The acidification of coastal waters is distinguished from the open ocean because of much stronger synergistic effects between anthropogenic forcing and local biogeochemical processes. However, ocean ...acidification research is still rather limited in polar coastal oceans. Here, we present a 17‐year (2002–2019) observational data set in the Chukchi Sea to determine the long‐term changes in pH and aragonite saturation state (Ωarag). We found that pH and Ωarag declined in different water masses with average rates of −0.0047 ± 0.0026 years−1 and −0.017 ± 0.009 years−1, respectively, and are ∼2–3 times faster than those solely due to increasing atmospheric CO2. We attributed the rapid acidification to the increased dissolved inorganic carbon owing to a combination of ice melt‐induced increased atmospheric CO2 invasion and subsurface remineralization induced by a stronger surface biological production as a result of the increased inflow of the nutrient‐rich Pacific water.
Plain Language Summary
Anthropogenic CO2 absorbed by the ocean leads to a lower pH and the calcium carbonate saturation state (Ω) and threatens the marine ecosystems state of healthiness via a process called ocean acidification (OA). The Arctic Ocean is particularly sensitive to OA because more CO2 can be dissolved in cold water. This study used the observations collected over 17 years from 2002 to 2019 to estimate long‐term trends of Ωarag and pH in the Chukchi Sea. The results show that rapid acidification occurred throughout all water masses from 2002 to 2019, leading to or approaching aragonite undersaturation. The rapid acidification is attributed to the enhanced increasing concentration of dissolved inorganic carbon. While sea ice melt induced uptake of anthropogenic CO2 partly explains the long‐term acidification, the remainder is due to the increased nutrient‐rich Pacific inflow water which promotes the high biological CO2 utilization in the surface waters but leads to stronger subsurface acidification due to the regenerated CO2. We suggest that the acidity in Chukchi Arctic Shelf waters will increase in the future if the increased inflow of Pacific water continues.
Key Points
pH and Ωarag declined at −0.0047 ± 0.0026 years−1 and −0.017 ± 0.009 years−1 from 2002 to 2019, 2–3 times greater than atmospheric CO2 projected
The enhanced acidification in Chukchi Sea is mainly driven by enhanced dissolved inorganic carbon, owing to atmospheric CO2 uptake and biological activity
Aragonite undersaturation in Pacific Winter Water has been observed from 2010; other water masses are expected to encounter Ωarag < 1 within 15 years
This paper presents the spatial distribution and seasonal changes of the carbonate system and CO2 fluxes in a complex river‐estuary system located in a subtropical region, the Pearl River Estuary, ...based on five surveys covering primarily a wet and dry seasonal cycle on two major subestuaries of the Pearl River, namely Lingdingyang and Huangmaohai. Significant spatial and seasonal variations of surface water partial pressure of CO2 (pCO2) were observable in these two subestuaries. While both Lingdingyang and Huangmaohai had higher pCO2 in their upper estuaries, which quickly decreased downstream as seen in many estuarine settings elsewhere, significant differences occurred between the two subestuaries in terms of pCO2 level, with much higher pCO2 in the upper Lingdingyang than the upper Huangmaohai. In terms of seasonality, substantially higher pCO2 was observed in warm and wet seasons in both upper estuaries (2100–8350 μatm in the Lingdingyang and 1040–3590 μatm in the Huangmaohai) than in cold and dry seasons (1100–7460 μatm and 560–970 μatm in the Lingdingyang and the Huangmaohai, respectively). As a consequence, CO2 emission from the Pearl River Estuary system in summer was ∼6 times of that in winter. At the same time, we observed a clear drawdown of pCO2 in the lower estuary in both summer and winter, reaching a level of water pCO2 which was below the atmospheric level. This seasonal and spatial contrast can also be seen in the distribution of dissolved inorganic carbon (DIC) and total alkalinity. On the basis of a seasonal and zonal distribution of pCO2, the annual CO2 emission from the Pearl River Estuary was estimated to be ∼3 × 1010 mol C, which is equivalent to ∼6% of the total DIC export flux to the South China Sea from the Pearl River system.
