The concentrations of particulate organic carbon (POC) in the ocean are the result of a dynamic balance between multiple sources and sinks. Here, measurements of POC concentration in the small size fraction (SSF; 1-5 ) and the large size fraction (LSF; ) from the North Atlantic EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) cruise in the Porcupine Basin are combined with a non-steady state POC cycling model to estimate the temporal variations in rates of POC production, (dis)aggregation, sinking, remineralization, and POC ingestion/egestion by migrating zooplankton over the decline of a phytoplankton bloom. We infer coherent variations in POC cycling rates throughout the water column, with distinct temporal variability. Throughout the upper 500 m, disaggregation exerts a major control on both size fractions. Near the surface, disaggregation rates increase with time and are the major source of POC in the SSF. Aggregation strongly influences surface POC in both size fractions, although it becomes negligible with depth. POC is supplied to the LSF between 175 and 500 m by migrating zooplankton, which contribute between 15% and 100% of the total LSF source in this depth interval. Our results highlight a need to improve estimates of POC sinking fluxes, stressing differences in multiple approaches. In general, we quantify the intensity of particle cycling processes that are hard to observe and identify key mechanisms that lead to the observed temporal and vertical variations in POC concentrations.

Zooplankton community structure plays a key role in determining the fate of net primary production and export of organic matter to the deep sea. We compared diel changes in zooplankton (>200 mu m) vertical structure in the subarctic NE Pacific and Atlantic oceans during late summer 2018 and spring 2021, respectively, by analyzing biomass size structure and abundance of major taxa in discrete depth intervals between 0 and 1000 m. Diel vertical migration (DVM) was pronounced at both sites, with most taxa migrating from daytime depths of similar to 300-500 m into the surface 0-100m at night. Total dry weight biomass was 2 to 5-fold higher in the NE Atlantic than the NE Pacific, except for depths >200 m at night. Zooplankton biomass during month-long sampling at both sites was relatively unchanged in the NE Pacific and influenced by passage of four storms in the NE Atlantic. Biomass in the NE Pacific was mostly in the larger (>2 mm) size fractions due to large, seasonally migrating copepods Neocalanus and Eucalanus spp., and salps, versus in the NE Atlantic in the epipelagic zone where smaller (<2 mm) size classes comprised most of the biomass. Night:day biomass and abundance ratios in the epipelagic zone and migration amplitudes increased with increasing animal size, due to effects of size on susceptibility to predation regulating DVM behavior. Calanoid copepod genera at both sites that were strong, long-distance migrators included Metridia and Pleuromama spp., and in the NE Pacific there was a short-distance DVM from 50 to 100 m in the day into the top 0-50 m at night by Neocalanus cristatus. Themisto compressa amphipods comprised a sizable component of the DVM community in the NE Atlantic. Large gelatinous zooplankton such as the salp Salpa aspera in the NE Pacific and the pteropods Cymbulia peroni and Clio recurva in the NE Atlantic were also conspicuous diel migrators. This diversity in zooplankton taxa, life history, and size, along with trophic ecology and physiology, can be used to improve predictions of future changes in carbon flows and export.

Zooplankton fecal pellets constitute a high proportion of particulate organic carbon (POC) export in the West Antarctic Peninsula (WAP), yet the extent to which fecal pellet carbon (FPC) drives regional and seasonal variability in POC export remains unclear. We deployed sediment traps to examine spatial, interannual, and seasonal variability of zooplankton FPC export across two austral summer research cruises (2023, 2024) and two austral spring to fall Palmer Station field seasons (2023-2024, 2024-2025). Image analysis distinguished FPC contributions from cylindrical (krill), ovoid (copepod and pteropod), and tabular (salp) fecal pellets. Total POC export in the northern, coastal WAP averaged 156 and 199 mg C m: d. at 100 and 200m depth, respectively, higher than prior regional measurements. Zooplankton FPC constituted ~63% of total POC export observed throughout our study period. Cylindrical pellets dominated FPC export across most regions and seasons, reflecting the importance of krill to WAP POC export. A seasonal decrease in cylindrical FPC export during 2023-2024 corresponded with a shift toward smaller krill species which produce smaller, lower-carbon pellets. Regional and interannual trends in FPC export were associated with changes in zooplankton taxa. This included episodic salp and pteropod dominance that was inconsistently or modestly represented in FPC export, likely reflecting zooplankton bloom patchiness or pellet fragmentation. Increases in ovoid/cylindrical FPC export with depth may represent particle advection or repackaging at depth. Predicted shifts in zooplankton community composition due to climate change would thus influence fecal pellet characteristics and POC export, with consequences for carbon sequestration.

