First winter measurements of dissolved zinc (dZn) and particulate zinc (pZn) are presented from seven stations, between 41 and 58°S, occupied in July 2017 along the 30°E longitude in the Indian Sector of the Southern Ocean. This unique spatial and seasonal dataset provided the opportunity to investigate Zn biogeochemical cycling in a region which is extremely data scarce and during a period when conditions

The high influx of freshwater in the Bay of Bengal (BoB) region forms a freshwater plume at the surface. This plume's dispersal spreads a low-density layer of water on the surface, forming a barrier layer between the mixed layer depth and the isothermal layer. The low saline water reduces the sea surface partial pressure of carbon dioxide (pCO2), and the barrier layer thickness (BLT) inhibits the interaction

Tracing riverine freshwater transport pathways within the Arctic Ocean is key to understanding changes in Arctic Ocean freshwater inventories. Dissolved Ba concentrations have been used in this capacity but are compromised by non-conservative processes. To assess the potential for Ba isotopes to provide insights into the impact of such processes on Arctic Ocean dissolved Ba inventories, Ba concentration

Continental margins are an important external source of dissolved iron to the marine environment. However, the mechanisms responsible for the offshore transport of dissolved iron is impacted by the resulting iron speciation. We characterized the iron speciation in the Eastern Tropical North Pacific (ETNP) oxygen deficient zone (ODZ), including dissolved iron, organic iron-binding ligands, and reduced

Analysis of a global hydrographic data product showed a clear pH-dependent discrepancy between pH on the total scale measured spectrophotometrically (pHspec) using purified meta-cresol purple (mCP) and pH calculated from total alkalinity and dissolved inorganic carbon. However, this was based mainly on US cruises, and three recent Japanese cruises do not show this pH-dependent discrepancy. One potential

Distribution of dissolved aluminum is strongly coupled with dissolution of diatom frustules, since opal is the main scavenger of dissolved oceanic Al. Given Al has a much shorter residence time compared with silicic acid, vertical processes affecting Al must be much more important. It may therefore be possible to understand dissolution behavior of diatom frustules indirectly via Al distribution. In

The Amundsen Sea is the most rapidly melting part of the West Antarctic Ice Sheet, due to increased heat transport by Circumpolar Deep Water (CDW). Tracing CDW and resulting glacial meltwater is important since glacial meltwater may change the water mass properties, leading to the change of the biogeochemical cycles. In this study, in order to investigate the potential for using the humic-like component

Processes controlling preservation and accumulation of organic matter (OM) in marine sediments are highly sensitive towards both natural and anthropogenic impacts. Thus, the sedimentary OM is considered a key proxy for the characterization of recent and past sedimentary environments. Along the Peruvian continental margin (PCM), high primary production and an intense oxygen minimum zone (OMZ) favor

The Mississippi Bight, east of the Mississippi River, is a complex coastal ecosystem that, like the better-known Louisiana Shelf to the west, experiences seasonal bottom water hypoxia. However, input of allochthonous nutrients from the Mississippi River to the Mississippi Bight appears to be limited, begging the question of what drives seasonal hypoxia in this system. Prior research has suggested submarine

Hydroclimatic disturbances, like flooding, may greatly impact dissolved organic matter (DOM) composition in coastal waters by altering hydraulic gradients, groundwater residence times, and seafloor recirculation. This study provides new evidence regarding seasonal molecular DOM changes, in a submarine groundwater discharge influenced semi-arid estuary, across different hydroclimatic conditions: from

Growing anthropogenic activity in the Arctic, especially near regional municipal and transportation hubs, threatens coastal environments with significant changes and contamination. A detailed study of a wide set of organic-geochemical proxies in surface and subsurface sediments and soils around the typical urbanized Arctic area (Tromsø, Norway) was performed to investigate natural and anthropogenic

The content of free and hydrolyzed primary amino acids was determined for five species of microalgae: Haematococcus pluvialis, Skeletonema costatum, Arthrospira sp., Acutodesmus acuminatus, and Botryococcus braunii. The amino acid profile was determined using an automated HPLC-DAD reverse phase pre-column analysis method, which is described in detail. Acid hydrolysis using 6 M HCl and autoclaving at

