Showing papers on "Water column published in 2019"
TL;DR: The meta-analysis demonstrates that some of the most abundant and recalcitrant manufactured plastics are more persistent in the sea surface than previously anticipated and that further research is required to determine the ultimate fate of these polymers as current knowledge does not support the deep sea as the final sink for all polymer types.
406 citations
TL;DR: Examination of two abundant particle feeders in this ecosystem, pelagic red crabs and giant larvaceans, showed that microplastic particles readily flow from the environment into coupled water column and seafloor food webs, suggesting that one of the largest and currently underappreciated reservoirs of marine microplastics may be contained within theWater column and animal communities of the deep sea.
Abstract: Plastic waste has been documented in nearly all types of marine environments and has been found in species spanning all levels of marine food webs. Within these marine environments, deep pelagic waters encompass the largest ecosystems on Earth. We lack a comprehensive understanding of the concentrations, cycling, and fate of plastic waste in sub-surface waters, constraining our ability to implement effective, large-scale policy and conservation strategies. We used remotely operated vehicles and engineered purpose-built samplers to collect and examine the distribution of microplastics in the Monterey Bay pelagic ecosystem at water column depths ranging from 5 to 1000 m. Laser Raman spectroscopy was used to identify microplastic particles collected from throughout the deep pelagic water column, with the highest concentrations present at depths between 200 and 600 m. Examination of two abundant particle feeders in this ecosystem, pelagic red crabs (Pleuroncodes planipes) and giant larvaceans (Bathochordaeus stygius), showed that microplastic particles readily flow from the environment into coupled water column and seafloor food webs. Our findings suggest that one of the largest and currently underappreciated reservoirs of marine microplastics may be contained within the water column and animal communities of the deep sea.
304 citations
TL;DR: The spatiotemporal distribution of microplastics in the Nakdong River down to 20 μm in size is investigated and it is estimated that it is necessary to reflect seasonal variation and sample both in the surface water and water column to estimate microplastic transport.
267 citations
TL;DR: Results demonstrated that polymer density influenced partitioning between the water surface and subsurface and the underlying surficial sediment and the common practice of sampling only the watersurface can result in substantial bias, especially in estuarine, harbor, and lake locations where water surface concentrations tend to overestimate mean water column concentrations.
Abstract: Microplastic contamination was studied along a freshwater continuum from inland streams to the Milwaukee River estuary to Lake Michigan and vertically from the water surface, water subsurface, and sediment. Microplastics were detected in all 96 water samples and 9 sediment samples collected. Results indicated a gradient of polymer presence with depth: low-density particles decreased from the water surface to the subsurface to sediment, and high-density particles had the opposite result. Polymer identification results indicated that water surface and subsurface samples were dominated by low-density polypropylene particles, and sediment samples were dominated by more dense polyethylene terephthalate particles. Of the five particle-type categories (fragments, films, foams, pellets/beads, and fibers/lines), fibers/lines were the most common particle-type and were present in every water and sediment sample collected. Fibers represented 45% of all particles in water samples and were distributed vertically throughout the water column regardless of density. Sediment samples were dominated by black foams (66%, identified as styrene-butadiene rubber) and to a lesser extent fibers/lines (29%) with approximately 89% of all of the sediment particles coming from polymers with densities greater than 1.1 g cm-3. Results demonstrated that polymer density influenced partitioning between the water surface and subsurface and the underlying surficial sediment and the common practice of sampling only the water surface can result in substantial bias, especially in estuarine, harbor, and lake locations where water surface concentrations tend to overestimate mean water column concentrations.
198 citations
TL;DR: It could be inferred that the water body is conspicuously polluted; hence, efforts should be made to control all the activities contributing to such magnitude of pollution at the sites, Diagnostic ratios suggest that the target hydrocarbons are predominantly from pyrolytic sources.