The contribution of sinking fecal pellets to the biological carbon pump depends on pellet properties, producer abundance, and the depth and timing of pellet production, which can be modulated by diel vertical migration. We examined diel variability in zooplankton fecal pellet flux in the subarctic Northeast Pacific using two image-based tools: the Underwater Vision Profiler (UVP5) and upward-facing cameras (GelCam) on a surface-tethered sediment trap array. Three fecal pellet types were classified across both platforms, enabling complementary estimates of pellet abundance, modeled carbon content, and flux. Daily composites revealed distinct diel patterns in three zooplankton types (crustacea, salps, and appendicularia) and their associated pellet flux. A simple model linking zooplankton vertical migration and pellet production, sinking, and attenuation reproduced the observed temporal variability for the migrators. A compelling diel pattern in appendicularian pellets warrants further investigation. Together, these results highlight how diel behavior and physiology impact vertical carbon transport.

Abstract Mesoscale eddies are physically dynamic environments, yet biological responses within them are often treated as static, with eddy polarity (anticyclones vs. cyclones) serving as the dominant conceptual framework. Temporal dynamics of animals within eddies—particularly at mid‐trophic levels—remain largely unresolved. We tracked a long‐lived anticyclonic eddy in the Northeast Atlantic for nearly a month using a Lagrangian framework, generating one of the few continuous time series of mesopelagic fish distribution within an eddy. Coupled physical–biological observations revealed marked vertical changes following a major wind storm: compact fish aggregations dispersed as phytoplankton distributions expanded and zooplankton deepened, despite comparable integrated fish biomass before and after. These results show that aggregation dynamics of mesopelagic fishes are modulated by bottom‐up variability on weekly to monthly timescales. By moving beyond static snapshots, our study demonstrates that eddies function as dynamic ecosystems whose ecological roles in pelagic food webs evolve through time.

Abstract The contribution of sinking fecal pellets to the biological carbon pump depends on pellet properties, producer abundance, and the depth and timing of pellet production, which can be modulated by diel vertical migration. We examined diel variability in zooplankton fecal pellet flux in the subarctic Northeast Pacific using two image‐based tools: the Underwater Vision Profiler (UVP5) and upward‐facing cameras (GelCam) on a surface‐tethered sediment trap array. We classified three morphologically distinct fecal pellet types across both platforms: long fecal pellets from crustaceans, tabular pellets from salps, and ellipsoid pellets from appendicularians. This enabled complementary estimates of pellet abundance, modeled carbon content, and flux. Daily composites revealed distinct diel patterns in three zooplankton groups and their associated pellet flux. A simple model linking vertical migration with pellet production, sinking, and attenuation reproduced the observed temporal variability. Together, these results highlight how diel behavior and physiology impact vertical carbon transport.

RATIONALE:IL-33 is a key driver of type 2 inflammation relevant to airway epithelial biology. However, the mechanisms for IL-33 secretion and regulation in the context of chronic airway disease is poorly understood. OBJECTIVES:We sought to define how a disease associated isoform IL-33d34 that escapes nuclear sequestration and is tonically secreted from epithelial cells can be recruited to non-canonical secretory pathways. METHODS:IL-33d34 interaction with HSP70 was assessed and validated by affinity purification, mass-spectrometry and miniTurboID proximity labeling. Secretion and activity reporter assays were used to probe the effect of HSP70 on epithelial IL-33d34 secretion and receptor binding. Human airway disease biospecimens were analyzed for dysregulation of heat shock pathways revealing modulation of TCP1 complex intermediates. MEASUREMENTS AND MAIN RESULTS:We confirmed that HSP70 interacts directly with IL-33d34, recruits the cytokine to a vesicular compartment and enhances stability upon secretion. IL-33, HSP70 and other key mediators of proteostasis were found to be dysregulated in airway disease biospecimens and secreted extracellular vesicles. The IL-33d34 interactome was characterized and novel secretion modulators were identified. CONCLUSIONS:This study confirms a role for HSP70 in non-canonical IL-33d34 secretion and function that may be amenable for therapeutic targeting in airway diseases.

