Marine Particles Research Articles

Pelagic shark intestine as a potential temporary sink for plastic and non-plastic particles.

Highly migratory pelagic sharks have the potential to serve as carriers of particle contamination in a vast three-dimensional space. We investigate the occurrence, abundance and characteristics of plastic and non-plastic particles in the scroll intestine of the blue shark (Prionace glauca), one of the most abundant pelagic shark species worldwide. We detected both plastic and non-plastic particles in all sections of the intestine, with the posterior region exhibiting the highest concentration. We estimated that individual intestine may contained 11.21±9.62 and 48.00±23.90 plastic or non-plastic particles, respectively. Fibers dominated particle morphology (95.58%), primarily composed of plastic polymers (polyester and polyethylene terephthalate) (plastic) and non-plastic material (rayon and cotton). Given their size range (102.08-8113.54μm), these particles are likely to be released into the water column through excretion. The intestine of P. glauca may act as a temporary particle sink, a phenomenon potentially common among pelagic sharks worldwide. This study provides new insights for the role of highly migratory fish species in the transport and distribution dynamics of marine particle contamination.

A computer vision‐based approach for estimating carbon fluxes from sinking particles in the ocean

AbstractThe gravitational settling of organic particles in the ocean drives long‐term sequestration of carbon from surface waters to the deep ocean. Quantifying the magnitude of carbon sequestration flux at high spatiotemporal resolution is critical for monitoring the ocean's ability to sequester carbon as ecological conditions change. Here, we propose a computer vision‐based method for classifying images of sinking marine particles and using allometric relationships to estimate the amount of carbon that the particles transport to the deep ocean. We show that our method reduces the amount of time required by a human image annotator by at least 90% while producing ecologically informed estimates of carbon flux that are comparable to estimates based on purely manual review and chemical bulk carbon measurements. This method utilizes a human‐in‐the‐loop domain adaptation approach to leverage images collected from previous sampling campaigns in classifying images from novel campaigns in the future. If used in conjunction with autonomous imaging platforms deployed throughout the world's oceans, this method has the potential to provide estimates of carbon sequestration fluxes at high spatiotemporal resolution while facilitating an understanding of the ecological pathways that are most important in driving these fluxes.

Bacterial clustering amplifies the reshaping of eutrophic plumes around marine particles: A hybrid data-driven model.

Multifaceted interactions between marine bacteria and particulate matter exert a major control over the biogeochemical cycles in the oceans. At the microbial scale, free-living bacteria benefit from encountering and harnessing the plumes around nutrient-releasing particles, like phyto-plankton and organic aggregates. However, our understanding of the bacterial potential to reshape these eutrophic microhabitats remains poor, in part because of the traditional focus on fast-moving particles that generate ephemeral plumes with lifetime shorter than the uptake timescale. Here we develop a novel hybrid model to assess the impacts of nutrient uptake by clustered free-living bacteria on the nutrient field around slow-moving particles. We integrate a physics-based nutrient transport model with data-derived bacterial distributions at the single-particle level. We inferred the functional form of the bacterial distribution and extracted parameters from published datasets of in vitro and in silico microscale experiments. Based on available data, we find that exponential radial distribution functions properly represent bacterial microzones, but also capture the trend and variation for the exposure of bacteria to nutrients around sinking particles. Our computational analysis provides fundamental insight into the conditions under which free-living bacteria may significantly reshape plumes around marine aggregates in terms of the particle size and sinking velocity, the nutrient diffusivity, and the bacterial trophic lifestyle (oligotrophs < mesotrophs < copiotrophs). A high potential is predicted for chemotactic copiotrophs like Vibrio sp. that achieve fast uptake and strong clustering. This microscale phenomenon can be critical for the microbiome and nutrient cycling in marine ecosystems, especially during particulate blooms.

