The wineglass effect shapes particle export to the deep ocean in mesoscale eddies

Mesoscale eddies in the ocean strongly impact the distribution of planktonic particles, mediating carbon fluxes over ~1/3 of the world ocean. However, mechanisms controlling particle transport through eddies are complex and challenging to measure in situ. Here we show the subsurface distribution of eddy particles funneled into a wineglass shape down to 1000 m, leading to a sevenfold increase of vertical carbon flux in the eddy center versus the eddy flanks, the “wineglass effect”. We show that the slope of the wineglass (R) is the ratio of particle sinking velocity to the radially inward velocity, such that R represents a tool to predict radial particle movement (here 0.05 m s−1). A simple model of eddy spindown predicts such an ageostrophic flow concentrating particles in the eddy center. We explore how size-specific particle flux toward the eddy center impacts eddies' biogeochemistry and export fluxes

The wineglass effect shapes particle export to the deep ocean in mesoscale eddies

Mesoscale eddies in the ocean strongly impact the distribution of planktonic particles, mediating carbon fluxes over ~1/3 of the world ocean. However, mechanisms controlling particle transport through eddies are complex and challenging to measure in situ. Here we show the subsurface distribution of eddy particles funneled into a wineglass shape down to 1000 m, leading to a sevenfold increase of vertical carbon flux in the eddy center versus the eddy flanks, the “wineglass effect”. We show that the slope of the wineglass (R) is the ratio of particle sinking velocity to the radially inward velocity, such that R represents a tool to predict radial particle movement (here 0.05ms�1). A simple model of eddy spindown predicts such an ageostrophic flow concentrating particles in the eddy center. We explore how size-specific particle flux toward the eddy center impacts eddies' biogeochemistry and export fluxes

Cross-Hemisphere Study Reveals Geographically Ubiquitous, Plastic-Specific Bacteria Emerging from the Rare and Unexplored Biosphere

While it is now appreciated that the millions of tons of plastic pollution travelling through marine systems carry complex communities of microorganisms, it is still unknown to what extent these biofilm communities are specific to the plastic or selected by the surrounding ecosystem. To address this, we characterized and compared the microbial communities of microplastic particles, nonplastic (natural and wax) particles, and the surrounding waters from three marine ecosystems (the Baltic, Sargasso and Mediterranean seas) using high-throughput 16S rRNA gene sequencing. We found that biofilm communities on microplastic and nonplastic particles were highly similar to one another across this broad geographical range. The similar temperature and salinity profiles of the Sargasso and Mediterranean seas, compared to the Baltic Sea, were reflected in the biofilm communities. We identified plastic-specific operational taxonomic units (OTUs) that were not detected on nonplastic particles or in the surrounding waters. Twenty-six of the plastic-specific OTUs were geographically ubiquitous across all sampled locations. These geographically ubiquitous plastic-specific OTUs were mostly low-abundance members of their biofilm communities and often represented uncultured members of marine ecosystems. These results demonstrate the potential for plastics to be a reservoir of rare and understudied microbes, thus warranting further investigations into the dynamics and role of these microbes in marine ecosystems

A Holistic Approach to Marine Eco-Systems Biology

With biology becoming quantitative, systems-level studies can now be performed at spatial scales ranging from molecules to ecosystems. Biological data generated consistently across scales can be integrated with physico-chemical contextual data for a truly holistic approach, with a profound impact on our understanding of life [1]–[5]. Marine ecosystems are crucial in the regulation of Earth's biogeochemical cycles and climate [6],[7]. Yet their organization, evolution, and dynamics remain poorly understood [8],[9]. The Tara Oceans project was launched in September 2009 for a 3-year study of the global ocean ecosystem aboard the ship Tara. A unique sampling programme encompassing optical and genomic methods to describe viruses, bacteria, archaea, protists, and metazoans in their physico-chemical environment has been implemented. Starting as a grassroots initiative of a few scientists, the project has grown into a global consortium of over 100 specialists from diverse disciplines, including oceanography, microbial ecology, genomics, molecular, cellular, and systems biology, taxonomy, bioinformatics, data management, and ecosystem modeling. This multidisciplinary community aims to generate systematic, open access datasets usable for probing the morphological and molecular makeup, diversity, evolution, ecology, and global impacts of plankton on the Earth system

Globally consistent quantitative observations of planktonic ecosystems

In this paper we review the technologies available to make globally quantitative observations of particles in general—and plankton in particular—in the world oceans, and for sizes varying from sub-microns to centimeters. Some of these technologies have been available for years while others have only recently emerged. Use of these technologies is critical to improve understanding of the processes that control abundances, distributions and composition of plankton, provide data necessary to constrain and improve ecosystem and biogeochemical models, and forecast changes in marine ecosystems in light of climate change. In this paper we begin by providing the motivation for plankton observations, quantification and diversity qualification on a global scale. We then expand on the state-of-the-art, detailing a variety of relevant and (mostly) mature technologies and measurements, including bulk measurements of plankton, pigment composition, uses of genomic, optical and acoustical methods as well as analysis using particle counters, flow cytometers and quantitative imaging devices. We follow by highlighting the requirements necessary for a plankton observing system, the approach to achieve it and associated challenges. We conclude with ranked action-item recommendations for the next 10 years to move toward our vision of a holistic ocean-wide plankton observing system. Particularly, we suggest to begin with a demonstration project on a GO-SHIP line and/or a long-term observation site and expand from there, ensuring that issues associated with methods, observation tools, data analysis, quality assessment and curation are addressed early in the implementation. Global coordination is key for the success of this vision and will bring new insights on processes associated with nutrient regeneration, ocean production, fisheries and carbon sequestration

