María Celeste López Abbate

Marine Carbon Dioxide Removal (mCDR) approaches are increasingly considered for climate change mitigation as a supplement to rapid emissions reduction. However, it is still unclear if mCDR approaches could be effective, safe, and accountable. A critical requirement for mCDR to work, potentially, is robust monitoring, reporting, and verification (MRV) of greenhouse gas(es) removed through mCDR activities. MRV frameworks and protocols are currently developed in a scattered manner by individual stakeholders, so that the principles they are built upon may or may not appeal to the broader international community that is interested in the ocean commons. International agreement and consolidation on MRV for mCDR seem crucial to legitimize and validate mCDR, considering that the ocean is a globally interconnected fluid and that activities by some may affect many others. Here, we undertake a step toward consolidation of MRV by consulting the international scientific community. We established a global network of scientists organized into 6 “continental” nodes, each of which addressed the same set of MRV-related questions and whose thoughts were equally weighted in the synthesis. Our consultation shows that while there are many converging views on MRV (e.g., the importance of modeling for MRV), there are also differences in the regional MRV priorities (e.g., the importance of regional vs global models). The areas of consensus and divergence identified herein may be instrumental in the design of more widely accepted MRV frameworks, informed equally by scientists from 6 continents.

The Patagonian Shelf is recognized for its high potential for carbon uptake, driven by intense biological productivity. While net CO2 uptake persists much of the year, the mechanisms shaping sea-air CO2 fluxes (FCO2) under low-productivity conditions remain unclear. We examined surface FCO2 during autumn 2022 on the northern Patagonian Shelf, influenced by the Brazil and Malvinas Currents, where submesoscale activity generates patchy flux regimes. Even under low productivity, chlorophyll-a (Chl-a) was the strongest predictor of seawater pCO2 and modulated FCO2: high Chl-a areas acted as CO2 sinks, whereas low-Chl-a regions were near equilibrium or sources. Bloom phenology explained coherent patterns, with sinks associated with off-season peaks and sources with late-stage declines. Strongest uptake occurred in a retention zone offshore the upwelling front, where Malvinas Current circulation concentrated pigmented cells. Conversely, adjacent upwelling areas with stronger advection promoted outgassing of aged, carbon-rich waters that offset biological uptake, underscoring the dual role of upwelling. Planktonic assemblages also modulated carbon cycling: Prochlorococcus dominated oligotrophic Brazil Current waters with low Chl-a, depleted microbes, and reduced fluorescent dissolved organic matter (DOM), reflecting limited sequestration and persistent outgassing. Conversely, Synechococcus, picoeukaryotes, and heterotrophic bacteria co-occurred in sink regions, where DOM showed signatures of recent production. On the shelf, abundant bacteria and viruses were linked to humic-like refractory DOM, suggesting microbial reworking as a pathway for long-term storage. These findings demonstrate that while temperature set the FCO2 landscape at the Brazil-Malvinas confluence, while physical transport, bloom dynamics, and microbial transformations interact to produce heterogeneous CO2 source-sink patterns.

The Patagonian Shelf is recognized for its high potential for carbon uptake, largely driven by intense biological productivity. While net CO2 uptake persists much of the year, the mechanisms shaping sea–air CO2 fluxes (FCO2) in the low-productivity season remain unclear. We examined surface FCO2 during autumn 2022 on the northern Patagonian Shelf, influenced by the Brazil and Malvinas Currents, where submesoscale activity generates patchy flux regimes. Even under low productivity (mean surface chlorophyll-a (Chl-a) 1.1 mg m⁻³), Chl-a was the strongest predictor: high Chl-a areas acted as CO2 sinks, whereas low-Chl-a regions were near equilibrium or acted as net sources. Bloom phenology explained coherent patterns, with sinks associated with off-season peaks and sources to late-stage declines. Strongest uptake occurred in a retention zone offshore the upwelling front, where Malvinas Current circulation concentrated pigmented cells. Conversely, adjacent upwelling areas with stronger advection promoted outgassing of aged, carbon-rich waters that offset biological uptake, underscoring the dual role of upwelling. Planktonic assemblages also modulated carbon cycling: Prochlorococcus dominated oligotrophic Brazil Current waters with low Chl-a, depleted microbes, and reduced fluorescent dissolved organic matter (DOM), reflecting limited sequestration and persistent outgassing. Conversely, Synechococcus, picoeukaryotes, and heterotrophic bacteria co-occurred in sink regions, where DOM showed signatures of recent production. On the shelf, abundant bacteria and viruses were linked to humic-like refractory DOM, suggesting microbial reworking as a pathway for long-term storage. These findings demonstrate how physical transport, bloom dynamics, and microbial transformations interact to produce heterogeneous CO2 source–sink patterns in the Brazil/Malvinas confluence.

