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Examples of phytoplankton cells, their shape and elongation class. (a) Cerataulina pelagica (Cylinder, prolate); (b) Ditylum brightwellii (prism on triangular base, prolate); (c) Thalassionema nitzschioides (parallelepiped, prolate); (d) Protoperidinium sp. (cone + half sphere, compact); (e) Tripos fusus (double cone, prolate); (f) Coscinidiscus sp. (cylinder, oblate); (g) Akashiwo sanguinea (ellipsoid, oblate); (h) Phalacroma sp. (ellipsoid, oblate); (i) Prorocentrum micans (cone + half sphere, prolate); (j) Dinophysis caudata (ellipsoid + cone, prolate); (k) Chaetoceros didymus (prism on elliptic base, oblate); (l) Podolampas bipes (cone, compact); (m) Tripos sp. (ellipsoid + 2 cones + cylinder, prolate); (n) Pleurosigma sp. (prism on parallelogram base, prolate). Scale bar = 20 µm.
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Size and shape profoundly influence an organism’s ecophysiological performance and evolutionary fitness, suggesting a link between morphology and diversity. However, not much is known about how body shape is related to taxonomic richness, especially in microbes. Here we analyse global datasets of unicellular marine phytoplankton, a major group of p...
Citations
... As such, we view our study as an initial attempt at understanding the first-order, large-picture, patterns. Traits such as buoyancy control, morphology (see, e.g., Ryabov et al. 2021), symbiosis, chain/colony formation, and mixotrophy might allow larger size classes to coexist in lower nutrient regions than the theory suggests. Other components of the marine food web, such as higher trophic levels and, in particular, viruses will also interact in ways that are likely important. ...
The combination of taxa and size classes of phytoplankton that coexist at any location affects the structure of the marine food web and the magnitude of carbon fluxes to the deep ocean. But what controls the patterns of this community structure across environmental gradients remains unclear. Here, we focus on the North East Pacific Transition Zone, a ~ 10° region of latitude straddling warm, nutrient‐poor subtropical and cold, nutrient‐rich subpolar gyres. Data from three cruises to the region revealed intricate patterns of phytoplankton community structure: poleward increases in the number of cell size classes; increasing biomass of picoeukaryotes and diatoms; decreases in diazotrophs and Prochlorococcus; and both increases and decreases in Synechococcus. These patterns can only be partially explained by existing theories. Using data, theory, and numerical simulations, we show that the patterns of plankton distributions across the transition zone are the result of gradients in nutrient supply rates, which control a range of complex biotic interactions. We examine how interactions such as size‐specific grazing, multiple trophic strategies, shared grazing between several phytoplankton size classes and heterotrophic bacteria, and competition for multiple resources can individually explain aspects of the observed community structure. However, it is the combination of all these interactions together that is needed to explain the bulk compositional patterns in phytoplankton across the North East Pacific Transition Zone. The synthesis of multiple mechanisms is essential for us to begin to understand the shaping of community structure over large environmental gradients.
... In marine sediments, macronutrients are typically not limiting, as sediments host high densities of heterotrophic bacteria and fauna that degrade sedimentary organic matter and release bioavailable nutrients such as ammonium (NH 4 + ) and nitrate (NO 3 − ), which benthic phototrophs take up (thereby affecting nutrient budgets and competing with other nutrient-consuming processes, such as denitrification) (55)(56)(57). Light-and nutrient-replete surface sediments constitute an important niche for benthic diatoms, the predominant primary producer in Arctic sedimentary environments (32,(58)(59)(60), which have evolved both structurally [e.g., the shape of the silica cell wall frustule; (61)(62)(63)] and behaviorally [e.g., motility, adhesion, chemokinesis, and chemotaxis; (52,(64)(65)(66)(67)(68)] to exploit the dynamic conditions in surface sediments (69). Field observations of high benthic microalgal density and Arctic surface sediment chlorophyll-a (Chl-a) concentration often exceeding 50 mg Chl a m -2 is evidence of their success (32,60). ...
Phytoplankton and sea ice algae are traditionally considered to be the main primary producers in the Arctic Ocean. In this Perspective, we explore the importance of benthic primary producers (BPPs) encompassing microalgae, macroalgae, and seagrasses, which represent a poorly quantified source of Arctic marine primary production. Despite scarce observations, models predict that BPPs are widespread, colonizing ~3 million km 2 of the extensive Arctic coastal and shelf seas. Using a synthesis of published data and a novel model, we estimate that BPPs currently contribute ~77 Tg C y −1 of primary production to the Arctic, equivalent to ~20 to 35% of annual phytoplankton production. Macroalgae contribute ~43 Tg C y −1 , seagrasses contribute ~23 Tg C y −1 , and microalgae-dominated shelf habitats contribute ~11 to 16 Tg C y −1. Since 2003, the Arctic seafloor area exposed to sunlight has increased by ~47,000 km 2 y −1 , expanding the realm of BPPs in a warming Arctic. Increased macrophyte abundance and productivity is expected along Arctic coastlines with continued ocean warming and sea ice loss. However, microalgal benthic primary production has increased in only a few shelf regions despite substantial sea ice loss over the past 20 y, as higher solar irradiance in the ice-free ocean is counterbalanced by reduced water transparency. This suggests complex impacts of climate change on Arctic light availability and marine primary production. Despite significant knowledge gaps on Arctic BPPs, their widespread presence and obvious contribution to coastal and shelf ecosystem production call for further investigation and for their inclusion in Arctic ecosystem models and carbon budgets.
