Hotspots Of Production Research Articles

Uberizing Agriculture in Drylands: A Few Enriched, Everyone Endangered

The future of water resources relies heavily on food production. Large-scale agriculture, driven by irrigation technology and cost reduction, has transformed traditional dryland croplands into a very profitable but environmentally and socially impactful agribusiness. The study of groundwater-dependent food systems is fragmented. Hydrology, on one hand, concentrates on water resources while overlooking surface agricultural processes. Meanwhile, the agro-economic sector is fixated on optimizing resource utilization for short-term profit maximization. Consequently, numerous adverse environmental and social consequences are overlooked by these conventional approaches. To steer resource usage and our food systems in a new direction, prioritizing the integration of this collective knowledge is imperative. Here, we analyze the impacts of greenhouse agriculture in SE Spain, one of the global hotspots of fruit and vegetable production. Through the lens of the treadmill of production theory we uncover the model’s significant profitability and its environmental and social effects, which include unequal wealth distribution, precarious working conditions, and the depletion and pollution of belowground water reserves. Reducing water use and limiting the development of new irrigated areas, using crop species adapted to available water resources, and empowering farmers against large distributors are key measures to avoid the social and economic collapse of this region, and of other dryland areas that have followed a similar unsustainable development model. The need for these changes becomes more pressing as the impacts of climate change continue to escalate. Within this context, groundwater reserves represent vital strategic resources that must not be wasted.

Characterization of atmospheric methane release in the outer Mackenzie River delta from biogenic and thermogenic sources

Abstract. The Mackenzie River delta is the second largest Arctic river delta in the world. Thin and destabilizing permafrost coupled with vast natural gas reserves at depth, high organic-content soils, and a high proportion of wetlands create a unique ecosystem conducive to high rates of methane (CH4) emission from biogenic and thermogenic sources. Hotspots are known to have a significant contribution to summertime CH4 emissions in the region. Still, little research has been done to determine how often geologic or biogenic CH4 contributes to hotspots in the Mackenzie River delta. In the present study, stable carbon isotope analysis was used to identify the source of CH4 at several aquatic and terrestrial sites thought to be hotspots of CH4 flux to the atmosphere. Walking transects and point samples of atmospheric CH4 and CO2 concentrations were measured. Source stable carbon isotope (δ13C-CH4) signatures were derived from keeling plots of point samples and ranged from −42 ‰ to −88 ‰ δ13C-CH4, identifying both biogenic and thermogenic sources. A CH4 source was determined for eight hotspots, two of which were thermogenic in origin (−42.5 ‰, −44.7 ‰), four of which were biogenic in origin (−71.9 ‰ to −88.3 ‰), and two of which may have been produced by the oxidation of biogenic CH4 (−53.0 ‰, −63.6 ‰), as evidenced by δ13C-CH4 signatures. This indicates that the largest hotspots of CH4 production in the Mackenzie River delta are caused by a variety of sources.

Corals and sponges are hotspots of reactive oxygen species in the deep sea.

Reactive oxygen species (ROS) are central to diverse biological processes through which organisms respond to and interact with their surroundings. Yet, a lack of direct measurements limits our understanding of the distribution of ROS in the ocean. Using a recently developed in situ sensor, we show that deep-sea corals and sponges produce the ROS superoxide, revealing that benthic organisms can be sources and hotspots of ROS production in these environments. These findings confirm previous contentions that extracellular superoxide production by corals can be independent of the activity of photosynthetic symbionts. The discovery of deep-sea corals and sponges as sources of ROS has implications for the physiology and ecology of benthic organisms and introduces a previously overlooked suite of redox reactants at depth.