Abstract: The incidence and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in the Buffalo River Estuary in the Eastern Cape Province of South Africa were assessed in this study. A total of 60 surface water and 19 sediment samples were collected from 5 sites of the estuary over a period of 6 months (December 2015 to May 2016). Extraction of PAHs from the water and sediment samples was achieved by using liquid–liquid and soxhlet extraction methods respectively, followed by column clean up with silica gel and quantification by gas chromatography–flame ionization detection. Individual PAH levels in the water and sediment samples ranged from not detected (ND) to 24.91 μg/L and ND to 7792 μg/kg, respectively. Total concentrations of the PAHs in the water and sediment samples varied as 14.91–206 μg/L and 1107–22,310 μg/kg in that order. Total levels of the contaminants were above the target values in the two matrices and were higher in summer than autumn. Although the noncarcinogenic risk of PAHs estimated in the water column through dermal absorption was very low compared with the target value, the carcinogenic risk determined was high for both adults and children. Similarly, benzo(a)pyrene and dibenzo(a,h)anthracene were found to be of higher carcinogenic and mutagenic risks in the sediments collected from the study area. Diagnostic ratios suggest that the target hydrocarbons are predominantly from pyrolytic sources. It therefore could be inferred that the water body is conspicuously polluted; hence, efforts should be made to control all the activities contributing to such magnitude of pollution at the sites.
124 citations
TL;DR: Analysis of particle-associated nucleic acids captured and preserved in sediment traps at 4,000-m depth in the North Pacific Subtropical Gyre revealed the variable and heterogeneous biological origins and microbial activities of sinking particles that connect their downward transport, transformation, and degradation to deep-sea biogeochemical processes.
Abstract: Sinking particles are a critical conduit for the export of organic material from surface waters to the deep ocean. Despite their importance in oceanic carbon cycling and export, little is known about the biotic composition, origins, and variability of sinking particles reaching abyssal depths. Here, we analyzed particle-associated nucleic acids captured and preserved in sediment traps at 4,000-m depth in the North Pacific Subtropical Gyre. Over the 9-month time-series, Bacteria dominated both the rRNA-gene and rRNA pools, followed by eukaryotes (protists and animals) and trace amounts of Archaea. Deep-sea piezophile-like Gammaproteobacteria, along with Epsilonproteobacteria, comprised >80% of the bacterial inventory. Protists (mostly Rhizaria, Syndinales, and ciliates) and metazoa (predominantly pelagic mollusks and cnidarians) were the most common sinking particle-associated eukaryotes. Some near-surface water-derived eukaryotes, especially Foraminifera, Radiolaria, and pteropods, varied greatly in their abundance patterns, presumably due to sporadic export events. The dominance of piezophile-like Gammaproteobacteria and Epsilonproteobacteria, along with the prevalence of their nitrogen cycling-associated gene transcripts, suggested a central role for these bacteria in the mineralization and biogeochemical transformation of sinking particulate organic matter in the deep ocean. Our data also reflected several different modes of particle export dynamics, including summer export, more stochastic inputs from the upper water column by protists and pteropods, and contributions from sinking mid- and deep-water organisms. In total, our observations revealed the variable and heterogeneous biological origins and microbial activities of sinking particles that connect their downward transport, transformation, and degradation to deep-sea biogeochemical processes.
123 citations
TL;DR: In this article, a review provides insight into the abundance, origin, distribution and composition of MPs in the sea surface and water column of the Mediterranean Sea, with marked geographical differences between Mediterranean sub-basins.
Abstract: This review provides insight into the abundance, origin, distribution and composition of MPs in the sea surface and water column of the Mediterranean Sea. Literature data on MP particles on the sea surface showed an evident heterogeneous distribution and composition, with marked geographical differences between Mediterranean sub-basins. A standardized protocol for water sampling, extraction and detection of plastic debris is strongly recommended. The heterogenicity of MPs distribution and its concentration levels could be related to several factors, such as the different methodological approaches. In addition, the influence of hydrodynamic features such as currents, up and down-welling, gyres and fronts could also be responsible for this heterogeneity in concentrations. Marine litter modelling studies have been applied to understand litter sources, fate, transport and accumulation in oceans. Recent studies focused on the “plastisphere” in order to better understand the potential risk of pathogen dispersion with plastic transport in the Mediterranean Sea.
116 citations
TL;DR: The heterogeneity of MPs distribution suggests that MPs particles can be retained above the density-gradient layers in coastal seas and the World Ocean.
88 citations
TL;DR: This study confirms the ubiquity of MP in the Mediterranean Sea and imparts low occurrence in fish digestive tracts.
87 citations
TL;DR: Most of the OSA that formed in this process remained in the water column, where the degradation processes were more effective, and there was no evidence of the transport of hydrocarbons in bottom sediments associated with fine sediments that would have accelerated the dispersion and degradation rates of the oil.
