Estuaries are essential drivers of primary productivity in coastal waters through the export of dissolved and suspended material. This study aims at quantifying this fertilization process at the two main estuaries in South Portugal, where typical low river discharge conditions occur in winter due to strong flow regulation by upstream dams and seldom-local rain events. Data were collected across the

Experimental studies characterizing the reactivity of siliceous materials, such as biogenic silica from the field or laboratory cultures, typically require organic matter removal prior to experimental analysis. Consequently, it is highly desired to develop and optimize a cleaning protocol that imposes minimal alterations to the reactivity of the siliceous substrate and can be robustly employed among

Submarine groundwater discharge (SGD) is an important component of the marine 87Sr/86Sr budget, which is currently in an imbalance with a missing source. In this contribution, dissolved Sr concentrations and 87Sr/86Sr of the Chilika lagoon (India), the largest brackish-water lagoon in Asia, have been investigated for three different seasons (pre-monsoon (May 2017), monsoon (Aug., 2017) and post-monsoon

Understanding the natural dynamics of estuaries and their response to changes in the human-related or climatic drivers is fundamental to guarantee their environmental quality. This study aims to contribute to a better understanding of the water quality dynamics in an urban estuary, the Tagus estuary (Portugal), across different temporal scales. This estuary supports diverse uses and activities and

The diversity of nitrogen-based dissimilatory metabolisms in anoxic waters continues to increase with additional studies to the marine oxygen deficient zones (ODZs). Although the microbial oxidation of nitrite (NO2–) has been known for over a century, studies of the pathways and microbes involved have generally proceeded under the assumption that nitrite oxidation to nitrate requires dioxygen (O2)

There is a paucity of data on Fe-binding ligands in the Arctic Ocean. Here we investigate the distribution and chemical properties of natural Fe-binding ligands in Fram Strait and over the northeast Greenland shelf, shedding light on their potential sources and transport. Our results indicate that the main sources of organic ligands to surface waters of Fram Strait included primary productivity and

Aerosol samples (n = 14), collected over the eastern North Pacific (ENP, 27–52°N and 150–172°W), were studied for dicarboxylic acids (hereafter diacids, C2-C10), ω-oxoacids, pyruvic acid, and α-dicarbonyls as well as water-soluble organic carbon (WSOC) and total nitrogen (WSTN). We found diacids as the most abundant compound class followed by ω-oxoacids and α-dicarbonyls. Molecular distributions of

Sulfur cycling is ubiquitous in marine sedimentary environments and is influenced by microbial and abiotic processes that alter both the abundance and isotopic composition of sulfur species that can ultimately be captured as sedimentary minerals. Microbial metabolisms that generate sulfur isotopic (δ34S) signatures in hydrogen sulfide have a spatial distribution that varies on the micron scale, yet

The hadal trenches (>6000 m) are considered to be ultimate sinks of organic carbon (OC) from biosphere. However, highly spatial heterogeneity of geographic background and organic matter in different zones make significant influences on the OC cycling, and further the carbon burial. In this study, three sediment cores were drilled across the northern Yap Trench axis (9.8–9.9°N, 138.3–138.7°E). The elemental

The impact of aquaculture chemotherapeutants (antibiotics, and anti-lice parasiticides) on non-target organisms is dependent on their dissipation and degradation in marine sediments. Abiotic and biotic weathering may change their composition and toxicity, and influence their fate. In this study, biodegradation of a few aquaculture chemotherapeutants was investigated over a 96 days period at 4 °C in

Discharges of freshwater into the Arctic Ocean from rivers in Eurasia and North America account for approximately 11% of the global riverine freshwater input, and contain weathering products including dissolved continental boron. Much of this freshwater flows into the North Atlantic Ocean, primarily via the East Greenland Current carrying the Polar Water with salinity <34.4. As a result, the input

About 70 fossil and live-collected specimens of Desmophyllum dianthus were collected from steep rocky surfaces and time-averaged assemblages at their base (“coral graveyards”) in the southern Labrador Sea at depths ranging from ~1700 m (Orphan Knoll) to ~2200 m (Flemish Cap). Aside from stable isotope and mineralogical analysis, U-series and 14C age determinations were performed on the samples. Fossil

Yttrium and lanthanides (REE) contents were quantified in Rosário's salt marsh (SW Europe) sediments and in the halophyte plant Halimione portulacoides, to evaluate the plant's ability to accumulate these elements as well as the translocation into their aerial organs, and increase the knowledge on the relations between these metals and the salt marsh halophytes plants. Metal sediment contents ranged