Reaction with iodide (I−) at the sea surface is an important sink for atmospheric ozone, and causes sea-air emission of reactive iodine which in turn drives further ozone destruction. To incorporate this process into chemical transport models, improved understanding of the factors controlling marine iodine speciation, and especially sea-surface iodide concentrations, is needed. The oxidation of I−

The Amazon is Earth's largest river by volume output, making it an important source of trace metals and dissolved organic matter (DOM) to the Atlantic Ocean. Despite major recent anthropogenic disruptions to the Amazon catchment area, data for trace metals such as copper (Cu) in the Amazon River estuary and associated mixing plume are still rare. Furthermore, there is currently no existing data in

Phenolic compounds excreted by marine microalgae are part of the ligand pool in natural waters. The effect of the polyphenol gentisic acid (GA; 2,5 dihydroxybenzoic acid) on the Fe(III) reduction as a function of organic ligand concentration (100 nM – 1000 nM) and the pH (7.00–8.01) was investigated in seawater. Major seawater ions interactions with both GA and Fe(III) were also considered using 0

The distribution of dissolved manganese (dMn) was studied in the Yellow Sea (YS) and East China Sea (ECS) onboard the GEOTRACES GP06-CN cruise in October 2015. Dissolved Mn samples were collected by both Niskin-X and CTD-Niskin systems at 8 clean stations and collected by the CTD-Niskin system at all 27 grid stations. There was no significant difference in dMn between the two systems (r = 0.98, p < 0

Dissolved chemical speciation of metals in natural waters encompasses a wide range of inorganic and organic compounds including metal organic ligand complexes, ML. Because of the different filters used, “dissolved” speciation can range from simple metal-ligand complexes with an average size of about 0.66 nm (mass of <3 k-daltons) to nanoparticles of 1 to 100 nm to colloidal forms that are 10 to 200–400 nm

This study explores the potential of geochemical data to accurately date Mactromeris polynyma shells collected in the Lower St. Lawrence Estuary, and to assess the species' utility as an environmental archive. Previous growth studies of M. polynyma from the St. Lawrence ecosystem showed a possible overestimation of annual growth lines using the classic sclerochronology methodology. Our study proposes

By diffusing from the sediments into the ocean, 227Ac (half-life = 21.8 y) is a powerful tracer of vertical mixing in the deep ocean on decadal time scales. However, its use is limited by its very low concentration resulting in large volumes (hundreds of L) of water required for its analysis. We have developed a new method of 227Ac analysis by isotope dilution and MC-ICPMS that significantly improves

Gypsum (CaSO4·2H2O) of non-evaporitic origins has been observed in marine sedimentary environments over the past decade. Our understanding of related diagenetic processes has improved by analyzing the sulfur and oxygen isotopic compositions of gypsum, but, a comprehensive study of the isotopic composition of authigenic gypsum precipitated in methane-rich marine environments has not been performed to

Marine sediments are an important source and sink of bio-essential trace metals to the ocean. However, the different mechanisms leading to trace metal release or burial are not fully understood and the associated fluxes are not well quantified. Here, we present sediment, pore water, sequential extraction and benthic flux data of Mn, Co, Ni, Cu, Zn and Cd along a latitudinal depth transect across the

Seafloor hydrothermal activity may constitute a considerable mercury (Hg) source to the oceans, but the flux from marine shallow-water hydrothermal systems (MSWHS) remains poorly constrained to date. To study the presence of Hg in MSWHS in Paleochori Bay (Milos Island, Greece), sea surface, bottom, pore fluid and hydrothermal gas samples were collected in June of 2017, October of 2018 and July of 2020

Estuarine carbonate chemistry predicts that thermodynamic equilibration during the mixing of freshwater with seawater will generate a carbon dioxide (CO2) sink in the case of warm and poorly buffered tropical rivers. The São Francisco River estuary has historically become oligotrophic after the construction of a series of hydroelectric dams in its watershed, where organic matter and nutrients are retained

The hydrolysis pathway of a given peptide or protein in seawater, or how it is hydrolyzed by extracellular enzymes, may depend on its chemical structure or specific amino acid composition. This knowledge is important for a better understanding of the first steps on decomposition of labile organic matter that is often dominated by proteins. The hydrolysis pathway can be estimated from the hydrolyzed