Near-Surface Particulate Backscattering Observations with Bio-Optical Lagrangian Drifters

Abstract Particulate matter concentration is an essential ocean variable (EOV) useful for understanding biogeochemical processes, improving ocean productivity estimates, and constraining coupled physical and biogeochemical numerical models. While direct observations of this parameter are difficult to obtain, the optical backscattering coefficient of marine particles (bbp) can be used as a reliable proxy. However, most in situ multispectral bbp measurements are ship-borne or obtained from moored systems, thus with a limited spatial and temporal coverage. Utilizing Surface Velocity Programme (SVP) drifting buoys with self-contained backscatter sensors designed for extended deployment periods offers a promising solution for collecting data in challenging marine environments. In this study, we presented for the first time the integration of a commercially available, high-frequency, and multispectral optical backscatter sensor into an SVP drifter, the so-called backscatter optical-SVP (BO-SVP) drifter designed to collect bbp measurements near the ocean surface. The bbp measurements obtained by the BO-SVP drifter were reliable over a wide range of environmental conditions, showing a good agreement with independent datasets (relative bias &lt; 10%; relative standard deviation &lt; 36%). The BO-SVP drifter captures the satellite sub- and pixel-scale variability by combining the Lagrangian approach and a high-frequency sampling. This configuration enables the acquisition of measurements across numerous pixels in a single day, enhancing validation activities for ongoing and future satellite products and the quantification of associated uncertainties. The measurements acquired by these platforms can offer valuable insights into particle distribution at fine spatial scales, daily variability, and its relationship with water masses type and ocean dynamics.

Structuring of particle-associated bacterial communities along the extracellular polymeric substance gradient of sinking and suspended particles in an oligotrophic, subtropical region of the western North Pacific Ocean

Extracellular polymeric substances, such as transparent exopolymer particles (TEP) composed of acidic polysaccharides, are important particulate organic carbon (POC) components of marine environments that affect particle dynamics and ocean carbon export. However, how polymeric substances interact with and shape bacterial communities associated with marine particles is poorly understood. This study investigated whether the composition of particle-associated bacterial communities differs between sinking and suspended particles, which differ in their polymeric substance contents, in the upper water column of the subtropical, oligotrophic Kuroshio region. Bacterial taxa likely involved in polymer degradation (Alphaproteobacteria, Gammaproteobacteria, and Bacteroidia) were enriched on sinking particles with a lower TEP: POC ratio, indicating that bacterial degradation of polymeric substances promotes particle sinking by removing positively buoyant polymers. By contrast, suspended particles were increasingly enriched for Bdellovibrionota and Desulfobacterota as the TEP: POC ratio increased. These taxa, which include predatory microbes, seem to prefer polymer-rich environments with a high density of potential prey. Planctomycetota were not significantly related to the TEP: POC ratio, indicating their broad niche breadth on particles’ polymeric substance contents. The results suggest that the bacterial niche differentiation associated with the particle polymeric-substance gradient shapes bacterial communities in a subtropical ocean.

Carbon Cycling in Marine Particles Based on Inorganic and Organic Stable Isotopes

The marine carbon cycle has a central role in biogeochemical cycling and a close interaction with the climate system. Here, we use the stable carbon isotope (δ13C) of particulate inorganic carbon (PIC) and particulate organic carbon (POC) in marine particles to diagnose carbonate dissolution and organic matter respiration processes in the ocean water column. We show PIC dissolution both in the euphotic zone, potentially driven by POC remineralization, and a preferential dissolution of coccoliths compared to foraminifera below the saturation horizon in the water column. Within the oxygen deficient zone (ODZ), POC remineralization and consequent respiration-driven PIC dissolution are both significantly diminished. We also demonstrate that POC remineralization preferentially removes a 13C-enriched component compared to isotopically-light bulk POC in both the large size fraction (LSF, > 51μ m) and small size fraction (SSF, 0.5 – 51μ m) of the pump particles, but exhibits a greater impact on the large particles because of its smaller inventory. Simultaneously, addition of a 13C-enriched heterotrophic or chemoautotrophic component to the SSF further increases the isotopic offset between SSF and LSF POC. Overall, this study uses δ13C to provide novel evidence for different biogeochemical processes in marine particles, and demonstrates carbonate dissolution in the ocean water column, both driven by bulk seawater chemistry and organic matter respiration within particles. The absence of O2 in the ODZ likely protects carbonate from dissolving by severely limiting organic matter respiration, thus reducing shallow PIC dissolution within the ODZs.