Dissolved oxygen (DO) is considered one of the most important environmental variables of water quality. This work aimed to provide, for the first time, insights regarding DO dynamics on a representative site of the productive Ria Formosa coastal lagoon, south Europe, using a real time monitoring station observatory (acquiring data every 15 min) deployed for a period of two and a half years. This comprehensive

Estuaries are unique water systems and represent a vital link between land and sea. River transported contaminants, among which trace elements are of major concern, are subjected to a variety of physical, chemical and biogeochemical processes in the estuarine mixing zone. The Isonzo/Soča River is the main source of freshwater into the Gulf of Trieste (northern Adriatic Sea) and is known as the primary

The photochemical degradation of the neurotoxin methylmercury (MeHg) in marine surface waters is of great interest because it reduces the amount of MeHg available for uptake and bioaccumulation in marine aquatic food webs. Studies have shown that the dominant cause of odd isotope mass independent fractionation (odd-MIF) of Hg in marine foodwebs is the photo-degradation of MeHg. Residual MeHg is then

A recent analysis of full water column hydrographic data revealed a pH-dependent discrepancy between spectrophotometrically measured pH using purified meta-cresol purple and pH calculated from dissolved inorganic carbon (DIC) and total alkalinity (TA). The discrepancy (pHspec – pHTA,DIC) is approximately −0.018 and 0.014 at pH 7.4 and 8.2, respectively. This discrepancy has a wide range of implications

Continental margin sediments represent a potentially large, but poorly constrained, source of iron to surface waters to support primary productivity. To investigate this problem, we examined iron redox cycling in the sediments of Santa Monica Basin (SMB), CA as it relates to benthic sources of iron to the water column. Our results show that iron redox cycling in SMB sediments results in the formation

Continental dust can be suspended and transported by the wind, reaching seawater masses far away from its source. The deposition of the aerosols on the ocean surface can alter the abundance of chemical species in the water column and contribute to element inventories in seafloor sediments. A major Saharan dust intrusion into the Western Mediterranean Sea was recorded at the DYFAMED site (Ligurian Sea)

Short-term variations of Pt concentrations and primary production indicators were compared in three contrasting coastal sites during spring bloom: (i) the Gironde Estuary mouth (SW France), (ii) the semi-enclosed Arcachon Bay (SW France), and (iii) the urbanized Genoa Harbor (NW Italy). At each site, surface seawater sampling and physical-chemical measurements were combined to study diel cycles (over

Trace element (TE) fluxes and their residence times (Fe, Mn, Cu, Pb, Cd, and V) within the surface ocean were determined along the GEOTRACES East Pacific Zonal Transect (GP16/EPZT) and found to reflect the diverse physical and geochemical conditions encountered across the track. The TE flux from atmospheric deposition, vertical mixing, and upwelling into the mixed layer and into the particle production

Recent studies have provided a better understanding of carbonate system parameters and their spatial and temporal variability in several areas of the Mediterranean Sea. This study uses a new dataset that covered the entire Algerian Basin during the summer of 2014 (SOMBA cruise) to describe the distribution of carbonate system parameters. The findings show that almost the entire basin was a source of

Microplastics (MPs) pollution in marine environments has received considerable attention over the past two decades due to the increased awareness of its potential risks to ecosystems. Numerical simulations can be used to provide estimates of MPs fate and distribution, but so far this approach has been largely applied to the open ocean. In this work, the distribution patterns of MPs in a prototype coastal

Nitrous oxide (N2O) production and emissions are observed in estuary waters, yet little is known about estuary N2O fluxes under low dissolved inorganic nitrogen (DIN) conditions. We present high-resolution spatial surveys of N2O concentrations in three low-DIN (NO3− < 30 μmol L−1) tropical estuaries in Queensland, Australia (Johnstone River, Fitzroy River, Constant Creek), during consecutive wet and

Isotherm adsorption experiments for Pb, Cd and Zn were carried out with coastal sediments from China under oxic sediment-water conditions. The conditional equilibrium constants (Kads) determined from the adsorption isotherms were found to be most strongly correlated with Mn oxides (MnOx) for Pb and Cd, and with particulate organic carbon (POC) for Zn. MnOx and POC were then used as the surrogate metal-binding