Flow of dense shelf water provide an efficient mechanism for pumping CO2 to the deep ocean along the continental shelf slope, particularly around the Antarctic bottom water (AABW) formation areas ...where much of the global bottom water is formed. However, the contribution of the formation of AABW to sequestering anthropogenic carbon (Cant) and its consequences remain unclear. Here, we show prominent transport of Cant (25.0 ± 4.7 Tg C yr−1) into the deep ocean (>2,000 m) in four AABW formation regions around Antarctica based on an integrated observational data set (1974–2018). This maintains a lower Cant in the upper waters than that of other open oceans to sustain a stronger CO2 uptake capacity (16.9 ± 3.8 Tg C yr−1). Nevertheless, the accumulation of Cant can further trigger acidification of AABW at a rate of −0.0006 ± 0.0001 pH unit yr−1. Our findings elucidate the prominent role of AABW in controlling the Southern Ocean carbon uptake and storage to mitigate climate change, whereas its side effects (e.g., acidification) could also spread to other ocean basins via the global ocean conveyor belt.
Plain Language Summary
The Southern Ocean is thought to uptake and store a large amount of anthropogenic CO2 (Cant), but little attention has been paid to the Antarctic coastal regions in the south of 60°S, mainly due to the lack of observations. Based on an integrated data set, we discovered the deep penetration of Cant and a visible pattern of relatively high concentration of Cant along the AABW formation pathway, and the concentration of Cant along the shelf‐slope is higher than that of other marginal seas at low‐mid latitudes, implying a highly effective Cant transport in AABW formation areas. We also found strong upper‐layer CO2 uptake and a significant acidification rate in the deep waters of the Southern Ocean due to the AABW‐driven CO2 transport, which is 3 times faster than those in other deep oceans. It is therefore crucial to understand how the Antarctic shelf regions affect the global carbon cycle through the uptake and transport of anthropogenic CO2, which also drives acidification in the other ocean basins.
Key Points
We show evidence for the accumulation of Cant along the Antarctic shelf‐slope into the deep ocean
The process of AABW formation drives Cant downward transport at 25.0 ± 4.7 Tg C yr−1, sustaining the CO2 uptake in the surface ocean
This further triggers acidification of AABW at a rate of −0.0006 ± 0.0001 pH unit yr−1, which is faster than in other deep oceans
The SARS-CoV-2-infected disease (COVID-19) outbreak is a major threat to human beings. Previous studies mainly focused on Wuhan and typical symptoms. We analysed 74 confirmed COVID-19 cases with GI ...symptoms in the Zhejiang province to determine epidemiological, clinical and virological characteristics.
COVID-19 hospital patients were admitted in the Zhejiang province from 17 January 2020 to 8 February 2020. Epidemiological, demographic, clinical, laboratory, management and outcome data of patients with GI symptoms were analysed using multivariate analysis for risk of severe/critical type. Bioinformatics were used to analyse features of SARS-CoV-2 from Zhejiang province.
Among enrolled 651 patients, 74 (11.4%) presented with at least one GI symptom (nausea, vomiting or diarrhoea), average age of 46.14 years, 4-day incubation period and 10.8% had pre-existing liver disease. Of patients with COVID-19 with GI symptoms, 17 (22.97%) and 23 (31.08%) had severe/critical types and family clustering, respectively, significantly higher than those without GI symptoms, 47 (8.14%) and 118 (20.45%). Of patients with COVID-19 with GI symptoms, 29 (39.19%), 23 (31.08%), 8 (10.81%) and 16 (21.62%) had significantly higher rates of fever >38.5°C, fatigue, shortness of breath and headache, respectively. Low-dose glucocorticoids and antibiotics were administered to 14.86% and 41.89% of patients, respectively. Sputum production and increased lactate dehydrogenase/glucose levels were risk factors for severe/critical type. Bioinformatics showed sequence mutation of SARS-CoV-2 with m
A methylation and changed binding capacity with ACE2.
We report COVID-19 cases with GI symptoms with novel features outside Wuhan. Attention to patients with COVID-19 with non-classic symptoms should increase to protect health providers.
Abstract
Rapid warming and sea-ice loss in the Arctic Ocean are among the most profound climatic changes to have occurred in recent decades on Earth. Arctic Ocean biological production appears that ...it may be increasing as a result, but the consequences for nutrient concentrations are unknown. We have assembled a collection of historical field data showing that average concentrations of the macronutrients nitrate and phosphate have decreased by 79% and 29%, respectively, in surface waters of the western Arctic Ocean basin over the past three decades. The field observations and results from numerical ocean simulations suggest that this long-term trend toward more oligotrophic (nutrient-poor) conditions is driven primarily by the compound effects of sea-ice loss: a reduced resupply of nutrients from subsurface waters (due to fresh water addition and stronger upper-ocean stratification) coincident with increased biological consumption of nutrients (due to the greater availability of light needed for photosynthesis).
