Summer Autumn Research Articles

Estimation of Grazing Activity of Dairy Goats Using Accelerometers and Global Positioning System.

The recent development of advanced electronic sensors to monitor and record animal grazing activity provides a real opportunity to facilitate understanding of their behavioral responses. This study aimed to characterize the grazing activity and protein–energy requirements of grazing dairy goats in a Mediterranean woodland in northern Morocco by combining two sensors, the Global Positioning System (GPS) and three axis accelerometers. An experiment was conducted in a representative woodland with eight dairy goats. Measurements were undertaken during the three main grazing seasons (spring, summer, and autumn) for two consecutive and contrasting years. Grazing activity parameters were assessed using GPS collars and leg position sensors. The results showed that grazing time was higher in spring (57% and 59%) than in summer (39% and 36%) and autumn (41% and 45%), respectively, for the dry and wet years (p < 0.001). During the two studied years, the daily horizontal distance traveled by the goats increased from spring (about 4.5 km) to summer (about 6.5 km) and autumn (about 7.4 km), while greater daily vertical distances were recorded over similar distances during summer–autumn. Several protein–energy intakes that were insufficient to cover the requirements of the grazing goats were recorded, especially in summer. The combination of GPS collars and accelerometers contributed to a better understanding of the grazing activities of dairy goats in the studied Mediterranean woodland. These findings provide useful data on the protein–energy balances of dairy goats and offer additional information that could be useful for herders and managers to enhance goat-feeding strategies and guarantee high-performance in the semi-extensive traditional goat farming system.

Chemical compositions of raspberry leaves influenced by growth season, cultivars and leaf position

Raspberry leaves with high polyphenols have high utilization value, but the accumulation trend of phenolics in raspberry leaves in different growing seasons, cultivars, and leaf positions, is not clear. The utilization of leaves and raspberry comprehensive income are limited due to the uncertain factors. Therefore, the content changes of chlorophyll a, chlorophyll b, carotenoids, total phenolic content (TPC), total flavonoids content (TFC), saponins, hydrolyzed tannins and condensed tannins of raspberry leaves from May to October, in annual-fruiting (AF) raspberry (cv. Heritage) and biennial-fruiting (BF) raspberry (cv. Reveille, cv. Tulameen and cv. Australian Red), and three leaf positions were investigated. Eighteen phenolic compounds were identified in which quercetin-3-glucuronide, kaempferol-3-rutinoside, ellagic acid, chlorogenic acid, epicatechin and procyanidin B1 were quantitatively analyzed by HPLC-MS. The results showed that chlorophyll a, chlorophyll b, carotenoids showed a parabolic trend of rising first and then falling, while TPC, TFC, hydrolyzed tannins, condensed tannins and saponins showed a gradual increase trend from May to October. The total accumulation of secondary metabolites was the Heritage, Australian Red, Tulameen and the Reveille from high to low. The apical leaves accumulated TPC, TFC and quercetin-3-glucuronide, kaempferol-3-rutinoside, ellagic acid, while the basal leaves accumulated condensed tannins and saponins. Overall, growth season was the main factor affecting the accumulation of secondary metabolites, followed by cultivar and leaf positions. Therefore, according the properties of cultivars, it can be recommended that AF and BF cultivar leaves can be harvested twice in early summer and late autumn after reproductive shoot preservation, while the leaves of BF cultivar without fruiting shoots can be extensively harvested once in late autumn.

Hydrological and Meteorological Variability in the Volga River Basin under Global Warming by 1.5 and 2 Degrees

The idea of the research to assess the impact of 1.5 °C and 2 °C global warming in the 21st century on the runoff formation in the Volga basin corresponds to the Paris agreement on climate change 2016 with the main goal to keep the global air temperature rise to below 2 °C relative to the pre-industrial level and to take measures to limit warming to 1.5 °C by the end of the 21st century. The purpose of this study was to obtain physically based results of changes in the water regime of the Volga basin rivers under global warming by 1.5 °C and 2 °C relative to pre-industrial values. The physical and mathematical model of runoff generation ECOMAG (ECOlogical Model for Applied Geophysics) was applied in calculations using data from global climate models (GCMs). The estimation of flow anomalies of the Volga River and its major tributaries showed a decrease in annual runoff by 10–11% relative to the period from 1970 to 1999. The largest relative decrease in runoff by 17–20% was noted for the Oka and Upper Volga rivers, while the Kama River had only a 1–5% decrease. The Volga winter runoff increased by 17% and 28% under global warming by 1.5 °C and 2 °C, respectively, and negative runoff anomalies during the spring flood and the summer–autumn period turned out to be in the range of 21 to 23%. Despite the increase in precipitation, the role of evaporation in the water balance of the Volga basin will only increase.

