Relative importance of nanoflagellate grazing and viral lysis for the mortality of heterotrophic bacteria and Synechococcus spp. in a high-latitude fjord (Adventfjorden, Svalbard) during the summer

Viral lysis and grazing play crucial but distinct roles in microbial community dynamics and carbon cycling. Yet, their relative influence on the abundance of heterotrophic bacterial and picophytoplankton populations, especially in Arctic fjords, remains poorly understood. To address this knowledge g...

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Published in:Polar research Vol. 44
Main Authors: Olivia, Madeline, Shiu, Ruei-Feng, Wei-Yi Chen, Patrichka, Chang, Chia-Mei, Annabel, Clara Natalie, Ni, Chuen-Fa, Chien, Hwa, Giletycz, Slawomir Jack, Tsai, An-Yi
Format: Journal Article
Language:English
Published: Spånga Open Academia 18.11.2025
Subjects:
Abundance
Bacteria
Carbon
Carbon cycle
Coastal waters
Dilution
Experiments
Fjords
Freshwater
Grazing
Heterotrophic bacteria
Inland water environment
Lysis
Meltwater
Microorganisms
Mortality
Phytoplankton
Plankton
Populations
Salinity
Salinity effects
Seawater
Sediments
Summer
Synechococcus
Virus-like particles
Viruses
Arctic region
ISSN:1751-8369, 0800-0395, 1751-8369
Online Access:Get full text
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Summary:Viral lysis and grazing play crucial but distinct roles in microbial community dynamics and carbon cycling. Yet, their relative influence on the abundance of heterotrophic bacterial and picophytoplankton populations, especially in Arctic fjords, remains poorly understood. To address this knowledge gap, we conducted modified dilution experiments in Adventfjorden, Svalbard, to quantify microbial growth, grazing pressure and virus-induced mortality. Our results showed that the abundance of virus-like particles (VLP) ranged between 1.4 and 8.9 × 106 viruses ml−1, with a negative correlation to salinity. This suggests that freshwater inputs, such as meltwater, could contribute to higher VLP abundance in these waters. The VLP-to-bacteria ratio varied between 9.8 and 700.9, with a large variation below a salinity of 28 PSU and an inverse correlation with salinity. Grazing, primarily by nanoflagellates, emerged as the dominant factor in reducing heterotrophic bacterial and Synechococcus spp. populations, accounting for 12–55% and 20–110% of their production losses, respectively. This study was conducted in summer, when meltwater discharges entered coastal waters in Svalbard fjords at an extremely high rate, providing an opportunity to study microbial processes under projected future warming conditions.
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ISSN:1751-8369
0800-0395
1751-8369
DOI:10.33265/polar.v44.11295