The capacity of CO2 uptake in the Chukchi Sea is particularly sensitive to rapid physical and biological changes. However, scarce field observations pose a challenge in understanding the long‐term ...trend of CO2 uptake capacity on this continental shelf. We adopted a machine‐learning‐based approach to construct a 17‐years (2003–2019) long‐term time series of summer sea surface partial pressure of CO2 (pCO2) from remote sensing products. We show that the long‐term increase in CO2 uptake capacity can be attributed to strong and enhanced biological uptake. In addition, the intraseasonal variability of surface pCO2 in early summer confirms the crucial role of sea ice melt and the subsequently enhanced photosynthesis as soon as the surface ocean converts into an open system. Our results thus highlight the use of remote sensing data in interpolating/extrapolating the highly dynamic carbonate system in the continental shelf sea and shed light into future studies involving machine learning or algorithms.
Plain Language Summary
The climate change in the recent decades has caused remarkable sea surface warming in the Arctic Ocean, with its warming rate twice higher than the global average. The Arctic warming could have some consequences such as shrinkage of sea ice and increase of freshwater storage which profoundly affect the carbon cycle in the Arctic Ocean. The Chukchi Sea serves as the largest oceanic CO2 sink in the Arctic Ocean, yet its long‐term variation and associated mechanism remain unclear due to undersampling. In this study, we adopted a machine‐learning‐based model to construct a 17‐years long‐term time series of sea surface partial pressure of CO2 (pCO2) from satellite observations. Results showed that the CO2 uptake capacity in the Chukchi Sea has increased in the recent decades, primarily owing to the increased primary productivity. This study demonstrated the great potential of ocean color remote sensing in retrieving key biogeochemical parameters in polar regions, and providing a powerful tool for monitoring carbonate system for the oceanographic community.
Key Points
A machine learning approach was calibrated and validated to obtain sea surface pCO2 from satellite observations in the Chukchi Sea
Increase in CO2 uptake capacity is revealed by a 17‐years (2003–2019) long‐term time series of summer pCO2
Strong and enhanced biological uptake contribute to the increase in CO2 uptake capacity
Key Points
Significant regional differences in ET and R trends are found.
Land use change, as well as climate change, affects trends of water fluxes
None significant long‐term trends in freshwater ...discharge to the GOM is found
The Gulf of Mexico (GOM) is facing large pressures from environmental changes since the beginning of the last century. However, the magnitude and long‐term trend of total water discharge to the GOM and the underlying processes are not well understood. In this study, the dynamic land ecosystem model (DLEM) has been improved and applied to investigate spatial and temporal variations of evapotranspiration (ET) and runoff (R) over drainage basins of the GOM during 1901–2008. Modeled ET and discharge were evaluated against upscaled data sets and gauge observations. Simulated results demonstrated a significant decrease in ET at a rate of 15 mm yr−1 century−1 and an insignificant trend in runoff/precipitation (R/P) and river discharge over the whole region during 1901–2008. However, the trends in estimated water fluxes show substantial spatial and temporal heterogeneities across the study region. Generally, in the west arid area, ET, R, and R/P decreased; while they increased in the eastern part of the study area during the last 108 years. In the recent 30 years, this region experienced a substantial decrease in R. Factorial simulation experiments indicate that climate change, particularly P, was the dominant factor controlling interannual variations of ET and R; while land use change had the same magnitude of effects on long‐term trends in water fluxes as climate change did. To eliminate modeling uncertainties, high‐resolution historical meteorological data sets and model parameterizations on anthropogenic effects, such as water use and dam constructions, should be developed.