Plankton, a diverse group of aquatic organisms, make Earth livable, regulate aquatic life, and provide benefits to human societies such as access to clean water, food security, and well-being. They also support economies and inspire biotechnological innovations. This article aims to raise awareness of the value of plankton to humanity and serves as an informative guide for aquatic professionals, policymakers, and anyone interested in plankton. We present the value of plankton across six themes of human interest: biogeochemistry; ecology; climate; the evolution of science; economy; and culture, recreation, and well-being. Guided by the 2022 Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services values assessment, we introduce the six themes under the Life Framework of Values to offer a comprehensive summary of the significance of plankton to humanity. In addition, we provide examples of plankton variables used in policy frameworks and recommendations for enhancing understanding of their value through long-term sustainable research and monitoring.

While the sources of dissolved organic matter (DOM) in the open ocean are relatively well identified, its fate due to microbial activity is still evolving. Here, we explored how microbial community structure, growth, and grazing of phytoplankton and heterotrophic bacteria influenced the DOM pool and the transformation of its fluorescent fraction. Dilution experiments were performed during the productive season on the Patagonian Shelf (SW Atlantic Ocean), a region of intense biological activity, with peak productivity observed at the shelf break front. Although phytoplankton biomass was higher than that of bacteria, protists selectively preyed on the faster-growing bacterial population, denoting trophic specificity of grazers. High trophic coupling was suggested by the biomass distribution of protistan consumers and their prey, which predominantly exhibited an inverted trophic pyramid structure. An exception to this pattern was observed at the highly productive shelf break front, where a traditional bottom-heavy pyramid emerged, indicating that most phytoplankton evaded protist predation despite evidence of herbivory. Bacterial consumption of DOM appeared uncoupled from its total amount but was influenced by DOM complexity, while the bacterial production of humic-like substances from protistan plankton precursors observed in most experiments highlighted a potential pathway for carbon sequestration. Protistan grazers also significantly influenced DOM dynamics by scaling their DOM contribution in response to the intensity of grazing on heterotrophic bacteria, regardless of productivity levels. This effect likely arises from reducing the number of active DOM-consuming bacteria and by providing egestion DOM compounds. At the onset of the productive season, high bacterial growth rates stimulate protistan grazing, which serves as a link between bacterial biomass and higher trophic levels. However, as grazing pressure increases, protists can also contribute to the accumulation of a fraction of DOM.

Motivation: Here, we make available a second version of the BioTIME database, which compiles records of abundance estimates for species in sample events of ecological assemblages through time. The updated version expands version 1.0 of the database by doubling the number of studies and includes substantial additional curation to the taxonomic accuracy of the records, as well as the metadata. Moreover, we now provide an R package (BioTIMEr) to facilitate use of the database.Main Types of Variables Included: The database is composed of one main data table containing the abundance records and 11 metadata tables. The data are organised in a hierarchy of scales where 11,989,233 records are nested in 1,603,067 sample events, from 553,253 sampling locations, which are nested in 708 studies. A study is defined as a sampling methodology applied to an assemblage for a minimum of 2 years.Spatial Location and Grain: Sampling locations in BioTIME are distributed across the planet, including marine, terrestrial and freshwater realms. Spatial grain size and extent vary across studies depending on sampling methodology. We recommend gridding of sampling locations into areas of consistent size.Time Period and Grain: The earliest time series in BioTIME start in 1874, and the most recent records are from 2023. Temporal grain and duration vary across studies. We recommend doing sample‐level rarefaction to ensure consistent sampling effort through time before calculating any diversity metric.Major Taxa and Level of Measurement: The database includes any eukaryotic taxa, with a combined total of 56,400 taxa.Software Format: csv and. SQL.

