Phytoplankton functional groups distribution and dynamics builds nutrients and carbon energy pathways in the ocean. They respond fast to changes in their environment, and the understanding of their dynamics relies on regular sampling to resolve daily to weekly scales. The Bonifacio Cyclonic Gyre (BCG) is an area prone to intermittent phytoplankton blooms triggered by westerly winds, and close to coastal areas capable of fuelling open waters with nutrients from flooding. To study phytoplankton evolution in this dynamical area, the distribution of phytoplankton functional groups in the surface waters of the western Mediterranean Sea was investigated semi-continuously (30 min) using an automated CytoSense flow cytometer coupled to a FerryBox, onboard the ferry Le Carthage, between October 20, 2016 and January 12, 2017 and along the route from Tunis (Tunisia) to Genova (Italy). The BCG signature was identified by its surface temperature anomaly and evidenced significant higher abundances of the RedPicoProk, the RedPico, the HsNano and the OraNano over the full sampling period, except for the RedNano1, the RedNano2 and the OraPicoProk. Their estimated chlorophyll a concentration per group were higher within the gyre than outside, but did not affect the carbon/chlorophyll a ratio. A high carbon/chlorophyll a ratio can indicate recently uplifted cells that are not yet adapted to high light conditions. In this case, the observed ratios suggest that the cells were not recently upwelled, but instead had time to adjust their photophysiology to surface conditions. During 19–20 December, extreme overflow occurred over Corsica and Sardinia, considered as one of the highest rainfall events of the past 20 years. The runoff was evidenced by the low salinity intrusion that lasted several days after the storm. After the runoff and within the Bonifacio gyre region, biomasses of all groups increased and remained high until the end of the sampling, except for the RedPico. The runoff triggered an early bloom end of December that persisted for several weeks, being trapped and repleted by the uplift of the isopycnals from the BCG. Regular observation of the sea surface temperature and salinity together with phytoplankton community structure provides essential insights into the fast response of phytoplankton communities to an extreme event at unprecedented resolution.

Seamounts are ubiquitous features in the world ocean with potential for increasing plankton biodiversity and abundance, and providing important habitats for aquatic predators. Although ecological importance of seamount is well known, the mechanisms for supporting seamount-associated microzooplankton (e.g., pelagic ciliates) communities remains to be substantiated. In this study, pelagic ciliate community structure variations and their relationship with environmental variables were investigated in the Caroline seamount in late (2017) and early summer (2019). Above the seamount in 2019, ciliates exhibited higher abundance and biomass than off the seamount, which supported the classic hypothesis of seamount effect. Aloricate ciliate small size-fraction (10-20 mu m) was dominant in bathypelagic (>1000 m) zone. Although relative abundance of small size-fraction was similar in both 2017 and 2019, the absolute abundance in 2019 seamount-effect stations were obviously higher than that in 2017. All abundant tintinnids were classified into surface-and DCM (deep Chl a maximum layer)-peak groups. Among them, four abundant tintinnids (Acanthostomella conicoides, Eutintinnus hasleae, Salpingella curta and S. minutissima) had higher abundance at DCM and might uplifted to shallower waters by upwelling at 2019 seamount-effect stations. The multivariate biota-environment analysis showed that environmental variables have significant impacts on the ciliate community structures in 2017 and 2019. Higher Chl a and nutrient concentrations, and sustained upwelling might be two potential mechanisms for microzooplankton seamount effect. Our study constitutes a rather solid foundation for quantitative and functional study of microzooplankton populations over oligotrophic tropical seamounts.

Though diel variations are geographically widespread phenomena among phytoplankton and zooplankton, knowledge is limited regarding diel variations in planktonic ciliate (microzooplankton) community structure. In this study, we analyzed diel variations in community structure of planktonic ciliates in the northern South China Sea (nSCS) and tropical Western Pacific (tWP). Hydrological characteristics during day and night were slightly different over both the nSCS and tWP, while ciliate average abundance at night was clearly higher than in the day in the upper 200 m. In both the nSCS and tWP, abundance proportions of large size-fraction (> 30 μm) aloricate ciliates at night were higher than in the day. While for tintinnids, abundance proportion of large lorica oral diameter at night were lower than in the day. The relationship between environmental factors and ciliate abundance pointed out that depth and temperature were main factors influencing aloricate ciliate and tintinnid in both day and night. For some dominant tintinnid species, chlorophyll a was another important factor influencing their diel vertical distribution. Our results provide fundamental data for better understanding the mechanisms of planktonic ciliate community diel variation in the tropical Western Pacific Ocean.