Defining highly variable freshwater plume area from space is important for characterizing the dynamics of biogeochemical properties and understanding the effects of climate change and human ...activities on plume‐related processes. The absorption coefficient of colored dissolved organic matter (aCDOM) from satellite ocean color data can be used to estimate the salinity and thus the plume area in coastal oceans if a robust conservative salinity and aCDOM relationship and an accurate satellite aCDOM algorithm can be established. In this paper, tight relationships between surface water salinity and in situ aCDOM were found during several cruises covering all seasons and the full salinity range in the East China Sea. Thus, a salinity inversion model from aCDOM was developed and validated with an independent data set, in which 73.6% of the data were within the absolute salinity error of ±1 and 87.1% were within ±1.5. Factors influencing the conservative behavior of colored dissolved organic matter are analyzed, with a particular focus on the effect of the phytoplankton‐induced autochthonous colored dissolved organic matter. In addition, several satellite aCDOM algorithms were compared and validated with our in situ data. Monthly satellite‐derived salinity images were mapped in August from 2008 to 2010 and showed the significant interannual variability in the plume coverage. This study demonstrated that the salinity derived from satellite‐derived aCDOM can provide a reliable and good synoptic view of the plume area, and help with biogeochemical studies, in particular, those properties related to the interannual variability of plume coverage, although the development of a localized satellite algorithm of aCDOM is still desirable.
Key Points
Relationship between salinity and CDOM was analyzed using nine cruises data
A salinity inversion model applicable to all seasons was developed in the ECS
Satellite CDOM algorithms were validated by in situ data in the ECS
Human‐induced nitrogen–phosphorus (N, P) imbalance in terrestrial ecosystems can lead to disproportionate N and P loading to aquatic ecosystems, subsequently shifting the elemental ratio in estuaries ...and coastal oceans and impacting both the structure and functioning of aquatic ecosystems. The N:P ratio of nutrient loading to the Gulf of Mexico from the Mississippi River Basin increased before the late 1980s driven by the enhanced usage of N fertilizer over P fertilizer, whereafter the N:P loading ratio started to decrease although the N:P ratio of fertilizer application did not exhibit a similar trend. Here, we hypothesize that different release rates of soil legacy nutrients might contribute to the decreasing N:P loading ratio. Our study used a data‐model integration framework to evaluate N and P dynamics and the potential for long‐term accumulation or release of internal soil nutrient legacy stores to alter the ratio of N and P transported down the rivers. We show that the longer residence time of P in terrestrial ecosystems results in a much slower release of P to coastal oceans than N. If contemporary nutrient sources were reduced or suspended, P loading sustained by soil legacy P would decrease much slower than that of N, causing a decrease in the N and P loading ratio. The longer residence time of P in terrestrial ecosystems and the increasingly important role of soil legacy nutrients as a loading source may explain the decreasing N:P loading ratio in the Mississippi River Basin. Our study underscores a promising prospect for N loading control and the urgency to integrate soil P legacy into sustainable nutrient management strategies for aquatic ecosystem health and water security.
The longer residence time of P in terrestrial ecosystems results in a much slower release of P to coastal oceans than N. With the reduction in the newly introduced nutrient surplus in the Mississippi River Basin, riverine N loading would decrease more rapidly due to the quick loss of soil labile N relative to P. While the N:P ratio has remained stable in agricultural nutrient surplus, a declining N:P ratio in total nutrient loading can be observed as legacy sources became dominant at one point with cumulative legacy impacts over time.
Obesity leads to multiple health problems, including diabetes, fatty liver, and even cancer. Here, we report that urolithin A (UA), a gut-microflora-derived metabolite of pomegranate ellagitannins ...(ETs), prevents diet-induced obesity and metabolic dysfunctions in mice without causing adverse effects. UA treatment increases energy expenditure (EE) by enhancing thermogenesis in brown adipose tissue (BAT) and inducing browning of white adipose tissue (WAT). Mechanistically, UA-mediated increased thermogenesis is caused by an elevation of triiodothyronine (T3) levels in BAT and inguinal fat depots. This is also confirmed in UA-treated white and brown adipocytes. Consistent with this mechanism, UA loses its beneficial effects on activation of BAT, browning of white fat, body weight control, and glucose homeostasis when thyroid hormone (TH) production is blocked by its inhibitor, propylthiouracil (PTU). Conversely, administration of exogenous tetraiodothyronine (T4) to PTU-treated mice restores UA-induced activation of BAT and browning of white fat and its preventive role on high-fat diet (HFD)-induced weight gain. Together, these results suggest that UA is a potent antiobesity agent with potential for human clinical applications.
PDF
