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The Southern Ocean contributes substantially to the global biological carbon pump (BCP). Salps in the Southern Ocean, in particular Salpa thompsoni, are important grazers that produce large, fast-sinking fecal pellets. Here, we quantify the salp bloom impacts on microbial dynamics and the BCP, by contrasting locations differing in salp bloom presence/absence. Salp blooms coincide with phytoplankton dominated by diatoms or prymnesiophytes, depending on water mass characteristics. Their grazing is comparable to microzooplankton during their early bloom, resulting in a decrease of ~1/3 of primary production, and negative phytoplankton rates of change are associated with all salp locations. Particle export in salp waters is always higher, ranging 2- to 8- fold (average 5-fold), compared to non-salp locations, exporting up to 46% of primary production out of the euphotic zone. BCP efficiency increases from 5 to 28% in salp areas, which is among the highest recorded in the global ocean.

The combination of iron limitation and microzooplankton grazing controls phytoplankton productivity and taxonomic composition in high-nutrient low-chlorophyll (HNLC) regions. While increased productivity and diatom contribution triggered by iron enrichment support this view, direct measurements of underpinning group-specific growth and grazing rates are scarce for the Southern Ocean. To assess these rates, we conducted dilution experiments coupled to high-performance liquid chromatography and flow-cytometry in sub-Antarctic waters on and off Campbell Plateau, southeast of Aotearoa-New Zealand. Off the plateau, growth and grazing were closely balanced for all groups despite a two-fold difference between slow- and fast-growing groups. On Campbell Plateau, where HNLC conditions were alleviated, the balance was disrupted, mainly by the preferential growth of diatoms and green algae, which was stimulated beyond grazing. Our results expand the recognized ability of diatoms to escape grazing control to picoplanktonic green algae that also avoid grazing and contribute significantly to phytoplankton productivity and biomass accumulation.

Pigment-based chemotaxonomy is a widely utilized tool to determine the biomass of phytoplankton classes from pigment biomarkers. The CHEMTAX approach is sensitive to the initial estimates of pigment-to-chlorophyll a (Chl a) ratios for the phytoplankton classes required, even though these are modified by the CHEMTAX process. We present an alternative chemotaxonomic method that utilizes simulated annealing with a steepest descent algorithm to derive class abundances and pigment-to-Chl a ratios. The simulated annealing algorithm is tested on two synthetic datasets of Southern Ocean phytoplankton communities. Each dataset is composed of 1000 inversion samples (set of phytoplankton class abundances, pigment ratios, and pigment profiles) with sizes ranging between 5 and 60 individual samples. We show that the new simulated annealing approach displays higher accuracy than two common configurations of the CHEMTAX method, with lower differences between true and estimated class abundances. Symmetric mean absolute percentage error were 4.8–11%, compared to 18–70% with CHEMTAX approaches. Proportions of variance explained (R) between true and estimated class abundances using the simulated annealing approach were 0.98–0.99 compared to 0.71–0.89 for CHEMTAX. Overall, this new methodology is capable of determining phytoplankton class abundances at higher accuracy than CHEMTAX without sensitivity to initial estimates of pigment-to-Chl a ratios.

The molecular diversity of marine picocyanobacterial populations, an important component of phytoplankton communities, is better characterized using high-resolution marker genes than the 16S rRNA gene as they have greater sequence divergence to differentiate between closely related picocyanobacteria groups. Although specific ribosomal primers have been developed, another general disadvantage of bacterial ribosome-based diversity analyses is the variable number of rRNA gene copies. To overcome these issues, the single-copy petB gene, encoding the cytochrome b6 subunit of the cytochrome b6f complex, has been used as a high-resolution marker gene to characterize Synechococcus diversity. We have designed new primers targeting the petB gene and proposed a nested PCR method (termed Ong_2022) for metabarcoding of marine Synechococcus populations obtained by flow cytometry cell sorting. We evaluated the specificity and sensitivity of Ong_2022 against the standard amplification protocol (termed Mazard_2012) using filtered seawater samples. The Ong_2022 approach was also tested on flow cytometry-sorted Synechococcus populations. Samples (filtered and sorted) were obtained in the Southwest Pacific Ocean, from subtropical (ST) and subantarctic (SA) water masses. The two PCR approaches using filtered samples recovered the same dominant subclades, Ia, Ib, IVa, and IVb, with small differences in relative abundance across the distinct samples. For example, subclade IVa was dominant in ST samples with the Mazard_2012 approach, while the same samples processed with Ong_2022 showed similar contributions of subclades IVa and Ib to the total community. The Ong_2022 approach generally captured a higher genetic diversity of Synechococcus subcluster 5.1 than the Mazard_2012 approach while having a lower proportion of incorrectly assigned amplicon sequence variants (ASVs). All flow cytometry-sorted Synechococcus samples could be amplified only by our nested approach. The taxonomic diversity