Microbial dietary preference and interactions affect the export of lipids to the deep ocean.

Lipids comprise a significant fraction of sinking organic matter in the ocean and play a crucial role in the carbon cycle. Despite this, our understanding of the processes that control lipid degradation is limited. We combined nanolipidomics and imaging to study the bacterial degradation of diverse algal lipid droplets and found that bacteria isolated from marine particles exhibited distinct dietary preferences, ranging from selective to promiscuous degraders. Dietary preference was associated with a distinct set of lipid degradation genes rather than with taxonomic origin. Using synthetic communities composed of isolates with distinct dietary preferences, we showed that lipid degradation is modulated by microbial interactions. A particle export model incorporating these dynamics indicates that metabolic specialization and community dynamics may influence lipid transport efficiency in the ocean's mesopelagic zone.

Impact of seawater temperature and physical-chemical properties on sorption of pharmaceuticals, stimulants, and biocides to marine particles

Pharmaceuticals, stimulants, and biocides enter the environment via wastewater from urban, domestic, and industrial areas, in addition to sewage, aquaculture and agriculture runoff. While some of these compounds are easily degradable in environmental conditions, others are more persistent, meaning they are less easily degraded and can stay in the environment for long periods of time. By exploring the adsorptive properties of a wide range of pharmaceuticals, stimulants, and biocides onto particles relevant for marine conditions, we can better understand their environmental behaviour and transport potential. Here, the sorption of 27 such compounds to inorganic (kaolin) and biotic (the microalgae Cryptomonas baltica) marine particles was investigated. Only two compounds sorbed to microalgae, while 23 sorbed to kaolin. The sorption mechanisms between select pharmaceuticals and stimulants and kaolin was assessed through exploring adsorption kinetics (caffeine, ciprofloxacin, citalopram, fluoxetine, and oxolinic acid) and isotherms (ciprofloxacin, citalopram, and fluoxetine). Temperature was shown to have a significant impact on partitioning, and the impact was more pronounced closer to maximum sorption capacity for the individual compounds.

Diverse sources and aging change the mixing state and ice nucleation properties of aerosol particles over the western Pacific and Southern Ocean

Abstract. Atmospheric particles can impact cloud formation and play a critical role in regulating cloud properties. However, particle characteristics at the single-particle level and their ability to act as ice-nucleating particles (INPs) over the marine atmosphere are poorly understood. In this study, we present micro-spectroscopic characterizations and ice nucleation properties of particles collected during a cruise from South Korea to Antarctica in 2019. Most of the samples were dominated by fresh sea salt, aged sea salt, and sea salt mixed with sulfate particles, with total number percentages ranging from 48 % to 99 % over the western Pacific and the Southern Ocean. The mixing-state index of the particle population ranged from 50 % to 95 % over the Northern Hemisphere and Southern Hemisphere. Multiphase processes on sea salt particles resulted in chlorine deficiency. This selective aging process made the marine particle population more externally mixed. Ice nucleation onset conditions primarily for the deposition mode were measured and the investigated particles showed diverse ice nucleation abilities. The fresh sea salt particles with organic coatings exhibited the highest ice nucleation ability at a relative humidity with respect to ice as low as 121 %. The sea salt mixed sulfate particle was enriched in INPs by a factor of 1.9. Aging processes affected both the mixing state of the particles and their ice nucleation abilities. Our analysis shows that assuming an internally mixed particle population in the marine atmosphere can lead to errors of several orders of magnitude in predicting ice nucleation rates.

