Environmental drivers of increased ecosystem respiration in a warming tundra.

Arctic and alpine tundra ecosystems are large reservoirs of organic carbon1,2. Climate warming may stimulate ecosystem respiration and release carbon into the atmosphere3,4. The magnitude and persistency of this stimulation and the environmental mechanisms that drive its variation remain uncertain5-7. This hampers the accuracy of global land carbon-climate feedback projections7,8. Here we synthesize 136 datasets from 56 open-top chamber in situ warming experiments located at 28 arctic and alpine tundra sites which have been running for less than 1 year up to 25 years. We show that a mean rise of 1.4 °C [confidence interval (CI) 0.9-2.0 °C] in air and 0.4 °C [CI 0.2-0.7 °C] in soil temperature results in an increase in growing season ecosystem respiration by 30% [CI 22-38%] (n = 136). Our findings indicate that the stimulation of ecosystem respiration was due to increases in both plant-related and microbial respiration (n = 9) and continued for at least 25 years (n = 136). The magnitude of the warming effects on respiration was driven by variation in warming-induced changes in local soil conditions, that is, changes in total nitrogen concentration and pH and by context-dependent spatial variation in these conditions, in particular total nitrogen concentration and the carbon:nitrogen ratio. Tundra sites with stronger nitrogen limitations and sites in which warming had stimulated plant and microbial nutrient turnover seemed particularly sensitive in their respiration response to warming. The results highlight the importance of local soil conditions and warming-induced changes therein for future climatic impacts on respiration.

Save the Mekong Delta from drowning.

Policy must address drivers, not just symptoms, of subsidence.

Physical water scarcity metrics for monitoring progress towards SDG target 6.4: An evaluation of indicator 6.4.2 "Level of water stress".

Target 6.4 of the recently adopted Sustainable Development Goals (SDGs) deals with the reduction of water scarcity. To monitor progress towards this target, two indicators are used: Indicator 6.4.1 measuring water use efficiency and 6.4.2 measuring the level of water stress (WS). This paper aims to identify whether the currently proposed indicator 6.4.2 considers the different elements that need to be accounted for in a WS indicator. WS indicators compare water use with water availability. We identify seven essential elements: 1) both gross and net water abstraction (or withdrawal) provide important information to understand WS; 2) WS indicators need to incorporate environmental flow requirements (EFR); 3) temporal and 4) spatial disaggregation is required in a WS assessment; 5) both renewable surface water and groundwater resources, including their interaction, need to be accounted for as renewable water availability; 6) alternative available water resources need to be accounted for as well, like fossil groundwater and desalinated water; 7) WS indicators need to account for water storage in reservoirs, water recycling and managed aquifer recharge. Indicator 6.4.2 considers many of these elements, but there is need for improvement. It is recommended that WS is measured based on net abstraction as well, in addition to currently only measuring WS based on gross abstraction. It does incorporate EFR. Temporal and spatial disaggregation is indeed defined as a goal in more advanced monitoring levels, in which it is also called for a differentiation between surface and groundwater resources. However, regarding element 6 and 7 there are some shortcomings for which we provide recommendations. In addition, indicator 6.4.2 is only one indicator, which monitors blue WS, but does not give information on green or green-blue water scarcity or on water quality. Within the SDG indicator framework, some of these topics are covered with other indicators.

The world's road to water scarcity: shortage and stress in the 20th century and pathways towards sustainability.

Water scarcity is a rapidly growing concern around the globe, but little is known about how it has developed over time. This study provides a first assessment of continuous sub-national trajectories of blue water consumption, renewable freshwater availability, and water scarcity for the entire 20th century. Water scarcity is analysed using the fundamental concepts of shortage (impacts due to low availability per capita) and stress (impacts due to high consumption relative to availability) which indicate difficulties in satisfying the needs of a population and overuse of resources respectively. While water consumption increased fourfold within the study period, the population under water scarcity increased from 0.24 billion (14% of global population) in the 1900s to 3.8 billion (58%) in the 2000s. Nearly all sub-national trajectories show an increasing trend in water scarcity. The concept of scarcity trajectory archetypes and shapes is introduced to characterize the historical development of water scarcity and suggest measures for alleviating water scarcity and increasing sustainability. Linking the scarcity trajectories to other datasets may help further deepen understanding of how trajectories relate to historical and future drivers, and hence help tackle these evolving challenges.