Abstract: This paper presents the oil-suspended particulate matter aggregate (OSA) resulted from the interaction of droplets of dispersed oil in a water column and particulate matter. This structure reduces the adhesion of oil on solid surfaces, promotes dispersion, and may accelerate degradation processes. The effects of the addition of fine sediments (clay + silt) on the formation of OSA, their impact on the dispersion and degradation of the oil, and their potential use in recovering reflective sandy beaches were evaluated in a mesoscale simulation model. Two simulations were performed (21 days), in the absence and presence of fine sediments, with four units in each simulation using oil from the Reconcavo Basin. The results showed that the use of fine sediment increased the dispersion of the oil in the water column up to four times in relation to the sandy sediment. There was no evidence of the transport of hydrocarbons in bottom sediments associated with fine sediments that would have accelerated the dispersion and degradation rates of the oil. Most of the OSA that formed in this process remained in the water column, where the degradation processes were more effective. Over the 21 days of simulation, we observed a 40 % reduction on average of the levels of saturated hydrocarbons staining the surface oil.
85 citations
TL;DR: In this paper, the authors analyzed the water column descriptors dynamic during the last 22 years in this coastal lagoon, in the context of a eutrophication process produced by an increase in nutrient inputs, mainly derived from agriculture.
Abstract: Coastal lagoons are considered among the marine habitats with the highest biological productivity, and support a great variety of human activities and pressures that make them especially vulnerable to trophic imbalances. While dystrophic crises are common in many lagoons, others like the Mar Menor show homeostatic mechanisms, high resilience, and clear waters. This paper analyses the water column descriptors dynamic during the last 22 years in this coastal lagoon, in the context of a eutrophication process produced by an increase in nutrient inputs, mainly derived from agriculture. Despite water column nitrate concentration increased by one order of magnitude, the lagoon maintained homeostatic regulation for two decades, keeping the water transparency and relatively low levels of nutrients and chlorophyll a (Prebreak phase), followed by a sudden change of state in 2016 with an abrupt increase in average nutrients and chlorophyll a concentration and loss of water transparency (Break phase), and a relatively rapid recovery after the reduction of nutrient discharges (Recovery phase). The activation of the regulation mechanisms seems to manifest through an ammonium production in the water column, as a consequence of the activity in the trophic web. The low correlation between chlorophyll a and nutrients concentration, mainly at small spatio-temporal scales, is in disagreement with eutrophication traditional models, and suggests a rapid response of primary producers to nutrient inputs and a zooplankton control in the short-term, which in turn is controlled by the rest of the trophic web components. Homeostatic properties that in the Mar Menor lagoon have provided resistance to eutrophication are based on several mechanisms: channeling its production toward the benthic system (maintaining high biomasses of primary producers, filter feeders, and detritivores), a top-down control of the pelagic trophic web exerted by ichthyoplankton and jellyfish, and exporting surplus production outside the system. Resilience of the system would be based on the high turnover in the species composition related to the restricted connectivity to the sea, the spatio-temporal variability of the environmental conditions, and the multiplicity of spatial–temporal scales involved in lagoon processes. TRIX index was sensitive to the trophic and water quality changes. However, in our study, its current score does not allow to anticipate or alert the eutrophication risk and the trophic breakpoint of the system.
TL;DR: Higher metal bioavailability in sediments could facilitate the metal release, but the process could be restrained by the higher aqueous phosphorus due to the precipitation of metal phosphates.
TL;DR: In this article, the authors exploit the sensitivity of organic matter preservation in marine sediments to bottom water oxygen concentration to constrain the level of dissolved oxygen in the deep central equatorial Pacific Ocean during the last glacial period (18,000-28,000 years BP).
Abstract: Enhanced ocean carbon storage during the Pleistocene ice ages lowered atmospheric CO2 concentrations by 80 to 100 ppm relative to interglacial levels. Leading hypotheses to explain this phenomenon invoke a greater efficiency of the ocean's biological pump, in which case carbon storage in the deep sea would have been accompanied by a corresponding reduction in dissolved oxygen. We exploit the sensitivity of organic matter preservation in marine sediments to bottom water oxygen concentration to constrain the level of dissolved oxygen in the deep central equatorial Pacific Ocean during the last glacial period (18,000–28,000 years BP) to have been within the range of 20–50 μmol/kg, much less than the modern value of ~168 μmol/kg. We further demonstrate that reduced oxygen levels characterized the water column below a depth of ~1,000 m. Converting the ice age oxygen level to an equivalent concentration of respiratory CO2, and extrapolating globally, we estimate that deep‐sea CO2 storage during the last ice age exceeded modern values by as much as 850 Pg C, sufficient to balance the loss of carbon from the atmosphere (~200 Pg C) and from the terrestrial biosphere (~300–600 Pg C). In addition, recognizing the enhanced preservation of organic matter in ice age sediments of the deep Pacific Ocean helps reconcile previously unexplained inconsistencies among different geochemical and micropaleontological proxy records used to assess past changes in biological productivity of the ocean.