We present annual cycles of chlorophyll a, phytoplankton carbon, nitrate and oxygen for Subtropical (STW), Subantarctic (SAW), and Subantarctic Mode (SAMW) waters near Aotearoa New Zealand from data collected by two Biogeochemical (BGC) Argo floats. We develop two simple models of depth-integrated net primary production (NPP), tuned against 14C-uptake measurements, to compare with Vertically-Generalised Production Model (VGPM) satellite-based estimates of NPP. One model is the simplest possible, and assumes production is proportional to light multiplied by chlorophyll a concentration. The second model modifies the light response profile to account for photoacclimation. In STW at 30–35°S, enhanced production is initiated in austral autumn when the mixed layer deepens to entrain nutrients into the photic zone. For about half the year, there is substantial production within a deep chlorophyll maximum that sits below the mixed layer. Consequently, depth-integrated NPP is only loosely related to surface biomass as imaged from satellite remote-sensing, and BGC Argo-based model estimates of depth-integrated NPP are about double VGPM estimates. In SAW at 45–55°S, production is initiated when vertical mixing decreases in austral spring. Production is largely within the mixed layer, and depth-integrated phytoplankton biomass and depth-integrated NPP follow surface phytoplankton biomass. Model estimates of depth-integrated NPP based on BGC Argo float profiles are comparable with VGPM estimates for the southern water masses.

Metabarcoding or high-throughput sequencing of a specific genetic marker is a powerful technique, widely used today, to analyze biodiversity across distinct environments and taxonomic groups. Plankton ecologists have benefited tremendously from the growing accumulation of metabarcoding studies. Novel biogeographic patterns have been established by the analysis of datasets from the Tara Oceans and Ocean Sampling Day projects. Novel lineages without cultured representatives have been uncovered. This chapter begins by going back to the steps that led Carl Woese and George Fox to define the concept of “molecular marker.” Among the multitude of exciting findings brought by high-throughput sequencing technologies, perhaps the major impacts are found in the study of picocyanobacteria and microbial eukaryotes from plankton communities. We then detail the different steps and choices that are involved in designing, performing, and analyzing a metabarcoding study. We are using a compilation of about 250 metabarcoding studies to present the major trends in terms of the gene marker used and environment probed. An alternative approach to metabarcoding developed for marine picocyanobacteria is also briefly discussed. We are then focusing on specific habitats and processes that have benefited from metabarcoding: the study of polar ecosystems, the functioning of the marine biological carbon pump, predator-prey interactions, and picoeukaryotic phytoplankton in highly urbanized lakes. Finally, we offer some perspectives on emerging trends, such as the use of metabarcodes combined with supervised machine learning for biomonitoring, the link between metabarcoding and functional diversity in trait-based studies and the massive sequencing of long DNA fragments.

A detailed study of phytoplankton composition and dynamics was carried out during three contrasting situations (cruises F1, F2, and F3) in the northwestern (NW) Mediterranean Sea. Haptophytes, diatoms, and green algae dominated in F1, during the spring bloom, with high nutrients and high phytoplankton biomass. In F2, the post-bloom situation with a still weak stratification and lower nutrient concentrations, we found a high spatial variability. Stations were clearly dominated by either Synechococcus, haptophytes or cryptophytes; with Synechococcus reaching the highest abundance (4 × 105 cells mL−1, 60% of the integrated chlorophyll a) reported to date for the open Mediterranean Sea. Cryptophytes accumulated close to the surface in very shallow mixed layer stations. In late summer, F3 revealed a fully developed stratification with low nutrients and a marked deep chlorophyll maximum (DCM). Prochlorococcus was present only during this cruise, mainly in deep layers together with haptophytes and pelagophytes, while haptophytes and Synechococcus dominated the upper mixed layer. Flow cytometry (FCM) and pigment-based abundance estimates for Prochlorococcus, Synechococcus and cryptophytes were well correlated, as happened also between small picoeukaryotes (FCM) and green algae (pigments), and between large picoeukaryotes (FCM) and haptophytes (pigments). Dinoflagellate abundance by microscopy and by pigments did not agree well, probably due to the presence of heterotrophic forms or because they contained pigments other than peridinin, the standard dinoflagellate marker. The decrease in size of the FCM large picoeukaryotes group with depth was presumably related to the increasing contribution of pelagophytes, with smaller cells than haptophytes, the other main component of this fraction. Cell size increase of Prochlorococcus and Synechococcus with depth suggests vertical segregation of genotypes or photoadaptation. The groups' ecological preferences are presented with respec

