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Allochthonous groundwater microorganisms affect coastal seawater microbial abundance, activity and diversity
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  • Keren Yanuka-Golub,
  • Natalia Belkin,
  • Nurit Weber,
  • Meor Mayyani,
  • Yehuda Levy,
  • Itay Jacob Reznik,
  • Maxim Rubin-Blum,
  • Eyal Rahav,
  • Yael Kiro
Keren Yanuka-Golub
​The Institute of Applied Research, The Galilee Society.

Corresponding Author:[email protected]

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Natalia Belkin
Israel Oceanographic and Limnological Research
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Nurit Weber
Weizmann Institute of Science
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Meor Mayyani
Weizmann Institute of Science
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Yehuda Levy
Geological Survey of Israel
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Itay Jacob Reznik
Geological Survey of Israel
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Maxim Rubin-Blum
Israel Oceanographic and Limnological Research, National Institute of Oceanography
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Eyal Rahav
Israel Oceanographic and Limnological Research
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Yael Kiro
Weizmann Inst Sci, Dept Earth & Planetary Sci, 234 Herzl St, IL-7610001 Rehovot, Israel
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Abstract

Submarine groundwater discharge (SGD) is a globally important process supplying nutrients and trace elements to the coastal environment, thus playing a pivotal role in sustaining marine primary productivity. Along with nutrients, groundwater also contains allochthonous microbes that are discharged from the terrestrial subsurface into the sea. Currently, little is known about the interactions between groundwater-borne and coastal seawater microbial populations, and their role upon introduction to coastal seawater populations. Here, we investigated seawater microbial abundance, activity and diversity in a site strongly influenced by SGD (in-situ observations), and through laboratory-controlled bottle incubations mimicking different mixing scenarios between SGD (either ambient or filtered through 0.1 µm/0.22 µm) and seawater. Our results demonstrate that the addition of <0.1 µm SGD stimulated heterotrophic activity and increased microbial abundance compared to control, whereas <0.22 µm filtration treatments induced primary productivity rates and Synechococcus growth. Amplicon sequencing of the 16S rRNA gene showed a strong shift from a SAR11-rich community in the reference SGD-unaffected coastal samples to a Rhodobacteraceae-dominated one in the <0.1 µm treatment, in agreement with their in-situ enrichment in the SGD field site. These results suggest that despite the significant nutrient input, microbes delivered by SGD may affect the abundance, activity and diversity of intrinsic microbes in coastal seawater. Our results highlight the cryptic interplay between groundwater and seawater microbes in coastal environments, which has important implications for carbon cycling.
14 Jun 2023Submitted to ESS Open Archive
14 Jun 2023Published in ESS Open Archive