Particle composition-specific approach to estimate the particulate organic carbon concentration off the coastal areas of Guangdong and eastern Hainan Island.

High optical complexity caused by the variability of marine particles poses a major challenge to the development of bio-optical algorithms for particulate organic carbon (POC) concentration retrievals from optical measurements in coastal waters. Here, we developed a particle composition-specific approach to estimate POC off the coastal areas of Guangdong and eastern Hainan Island, China. The ratio of phytoplankton absorption to detritus absorption coefficient aph(443)/ad(443) was used to optically discriminate water types. The samples with aph(443)/ad(443) ≤ 4.9 showed a significant correlation between POC and absorption line height at 676 nm aLH(676) (R2 = 0.75, n = 70, p < 0.01). In contrast, aph-dominant samples with aph(443)/ad(443) > 4.9 had a high covariance between POC and particle scattering coefficient at 675 nm bp(675) (R2 = 0.85, n = 37, p < 0.01). Validation with an independent dataset yielded a small positive bias (R2 = 0.81, APD = 23.10%, RMSE = 29.01 mg m-3, RPD = 16.31%). The approach provided a better estimation of POC concentration in coastal waters compared with univariate algorithms. A depth-resolved index aLH(676)/bbp(442) was defined as the ratio of absorption line height to particle backscattering coefficient. Using the depth-resolved index instead of aph(443)/ad(443) for optical water type classification can be utilized to represent the vertical variations of POC in 1 m bins, and can complement remote sensing observations to accurately characterize the three-dimensional structure of POC distribution in the oceans.

Modeling the Concentration Enhancement and Selectivity of Plastic Particle Transport in Sea Spray Aerosols

AbstractBursting bubbles transport bacteria, viruses, and other marine particles across the air‐sea interface. This effect is enhanced when particles are hydrophobic and cling to the bubbles as they rise. Recent studies suggest that plastic particles, a major ocean pollutant, can also be transported by sea spray. However, estimates of plastic transport via this pathway have large uncertainties due to limited size detection techniques in field studies and few lab studies. An understanding of the number and size of particles carried in the smallest drops, which have the longest residence time in the atmosphere, is missing from current literature. Here, we develop a modeling framework to provide bounds on the number, area, and volume transport of non‐scavenged hydrophilic and fully‐scavenged hydrophobic particles of radii between 0.1 and 100 μm for a range of jet and film drops. For droplets containing plastic particulates, we predict particle enrichment is significantly higher in jet drops than film drops. For particles in these jet drops, our results suggest that in the absence of bubble scavenging, the number distribution is dominated by smaller plastics, the mass/volume distribution by larger plastics, and surface area distribution is balanced across plastic size. Whereas for hydrophobic particles, scavenging dramatically modifies these distributions, enhancing certain particle–droplet size combinations by over four orders of magnitude. Our predictions suggest critical effects of enrichment in air‐sea particle transport and highlight the variable dependencies on bubble and particle size, improving our theoretical understanding of plastic and marine particle transport and identifying modeling assumptions to refine with experimental measurements.

Bridging the Gap: Establishing Spatial Correlations and Type Conversion Relationships among Different Aerosol Idetification Methods