Time Shift in the Exploitation of Fish Stocks by Great Cormorants Phalacrocorax carbo at Lake IJsselmeer: How Wintering Birds began Competing for Fish with Breeding Conspecifics

Monthly aerial bird counts showed a strong increase in the number of wintering Great Cormorants Phalacrocorax carbo sinensis since the late 1990s at Lake IJsselmeer but not at Lake Markermeer-IJmeer. Compared to the 1980–1990s, breeding numbers also increased in this part of the system. The resulting increased exploitation of fish stocks was thought to have been possible because of a long-term increase in the stock of Ruffe Gymnocephalus cernuus, despite a clear overall decline of total estimated fish biomass in the lake during the same period. The most likely cause of these shifts was thought to be the intensive commercial fishing regime, removing the large predatory fish first, followed by a strong reduction of stocks of large Bream Abramis brama, in turn paving the way for increases in the stocks of Ruffe. Increased predation by Cormorants on the enhanced stocks of small fishes was possible because of ameliorated underwater visibility in Lake IJsselmeer. Starting in 2000, there was a strong shift in both temporal habitat use and associated fish consumption by Cormorants towards the winter period. The local breeding birds, exploiting the same age- and size-structured community of fishes in the spring, thus face an already-depleted food resource. Compared to the 1980–1990s, fish consumption by Cormorants in winter increased by a factor of ten, whereas that by breeders did so by a factor of 1.6. Our calculations showed that the actual harvest of available fish stock by wintering and breeding Cormorants together was c. 5% in 1985–2000 and c. 15% in 2001–2015. The disproportionate division of the overall consumption (‘harvest’) of the fish stock towards the wintering birds is a strong argument for direct competition with their conspecifics breeding locally. In conclusion, we calculate that because of the increased winter exploitation initiated by the activities of an intensive commercial fishery, the fish consumption in summer and early autumn by breeding Cormorants and their offspring was suppressed by a factor of six.

Руси vs кармати: новий погляд на події в Барда’а в 40-х роках X століття

The article is dedicated to the Rus’ military campaign against Bardha’a, a major political center in Azerbaijan in the era of the Abbasid Caliphate. This was the military action of the Rus’ in the Caspian region, which found the most complete consecration in the written sources of the East. In the context of political events, the arrival of Rus’ in Azerbaijan should be attributed to August 944, and the departure from there at the turn of summer–autumn&nbsp;945. The likely participants of the campaign were contingents from the army of Prince Igor of Kyiv, who in 944 went on a campaign against Byzantium, which ended in peace negotiations. The campaign against Bardha’a took place with the support of Khazaria. Rus’ arrived in Azerbaijan by ship, so their most likely route is: the Black Sea&nbsp;– the Kerch Strait&nbsp;– the Sea of Azov&nbsp;– the Don&nbsp;– portage to Sarkel&nbsp;– the Volga&nbsp;– the Caspian Sea&nbsp;– the Kura. The version about the land route through the North Caucasus is not valid, and through the lands of the Byzantine vassals of Abkhazia, Kakheti, and Hereti is not confirmed by source information. The Rus’ campaign against the Bardha’a became possible in the context of a serious crisis that the Caliphate was experiencing. One of the manifestations of the crisis was the growing popularity of opposition religious trends. Ismailism occupied a special place among such trends, including in the form of Qarmatian teaching. The Emir Marzuban, an opponent of the Rus in Bardha’a, considered himself as belonging to this teaching. Countering the Ismaili was one of the main tasks of the policy of the Sunni ruling elites of the Samanid, Khwarazm, Shirvan, and Derbent States. In the middle of the 10th&nbsp;century, it was these Islamic policies that had stable ties with the Khazars. This circumstance explains the neutrality of the Muslim community of Khazaria in providing the squadron of Rus’ with the opportunity to enter the Caspian Sea and attack the possessions of Marzuban.