The Southern Ocean is the largest high-nutrient low-chlorophyll environment in the global ocean, and represents an important source of intermediate and deep waters to lower latitudes. Constraining Southern Ocean trace metal biogeochemical cycling is therefore important not just for understanding biological productivity and carbon cycling regionally, but also for understanding trace metal distributions

The particulate amino sugars (PAS), organic carbon (POC) and nitrogen (PN), the chlorophyll a (Chl-a), and the heterotrophic bacterial cell count (HBC) in the Yangtze River Estuary (YRE) were determined to study the biological source, bioavailability and bacterial contribution of particulate organic matter (POM) under the influence of algal bloom during the spring and autumn of 2017. The contents of

Volatile organic iodine compounds (VOICs) such as di-iodomethane (CH2I2) released from the ocean are important vectors of iodine in the atmosphere and play an important role in atmospheric chemistry. In temperate ocean waters, several studies observed or presumed CH2I2 production. Here, we investigated the ability of temperate marine phytoplankton to produce VOICs in a culture experiment. To evaluate

Glass electrodes are commonly used to measure the pH of natural waters over various, sometimes wide, ranges of salinity (S). For such applications, the electrodes must be calibrated against solutions of known pH and salinity identical to those of the sample solutions. Well-characterized buffer solutions may be used for these calibrations, but if a wide range of salinity is to be encountered in the

The size partitioning of dissolved trace metals is an important factor for determining reactivity and bioavailability of metals in marine environments. This, alongside the advent of more routine shipboard ultrafiltration procedures, has led to increased attention in determining the colloidal phase of metals such as Fe in seawater. While clean and efficient filtration, prompt acidification, and proper

The discovery of a pervasive subsurface methylmercury maximum in the world's oceans highlights the importance of understanding the processes that produce and destroy this potent neurotoxin in seawater. Two approaches have been published in the literature, one based on the spatial distribution of mercury species in seawater and, more recently, a second approach based on seawater incubation studies using

Gaseous elemental mercury (Hg0) comprises the majority of atmospheric mercury (Hg) and results in long-range transport of Hg. Secondary emissions from the marine surface mixed layer result in spatial and temporal Hg0 variability, which subsequently determine marine pools of divalent mercury (HgII) available for methylation. We measured atmospheric Hg0 concentrations in the marine boundary layer (MBL)

Cr isotope geochemistry is being explored in the context of a variety of geological problems as well as the environmental remediation of pollutant Cr(VI). There is a strong Cr isotope fractionation during reduction of oxidized Cr(VI) to reduced Cr(III). We present chromium concentration and Cr isotope data for samples from highly reducing environments ([O2] < 2 μmol/kg) in the Eastern Tropical North

The naturally occurring 210Po (t1/2 = 138.3d) and 210Pb (t1/2 = 22.3 y) radionuclide pair has been extensively used to study particle scavenging, cycling and transport in the ocean. However, the role of particle composition in the scavenging, sorption and fractionation of 210Po210Pb needs to be better understood to successfully utilize these radionuclides as oceanographic tracers. Here, we measure

Marine dissolved organic carbon (DOC) is the ocean's largest exchangeable reservoir of organic carbon. The biogeochemical cycling of DOC plays an important role in ocean carbon storage on various timescales. Solid-phase extraction (SPE) is a process used to isolate DOC from seawater for biogeochemical analysis. This study examines how DOC isotopic (Δ14C, δ13C) and optical (absorbance) properties of

Despite the undeniable effect of iron on shaping patterns of ocean productivity, the relative importance of the different sources of this limiting nutrient to the ocean is still under debate. Although global estimates indicate that the benthic input of iron to the oceans is significant, most studies have investigated continental margins exposed to either upwelling or large riverine inputs, environments

We present isotope ratios of Ni (δ60Ni) and Cu (δ65Cu) in sinking particles, aerosols, and seawater collected from the northern South China Sea to identify sources and transformation processes of the two metals. In aerosols, δ60Ni values are in the range +0.05‰ to +0.56‰, and δ65Cu values are in the range −0.33‰ to +0.83‰. The isotope ratios are different from those of lithogenic materials, indicating

Water-column data from seven cruises in 2007–2008 reveal pronounced temporal and spatial variations in the distribution of dissolved iron (DFe, <0.4 μm) over the upper 1000 m of the Sargasso Sea near Bermuda, in the western subtropical North Atlantic Ocean. In near-surface waters, DFe exhibits a clear seasonal cycle, increasing from ~0.1–0.3 nM in spring to ~0.4–1.0 nM in summer-early fall. The observed

