Particulate Cadmium Accumulation in the Mesopelagic Ocean

Global Biogeochemical Cycles, Journal Year: 2025, Volume and Issue: 39(1)

Published: Jan. 1, 2025

Abstract Observations of dissolved cadmium (dCd) and phosphate (PO 4 ) suggest an unexplained loss dCd to the particulate phase in tropical oxyclines. Here, we compile existing observations Cd phosphorus (P), present new data from US GEOTRACES GP15 Pacific Meridional Transect examine this phenomenon a perspective. We use simple algorithm reproduce station depth profiles P via regeneration possible subsurface accumulation. Our examination reveals decoupling driven by variable partitioning between two pools with differing labilities. Further, identify evidence for accumulation at 31 stations. Subsurface occurs most consistently mesopelagic but can be found all examined ocean basins. This is not well‐correlated oxygen or sulfide concentration. Instead, observe that regions where concentration relatively high compared zinc (dZn) speculate it result enhanced biological uptake response micronutrient balance.

Language: Английский

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A comparison of marine Fe and Mn cycling: U.S. GEOTRACES GN01 Western Arctic case study

Geochimica et Cosmochimica Acta, Journal Year: 2020, Volume and Issue: 288, P. 138 - 160

Published: Aug. 17, 2020

Language: Английский

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Cycling Rates of Particulate Organic Carbon Along the GEOTRACES Pacific Meridional Transect GP15

Global Biogeochemical Cycles, Journal Year: 2024, Volume and Issue: 38(1)

Published: Jan. 1, 2024

Abstract Understanding particle cycling processes in the ocean is critical for predicting response of biological carbon pump to external perturbations. Here, measurements particulate organic (POC) concentration two size fractions (1–51 and >51 μm) from GEOTRACES Pacific meridional transect GP15 are combined with a POC model estimate rates production, (dis)aggregation, sinking, remineralization, vertical transport mediated by migrating zooplankton, euphotic zone (EZ) upper mesopelagic (UMZ) distinct environments. We find coherent variations parameters fluxes throughout transect. Thus, settling speed μm fraction increased depth UMZ, presumably due higher densities at depth. The flux total (>1 out EZ was positively correlated primary production integrated over EZ; highest export occurred subarctic gyre while lowest subtropical gyres. ratio low (<5%) along GP15, which suggests an efficient recycling all trophic regimes. Specific remineralization did not show clear temperature or dissolved oxygen concentration, that is, apparently controlled other factors such as microbial colonization substrate lability. Particle cohesiveness, approximated second‐order rate constant aggregation, negatively regime: particles appeared more cohesive low‐productivity regions than high‐productivity regions.

Language: Английский

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Open-Ocean Minima in δ13C Values of Particulate Organic Carbon in the Lower Euphotic Zone

Frontiers in Marine Science, Journal Year: 2020, Volume and Issue: 7

Published: Sept. 8, 2020

Extensive studies in the 1980s-1990s led to characterization of latitudinal variations sea surface δ13C values particulate organic carbon (δ13CPOC), and relationships were found with CO2 concentrations, temperature, growth rates, cell geometries. Surprisingly, no large-scale efforts have been made describe δ13CPOC over depth water column. Here we compile published examples demonstrating a widespread isotopic pattern upper In 51 vertical profiles, lower euphotic zone on average are 1.4‰ than open ocean settings. majority locations this downward decrease is > 2‰ up 5‰, larger commonly recognized variation dissolved inorganic same depths. We briefly review hypotheses supporting evidence offered by previous individual columns: The observed patterns could result from differences photosynthetic rates or community composition, biochemical composition matter due degradation, disequilibrium within pool, particle dynamics, seasonal mixing. Coordinated isotopic, biological, seawater chemistry data sparse, consistent drivers currently elusive. Further work needed adequately characterize environmental conditions coinciding pattern, test its origins, determine if magnitude column be useful marker cycle dynamics.

Language: Английский

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Isotopes illustrate vertical transport of anthropogenic Pb by reversible scavenging within Pacific Ocean particle veils

Proceedings of the National Academy of Sciences, Journal Year: 2023, Volume and Issue: 120(23)

Published: May 30, 2023

Reversible scavenging, the oceanographic process by which dissolved metals exchange onto and off sinking particles are thereby transported to deeper depths, has been well established for metal thorium decades. scavenging both deepens elemental distribution of adsorptive elements shortens their oceanic residence times in ocean compared nonadsorptive metals, ultimately removes from via sedimentation. Thus, it is important understand undergo reversible under what conditions. Recently, invoked global biogeochemical models a range including lead, iron, copper, zinc fit modeled data observations distributions. Nonetheless, effects remain difficult visualize sections distinguish other processes such as biological regeneration. Here, we show that particle-rich "veils" descending high-productivity zones equatorial North Pacific provide idealized illustrations lead (Pb). A meridional section Pb isotope ratios across central shows where particle concentrations sufficiently high, within veils, vertical transport anthropogenic surface-dissolved toward deep manifested columnar anomalies. Modeling this effect waters allows surface penetrate ancient on timescales rapid overcome horizontal mixing water along abyssal isopycnals.