The distributions of dissolved iron (DFe) and organic iron-binding ligands (LFe) in the Kuroshio Current and its neighboring waters were elucidated from four cross-sectional surveys from the eastern coast of Taiwan to Sagami Bay. The Kuroshio surface water was characterized by a high salinity, low concentration of DFe, high concentration of LFe, and low fluorescence of humic-like substances, in comparison

Microalgae, dominating protists in aquatic systems, are rich in lipids, a complex molecular class regulating cell physiology and phytoplankton ecology. Investigation of microalgal lipid metabolism is increasing, but common strategies for comprehensive lipid analyses are still lacking. Major methodological gaps are represented by separate analytical procedures for extraction and characterization of

In situ pumps were used to collect size-fractionated particles (>53 μm and 1–53 μm) from the upper ocean of the high latitude North Atlantic during spring and summer 2010, and samples were subsequently analysed for Al, P, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Cd, Ba and Pb. Two research cruises during May 2010 coincided with an eruption of the Eyjafjallajökull volcano in southern Iceland, which resulted in

The North Yellow Sea is a semi-enclosed shallow-water marginal sea of the western North Pacific. Below the seasonal thermocline, subsurface aragonite saturation state (Ωarag) values of 1.0–1.5 have frequently been observed in summer and autumn, indicating that marine calcifying organisms in the area are under threat. In this study, we developed mechanism-based models relating summertime and autumnal

Surface sediments were collected in a transect from the Amazon river delta to open marine sites in the north Atlantic Ocean in order to characterize spatial contrasts in the deposited organic carbon (OC), allowing to uncover the role of the river plume on the sedimentation of OC. Analysis of isoprenoidal and branched glycerol dialkyl glycerol tetraethers (GDGTs), lignin phenols, fatty acids, n-alkanes

Seawater total alkalinity (TA) is one important determinant used to monitor the ocean carbon cycle, whose spatial distributions have previously been characterized along the United States East Coast via discrete bottle samples. Using these data, several regional models for TA retrievals based on practical salinity (S) have been developed. Broad-scale seasonal or interannual variations, however, are

The subtropical South Pacific Gyre (SPG) encompasses the largest oligotrophic region of the global ocean. In these remote waters dissolved organic matter (DOM) accumulates in the surface waters, though constituting a potential source of nutrients and energy to sustain microbial life. On a zonal transect across the SPG, we quantified bulk dissolved organic carbon (DOC) and assessed the DOM composition

Most of the ocean is deep with the majority of its volume (> 80%) lying under a depth greater than 1000 m. Deep-ocean substrates input is mainly supplied as organic matter (in particulate and/or dissolved forms) by physical and biological processes. Bioavailable dissolved organic carbon (DOC) is mainly consumed in surface water by prokaryotes, while most of DOC in the deep ocean is recalcitrant. Deep-sea

Air-to-sea deposition of water-soluble total nitrogen (WSTN) can influence the primary productivity in the coastal oceans. Here, we assessed the concentrations of aerosol inorganic (WSIN: NH4+ + NO3−) and WSTN over the Arabian Sea during winter season (SS379:6–24 December 2018). The mean concentrations of NH4+ (109 ± 83 nmol m−3) overwhelm that of NO3− (32 ± 13 nmol m−3) and water-soluble organic nitrogen

In this study, a model of remineralization patterns was developed to explore the particulate organic matters (POM) decomposition process among marine mesopelagic zone (200 to 1000 m) using data from the South China Sea. The results suggest that three high C/N remineralization patterns are identified at 200 to 400 m, 600 to 700 m and 900 to 1000 m, and two low C/N remineralization patterns are found

The Nutrient Diol Index (NDI) has been proposed as a paleo sea surface nutrient proxy. However, the NDI's broad applicability needs to be further assessed by examining its temporal variability in association with modern sea surface nutrient concentrations. This study is the first report to evaluate the NDI with respect to sinking particles in the East Sea. The NDI values showed seasonal variations

Sediments are a key sink for phosphorus (P) in coastal systems. This allows coastal areas to act as a filter for P that is transported from land to sea. Recent work suggests that vivianite-type ferrous iron (Fe(II))-P minerals may be more important as a sink for P in coastal sediments than previously thought. Here, we investigate the occurrence of such vivianite-type minerals in sediments of three