TL;DR: The Fe/Mn record accurately traced past changes in lake mixing intensity and related shifts in water column oxygenation, and showed that the Fe and Mn ratio mainly responded to changes in redox potential in hypolimnetic waters.
TL;DR: Adhesion of plastic to coral reef structures as a major sink for microplastics suspended in the water column after sinking is pointed at, helping explain low concentrations in Red Sea surface waters.
TL;DR: Pollution was albeit moderate, yet regular check is recommended to ensure safe and healthy environment for human and aquatic lives, suggesting possible carcinogenic effects to humans, with adults being the most vulnerable.
Abstract: Polycyclic aromatic hydrocarbons are amongst the pollutants of major concern in the terrestrial and aquatic habitats. They are mostly characterised by carcinogenic and non-carcinogenic effects. Distribution and potential health risks of sixteen priority PAHs in the water and sediment samples collected between December 2015 and June 2016 from Algoa Bay, South Africa, were evaluated. Water and sediment samples collected were extracted with liquid–liquid and soxhlet extraction methods, respectively, and then cleaned up using glass column loaded with silica gel. Final concentrations of the target PAHs were determined by gas chromatography interfaced with flame ionization detector. Results indicated that individual PAH concentrations in surface water, bottom water and sediment samples ranged from not detected (ND) to 24.66 µg/L, ND to 22.81 µg/L and ND to 5.23 mg/kg correspondingly. Total PAHs concentrations varied as 12.78–78.94 µg/L, 1.20–90.51 µg/L and 1.17–10.47 mg/kg in the three environmental matrices in that order. The non-carcinogenic risk was generally below 1, whereas risk indices (dermal contact) were above the acceptable limit of 1 × 10−4 in the water column, suggesting possible carcinogenic effects to humans, with adults being the most vulnerable. Similarly, highest contributions to TEQs and MEQs in the sediments were made by benzo(a)pyrene and dibenzo(a,h)anthracene, the two most toxic congeners, signifying the possibility of carcinogenicity and mutagenicity in humans. Diagnostic ratios of PAHs reflect a prevailing pyrogenic input all through. The pollution was albeit moderate, yet regular check is recommended to ensure safe and healthy environment for human and aquatic lives.
TL;DR: Algae bloom can boost the lake eutrophication not only through direct release of nutrients but also through the high production of ΣS2- and indirect promotion of phosphorus mobility in sediment, which suggest the sulfate reduction was dramatically promoted during algae decomposition.
TL;DR: The presence of microplastics in the gut of benthic oysters (Crassostrea gigas) and in the water column in a eutrophic estuary under high anthropogenic pressure, in the southwestern Atlantic was studied for the first time in this paper.
TL;DR: This work suggests a general strategy that can promote permanent recovery of lake ecosystems - including their sediments - and inactivation of sediment P may in fact delay the long-term recovery ofLake ecosystems and inhibit the re-use of nutrients.
TL;DR: The authors show that the elemental composition and energy content of sinking particulate matter can be used to develop a more comprehensive understanding of energy flow networks in the sea.
Abstract: The major biogeochemical cycles of marine ecosystems are driven by solar energy. Energy that is initially captured through photosynthesis is transformed and transported to great ocean depths via complex, yet poorly understood, energy flow networks. Herein we show that the chemical composition and specific energy (Joules per unit mass or organic carbon) of sinking particulate matter collected in the North Pacific Subtropical Gyre reveal dramatic changes in the upper 500 m of the water column as particles sink and age. In contrast to these upper water column processes, particles reaching the deep sea (4000 m) are energy-replete with organic carbon-specific energy values similar to surface phytoplankton. These enigmatic results suggest that the particles collected in the abyssal zone must be transported by rapid sinking processes. These fast-sinking particles control the pace of deep-sea benthic communities that live a feast-or-famine existence in an otherwise energy-depleted habitat.