Effective identification of aerosol type is the basis of accurate quantification of aerosol-climate and aerosol-environment interactions. However, there are different aerosol category settings and identifying parameter selections among different aerosol identification methods, which causes incoherence in data comparisons and uncertainty in quantifying thier climate and environment effects. To bridge the gap, this study establishes spatial correlations and aerosol type conversion relationships among four commonly-used aerosol identification methods, which includes AOD-AE, AE-SSA, FMF-SSA, and SAE-AAE. Aerosol optical properties observed at 37 typical AERONET sites are selected as the testbed, including marine, desert dust, clean continent, urban industry, and biomass burning sites. Results show that marine and desert dust aerosols are the most effectively identified types, while urban industry and biomass burning aerosols overlap much in the identification spaces since they contain similar chemical components. Dust and marine aerosol generally have the best agreement among the four identification methods, because desert dust and marine particles have distinctive chemical components from other kinds, thus the category setting from the perspective of emission source, light absorbing ability, or chemical components has less influence on the identification results. Spatial correlation between the four commonly-used aerosol identification methods futher refines the correspondence of aerosol category, light absorption capacity, and chemical components. And we find that uncertain aerosols defined in FMF-SSA are mostly marine aerosols.

Strong and efficient summertime carbon export driven by aggregation processes in a subarctic coastal ecosystem

AbstractSinking marine particles, one pathway of the biological carbon pump, transports carbon to the deep ocean from the surface, thereby modulating atmospheric carbon dioxide and supplying benthic food. Few in situ measurements exist of sinking particles in the Northern Gulf of Alaska; therefore, regional carbon flux prediction is poorly constrained. In this study, we (1) characterize the strength and efficiency of the biological carbon pump and (2) identify drivers of carbon flux in the Northern Gulf of Alaska. We deployed up to five inline drifting sediment traps in the upper 150 m to simultaneously collect bulk carbon and intact sinking particles in polyacrylamide gels and measured net primary productivity from deck‐board incubations during the summer of 2019. We found high carbon flux magnitude, low attenuation with depth, and high export efficiency. We quantitatively attributed carbon flux between 10 particle types, including various fecal pellet categories, dense detritus, and aggregates using polyacrylamide gels. The contribution of aggregates to total carbon flux (41–93%) and total carbon flux variability (95%) suggest that aggregation processes, not zooplankton repackaging, played a dominant role in carbon export. Furthermore, export efficiency correlated significantly with the proportion of chlorophyll a in the large size fraction (&gt; 20 μm), total aggregate carbon flux, and contribution of aggregates to total carbon flux. These results suggest that this stratified, small‐cell‐dominated ecosystem can have sufficient aggregation to allow for a strong and efficient biological carbon pump. This is the first integrative description of the biological carbon pump in this region.

Measurements of the inherent optical properties of aqueous suspensions of microplastics

AbstractLibraries of inherent optical properties (IOPs) of microplastics are sparse, yet they are essential for the development of optical techniques to detect and quantify microplastics in the ocean. In this study, we describe our results and technique for the measurement of the IOPs of microplastic suspensions generated from commonly utilized plastics. The measurements included angle‐resolved polarized light scattering, and spectral absorption and beam attenuation coefficients. We also performed ancillary characterization of particle properties, including size distribution, shape, and mass concentration of suspended matter. We observed several unique optical characteristics regarding absorption, scattering, and polarization properties compared with typical marine particle assemblages. We show that these results are useful for radiative transfer simulations as well as the potential development of novel plastic detection techniques from above‐ or in‐water optical measurements.

Functions of extracellular polymeric substances in partitioning suspended and sinking particles in the upper oceans of two open ocean systems

AbstractMarine particle dynamics and carbon export, involving extracellular polymeric substances (EPS) like transparent exopolymer particles (TEP) and Coomassie Brilliant Blue‐stained particles (CSP), are poorly understood. Although TEP adhesive properties may enhance carbon export by facilitating aggregate formation, their low density can also enhance particle suspension. Factors influencing TEP regulation of particle dynamics remain unclear. To investigate EPS contributions to particle dynamics, we investigated ratios of TEP to particulate organic carbon (POC) and of CSP to POC in suspended and sinking particles collected with marine snow catchers. Samples were collected in a subarctic region near Hokkaido during a spring phytoplankton bloom and in the oligotrophic, subtropical Kuroshio region. At Hokkaido, the mean TEP : POC ratio of sinking particles (0.075 μg Xeq. : μg C) was &gt; 30× lower than in suspended particles (2.3), consistent with a model prediction of selective retention of buoyant TEP‐rich particles in the upper water column. In the Kuroshio region, sinking particles also contained fewer TEP than suspended particles; however, the TEP : POC ratio of sinking particles (1.0) was &gt; 10× higher than at Hokkaido, suggesting that TEP constitute a significant carbon component of sinking particles. These findings indicate that TEP facilitate aggregation of high‐density particles and particle sinking in the Kuroshio region. Distributions of CSP : POC ratios between suspended and sinking particles resembled TEP : POC ratios in both regions, implying a significant contribution of CSP to particle dynamics. We propose that EPS have divergent effects on suspension and sinking of marine particles, which vary with particle composition and biogeochemical conditions.