Dissolved lignin phenols, chromophoric dissolved organic matter (DOM), and in situ fluorescence were determined in waters of the Laptev Sea and major Arctic basins, and they were compared with dissolved iron (dFe) distributions to elucidate the sources, molecular characteristics and distributions of iron-binding ligands in the Arctic Ocean. In the Transpolar Drift region (TPD), concentrations of dFe

Phosphorus (P) is frequently considered the limiting nutrient for marine phytoplankton growth and primary production in oceans. To explore P utilization by phytoplankton during spring blooms, field observations and incubation experiments were conducted during a cruise in the Yellow Sea (YS). In particular, phytoplankton cell-associated P pools were identified as intracellular P pool (Pintracellular)

Near-shore environments are a significant source of atmospheric methane but the size of this source is poorly constrained, particularly for fjords and fjards. This study investigated the methane emission rates and the drivers controlling the dynamics of dissolved methane in the Saguenay Fjord, a deep, stratified, and well‑oxygenated subarctic fjord system in eastern Canada. Dissolved methane concentrations

To reveal the effect of solar irradiation on the biogeochemical cycling of trace metals in the open ocean, the photodecomposition of organic iron- and copper-binding ligands was examined in an experiment using filtered seawater collected from a deep layer of the East China Sea. Six days of natural solar irradiation caused a significant decrease in the concentrations of both ligands, along with the

In a few recent studies, the action of a bacterial dioxygenase (10S-DOX) on palmitoleic acid was observed within some polar and estuarine settings. To add further mechanistic information regarding the action of this enzyme in marine settings, we measured a range of lipids (sterols, fatty acids and the chlorophyll phytyl side chain) and their biotic and abiotic degradation products in water samples

Amino acids (AAs) and amino sugars (ASs), compounds ubiquitous to living organisms, can provide information regarding degradation states and bacterial contributions to sedimentary organic matter (SOM). However, very few studies have utilized the combination of AAs and ASs as a proxy to assess the influence of bacterial degradation on SOM in the Yellow Sea (YS). In this study, surface sediments from

The toxicity and bioavailability of Cu in seawater were estimated using its chemical speciation. In this study, the concentrations and conditional stability constants (K'CuL) of Cu complexes with Cu-binding organic ligands (L) in seawater were determined using the reverse titration–competitive ligand exchange–adsorptive cathodic stripping voltammetry method. The concentrations of strong and weak ligands

Competition for limited iron resources is a key driver of microbial community structure in many regions of the surface ocean. The bacterial siderophores ferrioxamine and amphibactin have been identified in marine surface waters, suggesting that they may represent an important bacterial strategy for obtaining iron from a scarcely populated pool. Using proteomics, siderophore isolation, and iron uptake

Concentrations of 4 volatile halocarbons (VHCs) in seawater and atmosphere of the Northern South China Sea (NSCS) were measured during summer 2015. Mean surface seawater concentrations of CH3I, CH3Br, CHBr3, and C2Cl4 were 2.0, 4.2, 15.7, and 12.5 pM, respectively; mean atmospheric concentrations were 0.4, 4.1, 8.0, and 7.2 ppt, respectively. The surface seawater concentrations of the 4 VHCs were significantly

Pore water and solid phase geochemical profiles of sediment cores collected along two transects on the western and eastern sides of the Mississippi River mouth in the northern Gulf of Mexico were incorporated into a reactive transport model to determine the role of manganese and iron in the remineralization of carbon. Reactive transport model calculations indicate that sedimentation rates control the

Due to the uptake of anthropogenic carbon dioxide (CO2) from the atmosphere, and the resulting ocean acidification, long term monitoring of the marine carbon cycle is of utmost importance and requires high precision and accuracy across many laboratories over several decades. Despite this, many uncertainties still remain in carbon system measurements and calculations. Calculations of the carbon system

The organic matter occluded in the silica of fossil diatom frustules is thought to be protected from diagenesis and used for paleoceanographic reconstructions. However, the location of the organic matter within the frustule has hitherto not been identified. Here, we combined high spatial resolution imaging by nanoSIMS and Raman micro-spectroscopy to identify where the organic material is retained in

Dissolved organic matter in sea ice is rich in extracellular polymeric substances (EPS) secreted by sea ice algae and bacteria. Carbohydrates are the most abundant component of EPS and they may contribute to the Fe-binding organic ligand pool, increasing the residence time of bioavailable Fe in the euphotic zone when sea ice melts. A new method for the determination of EPS in sea ice samples is presented