryotes, for which the number of OTU differed significantly between sampling periods in all the regions, environmental changes associated with anthropogenic pressures seem to be better reflected by variations in the relative dominance of microbial groups. For example, elevated proportional abundances of nitrifying and sewage-/faecal-related bacteria at the impacted sites were observed compared with the coastal region. The recently developed microgAMBI also appeared to correlate well with the level of anthropogenic impact the regions experienced, showing the potential to be applied in oligotrophic waters.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: Acknowledgements: The authors would like to thank Richard Payumo, Saskia Kürten and various members of the Coastal & Marine Resources Core Lab for their help in collecting the samples. Further, the authors would like to express their thanks to Saskia Kürten and Pedro Ruiz Compean for their help with the nutrient analysis. The authors would also like to extend their gratitude to Ute Langner for her work in producing the maps used in this manuscript. We would also like to express our gratitude to the reviewers for their insightful comments, which improved this manuscript. Funding information: JKP and SC are funded by the Saudi Aramco/KAUST Center for Marine Environmental Observations. The funding source had no involvement in the design, undertaking or analysis of this study.