Marine plankton have different biogeographical distribution patterns. However, it is not clear how the entire plankton assemblage is composed of these species with distinct biogeographical patterns. Tintinnina (tintinnids) is single-celled planktonic protozoa commonly used as model organisms in planktonic studies. In this research, we investigated the organization of Tintinnina assemblages along the Atlantic Meridional Transect (AMT) spanning over 90 degrees of latitude during the 29th AMT cruise (2019). Tintinnina with high frequency of occurrence was classified into four biogeographic distribution patterns (equatorial, gyre, frontal, and deep Chl a maximum) according to their vertical and horizontal distribution. All species falling within each distribution pattern formed a sub-assemblage. Equatorial sub-assemblage dominated in upper waters of the equatorial zone and gyre centres. Equatorial and frontal sub-assemblages co-dominated in upper waters of the frontal zones. Deep Chlorophyll a maximum Layer (DCM) sub-assemblage dominated in the DCM waters. Some Tintinnina species with high abundance could be used as indicator species of sub-assemblages. The Tintinnina assemblages in the northern and southern hemispheres exhibited asymmetry in terms of species composition. The latitudinal gradient of Tintinnina species richness was bimodal, which was shaped by the superposition of the species number of the four sub-assemblages with latitude. The result of this study contributes to the understanding of Tintinnina assemblage in the equatorial zone and subtropical gyres of the Pacific and Indian Ocean. It is also valuable for predicting the influence of global warming on changes in Tintinnina distribution and species richness.

Fig. S1.Day (D)-night (N) variations of ciliate (total, aloricate ciliate and tintinnid) abundance at

The recent development of biological sensors has extended marine plankton studies from conducting laboratory bench work to in vivo and real-time observations. Flow cytometry (FCM) has shed new light on marine microorganisms since the 1980s through its single-cell approach and robust detection of the smallest cells. FCM records valuable optical properties of light scattering and fluorescence from cells passing in a single file in front of a narrow-collimated light source, recording tens of thousands of cells within a few minutes. Depending on the instrument settings, the sampling strategy, and the automation level, it resolves the spatial and temporal distribution of microbial marine prokaryotes and eukaryotes. Cells are usually classified and grouped on cytograms by experts and are still lacking standards, reducing data sharing capacities. Therefore, the need to make FCM data sets FAIR (Findability, Accessibility, Interoperability, and Reusability of digital assets) is becoming critical. In this paper, we present a consensus vocabulary for the 13 most common marine microbial groups observed with FCM using blue and red-light excitation. The authors designed a common layout on two-dimensional log-transformed cytograms reinforced by a decision tree that facilitates the characterization of groups. The proposed vocabulary aims at standardising data analysis and definitions, to promote harmonisation and comparison of data between users and instruments. This represents a much-needed step towards FAIRification of flow cytometric data collected in various marine environments.

The short term (hourly scale) variability of heterotrophic prokaryote (HP) vertical distribution and respiratory activity, was investigated in the north-western (NW) Mediterranean Sea. HP vertical distribution was determined on board by flow cytometry analysis of seawater samples collected by series of CTD casts. Cell counts and viability were determined for all samples. HP respiratory rates were determined later in the laboratory from filtered seawater samples (23 dm 3 ) from 300–1 150-m depth. The average cell viability was 94.8%±2.2% ( n =240). There was no accumulation of dead cells, due to quick decay of damaged cells. In the epipelagic layer, three HP groups were distinguished, two (HNA1, HNA2) whose cells exhibited a high nucleic acid content and one (LNA) with low nucleic acid content cells. HNA2 was most populated at 50 m but not detected at 90 m and below, presumably aerobic anoxygenic photoheterotrophic bacteria (AAPs). The variability in HP abundance was mainly confined in the upper 80 m. A few secondary peaks of HP abundance were observed (80–150 m) in connection with abundance troughs in the surface layer. HP cells were continuously present in a wide layer around 500 m (mean 191×10 3 cells/cm 3 ). Below this layer, HP abundance randomly exhibited peaks, coupled to respiratory rate peaks. The HP abundance and variability in the water column was suppressed during a strong wind event. The observed sporadic variability was tentatively interpreted through a pulsed carbon-export mechanism induced by the microorganism production of dissolved polysaccharides, followed by flocculation and rapid sinking. This mechanism would thus contribute to (i) preventing organic matter accumulation in the epipelagic layer, (ii) seeding the water column with live HP cells, and (iii) supplying the aphotic water column with fresh and labile organic matter. This important vertical flux mechanism needs further observations and modelling.

