Dynamics and functional diversity of the smallest phytoplankton on the Northeast US Shelf

Fowler, Bethany L; Neubert, Michael G.; Hunter-Cevera, Kristen R.; Olson, Robert J.; Shalapyonok, Alexi; Solow, Andrew R.; Sosik, Heidi M.

doi:10.1073/pnas.1918439117

Cited by 25 publications

(45 citation statements)

References 54 publications

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“…The role of phytoplankton functional groups and diversity in driving variation in primary and export production is a fundamental question in oceanography and carbon cycle science. While allometric approaches have been extensively used in oceanographic studies to scale particle size to metabolism, growth, and production (Brewin, Lavender, et al, 2010; Marañón et al, 2013; Uitz et al, 2008; White et al, 2015), our data and an emerging body of observational data (Bolaños et al, 2020; Fowler et al, 2020) suggest that the relationship between the PSD and production is more complex than previously thought. Both bottom‐up and top‐down processes, including regionally varying supply of limiting nutrients and differential grazing pressure relative to growth, are likely modes of controlling the size fractionation of the phytoplankton communities.…”

Section: Implications For Future Workmentioning

confidence: 72%

“…emerging body of observational data (Bolaños et al, 2020;Fowler et al, 2020) suggest that the relationship between the PSD and production is more complex than previously thought. Both bottom-up and top-down processes, including regionally varying supply of limiting nutrients and differential grazing pressure relative to growth, are likely modes of controlling the size fractionation of the phytoplankton communities.…”

Section: 1029/2020gb006702mentioning

confidence: 99%

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The Importance of the Phytoplankton “Middle Class” to Ocean Net Community Production

Juranek

White²,

Dugenne³

et al. 2020

Global Biogeochemical Cycles

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The net balance between photosynthesis and respiration in the surface ocean is a key regulator of ocean-atmosphere carbon dioxide (CO 2) partitioning, and by extension, Earth's climate. The slight excess of photosynthesis over community respiration in sunlit waters, known as net community production (NCP), sets the upper bound on the sequestration of carbon via biologically mediated export. Prevailing paradigms suggest a high/low binary where net primary production (NPP), NCP, and export are highest in ecosystems characterized by microplankton (>20 μm) and lowest in ecosystems dominated by picoplankton (<2 μm). This bifurcation model neglects the potential importance of nanoplankton (2-20 μm)-i.e., the "middle" size class-toward global biological pump functioning. Here, we show a relationship between the biomass of nanoplankton and oxygen-based estimates of NCP across natural ecological gradients in the North Pacific Ocean. Using a suite of high-resolution optical imaging approaches including SeaFlow, Imaging FlowCytobot, and laser-based scattering, nanoplankton dynamics are observed to dominate the particle size distribution throughout an~1,000 km transition between the subtropical and subpolar North Pacific, where NCP rates are threefold to fivefold higher than subtropical values. Based on ecological theory applied to the Darwin size-based ecosystem model, we hypothesize that intermediate size class organisms are capable of high rates of production via an optimization of bottom-up and top-down control inherent to the "middle class." More broadly, the model indicates the global importance of nanoplankton for ocean biological production.

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Section: Implications For Future Workmentioning

confidence: 72%

Section: 1029/2020gb006702mentioning

confidence: 99%

The Importance of the Phytoplankton “Middle Class” to Ocean Net Community Production

Juranek

White²,

Dugenne³

et al. 2020

Global Biogeochemical Cycles

View full text Add to dashboard Cite

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“…These patterns could be explained by the long lasting summer of 2018 58 which could have shifted PPE favorable temperatures to later in the autumn while concurrent light limitation may have restricted PPE growth 37 .…”

Section: Discussionmentioning

confidence: 99%

“…Picophytoplankton seasonal dynamics is determined by temperature, light, nutrient concentration [35][36][37] and biotic factors 14,38 . The few studies focusing on picophytoplankton seasonality in the Baltic Sea suggest that their community composition and abundance have a strong seasonal variation 21,26 .…”