... Specifically, when oxygen saturation levels and Total Algae sensor (YSI-ProDSS) indicated high photosynthetic activity, an additional depthsample was taken. For biovolume estimation, Lugol-fixed samples were taxonomically analyzed following the official Spanish protocol, implemented according to the WFD (MAGRAMA, 2013) and specific calculations for non-listed taxa (Ryabov et al., 2021). HPLC analysis was carried out following the method of Zapata et al. (2000), which was modified by reducing 10-fold the concentration of pyridine (final concentration 0.025 M) in eluent A, as described by Seoane et al. (2009). ...
Pigment analysis through high-performance liquid chromatography (HPLC) offers a faster and more replicable study of the phytoplankton community structure than traditional taxonomy, but its application to small-sized freshwater ecosystems is infrequent. We carried out a taxonomy-based validation for the application of HPLC to the management of two artificial water storage ponds. We also investigated the error and variability sources that affected the relationships between calculated biovolumes of phytoplankton groups and associated pigment concentrations. For both qualitative and quantitative approaches, agreement was obtained between techniques that consistently identified biomass peaks and structural trophic differences between the ponds. Considering the most relevant pigment to biovolume ratios for total biomass, and partial biomass proxies of green algae and fucoxanthin containing algae, a decreasing tendency was obtained as total and partial biomass increased in all the studied models. Bidirectional variability affecting these relationships scaled under high biomass conditions and suggested a better suitability of HPLC application under oligotrophic conditions, which is in line with previous studies. Additionally, pigment data was able to identify mean stored volume as the main environmental factor that drove trophic differences between the ponds. We conclude that HPLC is accurate not just for moni- toring purposes, but to carry out ecosystem-level assessments in artificial ponds. Therefore, we endorse the use of HPLC as part of the monitoring networks in small-sized freshwater ecosystems.
... 1101/2024 shape. Environmental factors can influence the selection for body size and shape differently (Ryabov et al. 2021) : shape variation represents a competitive strategy for medium and large phytoplankton forms to acquire an advantageous surface area-to-volume ratio (Stanca, Cellamare, and Basset 2013) , or to reduce sinking velocity (Padisák, Soróczki-Pintér, and Rezner 2003) . ...
The interplay between abiotic (resource supply, temperature) and biotic (herbivore grazing) factors determines growth and loss processes in phytoplankton through resource competition and trophic interactions, which are mediated by morphological traits like size. Here, we study the relative importance of different grazers, water physics and chemistry on the daily net accumulation rates (AR) of six phytoplankton size classes, obtained by grouping individual organisms from natural communities based on their realised dimensions. Using a Random Forest modelling approach and four years of daily underwater imaging data, we find that the AR of small phytoplankton is mostly predicted by water temperature and herbivore grazing whereas, with increasing size, resources become more important in predicting ARs. Our results show that microzooplankton is an important predictor of AR in all phytoplankton regardless of their size, but mesozooplankton is more important for small phytoplankton forms. Our results support previous expectations and reveal surprising new patterns.
Significance Statement
Understanding the relative importance of biotic and abiotic controls of biodiversity change, in terms of taxa and traits, is critical in times of global and local anthropogenic impact on ecosystem processes. The relative importance of different mechanisms driving phytoplankton community dynamics is still debated, and might vary depending on the environmental conditions. We harnessed four years of data from an underwater imaging microscope, and ancillary monitoring sensors, to study the biotic and abiotic controls of phytoplankton size classes using machine-learning. We find that, contrary to prior expectations, large (blooming) phytoplankton are favoured by high temperature and low levels of microzooplankton. These results help us understand phytoplankton dynamics and improve the modelling of plankton food-webs, with implications for predicting plankton community structure in changing aquatic ecosystems.