Zooplankton play a key role in the cycling of carbon in aquatic ecosystems, yet their production of carbon-rich fecal pellets, which sink to depth and can fuel benthic community metabolism, is rarely quantified in estuaries. We measured fecal pellet carbon (FPC) production by the whole near-surface mesozooplankton community in the York River sub-estuary of Chesapeake Bay. Zooplankton biomass and taxonomic composition were measured with monthly paired day/night net tows. Live animal experiments were used to quantify FPC production rates of the whole community and dominant individual taxa. Zooplankton biomass increased in surface waters at night (2- to 29-fold) due to diel vertical migration, especially by Acartia spp. copepods. Biomass and diversity were seasonally low in the winter and high in the summer and often dominated by Acartia copepods. Whole community FPC production rates were higher (3- to 65-fold) at night than during the day, with the 0.5–1 mm size class contributing 2–26

Ocean ecological time series grow more useful with longevity, but practical constraints hinder consistency, and evolving scientific priorities necessitate sampling adjustments. We leveraged 30 years of zooplankton observations (five species, 1993-2024) from the western Antarctic Peninsula to quantify how shifts in sampling intensity, timing, and survey frequency influenced accuracy, precision, and predictability. A 67% decline in sample size aliased a long-term trend in ice krill and increased uncertainty by 47% in log10 space across species. Moving survey dates by two weeks influenced the density of salps, pteropods, and Antarctic krill by 48-83%. The ability to predict krill species density declined 47% in a simulated shift from annual to biennial survey frequency. Reduced spatial resolution and slight changes in timing can be accounted for statistically, but temporal gaps represent a challenge. Autonomous approaches are complementary to (rather than substitutable for) net sampling, necessitating ship operations to maintain valuable zooplankton time series.

There are many potential approaches to marine carbon dioxide removal (mCDR), of which ocean iron fertilization (OIF) has the longest history of study. However, OIF studies to date were not primarily designed to quantify the durability of carbon (C) storage, nor how wise OIF might be as an mCDR approach. To quantify C sequestration, we introduce a metric called the “centennial tonne,” defined as 1,000 kg of C isolated from atmospheric contact for on average at least 100 years. We present the activities needed to assess OIF from a scientific and technological perspective, and additionally, how it might be responsibly studied and potentially deployed. The five activities include: field studies in the Northeast Pacific; improved modeling for field studies, data assimilation and predictions at larger scales; improvements in monitoring, reporting and verification (MRV) for C, and also MRV for tracking ecological and environmental impacts; and developing new iron sources and their delivery, to increase efficiencies and reduce costs. The fifth activity is to understand whether public and community support exists for OIF, and what governance structures might support further research and possible deployment of OIF. This article is written by a multidisciplinary experts group called Exploring Ocean Iron Solutions (ExOIS) that is organized around a responsible code of conduct. Of the mCDR approaches, OIF has the potential to be low cost, scalable, and rapidly deployable. Reducing CO2 emissions must lead the way, but there is also an urgency to decide under what conditions and whether OIF might be deployed or not.

The ocean's biological pump, a critical component of the Earth's carbon cycle, transports organic matter from the surface ocean to depth, which is dominated by the sinking particles, often in the form of large (>1 mm) marine snow aggregates. Controls on carbon export are thought to be driven solely by ecological processes that produce and repackage sinking particles. Here, we present observations illustrating the important roles that storm-generated turbulence has on the abundance, characteristics and sinking fluxes of sinking particles. Turbulence creates and destroys aggregates and the vertical mixing induced by storms enhances their vertical transport. Evidence of the importance of biological processes is also observed. In all, these observations illustrate the complex interplay of physical and biological processes regulating the ocean's biological pump and the challenges in creating a predictive understanding of its function.

Bathydraconidae (Notothenioidei) are a group of benthic fishes endemic to the Southern Ocean. Because of their recent evolutionary radiation and limited sampling efforts due to their occurrence in remote regions, their diversity is likely underestimated. Akarotaxis nudiceps, currently the only recognized member of its genus, is an especially poorly known bathydraconid. Although A. nudiceps has a circumpolar distribution on the Antarctic continental shelf, its deep habitat and rarity limit knowledge of its life history and biology. Using a combination of morphological and genetic analyses, we identified an undescribed species of this genus, herein named Akarotaxis gouldae sp. nov. (Banded Dragonfish). The separation of this species was initially identified from archived larval specimens, highlighting the importance of early life stage taxonomy and natural history collections. All currently known adult and larval A. gouldae sp. nov. specimens have been collected from a restricted ~400 km coastal section of the western Antarctic Peninsula, although this is possibly due to sampling bias. This region is targeted by the epipelagic Antarctic krill fishery, which could potentially capture larval fishes as bycatch. Due to the extremely low fecundity of A. gouldae sp. nov. and near-surface occurrence of larvae, we suggest the growing Antarctic krill fishery could negatively impact this speces.