Winter dormancy in trees

Plants growing in temperate and boreal regions of the world have to face strikingly different environmental conditions during summer and winter. Being sessile organisms, plants have had to develop various strategies to adapt to these changes in light, temperature, and water availability, thereby optimizing their 'economy of growth'. While annual plants can endure unfavorable winter conditions in the form of a seed, or under a protective cover of thick snow, perennial plants such as trees adapt by going into a stage of deep sleep called winter dormancy. To enter dormancy, vegetative growth is stopped in the late summer or early autumn and the shoots are converted into buds, where the shoot apical meristems are protected by tightly closed and hardened bud scales (Figures 1 and 2). At the same time, cold hardiness develops and the need for water and nutrient uptake is drastically reduced. Deciduous trees also go through leaf senescence whereby the leaves develop their autumn colors and are shed (Figure 1A). The trees then spend the beginning of the winter in a state of deep sleep in which they are completely unreceptive to any environmental signals telling them to wake up. However, as winter progresses, the trees are gradually released from this slumber and will eventually flush their buds in the spring. Vegetative growth then resumes with the formation of new leaves and shoots during summer until the trees again go into growth cessation and the cycle is closed (Figures 1 and 2). This cycle of growth and dormancy is central for the ability of trees to adapt to growth at different latitudes and elevations. The further north, or the higher the elevation at which the trees grow, the earlier in the season the trees enter growth cessation and the later they flush their buds in the spring. This is because meteorological winter arrives earlier in the season and lasts longer into the spring. The trees therefore have to stop growth earlier in the season to ensure that they have enough time to complete bud formation and to develop cold hardiness and dormancy. They also have to be sure that winter is really over before flushing their buds. Winter dormancy is therefore a clear case of a trade-off between the length of the growing season and the protection against winter damage - a nice example of 'economy in biology', the theme of this special issue. This primer will briefly summarize what we know about the environmental signals that influence the annual growth cycle in trees, as well as our current understanding of the genetic pathways and molecular mechanisms regulated by these signals.

Ice Coverage of the Laptev Sea and Air Temperature Variation during Recent Centuries: Observed Data and Reconstructions Using a Geochemical Proxy

Objective: The aim was to reconstruct the climatic parameters and ice of the Laptev Sea over the last centuries and to identify the causes of their variability. Background: The ice-free water area of the Arctic Ocean has increased considerably during the summer–autumn period in recent decades, which may be attributed to several climatic and oceanographic factors. Methods: The ice-free period duration and mean annual surface air temperature were reconstructed using the transfer function technique to compare hydrometeorological data and the chemical composition of bottom sediments accumulated during the observation period. This approach was based on sub-millimeter scanning of sediments using synchrotron radiation X-ray fluorescence. The results revealed a specific feature of the variations in the mean annual air temperature over the last 400 years in the Laptev Sea region, whereby higher (up to positive) temperature anomalies, were observed during the Little Ice Age. Some discrepancies in the ice coverage and climate fluctuations were observed during the period from the end of the Little Ice Age to the beginning of the period of accelerated ice-cover degradation in the Arctic (1850–1980). These discrepancies can be caused by the beginning of global warming, which have disturbed the natural cyclicality of atmospheric processes, whereas natural variations in ice coverage were more stable. Conclusion: A joint analysis of the reconstructed variations in air temperature and the duration of the ice-free period revealed the influence of atmospheric processes on the ice conditions of the Laptev Sea.

Impact of environmental factors on phytoplankton composition and their marker pigments in the northern Adriatic Sea

Phytoplankton composition, abundance and carbon biomass were investigated at monthly intervals during 2006–2007 at a coastal site, “Acqua Alta” an oceanographic tower, in the northern Adriatic Sea. Results were compared with chlorophyll a concentrations of phytoplankton classes attributed by HPLC-CHEMTAX analysis. Changes in the taxonomic structure were associated with environmental parameters. The total carbon biomass of phytoplankton was positively correlated with the temperature and negatively correlated with silicate concentrations. Nutrient concentrations were higher in the winter–spring period than in the summer-autumn period. The highest carbon biomass and abundance of phytoplankton were observed during summer–autumn months. Diatoms were the group that had the highest contribution to the total carbon biomass during the sampling period. Small flagellates, which were the major contributors to the total cell counts were dominant during the summer period. There was a significant correlation between carbon biomass and CHEMTAX-derived Chl a values of diatoms and dinoflagellates. However, the total carbon biomass of phytoplankton was not correlated with Chl a, which seemed to be related to seasonal changes in the ratios of C:Chl a of all taxonomic classes. This ratio was higher during the summer-autumn period (73 ± 33) than during the winter–spring period (17 ± 20).