Plankton and neuston microbes produce organic matter (OM), which accumulates in the sea surface microlayer (SML). Fluxes of heat and momentum exchange across the sea-air interface, as do fluxes of matter, including greenhouse gases, aerosols, microbes (algae, bacteria sensu lato and viruses) and other substances. At least at calm to moderate windspeeds, microbial OM (MOM) in the SML reduces these fluxes. Another MOM fraction, foam, covers a part of the ocean surface. Ocean foam increases mean ocean albedo because it reflects solar radiation, thus cooling the ocean and the Earth. The rheological properties of MOM and the reduction of sea-air fluxes depend on microbial abundance and taxonomic composition, as do the formation and persistence of foam. Genomic regulation of MOM secretion may thus be helping to regulate air-sea fluxes and climate. Unpredictable changes in abundance and taxonomic composition of these microbial communities may be adding uncertainty to global and more local climate. Some of this uncertainty could be mitigated by studying the ecology and genomics of the surface microbial community together with chemical and rheological properties of their secreted MOM and its effects on sea-air fluxes and foam coverage, to incorporate into climate models.

Microbial food web (MFW) in the seawater encompasses the smallest organisms: viruses, autotrophic prokaryotes and heterotrophic prokaryotes (HP), nanoflagellates, eukaryotic phytoplankton and ciliates. For many years, scientists investigated the MFW structure differences in distinct water masses. However, the MFW structure seasonal variation in coastal areas remains poorly documented. In this study, we report on the seasonal and spatial variations of the MFW structure in the temperate Sanggou Bay in four successive seasons, from spring to winter. With a temperature increase from 1.90 to 24.20 degrees C, HP biomass increased from 3.77 to 135.77 mu g C dm(-3), almost covering the whole variation range for the global ocean. The autotrophic (AUTO) components, including Synechococcus, phototrophic picoeukaryotes (PEUK) and pigmented nanoflagellates (PNF), exhibited biomass variation ranges as large as previously reported. The MFW structure seasonal variation was driven by MFW relative biomasses (biomass ratios of MFW components to HP). With the increase of HP biomass, PNF and PEUK relative biomasses increased more rapidly than those of other groups while that of ciliates slightly decreased. The HETE:AUTO (biomass ratio of heterotroph to autotroph organisms) decreased with temperature, it was 1 in other seasons. Cluster analyses distinguished Inside Bay and Outside Bay on the basis of hydrological characteristics. Consistently, the two subdivisions of Sanggou Bay exhibited different MFW structures as well as distinct tintinnid communities. The main MFW structure difference between Inside and Outside Bay was the biomass ratios of AUTO components to HP. Our results showed that the variations of autotrophic component biomass ratios relative to HP were the main factor responsible for the MFW structure seasonal variation. The spatial difference in MFW structure as well as in tintinnid taxonomic composition between Inside and Outside Bay was linked to the semienclosed nature of the Bay that does not favor efficient mixing with outside Yellow Sea waters.

EDITORIAL article Front. Hum. Neurosci., 14 October 2020Sec. Motor Neuroscience Volume 14 - 2020 | https://doi.org/10.3389/fnhum.2020.588199

In the eutrophic Ghar El Melh Lagoon (GML, Tunisia), the distribution of heterotrophic prokaryotes, pico- and nanophytoplankton was studied at five stations in November 2012 at the single cell level, along with environmental factors. Flow cytometry analysis of ultraplankton (<10 μm) resolved (i) two heterotrophic prokaryote groups, low and high nucleic acid contents (LNA and HNA, respectively), and (ii) eight to nine ultraphytoplankton groups (cryptophyte-like cells, two nanoeukaryote subgroups, two picoeukaryote subgroups and three Synechococcus-like cells subgroups). Prochlorococcus was not detected. According to redundancy analysis (RDA), a significant difference was found in the distribution of the ultraplankton between stations (F = 2.61, p < 0.05); maximum proliferations of heterotrophic prokaryotes were observed in the inner parts of the lagoon at stations 3, 4 and 5 affected by urban, agricultural and industrial discharges. Ultraphytoplankton concentrations were the highest near the outlet of the lagoon at stations 1 and 2 influenced by freshwater outflow and oligotrophic Mediterranean water inflow, respectively. At station 1, the large ultraphytoplankton concentration derives from the high abundance of cryptophyte-like cells favoured by the freshwater outflow whereas at station 2, the input of oligotrophic Mediterranean water enhanced the abundance of Synechococcus and picoeukaryotes at the expense of nanoeukaryotes. Two trophic regimes were thus differentiated in GML.

"Neuropsychology of space: Spatial functions of the human brain." Applied Neuropsychology: Adult, 25(6), p. 586