Assessing biases in computing size spectra of automatically classified zooplankton from imaging systems: A case study with the ZooScan integrated system

International audienceBody size constrains prey-predator interactions and physiology, therefore plankton size spectra have been appointed as synthetic descriptors of plankton community structure and functioning. Recently developed imaging systems and supervised classification tools provide size measurements of any object in situ or in net samples and automatically classify them into previously defined categories. But because the nature of objects detected by these imaging systems is diverse, from non-living detritus to organisms of different plankton taxa, and because the steps in the analysis could introduce specific biases, a careful analysis of such plankton size spectra is needed before going deeper into ecological considerations. Using a WP2 net time series, we propose a general framework to analyze and validate zooplankton size spectra collected with nets and analyzed with the ZooScan integrated system that includes supervised classification. Size spectra were controlled, at each step of the procedure, to assess the modification of their shape due to several possible biases: (i) the effect of objects touching each other during the image acquisition, (ii) the error of the automatic classification differing among size classes and (iii) the choice of model to estimate body biovolume

DECADAL VARIABILITY OF ZOOPLANKTON COMMUNITIES OF THE NW MEDITERRANEAN SEA (WEEKLY SAMPLED FROM 1995 TO 2006) IN RELATION WITH CLIMATIC FORCING.

participantThe inter-annual variability of the pelagic ecosystems of the Ligurian Sea is investigated combining original datasets (from 1995 to 2006 collected weekly) of zooplankton abundances, hydrology and local weather conditions obtained in the bay of Villefranche-sur-mer. Two main patterns of zooplankton dynamics were observed with a shift between 1999 and 2000. The first period was characterized by high precipitation and mild air temperature during the winter. This induced lower salinity and higher seawater temperature and low density of surface seawater during the winter. These waters were characterize by low loads of nutrients. During these years, zooplankton total biovolume was also lower as shown by the strong negative anomalies in the time series. Starting in 2000, the climate changed toward drier and colder winters with denser surface water and more intense convections as suggested by higher nutrients concentrations. An increase of the abundances of all zooplankton categories was observed with a doubling of the total zooplankton average annual means and a change in the zooplankton phenology with a spring development happening 2.5 weeks earlier during these years. These results could be explained by a strong bottom-up control on the pelagic ecosystem of the Ligurian Sea at the inter-annual scale. Whereas the summer thermal stratification increase was often suggested to drive long-term dynamic in Ligurian Sea zooplankton, our results highlight the strong influence of the Winter convection properties as the main factor governing inter-annual changes in zooplankton abundance. The effect of global climate cycles will be discussed as being possible factors driving the pelagic ecosystem in the NW Mediterranean Sea

Pulsed remineralisation in the northwestern Mediterranean Sea: a hypothesis

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Revealing and analyzing networks of marine microbial ecosystems

International audienceUnderstanding interactions between microbial communities and their environment well enough to be able to predict diversity or biotic response on the basis of physicochemical parameters is a fundamental pursuit of microbial ecology that still eludes us. Networks have become a key approach to understanding systems of interacting objects, and network based analysis recently shown great promises to decipher microbial interactions. However, modeling microbial communities is a complicated task, because (i) communities are complex, (ii) most are described qualitatively, and (iii) quantitative understanding of the way communities interacts with their surroundings remains incomplete.We propose herein a network analysis that aims to overcome these points while focusing on one open biological question: revealing and analyzing plankton networks driving carbon export in the global ocean.The biological carbon pump is the process by which photosynthesis transforms CO2 to organic carbon sinking to the deep-ocean as particles where it is sequestered. While the intensity of the pump correlate to plankton community composition, the underlying ecosystem structure and interactions driving this process remain largely uncharacterized Here we use environmental and metagenomic data gathered during the Tara Oceans expedition to improve understanding of these drivers. We show that specific plankton communities correlate with carbon export and highlight unexpected and overlooked taxa such as Radiolaria, alveolate parasites and bacterial pathogens, as well as Synechococcus and their phages, as key players in the biological pump. Additionally, we show that the abundances of just a few bacterial and viral genes predict most of the global ocean carbon export’s variability. Together these findings help elucidate ecosystem drivers of the biological carbon pump and present a case study for scaling from genes-to-ecosystems

Revealing and analyzing networks of marine microbial ecosystems

International audienceUnderstanding interactions between microbial communities and their environment well enough to be able to predict diversity or biotic response on the basis of physicochemical parameters is a fundamental pursuit of microbial ecology that still eludes us. Networks have become a key approach to understanding systems of interacting objects, and network based analysis recently shown great promises to decipher microbial interactions. However, modeling microbial communities is a complicated task, because (i) communities are complex, (ii) most are described qualitatively, and (iii) quantitative understanding of the way communities interacts with their surroundings remains incomplete.We propose herein a network analysis that aims to overcome these points while focusing on one open biological question: revealing and analyzing plankton networks driving carbon export in the global ocean.The biological carbon pump is the process by which photosynthesis transforms CO2 to organic carbon sinking to the deep-ocean as particles where it is sequestered. While the intensity of the pump correlate to plankton community composition, the underlying ecosystem structure and interactions driving this process remain largely uncharacterized Here we use environmental and metagenomic data gathered during the Tara Oceans expedition to improve understanding of these drivers. We show that specific plankton communities correlate with carbon export and highlight unexpected and overlooked taxa such as Radiolaria, alveolate parasites and bacterial pathogens, as well as Synechococcus and their phages, as key players in the biological pump. Additionally, we show that the abundances of just a few bacterial and viral genes predict most of the global ocean carbon export’s variability. Together these findings help elucidate ecosystem drivers of the biological carbon pump and present a case study for scaling from genes-to-ecosystems