Phenology of fine root and shoot using high frequency temporal resolution images in a temperate larch forest

Understanding tree phenology reveals the underlying mechanisms through plant functional and productive activities and carbon sinks in forest ecosystems. However, previous research on tree phenology has focused on shoot dynamics rather than tree root dynamics. Here, we aimed to explore seasonal temperature patterns of daily-based root and shoot dynamics by capturing high frequency information of plant images in a larch forest. Additionally, we focused on seasonal changes in fine root color, which white roots absorb nutrients or water; brown roots undergo secondary structural development with transport resources. We monitored continuous images using an automated digital camera for shoot dynamics and a flatbed scanner for the fine root dynamics. Using the images, we analyzed the relationship between temperature and plant area index as shoot growth status and total root-area proportion of white and brown roots. Larch shoot production had a single mountain-shaped peak, and there was a positive correlation between plant area index and air temperature. Fine root production had a bimodal root-growth pattern, with two peaks in early summer and late autumn. Soil temperature was positively correlated with white root proportion and negatively correlated with brown root proportion. We identified differences between shoots and roots regarding temperature relationships. In particular, the automated flatbed scanner method for root dynamics allowed the collection of detailed bimodal patterns of root production with a shift from whitening to browning color, which had previously been overlooked. Such high frequency temporal resolution analysis can illustrate the in-depth of mechanisms of fine-root and shoot phenology through different stages of plant development in terms of growth and senescence.

National‐scale impacts on wind energy production under curtailment scenarios to reduce bat fatalities

AbstractWind energy often plays a major role in meeting renewable energy policy objectives; however, increased deployment can raise concerns regarding the impacts of wind plants on certain wildlife. Particularly, estimates suggest hundreds of thousands of bat fatalities occur annually at wind plants across North America, with potential implications for the viability of several bat species. One approach to reducing bat fatalities is shutting down (or curtailing) turbines when bats are most at risk, such as at night during relatively low wind speed periods throughout summer and early autumn. While curtailment has consistently been shown to reduce bat fatalities, the lost power production reduces revenues for wind plants. This study conducted simulations with a range of curtailment scenarios across the contiguous United States to examine sensitivities of annual energy production (AEP) loss and potential impacts on economic metrics for future wind energy deployment. We found that AEP reduction can vary across the country from less than 1% to more than 10% for different curtailment scenarios. From an estimated 2891 gigawatts (GW) of simulated economically viable wind capacity (measured by a positive net present value), we found the mid curtailment scenario (6.0 m/s wind speed cut‐in from July 1 through October 31) reduced the quantity of economic wind capacity by 274 GW or 9.5%. Our results indicate that high levels of curtailment could substantially reduce the future footprint of financially viable wind energy. In this context, future work that illuminates cost‐effective strategies to minimize curtailment while reducing bat fatalities would be of value.

Using helicopter counts to estimate the abundance of Himalayan tahr in New Zealand's Southern Alps