Organic anion transporter 4 (OAT 4) modifies placental transfer of perfluorinated alkyl acids PFOS and PFOA in human placental ex vivo perfusion system.

INTRODUCTION: Perfluorinated alkyl acids (PFAAs) are widely used in industry and consumer products. Pregnant women are exposed to PFAAs and their presence in umbilical cord blood represents fetal exposure. Interestingly, PFAAs are substrates for organic anion transporters (OAT) of which OAT4 is expressed in human placenta. METHODS: To evaluate the contribution of OAT4 and ATP-binding cassette transporter G2 (ABCG2) proteins in the transplacental transfer of perfluoro octane sulfonate (PFOS) and perfluoro octanoate (PFOA) an ex vivo dual recirculating human placental perfusion was used. Altogether 8 placentas from healthy mothers with uncomplicated pregnancies were successfully perfused. RESULTS: Both PFOS and PFOA crossed the placenta as suggested by in vivo data in the literature. The expression of OAT4 and ABCG2 proteins were studied by immunoblotting and correlation with the transfer index %(TI %) of PFOS and PFOA at 120 and 240 min (n = 4) was studied. The expression of OAT4 was in negative correlation with TI % of PFOA (R(2) = 0.92, p = 0.043) and PFOS (R(2) = 0.99, p = 0.007) at 120 min while at 240 min the correlation was statistically significant only with PFOA. The expression of ABCG2 did not correlate with TI% of PFOS or PFOA. DISCUSSION: Data obtained in this study suggest the involvement of OAT4 in placental passage of PFAAs. Placental passage of PFOS and PFOA is modified by the transporter protein OAT4 but not by ABCG2. This is the first study indicating that OAT4 may decrease the fetal exposure to PFAAs and protect the fetus after maternal exposure to PFAAs but further studies are needed to confirm our findings.

Lost food, wasted resources: global food supply chain losses and their impacts on freshwater, cropland, and fertiliser use.

Reducing food losses and waste is considered to be one of the most promising measures to improve food security in the coming decades. Food losses also affect our use of resources, such as freshwater, cropland, and fertilisers. In this paper we estimate the global food supply losses due to lost and wasted food crops, and the resources used to produce them. We also quantify the potential food supply and resource savings that could be made by reducing food losses and waste. We used publically available global databases to conduct the study at the country level. We found that around one quarter of the produced food supply (614 kcal/cap/day) is lost within the food supply chain (FSC). The production of these lost and wasted food crops accounts for 24% of total freshwater resources used in food crop production (27 m(3)/cap/yr), 23% of total global cropland area (31 × 10(-3)ha/cap/yr), and 23% of total global fertiliser use (4.3 kg/cap/yr). The per capita use of resources for food losses is largest in North Africa & West-Central Asia (freshwater and cropland) and North America & Oceania (fertilisers). The smallest per capita use of resources for food losses is found in Sub-Saharan Africa (freshwater and fertilisers) and in Industrialised Asia (cropland). Relative to total food production, the smallest food supply and resource losses occur in South & Southeast Asia. If the lowest loss and waste percentages achieved in any region in each step of the FSC could be reached globally, food supply losses could be halved. By doing this, there would be enough food for approximately one billion extra people. Reducing the food losses and waste would thus be an important step towards increased food security, and would also increase the efficiency of resource use in food production.

Cadmium inhibits ABCG2 transporter function in BeWo choriocarcinoma cells and MCF-7 cells overexpressing ABCG2.