TL;DR: In this article, the particle mixing coefficient (DB) is estimated from the averaged penetration of particle-reactive radionuclides into sedimentary deposits in Long Island Sound, an estuarine system with well-defined sources of naturally-occurring radions.
Abstract: Bioturbation promotes priming and total remineralization of sedimentary organic matter (Corg) in multiple ways. A primary local mode is the injection of reactive Corg from the water column, surface sediment, and mucus secretions into deposits. During feeding, burrowing, and construction activities by benthic fauna, labile substrates are brought into close association with more refractory material over a wide range of time scales, geometries, and depths, enhancing decomposition of the less reactive components (priming). One measure of these local interactions is the particle mixing coefficient, DB, which can be estimated from the averaged penetration of particle-reactive radionuclides into deposits. Patterns of DB in Long Island Sound, an estuarine system with well-defined sources of naturally-occurring radionuclides, show consistent positive correlations between DB and total inventories of 234Th (t1/2 = 24 d) and 210Pb (t1/2 = 22 yr) at local and basin scales. These correlations, maintained seasonally in the case of 234Th, demonstrate not only the penetration of plankton-derived, reactive Corg into deeper regions of deposits during bioturbation over monthly (~ 5 – 10 cm) to decadal timescales (~ 20 – 100 cm) but also the enhanced capture of labile substrates from the water column across basin scales into bioturbated patches as the intensity of reworking increases. In Long Island Sound, sedimentary Chl-a distributions and benthic nutrient regeneration (e.g., NH4+ fluxes) reflect these particle exchange processes. Basin and regional scale capture of labile substrates into bioturbated deposits can be generally demonstrated, for example, along the highly productive Cape Hatteras continental margin. Thus, total and net remineralization necessarily increase with the biogenic enhancement of the quantity of labile particulate substrate in deposits. This capture, intermixing, and close association of reactive and refractory substrates (reductant mixing), and thus the optimization of priming potential, represent important, often overlooked, pathways by which bioturbation generates biogeochemical conditions conducive to maximum efficiency of remineralization.
TL;DR: Results from a natural experiment and the long-term record indicate that effects of hotter and drier climate are likely to increase water column stratification and decrease CO2 availability in eutrophic polymictic lakes, which combination will catalyze blooms of buoyant cyanobacteria.
TL;DR: In this article, a small eutrophic lake (Soppensee, Switzerland) was sampled for CH4 concentrations profiles and emissions, combined with water column hydrodynamics to investigate the fate of CH4 produced in hypolimnetic sediments.
Abstract: Methane (CH4), a potent greenhouse gas, is produced in and emitted from lakes at globally significant rates. The drivers controlling the proportion of produced CH4 that will reach the atmosphere, however, are still not well understood. We sampled a small eutrophic lake (Soppensee, Switzerland) in 2016–2017 for CH4 concentrations profiles and emissions, combined with water column hydrodynamics to investigate the fate of CH4 produced in hypolimnetic sediments. Using a mass balance approach for the periods between April and October of both years, net CH4 production rates in hypolimnetic sediments ranged between 11.4 and 17.7 mmol m−2 d−1, of which 66–88% was stored in the hypolimnion, 13–27% was diffused to the epilimnion, and 6–7% left the sediments via ebullition. Combining these results with a process‐based model we show that water column turbulent diffusivity (K z) had a major influence on the fate of produced CH4 in the sediments, where higher K z values potentially lead to greater proportion being oxidized and lower K z lead to a greater proportion being stored. During fall when the water column mixes, we found that a greater proportion of stored CH4 is emitted if the lake mixes rapidly, whereas a greater proportion will be oxidized if the water column mixes more gradually. This work highlights the central role of lake hydrodynamics in regulating CH4 dynamics and further suggests the potential for CH4 production and emissions to be sensitive to climate‐driven alterations in lake mixing regimes and stratification.
TL;DR: In this paper, a meridional transect of dissolved Cd and δ114Cd from Japanese GEOTRACES section GP19 along 170°W from 64°S in the Southern Ocean to the equatorial Pacific is presented.