AbstractEstimating the abundance and density of mountain ungulates is difficult because of rugged and remote terrain, high elevations, and rapidly changing weather. Helicopter surveys could overcome these problems, but researchers have seldom applied helicopter‐based survey methods at large spatial scales in mountain terrain. We used helicopters to count introduced Himalayan tahr (Hemitragus jemlahicus) at 117 plots, each of 4 km2, in New Zealand's Southern Alps during 2016–2019. The sampling frame was 7,844 km2 and we located the plots at the vertices of an 8‐km grid superimposed over the sampling frame (i.e., a systematic random sampling design). We conducted 3 repeat counts at each plot during summer–autumn. We used the repeat counts to estimate tahr abundance and density, corrected for imperfect detection, using a dynamic N‐mixture model for open populations. We estimated the population of tahr in the sampling frame using design‐based, finite sampling methods and model‐based inference procedures. The mean estimated density of tahr on each plot varied from zero to 31.7 tahr/km2. The mean densities of tahr varied among management units, ranging from 0.3 to 10.7 tahr/km2, and exceeded specified intervention densities in 6 of the 7 management units. The total design‐based estimate of tahr abundance in the sampling frame was 34,500 (95% CI = 27,750–42,900), with a coefficient of variation (CV) of 0.11. The corresponding model‐based estimate of total abundance was similar (34,550, 95% CI = 30,250–38,700) but was substantially more precise (CV = 0.06) than the design‐based estimate. The precision of the estimates for the individual management units was also better than that of the design‐based estimates, with CVs of &lt;0.20 for all but 1 management unit. Our study provides a repeatable method for sampling mountain ungulates. More generally, robust estimation of abundance and density of mountain ungulates is possible by combining aerial surveys and open population models with an objective, probabilistic sampling design.

Seasonal variations in marine polycyclic aromatic hydrocarbons off Oki Island, Sea of Japan, during 2015–2019

Concentrations of 13 phase-partitioned polycyclic aromatic hydrocarbons (PAHs) in seawater were monitored monthly off Oki Island, Japan, during 2015–2019 to elucidate seasonal variations, main source, and transport pathways of PAHs in the southwestern Sea of Japan. Total PAH (dissolved plus particulate) concentrations in surface seawater at 36°09.0′N, 133°17.3′E (site OK) were in the range 0.49–9.36 ng L−1 (mean 2.77, SD 2.05 ng L−1) with higher levels in summer–autumn, an order of magnitude lower than those in the East China Sea during 2005 and 2009–2011 and about one-third of those recorded in the Sea of Japan in 2008 and 2010. The main sources of dissolved and particulate PAHs were combustion products. Increasing dissolved PAH levels during July–October indicate that the area around southern Oki Island is impacted by PAH-rich summer continental-shelf water transported by the Tsushima Warm Current flowing from the East China Sea.

Novel passive detection approach reveals low breeding season survival and apparent lactation cost in a critically endangered cave bat.

Capture-mark-recapture/resight (CMR) methods are used for survival-rate studies, yet are often limited by small sample sizes. Advances in passive integrated transponder (PIT) technology have enabled passive detection or ‘resight’ of marked individuals using large antennas with greater read-ranges than previously possible. We used passively-detected resight data and CMR models to study survival rates of the southern bent-winged bat Miniopterus orianae bassanii, a critically endangered, cave-dwelling bat. Over three years, we used PIT-tagging to monitor 2966 individuals at the species’ largest breeding aggregation, using daily detection data (> 1.6 million detections) to estimate seasonal survival probabilities, structured by age, sex and reproductive status, and parameterise population projection matrices. This has hitherto been impossible using traditional CMR methods due to disturbance risk and low recapture rates. Bats exhibited lowest apparent seasonal survival over summer and autumn, particularly for reproductive females in summer (when lactating) and juveniles in autumn (after weaning), and high survival in winter. Lowest survival rates coincided with severe drought in summer–autumn 2016, suggesting that dry conditions affect population viability. Under all likely demographic assumptions, population projection matrices suggested the population is in deterministic decline, requiring urgent action to reduce extinction risk. Passively-collected resight data can now be used in combination with CMR models to provide extensive, robust information for targeted wildlife population management.

Seasonality of Four Types of Baroclinic Instability in the Global Oceans

AbstractDistinct geographical distributions of four types of mesoscale baroclinic instabilities (BCIs) exist in the global oceans, implying preferences of surface or subsurface mesoscale eddies to specific regions. This study explores seasonal variations of global BCI types and their dependence on varying background ocean states with a focus on three representative regions. First, the regions of the Kuroshio Extension and Gulf Stream are representative for distinctive seasonal transition of BCI types: the Charney surface BCIs prevail in winter, while the Phillips BCIs prevail in summer, which is controlled by weak (strong) upper‐layer stratification in winter (summer) but is less impacted by the seasonal changes in the mean flow‐induced shear. Second, the region covering both the tropics and subtropics of the North Pacific (10°N–35°N) is representative for seasonal meridional migration of the border between the domains of the Phillips and the Charney surface BCIs; their border migrates equatorward (poleward) in spring and summer (autumn and winter), which is primarily caused by the equatorward (poleward) shift of both the North Equatorial Current and the Subtropical Countercurrent in spring and summer (autumn and winter), and is secondarily modulated by the variation in the upper‐layer stratification. Third, the Antarctic Circumpolar Current region is chosen to represent a weak seasonal variation of BCIs. Those seasonal variations in BCI types are further demonstrated as being associated with seasonal variations of baroclinic conversion rate, implying possible generation of corresponding eddies.