Iron (Fe), a micronutrient for algal growth, and plutonium (Pu), an anthropogenic radionuclide, share some common features. This includes similar oceanic distributions when different input modes are taken into account, as well as their chemical behavior, such as a high affinity to natural organic matter (NOM). The NOM produced by various phytoplankton communities can potentially influence Fe cycling

Microbially secreted exopolymeric substances (EPS), rich in polysaccharides and proteins, make up an important part of natural organic matter in the ocean, especially marine snow. While the attention in the oceanographic literature is focused more on the role of polysaccharides and less of proteins in EPS functions, the role of proteins, especially the role of the protein/carbohydrate (P/C) ratio of

During the active 87-day Deepwater Horizon spill in the northern Gulf of Mexico, a significant fraction of the spilled Macondo oil was transported to the seafloor via the sedimentation of marine snow. Here we present a detailed characterization of oil that arrived together with marine snow at a 1400 m deep sediment trap six weeks to 13 months after the spill had ended. These data give insight into

Hydrothermal vent incidence is proportional to the spreading rate of the mid-oceanic ridges (MORs) (Baker et al., 1996). However, the ultra-slow spreading Southwest Indian Ridge (SWIR) is unique and has a relatively higher incidence of hydrothermal vent fields compared with other ultra-slow spreading ridges (German et al., 1998; Baker and German, 2004). In the present study, sediment samples from the

The meridional distributions of fluorescent dissolved organic matter (FDOM) and various hydrologic properties were investigated along 67°E in the western Indian Ocean. Our results showed that the highest fluorescence of the humic FDOM (FDOMH) was discovered in the Indian Deep Water (IDW), and relatively lower values were observed in the intruding water masses from the upper layer (e.g., Circumpolar

Characterizing the composition of marine dissolved organic matter (DOM) is important for gaining insight into its role in oceanic biogeochemical cycles. Using Fourier transform ion cyclotron resonance mass spectrometry, we analyzed the molecular composition of solid phase extracted (SPE) DOM from the northeast Atlantic to investigate the specificity of the DOM pool of the individual major water masses

A procedure is described for the analysis of the stable carbon isotopic composition of dissolved organic carbon (DOC) in natural waters from marine and higher-salinity environments. Rapid (less than 5 min) and complete oxidation of DOC is achieved using a modification of previous photochemical oxidation techniques. The CO2 evolved from DOC oxidation can be collected in less than 10 min for isotopic

Organic geochemical measurements of the lipid fraction, comparing saturated and aromatic hydrocarbons, fatty acids, alcohols and sterols, have been carried out on six sediments cores collected from the Atlantic shelf, slope and the rise areas to evaluate the cross-shelf transport of the organic carbon. The concentration of most of the organic compound classes studied is correlated with the total organic

Total organic carbon (TOC), lignin, amino acids, sugars and amino sugars were measured in recent sediments for the continental margin off southern New England. The various organic carbon fractions decreased in concentration with increasing distance from shore. The fraction of the TOC that was accounted for by these major components also decreased with increasing distance from shore. The concentration

The increased use of ethanol as an additive in gasoline is expected to increase atmospheric ethanol levels. Understanding future impacts requires an understanding of the current atmospheric ethanol budget. Air-sea exchange is one of the largest sources of uncertainty in budget estimates. Understanding processes that produce or destroy ethanol in seawater will help constrain air-sea exchange estimates

Measurements of net ecosystem productivity (NEP) and calcification (NEC) from contemporary coral reefs provide a baseline for monitoring the impacts of future stressors like ocean acidification and sea-surface warming. However, separating secular trends from natural variability requires NEP and NEC records across a wide range of spatial and temporal scales. One promising way to make these measurements

Deep-sea dissolved organic matter (DOM) constitutes a huge carbon reservoir in the worlds' oceans that – despite its abundance – is virtually unused as a substrate by marine heterotrophs. Heating within hydrothermal systems induces major molecular modifications of deep-sea DOM. Here, we tested the hypothesis that hydrothermal heating of deep-sea DOM enhances bioavailability. Aliquots of DOM extracted

Particle dynamics are an essential component of global ocean biogeochemistry as they transport essential nutrients, carbon, and other reactive elements and compounds from the surface ocean to depth in the water column. The North Pacific Ocean is characterized by spatial and temporal variations in particle export mediated by a diverse food web and variations in environmental conditions, such as oxygenation