... As P. tricornutum showed euryhaline characteristics with relatively high growth rates across all salinity treatments, other species with a narrower salinity tolerance range were outcompeted, even under a limited nutrient supply. Nevertheless, small spherical species, such as a haptophyte Diacronema lutheri, thrived under P-depleted conditions (Fig. 2) due to their high surface area to volume ratio, which makes it easier to assimilate limited nutrients (Padisák et al., 2003;Finkel et al., 2010;Durante et al., 2019;Ryabov et al., 2021). Similarly, a small cyanobacteria Synechococcus sp., which, although not observed to perform nitrogen fixation, can utilize diverse forms of nitrogen (Moore et al., 2002;Aldunate et al., 2020), was a good competitor under N-depleted conditions (Fig. 2). ...
Ongoing climate warming alters precipitation and water column stability, leading to salinity and nutrient supply changes in the euphotic zone of many coastal ecosystems and semi-enclosed seas. Changing salinity and nutrient conditions affect phytoplankton physiology by altering elemental ratios of carbon (C), nitrogen (N) and phosphorus (P). This study aimed to understand how salinity stress and resource acquisition affect phytoplankton stoichiometry. We incubated a phytoplankton polyculture composed of 10 species under different light, inorganic nutrient ratio and salinity levels. At the end of the incubation period, we measured particulate elemental composition (C, N and P), chlorophyll a and species abundances. The phytoplankton polyculture, dominated by Phaeodactylum tricornutum, accumulated more particulate organic carbon (POC) with increasing salinity. The low POC and low particulate C:N and C:P ratios toward 0 psu suggest that the hypoosmotic conditions highly affected primary production. The relative abundance of different species varied with salinity, and some species grew faster under low nutrient supply. Still, the dominant diatom regulated the overall POC of the polyculture, following the classic concept of the foundation species.
... This insensitivity indicated that there are probably other reasons for the different impact of light limitation to %DC between groups besides cell size. And a series of physiological and/or morphological adaptions of large cells to light limitation may be one of the reasons, such as adjustments of pigment composition to increase the diversity of light spectral capture (Fontana et al. 2019), formation of resting stages (Kvernvik et al. 2018), and cell flattening (Ryabov et al. 2021) to alleviate internal light shortage. This inconsistency illustrates the difference between the responses of growth and death to environmental changes, and it emphasizes the importance of understanding community changes from the perspective of death. ...
The growth and death of phytoplankton are two key processes that affect structure and function of marine ecosystem. However, current understanding is elaborated from the perspective of growth, and relatively little is known about the environment-driven death of phytoplankton. Our study is aimed to elucidate the differences in group-specific proportion of dead cells and their effects on community structure. Based on flow cytometry analysis, the proportion of dead cells among eukaryotic phytoplankton groups was analyzed in the oligotrophic South China Sea. The eukaryotic phytoplankton were divided into five groups (eukaryotic group 1, eukaryotic group 2, eukaryotic group 3, cryptophytes, and eukaryotic group 4) with successively larger cell size from pico to micro. The larger cells (from nano to micro size) had a higher proportion of dead cells and a lower relative abundance. Only the group of large cells showed a complete correspondence between the proportion of dead cells and abundance in the vertical profile. Above the deep chlorophyll maximum layer, death induced by nutrient limitation was apparent in most groups, and the larger the cell size, the greater the limitation. Below the deep chlorophyll maximum layer, all groups were light-limited, but differences in the degree of light limitation among groups were not significant. These results suggested that differences in cell size contribute to some extent to differences in the proportion of dead cells among groups, making the proportion of dead cells important in regulating community structure and thus further influencing the structure and function of pelagic marine ecosystems.
... Previous studies have also indicated a negative correlation between colony size and growth rate in colonial cyanobacteria ( Fig. S2; Li and Gao, 2004;Wilson et al., 2010). This correlation can be attributed to factors such as cell aggregation, exacerbated self-shading (Feng et al., 2022), and lower specific surface area (Naselli-Flores et al., 2020;Ryabov et al., 2021). In our study, a high initial cell concentration (approximately 20×10 4 cells mL − 1 ) promoted the formation of macroscopic colonies on the first day of the exposure test through cell-adhesion (see Fig. S8), which subsequently resulted in a decrease in the growth rate. ...
Colonial cyanobacteria have been identified as the primary contributor to the global occurrence of cyanobacterial harmful algal blooms (cyanoHABs), which are further intensified by the presence of “pseudo-persistent” antibiotics. Nevertheless, the impact of antibiotics on the growth and size of colonial cyanobacteria remains unclear. In this study, the response of cyanobacterium Microcystis to varying doses of antibiotics was assessed (0, 0.1, 0.5, 1, 10, and 50 μg L−1) by comparing the unicellular and colonial morphotypes. Interestingly, the morphological structure of cyanobacteria plays a significant role in their reaction to antibiotics. In comparison to the unicellular morphotype, the colonial morphotype exhibited a greater promotion in growth rate (11% – 22%) to low doses of antibiotics and was less inhibited (-121% – -62%) under high doses. Furthermore, antibiotics may affect the size of cyanobacterial colonies by disrupting the secretion of algal organic matter, which also exhibited a two-phase pattern. This work sheds light on the significance of methodology research involving both unicellular and colonial cyanobacteria. Future research and lake management should prioritize studying the morphological traits of cyanobacteria under different levels of antibiotic exposure. This approach may lead to novel strategies for predicting cyanoHABs under antibiotic pollution more effectively.