Language: Английский

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Microbial iron limitation in the ocean’s twilight zone

Nature, Journal Year: 2024, Volume and Issue: 633(8031), P. 823 - 827

Published: Sept. 25, 2024

Language: Английский

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Transmitted Cross-Polarized Light Detection of Particulate Inorganic Carbon Concentrations and Fluxes in the Ocean Water Column: Ships to ARGO Floats

Frontiers in Remote Sensing, Journal Year: 2022, Volume and Issue: 3

Published: March 8, 2022

Particulate inorganic carbon (PIC) plays a major role in the ocean cycle impacting pH, dissolved carbon, and alkalinity, as well particulate organic (POC) export transfer efficiency to deep sea. Remote sensing retrievals of PIC surface waters span two decades, yet knowledge concentration variability water column is temporally spatially limited due reliance on ship sampling. To overcome space–time gap observations, we have developed optical sensors for flux that exploit high mineral birefringence CaCO 3 minerals, thus enable real-time data when deployed operationally from CTDs ARGO-style Carbon Flux Explorer floats. For concentrations, describe fast (10 Hz) digital low-power (∼0.5 W) sensor utilizes cross-polarized transmitted light detect photon yield suspended birefringent particles column. This has been CTD-deployed depths great 6,000 m cross-calibrated against particulates sampled by large volume situ filtration CTD/rosettes. We report September–November 2018 GEOTRACES GP15 meridional transect Aleutian Islands Tahiti along 152°W where validated prototype separate CTD systems bottom at 39 stations, many which were taken nearly particle-free waters. compare results with particle phase composition (particularly aluminum) simultaneously collected size-fractionated samples filtration. also June 2017 California Current Ecosystem-Long Term Ecological Research (CCE-LTER) process study coastal levels found. demonstrate can 0.01 &gt;1 μM (except nepheloid layers) outline engineering needs progress its integration Explorer, an autonomous float.

Language: Английский

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Major processes of the dissolved cobalt cycle in the North and equatorial Pacific Ocean

Biogeosciences, Journal Year: 2022, Volume and Issue: 19(9), P. 2365 - 2395

Published: May 5, 2022

Abstract. Over the past decade, GEOTRACES and wider trace metal geochemical community has made substantial contributions towards constraining marine cobalt (Co) cycle its major biogeochemical processes. However, few Co speciation studies have been conducted in North equatorial Pacific Ocean, a vast portion of world's oceans by volume an important end-member deep thermohaline circulation. Dissolved (dCo) samples, including total dissolved labile Co, were measured at-sea during Meridional Transect (GP15) expedition along 152∘ W longitudinal from 56∘ N to 20∘ S. Along this transect, upper-ocean dCo (σ0<26) was linearly correlated with phosphate (slope = 82±3, µmol : mol) due phytoplankton uptake remineralization. As depth increased, concentrations became increasingly decoupled co-scavenging manganese oxide particles mesopelagic. The transect revealed organically bound coastal source Alaskan Stream associated low-salinity waters. An intermediate-depth hydrothermal flux observed off Hawaiian coast at Loihi Seamount, elevated potential xs3He above vent site; however, Seamount likely did not represent basin. Elevated within oxygen minimum zones (OMZs) South consistent suppression oxidative scavenging, we estimate that future deoxygenation could increase OMZ inventory 18 % 36 over next century. In Deep Water (PDW), fraction ligand-bound appeared protected scavenging high biogenic particle This finding is counter previous expectations low Compared global model, displayed more extreme inventories fluxes than predicted suggesting highly dynamic cycle.

Language: Английский

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Shelf-Basin Connectivity Drives Dissolved Fe and Mn Distributions in the Western Arctic Ocean: A Synoptic View into Polar Trace Metal Cycling

Oceanography, Journal Year: 2024, Volume and Issue: 37(2)

Published: Jan. 1, 2024

There have been many changes over the past few decades in physical environment and ecosystem health of Arctic Ocean, which is a sentinel global warming. Bioactive trace metal data important micronutrients for algae across ocean, such as iron (Fe) manganese (Mn), are key indicators biogeochemical change. However, historically sparse generally confined to ice-free regions. In 2015, three major GEOTRACES expeditions sought resolve distributions Arctic, covering western, eastern, Canadian sectors. The diverse shelves displayed unique controls on Fe Mn cycling due differing chemical, biological, properties. Here, we contrast shallow, reducing Chukchi Shelf western with tidally forced, advective deeper, less productive Barents eastern Arctic. Reductive dissolution resuspension both proved be large sources North Atlantic outflow. isolated intermediate deep waters, one-dimensional scavenging contrasts vertical biological signals Baffin Bay Labrador Sea.

Language: Английский

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Multiscale Superposition and Decomposition of Field‐Measured Suspended Sediment Concentrations: Implications for Extending 1DV Models to Coastal Oceans With Advected Fine Sediments

Journal of Geophysical Research Oceans, Journal Year: 2021, Volume and Issue: 126(3)

Published: Feb. 20, 2021

Abstract One‐dimensional vertical (1DV) diffusion‐settling models are practical tools for sediment transport analysis of sands, which is mostly a local process. However, fine sediments, the observed concentrations C ( t ) can be mixed via horizontal advection (HA) due to lower settling velocity, makes not necessarily process, thus making 1DV invalid. It important determine qualitative significance HA or quantitatively separate signals when applying environments with advected sediments. Here, novel methods combined (1) qualitatively identify physical mechanisms underlying variations and whether significant multiscale frequency superposition (2) decompose components according their spectral filter decomposition. In situ observational data concurrent hydrodynamics in subaqueous Yellow River Delta employed analyze methods' performance. The decomposed reasonable because they interpreted light other processes. results indicated that M2 tidal contributed 8.30% by carrying sediments from 1.6 km upstream flood tides, M4 M6 + M8 resuspension 4.16% 3.96%, respectively, periodically resuspending “fluffy layer.” Waves resuspended an erosion center 5 tides 76.49% elevated ). proposed exclude measured increase applicability fines measured.

Language: Английский

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