En Colombia se presentan múltiples deficiencias tanto a nivel espacial como a nivel de infraestructura en la educación superior que dificultan los procesos educativos, además de dificultar el desarrollo de los sentidos y capacidades de los estudiantes, así mismo ni en el municipio de Funza ni en los municipios cercanos cuentan este tipo de instituciones por lo cual el desarrollo de un proyecto universitario bajo unos parámetros de diseño que busquen estimular las habilidades cognitivas generará un gran beneficio para el municipio y toda la región. Los espacios que habitamos influyen directamente en como percibimos a nuestro entorno, a partir de esta premisa se hace una investigación de cuáles son los factores dentro de un espacio educativo que influyen en las capacidades cognitivas de los estudiantes. Partiendo de estos factores se generarán estrategias que permitan un desarrollo óptimo de estas capacidades dentro del entorno educativo enriqueciendo este lo que derivará en mejores y más eficaces procesos aprendizaje. Estrategias como los campus interactivo, las aulas naturalmente iluminadas, los paisajes naturales, el simbolismo dentro las aulas son claves a la hora de diseñar estos espacios que buscan apelar a los sentidos y a la experiencia cognitiva que tiene el estudiante con el espacio, ya sea de forma directa o indirecta, mejorando considerablemente la capacidad de estos para absorber e interpretar información así como despertando su sentido de la curiosidad mejorando significativamente no solo su calidad de educación si no también su calidad de vida.

Passive sinking of particulate organic matter (POM) is the main mechanism through which the biological pump transports surface primary production to the ocean interior. However, the contribution and variability of different biological sources to vertical export is not fully understood. Here, we use DNA metabarcoding of the 18S rRNA gene and particle interceptor traps (PITs) to characterize the taxonomic composition of particles sinking out of the photic layer in the California Current Ecosystem (CCE), a productive system with high export potential. The PITs included formalin-fixed and ‘live’ traps to investigate eukaryotic communities involved in the export and remineralization of sinking particles. Sequences affiliated with Radiolaria dominated the eukaryotic assemblage in fixed traps (90%), with Dinophyta and Metazoa making minor contributions. The prominence of Radiolaria decreased drastically in live traps, possibly due to selective consumption by copepods, heterotrophic nanoflagellates, and phaeodarians that were heavily enriched in these traps. These patterns were consistent across the water masses surveyed extending from the coast to offshore, despite major differences in productivity and trophic st

Symbiosis with micro-algae (photosymbiosis) is a common feature among marine planktonic protists, but very little is known about the physiology and ecological significance of these associations. High concentrations of dimethylsulfoniopropionate (DMSP), a metabolite produced by marine microalgae, are commonly observed in coral-microalgae symbiosis, where DMS(P) is involved in multiple physiological functions. Knowledge on concentration and role of DMSP in analogous photosymbiosis in plankton is lacking. Here, we assess the total DMSP (DMSPt = DMSP + DMS) concentration and natural stable isotopes of sulfur across ecologically relevant symbiotic plankton groups, the Radiolaria and Foraminifera. We found that intracellular DMSPt concentrations in microalgal symbionts were among the highest recorded (range = 170–702 mmol L), while lower concentrations (range = 0.1–23 mmol L) were characteristic of the holobiont (i.e., host-microalgae). The contribution of symbiotic Radiolaria to the water column particulate DMSPt concentration ranged 0.1–8%. Sulfur isotopic composition (S) of DMSPt in the Collodaria holobionts was significantly higher than their symbiotic microalgae isolated in culture. Despite their high intracellular DMSPt content, SO uptake in these holobionts throughout 3-d incubations was not detected. We observed a systematic S depletion (∼ 1.5‰) of DMS relative to DMSP in experimental incubations containing filtered seawater, which we hypothesize is related to the bacterial preference for the uptake of S-depleted DMS. Overall, the results indicate that plankton symbiosis can, at times, represent a potentially important source of DMS(P). Specific differences in S provided new insights into sulfur isotopic fractionation associated with DMS(P) biotransformation processes, with potential implications for current interpretations of isotopically tracked biogenic sources of marine aerosols.