... Because diatoms represent a diverse spectrum of ecological optima and tolerances and respond sensitively to environmental changes, their amorphous biogenic silica (bSiO 2 ) skeletons (frustules and resting stages) preserved in sediment are commonly used as paleoenvironmental indicators. Diatoms also display a broad range of size and silicification levels and show a continuous range of growth strategies, which affect crucial ecological processes such as the energy transfer to higher trophic levels, biogeochemical cycling, light harvesting, cell growth, and sinking rates (e.g., Behrenfeld et al., 2021;Finkel et al., 2004;Ryabov et al., 2021;and references therein). Although paleoenvironmental studies most often report diatom counts irrespective of cell size, diatoms appear to have scaledependent responses to environmental constraints, which can in turn affect ecosystem structure and function (Finkel et al., 2005;Snoeijs et al., 2002). ...
The Pikialasorsuaq (North Water polynya) is an area of local and global cultural and ecological significance. However, over the last decades, the region has been subject to rapid warming, and in some recent years, the seasonal ice arch that has historically defined the polynya's northern boundary has failed to form. Both factors are deemed to alter the polynya's ecosystem functioning. To understand how climate‐induced changes to the Pikialasorsuaq impact the basis of the marine food web, we explored diatom community‐level responses to changing conditions, from a sediment core spanning the last 3800 years. Four metrics were used: total diatom concentrations, taxonomic composition, mean size, and diversity. Generalized additive model statistics highlight significant changes at ca. 2400, 2050, 1550, 1200, and 130 cal years BP, all coeval with known transitions between colder and warmer intervals of the Late Holocene, and regime shifts in the Pikialasorsuaq. Notably, a weaker/contracted polynya during the Roman Warm Period and Medieval Climate Anomaly caused the diatom community to reorganize via shifts in species composition, with the presence of larger taxa but lower diversity, and significantly reduced export production. This study underlines the high sensitivity of primary producers to changes in the polynya dynamics and illustrates that the strong pulse of early spring cryopelagic diatoms that makes the Pikialasorsuaq exceptionally productive may be jeopardized by rapid warming and associated Nares Strait ice arch destabilization. Future alterations to the phenology of primary producers may disproportionately impact higher trophic levels and keystone species in this region, with implications for Indigenous Peoples and global diversity.
... There is a robust connection between phytoplankton cell morphology and physiological and metabolic processes [3][4][5][6][7]. In this regard, the morpho-functional traits of phytoplankton have been recognized as powerful tools to explain the development of specific phytoplankton groups in defined environmental conditions [8,9]. Despite this, improving our knowledge of phytoplankton morpho-functional trait distribution along natural environmental gradients is still challenging due to the overlap and interaction of environmental and biological forces in aquatic environments. ...
The pelagic environment is characterized by a great spatial and temporal heterogeneity [...]
... Phytoplankton communities vary according to the physicochemical conditions of the water (Margalef 1967), but knowledge on the specific composition of these communities remain challenging (Basterretxea et al. 2020). The occurrence and the dominance of a given phytoplankton species reflect its adaptation to the environment (e.g., Anderson et al. 2002, Kremer et al. 2017, Moser et al. 2017, Ryabov et al. 2021. Hence some large-scale generalizations about the taxonomic variability and abundance of phytoplankton can be made in the ocean. ...
Despite its small area, Araçá Bay (AB) holds cultural, historical, and economic value and displays great benthic biodiversity. Thus, it is crucial to monitor its environmental health, including knowing the main groups of phytoplankton and their temporal variability. The shallow waters of Araçá Bay are continuously modified by the complex hydrography of the adjacent São Sebastião channel (SSC), challenging standard experimental designs for phytoplankton collection. Here we report changes in phytoplankton composition at intervals of five to six weeks from September 2013 to August 2014 in both Araçá Bay and SSC. Samples were collected twice daily for three consecutive days to increase taxonomic resolution. Our goal was to provide an inventory of species occurrences to aid future public policies and environmental management of the area. Analyses revealed high species richness and 166 different phytoplankton taxa. Diatoms and dinoflagellates were always numerically dominant, but taxa occurrence changed markedly. Diatoms of the genera Pseudo-nitzschia were abundant during spring and summer concurrently to signatures of South Atlantic Central Water in the SSC, while Thalassiosira occurred when waters displayed relatively lower salinity. The inventory demonstrated several potentially harmful species of microalgae and cyanobacteria, strongly suggesting investments in monitoring programs in this area that currently experience an increase in population.
