ORIGINAL RESEARCH article
Front. Mar. Sci.
Sec. Aquatic Microbiology
This article is part of the Research TopicPlankton Metabolisms and Interactions in Fluctuating EnvironmentsView all 12 articles
Validation of a modified Landry-Hassett Dilution technique to quantify the growth and mortality rates of subpopulations of planktonic microbes
Provisionally accepted
- 1Duke University Marine Laboratory, Beaufort, United States
- 2Microbiome Center, Biology Department, and Civil & Environmental Engineering, Duke University, Durham, NC, United States
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Due to their importance in global ocean ecology and biogeochemistry, much is known about the abundance and diversity of marine microbes and this information informs our studies of microbial genetic variability and niche partitioning. However, much less is known about marine microbes’ vital rates, including phylogenetically-resolved intrinsic growth and mortality. Here, we use cyanobacteria to validate a recently-developed sequence-based modification of the Landry-Hassett Dilution (LHD) technique, which simultaneously assesses the growth and grazer-induced mortality of microbial subpopulations. Using laboratory cultures, we show that most approaches for quantifying cyanobacterial intrinsic growth yield similar results, providing a foundation for methods comparisons in complex communities. We then leverage these findings to validate the modified LHD approach by sampling from a highly-dynamic, coastal marine ecosystem. We find that LHD 16S rRNA gene-based rates returns the same intrinsic growth as other biomass estimates. Further, field sampling yields distinct intrinsic growth among closely-related lineages of both cyano- and heterotrophic bacteria. While grazer-mediated mortality was less variable, we did observe distinct mortality rates within the broader microbiome, supporting the importance of examining vital rates in subpopulations. This validated methodology (and initial field findings) opens the door to answer fundamental ecological and biogeochemical questions about the microbial oceanography of spatially and temporally-variable coastal and open ocean ecosystems.
Keywords: Cyanobacteria, growth rates, Marine microbes, methods, microbiome, mortality rates
Received: 18 Aug 2025; Accepted: 09 Dec 2025.
Copyright: © 2025 Gu, Foley, Hunt and Johnson. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Zackary I Johnson
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