Marine particle microbiomes during a spring diatom bloom contain active sulfate-reducing bacteria.

Phytoplankton blooms fuel marine food webs with labile dissolved carbon and also lead to the formation of particulate organic matter composed of living and dead algal cells. These particles contribute to carbon sequestration and are sites of intense algal-bacterial interactions, providing diverse niches for microbes to thrive. We analyzed 16S and 18S ribosomal RNA gene amplicon sequences obtained from 51 time points and metaproteomes from 3 time points during a spring phytoplankton bloom in a shallow location (6-10m depth) in the North Sea. Particulate fractions larger than 10µm diameter were collected at near daily intervals between early March and late May in 2018. Network analysis identified two major modules representing bacteria co-occurring with diatoms and with dinoflagellates, respectively. The diatom network module included known sulfate-reducing Desulfobacterota as well as potentially sulfur-oxidizing Ectothiorhodospiraceae. Metaproteome analyses confirmed presence of key enzymes involved in dissimilatory sulfate reduction, a process known to occur in sinking particles at greater depths and in sediments. Our results indicate the presence of sufficiently anoxic niches in the particle fraction of an active phytoplankton bloom to sustain sulfate reduction, and an important role of benthic-pelagic coupling for microbiomes in shallow environments. Our findings may have implications for the understanding of algal-bacterial interactions and carbon export during blooms in shallow-water coastal areas.

Marine particle size-fractionation indicates organic matter is processed by differing microbial communities on depth-specific particles.

Passive sinking flux of particulate organic matter in the ocean plays a central role in the biological carbon pump and carbon export to the ocean's interior. Particle-associated microbes colonize particulate organic matter, producing "hotspots" of microbial activity. We evaluated variation in particle-associated microbial communities to 500m depth across four different particle size fractions (0.2-1.2, 1.2-5, 5-20, >20μm) collected using in situ pumps at the Bermuda Atlantic Time-series Study site. In situ pump collections capture both sinking and suspended particles, complementing previous studies using sediment or gel traps, which capture only sinking particles. Additionally, the diagenetic state of size-fractionated particles was examined using isotopic signatures alongside microbial analysis. Our findings emphasize that different particle sizes contain distinctive microbial communities, and each size category experiences a similar degree of change in communities over depth, contradicting previous findings. The robust patterns observed in this study suggest that particle residence times may be long relative to microbial succession rates, indicating that many of the particles collected in this study may be slow sinking or neutrally buoyant. Alternatively, rapid community succession on sinking particles could explain the change between depths. Complementary isotopic analysis of particles revealed significant differences in composition between particles of different sizes and depths, indicative of organic particle transformation by microbial hydrolysis and metazoan grazing. Our results couple observed patterns in microbial communities with the diagenetic state of associated organic matter and highlight unique successional patterns in varying particle sizes across depth.

Direct observations of microbial community succession on sinking marine particles.