While the sources of dissolved organic matter (DOM) in the open ocean are relatively well identified, its fate due to microbial activity is still evolving. Here, we explored how microbial community structure, growth, and grazing of phytoplankton and heterotrophic bacteria influence the DOM pool and the transformation of its fluorescent fraction (FDOM) during dilution experiments in the Patagonian Shelf (SW Atlantic Ocean). This area constitutes a global hotspot of carbon sequestration due to intense biological productivity which peaks at the shelf break front. The productive stations at the shelf break front featured a food web primarily based on phytoplankton and heterotrophic bacteria, while less productive mid-shelf stations showed greater dependence of protistan predators on bacterial biomass. Although phytoplankton biomass was higher than that of bacteria, protists selectively preyed on the latter, which exhibited faster growth rates, denoting high trophic specificity of grazers. Trophic efficiency and omnivory favored a bottom-heavy biomass distribution, characterized by consumer biomass dominance over producers, except in highly productive stations influenced by nutrient-rich upwelling waters, where a typical pyramid structure was observed. Our results showed that in addition to the commonly accepted factors such as phytoplankton growth stage and bacterial community composition, DOM accumulation versus consumption is also linked to bacterial grazing. Intense grazing on heterotrophic bacteria promoted DOM accumulation, likely by reducing the number of active, DOM-consuming bacteria and by providing egestion compounds to the DOM pool. Moreover, bacterial consumption of DOM appeared uncoupled from its total amount but was influenced by FDOM properties. These findings suggest that under high bacterial growth rate that follows the onset of the productive season, protistan grazers act as a link between bacterial biomass and higher trophic levels, partially diverting DOM lysate production by virus.

While the sources of dissolved organic matter (DOM) in the open ocean are relatively well identified, its fate due to microbial activity is still evolving. Here, we explored how microbial community structure, growth, and grazing of phytoplankton and heterotrophic bacteria influence the DOM pool and the transformation of its fluorescent fraction (FDOM) during dilution experiments in the Patagonian Shelf (SW Atlantic Ocean). This area constitutes a global hotspot of carbon sequestration due to intense biological productivity which peaks at the shelf break front. The productive stations at the shelf break front featured a food web primarily based on phytoplankton and heterotrophic bacteria, while less productive mid-shelf stations showed greater dependence of protistan predators on bacterial biomass. Although phytoplankton biomass was higher than that of bacteria, protists selectively preyed on the latter, which exhibited faster growth rates, denoting high trophic specificity of grazers. Trophic efficiency and omnivory favored a bottom-heavy biomass distribution, characterized by consumer biomass dominance over producers, except in highly productive stations influenced by nutrient-rich upwelling waters, where a typical pyramid structure was observed. Our results showed that in addition to the commonly accepted factors such as phytoplankton growth stage and bacterial community composition, DOM accumulation versus consumption is also linked to bacterial grazing. Intense grazing on heterotrophic bacteria promoted DOM accumulation, likely by reducing the number of active, DOM-consuming bacteria and by providing egestion compounds to the DOM pool. Moreover, bacterial consumption of DOM appeared uncoupled from its total amount but was influenced by FDOM properties. These findings suggest that under high bacterial growth rate that follows the onset of the productive season, protistan grazers act as a link between bacterial biomass and higher trophic levels, partially diverting DOM lysate production by virus.

While the sources of dissolved organic matter (DOM) in the open ocean are relatively well identified, its fate due to microbial activity is still evolving. Here, we explored how microbial community structure, growth, and grazing of phytoplankton and heterotrophic bacteria influence the DOM pool and the transformation of its fluorescent fraction (FDOM) during dilution experiments in the Patagonian Shelf (SW Atlantic Ocean). This area constitutes a global hotspot of carbon sequestration due to intense biological productivity which peaks at the shelf break front. The productive stations at the shelf break front featured a food web primarily based on phytoplankton and heterotrophic bacteria, while less productive mid-shelf stations showed greater dependence of protistan predators on bacterial biomass. Although phytoplankton biomass was higher than that of bacteria, protists selectively preyed on the latter, which exhibited faster growth rates, denoting high trophic specificity of grazers. Trophic efficiency and omnivory favored a bottom-heavy biomass distribution, characterized by consumer biomass dominance over producers, except in highly productive stations influenced by nutrient-rich upwelling waters, where a typical pyramid structure was observed. Our results showed that in addition to the commonly accepted factors such as phytoplankton growth stage and bacterial community composition, DOM accumulation versus consumption is also linked to bacterial grazing. Intense grazing on heterotrophic bacteria promoted DOM accumulation, likely by reducing the number of active, DOM-consuming bacteria and by providing egestion compounds to the DOM pool. Moreover, bacterial consumption of DOM appeared uncoupled from its total amount but was influenced by FDOM properties. These findings suggest that under high bacterial growth rate that follows the onset of the productive season, protistan grazers act as a link between bacterial biomass and higher trophic levels, partially diverting DOM lysate production by virus.