Trait‐based analysis of subpolar North Atlantic phytoplankton and plastidic ciliate communities using automated flow cytometer

Glaucia Moreira Fragoso,Geir Johnsen,Duncan Alastair Purdie,Alex James Poulton,Nicola Jane Pratt

doi:10.1002/lno.11189

Glaucia Moreira Fragoso, Geir Johnsen + Show 3 more

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https://doi.org/10.1002/lno.11189

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Abstract

AbstractPlankton are an extremely diverse and polyphyletic group, exhibiting a large range in morphological and physiological traits. Here, we apply automated optical techniques, provided by the pulse‐shape recording automated flow cytometer—CytoSense—to investigate trait variability of phytoplankton and plastidic ciliates in Arctic and Atlantic waters of the subpolar North Atlantic. We used the bio‐optical descriptors derived from the CytoSense (light scattering [forward and sideward] and fluorescence [red, yellow/green and orange from chlorophyll a, degraded pigments, and phycobiliproteins, respectively]) and translated them into functional traits to demonstrate ecological trait variability along an environmental gradient. Cell size was the master trait varying in this study, with large photosynthetic microplankton (> 20 μm in cell diameter), including diatoms as single cells and chains, as well as plastidic ciliates found in Arctic waters, while small‐sized phytoplankton groups, such as the picoeukaryotes (< 4 μm) and the cyanobacteria Synechococcus were dominant in Atlantic waters. Morphological traits, such as chain/colony formation and structural complexity (i.e., cellular processes, setae, and internal vacuoles), appear to favor buoyancy in highly illuminated and stratified Arctic waters. In Atlantic waters, small cell size and spherical cell shape, in addition to photo‐physiological traits, such as high internal pigmentation, offer chromatic adaptation for survival in the low nutrient and dynamic mixing waters of the Atlantic Ocean. The use of automated techniques that quantify ecological traits holds exciting new opportunities to unravel linkages between the structure and function of plankton communities and marine ecosystems.

Highlights

We have shown that the CytoSense flow cytometer has the capacity to quantify morphological and pigment functional traits based on the optical fingerprints associated with light scattering and fluorescence of phytoplankton cells and plastidic ciliates
Functional traits derived from the CytoSense are demonstrated to be a good proxy to explain the segregation of phytoplankton communities, including size spectrum, in contrasting water masses of distinct origin (Arctic vs. Atlantic) in the sub-Arctic North Atlantic Ocean
This field promises to simplify our interpretation of functionality in biological communities and reduce the information complexity of ecological roles, processes, and interactions, which are fundamental in modeling approaches (Merico et al 2009)

Summary

Introduction

The combination of fluorescence probes with automated, 3D microscopic imaging (known as environmental High Content Fluorescence Microscopy) allowed plankton identification and computerized quantification of internal cell structures (Colin et al 2017) These characteristics include DNA content, intracellular membranes, organelles (e.g., chloroplasts, food vacuoles), and cell wall structures (polysaccharides, biogenic silica, calcium carbonate), in addition to biological interactions (e.g., mixotrophy, symbiosis, and parasitism) (Colin et al 2017). These techniques generate a large amount of data that, if aligned with supervised machine learning algorithms, could tackle the diversity of traits in biological communities across a broad spectrum of spatiotemporal scales (Pomati et al 2013; Breton et al 2017; Colin et al 2017)

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