Prokaryotic viability and active metabolism across a Greenland Sea transect (75°N latitude)

Alessandro Ciro Rappazzo; Gabriella Caruso; Alessandro Cosenza; Angelina Lo Giudice; Giovanna Maimone; Maria Papale; Manuel Bensi; Vedrana Kovacevic; Maurizio Azzaro; Alessandro Ciro Rappazzo; Gabriella Caruso; Alessandro Cosenza; Angelina Lo Giudice; Giovanna Maimone; Maria Papale; Manuel Bensi; Vedrana Kovacevic; Maurizio Azzaro

doi:10.3934/microbiol.2025041

AIMS Microbiology

2025, Volume 11, Issue 4: 921-945. doi: 10.3934/microbiol.2025041

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Research article

Prokaryotic viability and active metabolism across a Greenland Sea transect (75°N latitude)

1.
Institute of Polar Sciences, National Research Council, Spianata S. Raineri 86, Messina, 98122, Italy
2.
National Institute of Oceanography and Applied Geophysics, OGS, Borgo Grotta Gigante, Sgonico (Trieste), 34010, Italy

Received: 05 September 2025 Revised: 21 November 2025 Accepted: 01 December 2025 Published: 11 December 2025

In this study, we provided the first comprehensive assessment of prokaryotic viability and respiratory activity across a 75°N transect in the Greenland Sea. Seawater samples collected during the CASSANDRA cruise (early September 2021, Italian Arctic Research Program PRA) were analyzed using LIVE/DEAD BacLight viability staining (L/D) and 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) methods to quantify viable and metabolically active cells, respectively. Total prokaryotic abundance ranged between 0.13 and 8.8 × 10⁵ cells mL⁻¹, with metabolically active (CTC+) cells accounting for 0.1–12% of the total. Viable cells accounted for 7–48% of the bacterial community, showing a significant vertical variability that increased with depth (Coefficient of variability 44%), particularly in deeper, nutrient-rich water masses such as the Greenland Sea Deep Water and the Greenland Sea Arctic Intermediate Water, occupying the deep layer (below 2500 m depth) and the intermediate layer (500–2500 m depth), respectively. Significant correlations were found between microbial parameters and environmental variables associated with different water masses, notably nutrients (nitrates and phosphates), whereas temperature showed a more complex, indirect influence. These findings highlight that the prokaryotic community inhabiting the examined transect is well adapted to this extreme marine environment, emphasizing the complex interactions of multiple environmental factors in shaping microbial community structure and activity under low-temperature conditions.
- CTC,
- cell viability,
- water masses,
- Greenland Sea,
- Atlantic,
- Arctic
Citation: Alessandro Ciro Rappazzo, Gabriella Caruso, Alessandro Cosenza, Angelina Lo Giudice, Giovanna Maimone, Maria Papale, Manuel Bensi, Vedrana Kovacevic, Maurizio Azzaro. Prokaryotic viability and active metabolism across a Greenland Sea transect (75°N latitude)[J]. AIMS Microbiology, 2025, 11(4): 921-945. doi: 10.3934/microbiol.2025041

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Abstract

In this study, we provided the first comprehensive assessment of prokaryotic viability and respiratory activity across a 75°N transect in the Greenland Sea. Seawater samples collected during the CASSANDRA cruise (early September 2021, Italian Arctic Research Program PRA) were analyzed using LIVE/DEAD BacLight viability staining (L/D) and 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) methods to quantify viable and metabolically active cells, respectively. Total prokaryotic abundance ranged between 0.13 and 8.8 × 10⁵ cells mL⁻¹, with metabolically active (CTC+) cells accounting for 0.1–12% of the total. Viable cells accounted for 7–48% of the bacterial community, showing a significant vertical variability that increased with depth (Coefficient of variability 44%), particularly in deeper, nutrient-rich water masses such as the Greenland Sea Deep Water and the Greenland Sea Arctic Intermediate Water, occupying the deep layer (below 2500 m depth) and the intermediate layer (500–2500 m depth), respectively. Significant correlations were found between microbial parameters and environmental variables associated with different water masses, notably nutrients (nitrates and phosphates), whereas temperature showed a more complex, indirect influence. These findings highlight that the prokaryotic community inhabiting the examined transect is well adapted to this extreme marine environment, emphasizing the complex interactions of multiple environmental factors in shaping microbial community structure and activity under low-temperature conditions.

Acknowledgments

The CASSANDRA project is part of the Synoptic Arctic Survey (https://synopticarcticsurvey.w.uib.no/). Research was funded by the Italian Arctic Research Program (PRA), Ministry of Education and Scientific Research (MUR), within the “AdvanCing knowledge on the presentArcticOceanby chemical-phySical, biogeochemical and biological obServAtioNs to preDict the futuRechAnges” (CASSANDRA) funded by the Italian Arctic Research Program (CASSANDRA project; PRA21_0001). The work described in this paper has been supported by the Synoptic Arctic Survey (SAS)—an international research program that coordinates data acquisition of essential ocean variables measured on Arctic research cruises. SAS is partially funded by the European Union's Horizon 2020 research and innovation programme through the project Arctic PASSION under grant agreement number 101003472.

Conflict of interest

The authors declare no conflict of interest.

Author contributions

Alessandro Ciro Rappazzo: Writing—original draft, Methodology, Investigation; Formal analysis, Data curation; Gabriella Caruso: Writing—review & editing, Supervision; Alessandro Cosenza: Writing—original draft, Software, Formal analysis, Data curation; Angelina Lo Giudice: Writing—review & editing; Giovanna Maimone: Conceptualization; Writing—original draft, Methodology, Formal analysis, Data curation; Maria Papale: Writing—review & editing, Investigation; Manuel Bensi: Data acquisition and curation, review & editing; Vedrana Kovacevic: Data acquisition, review & editing; Maurizio Azzaro: Writing—review & editing, Investigation; Supervision, Project administration, Funding acquisition.

Data availability

Data presented here are available through the repository Italian Arctic Data Center (IADC), at the following links: CTD casts, available at https://doi.datacite.org/dois/10.71761%2Fc082c3ca-40bf-42b1-a61a-7b3697ab2c5a [25]. Physical, biological, and biogeochemical analyses on water samples from Niskin bottles available at https://doi.datacite.org/dois/10.71761%2Ff7474404-3331-43e5-883b-25755e94956d [53]. Datasets are available upon direct request to dr. Alessandro Ciro Rappazzo (CNR-ISP, Messina, Italy).

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