Large lipid-storing copepods dominate mesozooplankton biomass in the polar oceans and form a critical link between primary production and higher trophic levels. The ecological success of these species depends on their ability to survive periods of food deprivation in a highly seasonal environment, but the molecular changes that mediate starvation tolerance in these taxa are unknown. We conducted starvation experiments for two dominant Southern Ocean copepods, Calanoides acutus and Calanus propinquus , allowing us to compare the molecular starvation response between species. These species differ in life history, diet, and metabolic traits, and expressed overlapping but distinct transcriptomic responses to starvation. Most starvation-response genes were species-specific, but we identified a conserved core set of starvation-response genes related to RNA and protein metabolism. We used phylotranscriptomics to place these results in the context of copepod evolution and found that starvation-response genes are under strong purifying selection at the sequence level and stabilizing selection at the expression level, consistent with their role in mediating essential biological functions. Selection on starvation-response genes was especially strong in our focal lipid-storing lineage relative to other copepod taxa, underscoring the significance of starvation tolerance for these species. We also found that certain key lipid enzymes (elongases and desaturases) have experienced diversification and positive selection in lipid-storing lineages, reflecting the unique lipid storage needs of these animals. Our results shed light on the molecular adaptations of high-latitude zooplankton to variable food conditions, and suggest that starvation-response genes are under particularly strong sequence and expression constraints.

The Antarctic krill Euphausia superba is often considered an herbivore but is notable for its trophic flexibility, which includes feeding on protistan and metazoan zooplankton. Characterizing krill trophic position (TP) is important for understanding carbon and energy flow from phytoplankton to vertebrate predators and to the deep ocean, especially as plankton composition is sensitive to changing climate. We used repeated field sampling and experiments to study feeding by juvenile krill during three austral summers in waters near Palmer Station, Antarctica. Our approach was to combine seasonal carbon budgets, gut fluorescence measurements, imaging flow cytometry, and compound-specific isotope analysis of amino acids. Field measurements coupled to experimentally derived grazing functional response curves suggest that phytoplankton grazing alone was insufficient to support the growth and basal metabolism of juvenile krill. Phytoplankton consumption by juvenile krill was limited due to inefficient feeding on nanoplankton (2-20 mu m), which constituted the majority of autotrophic prey. Mean krill TP and the metazoan dietary fraction increased in years with higher mesozooplankton biomass, which was not coupled to phytoplankton biomass. Comparing TP estimates using delta 15N of different amino acids indicated a substantial and consistent food-web contribution from heterotrophic protists. Phytoplankton, metazoans, and heterotrophic protists all were important contributors to a diverse krill diet that changed substantially among years. Juvenile krill fed mostly on heterotrophic prey during summer near Palmer Station, and this food web complexity should be considered more broadly throughout the changing Southern Ocean.

This manuscript presents an overview of NASA’s EXport Processes in the Ocean from Remote Sensing 2021 Field Campaign in the North Atlantic (EXPORTS NA) and provides quantitative and dynamical descriptions of the physical processes modulating water transformations during the study. A major programmatic goal was to conduct the sampling in a Lagrangian mode so that ocean ecological and biogeochemical changes can be observed independent from physical advective processes. To accomplish this goal, EXPORTS NA conducted a multi-ship, multi-asset field sampling program within a retentive, anticyclonic mode water eddy. Beneath depths of ~100 m, Lagrangian sampling assets remained within the eddy core waters (ECWs) throughout the experiment, demonstrating that the ECWs within the mode water eddy were retentive. However, strong westerly winds from four storm events deepened the mixed layer (ML) of the surface core waters (SCWs) above the eddy’s mode water core by 25-40 m and exchanged some of the SCWs with surface waters outside of the eddy via Ekman transport. Estimates of flushing times ranged from 5-8 days, with surface exchange fractions ranging from 20-75% and were consistent with particle tracking advected by combined geostrophic and Ekman velocities. The relative contributions of horizontal and vertical advection on changes in SCW tracers depend on the horizontal and vertical gradients of that tracer. For example, in the surface waters, horizontal advection played a large role in salinity fluxes, yet vertical entrainment played a larger role in the fluxes of nutrients into the ML. Each storm injected nutrients and low oxygen waters into the ML, after which the surface ocean ecosystem responded by reducing nutrient concentrations and increasing %O2 saturation levels. Overall, SCW values of chlorophyll and POC were the largest at the onset of the field program and decreased throughout the campaign. The analysis presented provides a physical oceanographic context for the many measurements made during the EXPORTS NA field campaign. Illustrated are the many challenges of conducting a production-flux experiment even in a Lagrangian frame and the inherent uncertainties of interpreting biological carbon pump observations that were collected in a Eulerian frame of reference.