Rice variety and sustainable farming: A case study in the Mekong Delta, Vietnam

The Mekong Delta (MKD) produces more than half of the total rice production in Vietnam. In the context of climate change, the Vietnamese government has implemented a development strategy for rice production in the MKD region to improve quality and reduce greenhouse gas emissions. The proportion of aromatic and high-quality rice production is gradually increasing to satisfy the export market. However, there is still an over-reliance on agrochemicals and the impact of overall efficiency of major rice groups is not well understood. This study measures the overall efficiency (OE) and input slacks of rice production in the MKD and considered low-emission rice farming. Using primary survey data from 380 households, the super-slack based measure (super-SBM) in data envelopment analysis (DEA) was employed to calculate the efficiency scores and non-radial slacks of each farm. The results indicated that both aromatic rice (AR) and high-quality rice (HR) groups achieved higher OE in the autumn-winter (AW) season than in the summer-autumn (SA) season. In addition, OE also increased in paddy farms greater than two hectares and in households that have cooperative membership and practice climate smart agriculture (CSA). For the input reduction strategies based on slacks, it was found that each rice group should have the seed density reduced by amounts ranging from 29 to 45 kg/ha. N fertilizer should also be reduced by 33 kg/ha and 35 kg/ha in the SA and AW seasons, respectively. It was estimated that rice farming can correspondingly mitigate N2O emissions by 62−74.2 kg/km2 in the SA season and 64.7−73 kg/km2 in the AW season. Overall, the super-SBM model was effective in simultaneously estimating the overall efficiency and input overuse among paddy fields. In addition, the ranking of “super-efficient” rice farms also supports the restructuring policy of the government in establishing AR and HR production areas for export. Among the adaptation strategies, households that practice CSA techniques have smaller slacks of N fertilizer and irrigation. Low-emission paddy sector development in the MKD favors AR and HR if the CSA techniques are continuously promoted and strictly monitored by the Vietnamese government.

PM 7/20 (3) Erwinia amylovora

PM 7/20 (3) <i>Erwinia amylovora</i>

Stimulation, Reduction and Compensation Growth, and Variable Phenological Responses to Spring and/or Summer–Autumn Warming in Corylus Taxa and Cornus sanguinea L.

Understanding species-specific responses to climate change allows a better assessment of the possible impact of global warming on forest growth. We studied the responses of the shrub species Corylus avellana L., Corylus maxima Mill. and intermediate forms, together stated as the Corylus taxa, and Cornus sanguinea L. upon periodically elevated temperatures in spring and/or in summer–autumn. Experiments were performed in a common garden, with Belgian and Pyrenean provenances for Corylus avellana and Cornus sanguinea. In the Corylus taxa, a warmer spring resulted in a reduction in height and diameter growth. Remarkably, the reduced diameter increment was restored with full compensation in the following year. The height increment for Cornus sanguinea was larger upon a warmer summer–autumn, concurring with a later leaf senescence. Our results suggest that Corylus is more sensitive to spring warming, influencing growth negatively, whereas Cornus is more sensitive to summer–autumn warming, influencing height growth positively. These deviating responses can be explained, at least partly, by their diverging ecological niches, with the Corylus taxa being more shade-tolerant compared to Cornus sanguinea. The warm spring conditions advanced bud burst in all studied taxa, whereas the warm summer–autumn advanced leaf senescence but prolonged its duration in the Corylus taxa, as well as delayed this phenophase in Cornus sanguinea. Little to no after-effects of the temperature treatments were detected. Although Corylus avellana and Cornus sanguinea plants originated from similar origins, their growth and phenological responses in the common garden diverged, with Corylus being more stable and Cornus displaying more variation between the Belgian and Pyrenean provenances.