Heavy metals such as cadmium, lead and methylmercury are known to be neurotoxic to developing fetus. ABCG2 which is an efflux transporter located in the maternal facing membranes of human placenta protects fetus from xenobiotics by transferring compounds from syncytiotrophoblast to maternal circulation. The aim of this study was to clarify whether heavy metal compounds (CdCl(2), PbCl(2) and MeHgCl) affect the expression and function of ABCG2 transporter in human placental BeWo choriocarcinoma cells. The expression of ABCG2 was determined by immunoblotting and RT-PCR. The functional activity of ABCG2 was evaluated by measuring the efflux of two known ABCG2 substrates: fluorescent mitoxantrone and (14)C-labeled food carcinogen PhIP. According to MTT assay all compounds were cytotoxic as expected (MeHgCl > CdCl(2) > PbCl(2)). CdCl(2) inhibited the efflux of mitoxantrone and (14)C-PhIP suggesting inhibition of ABCG2 transporter function. PbCl(2) had no effect on mitoxantrone efflux. Because of high toxicity, the inhibitory potency of MeHgCl was not tested. According to protein data these heavy metals did not affect ABCG2 transporter protein expression. Also, the expression of ABCC1, ABCC2 or ABCG2 mRNA were not affected by heavy metals. In conclusion, although the studied metal salts did not affect mRNA or protein expression of ABCG2, CdCl(2) inhibited its function. Further studies to evaluate whether this leads to elevated placental transfer of ABCG2 substrates are needed.

Meta-analysis of data from human ex vivo placental perfusion studies on genotoxic and immunotoxic agents within the integrated European project NewGeneris.

In the E.U. integrated project NewGeneris, we studied placental transport of thirteen immunotoxic and genotoxic agents in three ex vivo placental perfusion laboratories. In the present publication, all placental perfusion data have been re-analyzed and normalized to make them directly comparable and rankable. Antipyrine transfer data differed significantly between the studies and laboratories, and therefore normalization of data was necessary. An antipyrine normalization factor was introduced making the variance significantly smaller within and between the studies using the same compound but performed in different laboratories. Non-normalized (regular) and normalized data showed a good correlation. The compounds were ranked according to their transplacental transfer rate using either antipyrine normalized AUC120 or transfer index (TI120(%)). Normalization generated a division of compounds in slow, medium and high transfer rate groups. The transfer rate differed slightly depending on the parameter used. However, compounds with passage similar to antipyrine which goes through the placenta by passive diffusion, and good recovery in media (no accumulation in the tissue or adherence to equipment) were highly ranked no matter which parameter was used. Antipyrine normalization resulted in the following ranking order of compounds according to AUC(120NORM) values: NDMA ≥ EtOH ≥ BPA ≥ IQ ≥AA ≥ GA ≥ PCB180 ≥ PhIP ≥ AFB1 > DON ≥ BP ≥ PCB52 ≥ TCDD. As the variance in all parameters within a study decreased after antipyrine normalization, we conclude that this normalization approach at least partially corrects the bias caused by the small methodological differences between studies.

Toxicokinetics of the food-toxin IQ in human placental perfusion is not affected by ABCG2 or xenobiotic metabolism.

Metabolizing enzymes and transporters affect toxicokinetics of foreign compounds (e.g. drugs and carcinogens) in human placenta. The heterocyclic amine, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) is a food-borne carcinogen being metabolically activated by cytochrome P450 (CYP) enzymes, especially by CYP1A1/2. IQ is also a substrate for ABCG2 transporter. Placental transfer of (14)C-IQ was evaluated in 4-6 h ex vivo human placental perfusions in Finland and Denmark. In Finland placentas were perfused with (14)C-IQ alone (0.5 microM, n = 6) or in combination with GF120918 (inhibitor of ABCG2, 1 microM, n = 6) or Ko143 (specific inhibitor of ABCG2, 2 microM, n = 4) to study the role of ABCG2 inhibition in transfer while in Denmark perfusions were performed with (14)C-IQ alone. Critical parameters (leak from fetal to maternal circulation, pH values, blood gases, glucose consumption, the production of hCG hormone and transport of antipyrine) were analyzed during the perfusions. (14)C-IQ on maternal and fetal sides was determined by liquid scintillation counting. In Finland IQ and its metabolites in final perfusates were determined also by LC/TOF-MS. ABCG2 expression and EROD activity (CYP1A1/2) were analyzed from perfused tissues. (14)C-IQ was easily transferred through the placenta from maternal to fetal side in both laboratories. Neither significant EROD activity nor IQ metabolites were found in placentas from non-smoking mothers. Inhibition of ABCG2 by GF120918 (FM-ratio of IQ 0.95) or Ko143 (FM-ratio of IQ 0.94) did not affect (14)C-IQ transfer (FM-ratio of IQ in IQ only perfusions 0.97), which indicates that placental ABCG2 does not have a significant role in protecting fetus from IQ.