Ocean warming of the North Atlantic Subtropical Gyre (NASG) induced oligotrophication and a decrease in integrated net primary production during the 2010s, potentially affecting higher trophic levels. We analyzed long-term records (1994-2019) of daytime and nighttime zooplankton biomass in five size classes from the NASG. Daytime biomass decreased in the three largest size classes during the 2010s, while decrease in nighttime biomass was less evident due to the relative stability in diel vertical migrator biomass. We used the normalized biomass size spectrum (NBSS) to estimate the relative transfer efficiency between trophic levels. The steepness of the NBSS slope at the end of the time series increased by 14% (daytime) and 24% (nighttime) from the maximum observed annual average values (2011 and 2009, respectively). This suggests oligotrophication during the 2010s led to a significant reduction in the transfer of biomass across trophic levels, with negative impacts on the NASG planktonic food web.

The Ca2+-activated Cl- channel regulator CLCA1 potentiates the activity of the Ca2+-activated Cl- channel (CaCC) TMEM16A by directly engaging the channel at the cell surface, inhibiting its reinternalization and increasing Ca2+-dependent Cl- current (ICaCC) density. We now present evidence of functional pairing between two other CLCA and TMEM16 protein family members, namely CLCA4 and the CaCC TMEM16B. Similar to CLCA1, (i) CLCA4 is a self-cleaving metalloprotease, and the N-terminal portion (N-CLCA4) is secreted; (ii) the von Willebrand factor type A (VWA) domain in N-CLCA4 is sufficient to potentiate ICaCC in HEK293T cells; and (iii) this is mediated by the metal ion-dependent adhesion site motif within VWA. The results indicate that, despite the conserved regulatory mechanism and homology between CLCA1 and CLCA4, CLCA4-dependent ICaCC are carried by TMEM16B, rather than TMEM16A. Our findings show specificity in CLCA/TMEM16 interactions and suggest broad physiological and pathophysiological links between these two protein families.

High-latitude pelagic marine ecosystems are vulnerable to climate change because of the intertwining of sea/continental ice dynamics, physics, biogeochemistry, and food-web structure. Data from the West Antarctic Peninsula allow us to assess how ice influences marine food webs by modulating solar inputs to the ocean, inhibiting wind mixing, altering the freshwater balance and ocean stability, and providing a physical substrate for organisms. State changes are linked to an increase in storm forcing and changing distribution of ocean heat. Changes ripple through the plankton, shifting the magnitude of primary production and its community composition, altering the abundance of krill and other prey essential for marine mammals and seabirds. These climate-driven changes in the food web are being exacerbated by human activity.

Abstract Lipid‐rich copepods form an essential link between primary producers and higher trophic levels in high‐latitude oceans. These zooplankton can take advantage of ephemeral phytoplankton blooms to fuel development and reproduction. However, we have limited understanding of how the physiological condition of these animals varies in relation to environmental factors such as food availability. Due to high advection, it is likely that physiological plasticity, rather than local adaptation, is primarily responsible for physiological differences within a region. We use transcriptomics and other physiological metrics to understand how two species of copepods (Calanoides acutus and Calanus propinquus) vary across environmental gradients along the West Antarctic Peninsula. For the primarily herbivorous C. acutus, physiological separation between sampling locations appears to be driven by feeding status, and gene expression differences indicate differential expression of genes regulating lipid metabolism, reproduction, aerobic metabolism, and protein translation. For the more omnivorous C. propinquus, physiology and gene expression did not segregate as clearly by location, showed minimal signs of food deprivation at any location, and had a weaker relationship with chlorophyll compared to C. acutus. By comparing these results with concurrent starvation experiments, we find that spatial variation in gene expression reflects short‐term differences in food availability (particularly for C. acutus), and we identify genes whose expression indicates recent feeding status. Further examination of the relationships between food availability, copepod physiology, and population dynamics will ultimately improve our capacity to predict how copepod populations will respond to rapidly changing environmental conditions in the West Antarctic Peninsula ecosystem.