Source analysis of dissolved methane in Chukchi Sea and Bering Strait during summer–autumn of 2012 and 2013

Rapid sea-ice retreat in the Arctic Ocean can promote the release of methane (CH4) from microbe and from sediment on the continental shelf. The released methane can be the cause or effect of strong climate feedback. Nevertheless, few observations have been reported of temporal changes of dissolved CH4 in the Arctic Ocean, especially in western coastal shelf areas (Chukchi Sea and Bering Strait). This study therefore describes the spatial and temporal distributions of the concentrations and stable carbon isotope ratios (δ13C value) of CH4 in the western Arctic Ocean during August–October in 2012 and 2013. In both years, surface water was supersaturated with CH4 with respect to the atmosphere, but concentrations in 2013 were 2–3 times higher than in 2012. In 2012, the concentrations in the bottom layer were higher (up to 55.9 nmol kg−1), whereas δ13C values were lower (down to −63.8‰) than in the surface layer, indicating that CH4 was produced mainly by organic matter degradation in seafloor sediment via methanogens. In 2013, however, because of stronger vertical mixing than in 2012, vertical gradients of CH4 concentration and δ13C value were not prominent. Short-term (19 days) time series observations were also conducted at a fixed station in 2013. An episodic high CH4 concentration in the surface layer (17.2 nmol kg−1 with δ13C = −52.9‰) observed after a strong wind event suggests that CH4 production is accelerated because nutrients are supplied from the bottom of the mixed layer increase plankton activity. These findings suggest that the dynamic variation of dissolved CH4 in the Chukchi Sea in autumn 2012 and 2013 depended mainly on the strength of stratification by sea-ice melt water. Strong winds increase biological activity in the surface layer, consequently accelerating CH4 production.

Development, Validation and Application of a Targeted LC-MS Method for Quantification of Microcystins and Nodularin: Towards a Better Characterization of Drinking Water

Cyanotoxins can be produced in surface waters by cyanobacterial blooms, mostly during summer and early autumn. Intoxications would result from consumption of water contaminated with the potent hepatotoxins, microcystins and nodularin. Therefore, the WHO has set a guideline value for drinking water quality concerning one congener of microcystin. Consequently, the design of a validated, public reference method to detect and quantify the hepatotoxins in drinking water is necessary. During this study, a method was developed to quantify cyanotoxins (eight microcystin congeners and nodularin) in water using liquid chromatography coupled with tandem mass spectrometry. Additionally, bottled and tap water samples were tested for the presence of cyanotoxins. No cyanotoxins were detected in any of the collected water samples. However, quality controls and the results of a proficiency test show the validity of the method.

Tracing anomalies in moisture recycling and transport to two record-breaking droughts over the Mid-to-Lower Reaches of the Yangtze River

The influence of moisture recycling and transport on major drought events is poorly understood, but essential to enhance our knowledge of the atmospheric water cycle. Here, we investigate this for two record-breaking droughts over the Mid-to-Lower Reaches of the Yangtze River (MLRYR), the winter-spring (WS) drought of 2011 and summer-autumn (SA) drought of 2019. Using a land–atmosphere water balance framework, we find the precipitation recycling ratio (the percentage of precipitation in a region derived from the same region’s evaporation) increased during both droughts, especially for the SA drought (from 14.5% to 22.9%). The WS drought was characterized by a 27.8% reduction in external advected moisture, originating principally from the northeast China and Bohai Sea (reduced by 22.3%) and from the northwest Pacific and South China Sea (25.7%). The SA drought was driven by a 43.8% reduction in external advected moisture, originating mainly from a southwesterly path, i.e. the Bay of Bengal and the South China Sea (reduced by 26.8%). From a regional viewpoint, moisture transportation from the Pacific Ocean (and South China Sea) decreased during the WS (SA) droughts, mainly resulting in moisture deficit over the MLRYR. Analyses reveal that this reduction was driven by strong negative convergence, which was unfavorable for precipitation formation and enhanced air flow out of the MLRYR. The weakened moisture transport was principally driven by seasonal mean flow rather than transient eddies. Changes in wind (i.e. dynamic processes), rather than specific humidity (i.e. thermodynamic processes) were dominant in regulating the seasonal mean moisture transport. Our study helps understand the atmospheric water cycle anomalies driving extreme drought events, and advances knowledge on moisture transportation and its controlling processes.