Microbial community dynamics on sinking particles control the amount of carbon that reaches the deep ocean and the length of time that carbon is stored, with potentially profound impacts on Earth's climate. A mechanistic understanding of the controls on sinking particle distributions has been hindered by limited depth- and time-resolved sampling and methods that cannot distinguish individual particles. Here, we analyze microbial communities on nearly 400 individual sinking particles in conjunction with more conventional composite particle samples to determine how particle colonization and community assembly might control carbon sequestration in the deep ocean. We observed community succession with corresponding changes in microbial metabolic potential on the larger sinking particles transporting a significant fraction of carbon to the deep sea. Microbial community richness decreased as particles aged and sank; however, richness increased with particle size and the attenuation of carbon export. This suggests that the theory of island biogeography applies to sinking marine particles. Changes in POC flux attenuation with time and microbial community composition with depth were reproduced in a mechanistic ecosystem model that reflected a range of POC labilities and microbial growth rates. Our results highlight microbial community dynamics and processes on individual sinking particles, the isolation of which is necessary to improve mechanistic models of ocean carbon uptake.

Improved multivariable algorithms for estimating oceanic particulate organic carbon concentration from optical backscattering and chlorophyll-a measurements

The capability to estimate the oceanic particulate organic carbon concentration (POC) from optical measurements is crucial for assessing the dynamics of this carbon reservoir and the capacity of the biological pump to sequester atmospheric carbon dioxide in the deep ocean. Optical approaches are routinely used to estimate oceanic POC from the spectral particulate backscattering coefficient bbp, either directly (e.g., with backscattering sensors on underwater platforms like BGC-Argo floats) or indirectly (e.g., with satellite remote sensing). However, the reliability of algorithms which relate POC to bbp is typically limited due to the complexity of interactions between light and natural assemblages of marine particles, which depend on variations in particle concentration, composition, and size distribution. This study expands on our previous work by analysis of an extended field dataset created with judicious data inclusion criteria with the aim to provide POC algorithms for multiple light wavelengths of measured bbp, which can be useful for applications with in situ optical sensors as well as above-water active or passive measurement systems. We describe an improved empirical multivariable approach to estimate POC from simultaneous measurements of bbp and chlorophyll-a concentration (Chla) to better account for the effects of variable particle composition on the relationship between POC and bbp. The multivariable regression models are formulated using a relatively large dataset of coincident measurements of POC, bbp, and Chla, including surface and subsurface data from the Atlantic, Pacific, Arctic, and Southern Oceans. We show that the multivariable algorithm provides reduced uncertainty of estimated POC across diverse marine environments when compared with a traditional univariate algorithm based on only bbp. We also propose an improved formulation of univariate algorithm based on bbp alone. Finally, we examine performance of several algorithms to estimate POC using our dataset as well as a dataset consisting of optical measurements from BGC-Argo floats and traditional POC measurements collected during a coincident research cruise in the Atlantic Ocean.

Global Variability of Phytoplankton Carbon and Non‐Algal Particles From Ocean Color Data Based on a Photoacclimation Model

AbstractPhytoplankton is the most important primary producer in the ocean, owing to its pivotal role at the base of the food chain and in the ocean carbon cycle. To better estimate ocean productivity, the retrieval of accurate observations of phytoplankton carbon (Cphy) biomass from ocean color satellites is of the utmost importance. When Cphy is retrieved using the backscattering signal generated by marine particles, the signal due to non‐algal particles—NAP (bbNAP) must be removed. However, algorithms currently used to retrieve bbNAP do not work globally, especially in the large mid‐ocean subtropical gyres. Here, we propose a new model to derive Cphy globally, including all subtropical gyres, that accounts for the estimation of phytoplankton photoacclimation when retrieving bbNAP. The new model shows more valid retrievable bbNAP coefficients than the previously published methods and values mainly around 0.0011 m−1, consistent with coefficients estimated with in situ observations. Moreover, the retrieved Cphy concentrations show a relative error of 7% with respect to in situ measured picophytoplankton carbon data. Our research indicates that the photoacclimation status of phytoplankton must be addressed to confidently retrieve bbNAP and Cphy at the global scale from ocean color measurements.