TL;DR: The findings indicate annual remobilization of As from contaminated lake sediments may be inhibiting recovery in small shallow lakes that undergo seasonal transitions in redox state, highlighting the importance of winter conditions and links between physical lake properties and biogeochemical processes in the chemical recovery of As-impacted subarctic landscapes.
TL;DR: In this article, the authors presented a comprehensive tungsten (W) dataset from the highly sulfidic Black Sea and the weakly sulfinic Landsort Deep (Baltic Sea), as the type localities of modern euxinic basins, that combines water column, pore water, and sediment records.
TL;DR: In this article, the authors investigated the kinetics of two-step nitrification and to simulate this process and emphasized the importance of considering the effect of pH, substrate and bacteria in nitrification modelling of river basins.
Abstract: Nitrification is simulated in existing water quality models by multiplying the rate with the attenuation factors for water temperature and dissolved oxygen The effect of pH, substrates and bacteria is mostly neglected Moreover, the two-step nitrification is simplified to a one-step process The aim of this study is to investigate the kinetics of two-step nitrification and to simulate this process Consequently, the importance of considering the effect of pH, substrate and bacteria in nitrification modelling of river basins is emphasized For this, an experiment was performed on water taken from the Tay Ninh River in Vietnam The results show a low actual ammonium oxidation rate in the water column of the river The ammonium oxidation is completely inhibited at pH 5 while the nitrite oxidation is strongly inhibited at pH 85 In comparison to the ammonium oxidizers (AOB), the nitrite oxidizers (NOB) are rarely inhibited at low pH Numerical simulation of the experiment delivered ammonium oxidation rates kA and nitrite oxidation rates kN for different pH values The kA for pH values lower than 6 is very low It increases rapidly as the pH increases from 6 to 65 We also found out that pH values of 75 and 7 are optimal for the activity of AOB and NOB, respectively Our results emphasize the importance of considering the effect of pH, substrate and bacteria on the nitrification research in river basins In doing so, nitrification can be simulated more realistically and sustainable water management can be carried out more successfully
TL;DR: In this article, the authors collected data from the northern Salish Sea (NSS) from December 2014 to June 2018, which consisted of continuous measurements at two sites as well as spatially and seasonally-distributed discrete seawater samples.
Abstract: Marine carbon dioxide (CO2) system data has been collected from December 2014 to June 2018 in the northern Salish Sea (NSS; British Columbia, Canada) and consisted of continuous measurements at two sites as well as spatially- and seasonally-distributed discrete seawater samples. The array of CO2 observing activities included high-resolution CO2 partial pressure (pCO2) and pHT (total scale) measurements made at the Hakai Institute’s Quadra Island Field Station (QIFS) and from an Environment Canada weather buoy, respectively, as well as discrete seawater measurements of pCO2 and total dissolved inorganic carbon (TCO2) obtained during a number of field campaigns. A relationship between NSS alkalinity and salinity was developed with the discrete datasets and used with the continuous measurements to highly resolve the marine CO2 system. Collectively, these datasets provided insights into the seasonality in this historically under-sampled region and detail the area’s tendency for aragonite saturation state () to be at non-corrosive levels (i.e. > 1) only in the upper water column during spring and summer months. This depth zone and time period of reprieve can be periodically interrupted by strong northwesterly winds that drive short-lived (~1 week) episodes of high-pCO2, low-pH, and low- conditions throughout the region. Interannual variability in summertime conditions was evident and linked to reduced northwesterly winds and increased stratification. Anthropogenic CO2 in NSS surface water was estimated using data from 2017 combined with the global atmospheric CO2 forcing for the period 1765 to 2100, and projected a mean value of 49 ± 5 µmol kg-1 for 2018. The estimated trend in anthropogenic CO2 was further used to assess the evolution of and pHT levels in NSS surface water, and revealed that wintertime corrosive conditions were likely absent pre-1900. The percent of the year spent above = 1 has dropped from ~98% in 1900 to ~60% by 2018. Over the coming decades, winter pHT and spring and summer are projected to decline to conditions below identified biological thresholds for select vulnerable species.
TL;DR: In this article, the authors investigate the mechanisms that control release of Fe from shelf sediments and its lateral transport (shuttling) in oxic and hypoxic waters on the northwestern Black Sea shelf.
TL;DR: In this paper, a detailed geochemical investigation of phosphorus cycling in the low sulfate, euxinic Lake Cadagno, Switzerland, is presented, which is considered a prime analogue for ancient euxinics.