Section: Introductionmentioning

confidence: 99%

Seasonality of Coastal Picophytoplankton Growth, Nutrient Limitation and Biomass Contribution

Zufia

Farnelid

Legrand

2021

Preprint

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Picophytoplankton in the Baltic Sea includes picocyanobacteria (Synechococcus/Cyanobium) and photosynthetic picoeukaryotes (PPE). Picophytoplankton are thought to be a key component of the phytoplankton community but their seasonal dynamics and relationships with nutrients and temperature are largely unknown. We monitored pico- and larger phytoplankton at a coastal site in Kalmar Sound (K-Station) weekly during 2018. Among the picocyanobacteria, phycoerythrin-rich Synechococcus (PE-rich) dominated in spring and summer while phycocyanin-rich Synechococcus (PC-rich) dominated during autumn. PE-rich and PC-rich abundances peaked during summer (1.1x105 and 2.0x105 cells mL− 1) while PPE reached highest abundances in spring (1.1x105 cells mL− 1). PPE was the main contributor to the total phytoplankton biomass (3–73%). To assess nutrient limitation, bioassays with combinations of nitrogen (NO3 or NH4) and phosphorus additions were performed. PE-rich and PC-rich growth was mainly limited by nitrogen, with a preference for NH4 at 15–19°C. The three groups had distinct seasonal dynamics and optimal temperatures for growth were 10°C and 17–19°C for PE-rich, 13–16°C for PC-rich and 11–15°C for PPE. We conclude that picophytoplankton contribute significantly to the carbon cycle in the coastal Baltic Sea and underscore the importance of investigating functional groups to assess the consequences of the combination of high temperature and NH4 in a future climate.

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“…Past work has assumed that changes in cell size result from two processes: carbon fixation and cell division [18][19][20][21][22][23][24]. We built upon these studies by evaluating the relevance of a range of assumptions and testing models that include an additional process: cell shrinkage through exudation and respiration.…”

Section: Modelsmentioning

confidence: 99%

A flexible Bayesian approach to estimating size-structured matrix population models

Mattern

Glauninger

Britten

et al. 2021

Preprint

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The rates of cell growth, division, and carbon loss of microbial populations are key parameters for understanding how organisms interact with their environment and how they contribute to the carbon cycle. However, the invasive nature of current analytical methods has hindered efforts to reliably quantify these parameters. In recent years, size-structured matrix population models (MPMs) have gained popularity for estimating rate parameters of microbial populations by mechanistically describing changes in microbial cell size distributions over time. And yet, the construction, analysis, and biological interpretation of these models are underdeveloped, as current implementations do not adequately constrain or assess the biological feasibility of parameter values, leading to inference which may provide a good fit to observed size distributions but does not necessarily reflect realistic physiological dynamics. Here we present a flexible Bayesian extension of size-structured MPMs for testing underlying assumptions describing the dynamics of a marine phytoplankton population over the day-night cycle. Our Bayesian framework takes prior scientific knowledge into account and generates biologically interpretable results. Using data from an exponentially growing laboratory culture of the cyanobacterium Prochlorococcus, we herein demonstrate the performance improvements of our approach over current models and isolate previously ignored biological processes, such as respiratory and exudative carbon losses, as critical parameters for the modeling of microbial population dynamics. The results demonstrate that this modeling framework can provide deeper insights into microbial population dynamics provided by flow-cytometry time-series data.

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Dynamics and functional diversity of the smallest phytoplankton on the Northeast US Shelf

Cited by 25 publications

References 54 publications

The Importance of the Phytoplankton “Middle Class” to Ocean Net Community Production

The Importance of the Phytoplankton “Middle Class” to Ocean Net Community Production

Seasonality of Coastal Picophytoplankton Growth, Nutrient Limitation and Biomass Contribution

A flexible Bayesian approach to estimating size-structured matrix population models

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