Spatially distributed tracer‐aided modelling to explore DOC dynamics, hot spots and hot moments in a tropical mountain catchment

AbstractTracer‐aided rainfall‐runoff modelling is a promising tool for understanding catchment hydrology, particularly when tracers provide information about coupled hydrological‐biogeochemical processes. Such models allow for predicting the quality and quantity of water under changing climatic and anthropogenic conditions. Here, we present the Spatially‐distributed Tracer‐Aided Rainfall‐Runoff model with a coupled biogeochemical reactive tracer module (STARR‐DOC) to simulate dissolved organic carbon (DOC) dynamics and sources. The STARR‐DOC model was developed and tested for a humid high Andean ecosystem (páramo) using high‐resolution hourly DOC and hydrometeorological data to simulate hourly discharge and DOC at a fine spatial (10 × 10 m) resolution. Overall, the model was able to acceptably reproduce discharge (KGE ~ 0.45) and stream DOC (KGE ~ 0.69) dynamics. Spatially distributed DOC simulations were independently compared using point DOC measurements for different soil types across the catchment, which allowed for identifying DOC production hot spots and hot moments. Results showed higher hydrological connectivity between slopes and valleys with increasing precipitation. Wetter conditions also favoured DOC production (wet month = 82 mg L−1, dry month = 5 mg L−1) and transport to the stream network (DOC concentrations: during events ~15 mg L−1, during baseflows ~4 mg L−1). Our results also suggest that minor changes in meteorological conditions directly affect páramo soil water dynamics and biogeochemistry. Knowledge of when and where DOC production in mountain catchments is greatest is important for water managers to understand when they make decisions about water security, especially considering climate change predictions for the Andean region.

Contact-free impacts of sessile reef organisms on stony coral productivity

Coral reefs are biodiversity and productivity hotspots where space limitation makes interactions between organisms inevitable. Biodiversity loss alters these interactions, however downstream effects on the productivity of individual species remain unexplored. Here, we quantified immediate and long-term changes in stony coral productivity in response to contact-free interactions with various benthic organisms (stony corals, soft corals, macroalgae, sponges). We show that corals sense the presence of other organisms and subsequently modulate their productivity. Each stony coral species had a characteristic reaction to contact-free stimuli, while the identity of the interaction partner was of subordinate importance. Our data highlight downstream effects that biodiversity loss and shifting coral reef communities may have through indirect modulation of productivity, resulting in uneven effects among species. The productivity response is probably mediated by secondary metabolites released into the water. The underlying communication pathways that mediate these interactions remain to be investigated.

Fish and aquatic salamander responses to the creation of riparian canopy gaps along forested headwater streams

Many headwaters across temperate North America have uniform mid‐succession riparian forests recovering from historic land clearing. These young riparian stands contrast with late‐succession forests, which have complex structural characteristics including canopy gaps. Canopy gaps provide structural diversity that can be important for terrestrial species, and they are also hypothesized to be important features for aquatic environments. The light patches below gaps create productivity hotspots in streams and therefore create potential for increased stream apex predator abundances through bottom‐up food web drivers. However, increasing light may also affect stream temperature, a consideration for coldwater fish (salmonids). We established an experimental before‐after control‐impact study to explicitly assess how creating canopy gaps in the riparian forest affects the abundance and biomass of coastal cutthroat trout (Oncorhynchus clarkii clarkii) and Pacific giant salamanders (Dicamptodon tenebrosus) in paired reference and treatment reaches at five replicate streams. Gaps were designed to resemble those in old‐growth forests in the treatment reach of each system although wood was explicitly left out of the stream. At four of five sites, we found small and generally consistent positive responses in adult cutthroat trout and total vertebrate biomass to localized increases in light but only 2 years after treatment. Results suggest that opening riparian canopies adjacent to streams via gaps is a viable tool to enhance structural complexity of riparian forests without negatively impacting stream vertebrates; however, a single gap alone had small effects on aquatic vertebrates. More or larger gaps would likely be needed to notably enhance aquatic apex predators.

Hydrologic and Organic Carbon Quality Controls on Nitrous Oxide Dynamics Across a Variably Confined Karst Aquifer

AbstractAtmospheric concentrations of the potent greenhouse gas nitrous oxide (N2O) have increased approximately 20% since the pre‐industrial era. Riverine systems represent an important atmospheric source of N2O however, the influence of varying hydrogeological conditions and dissolved organic carbon (DOC) quantity and quality on N2O dynamics remains poorly understood. We investigate effects of these processes on N2O dynamics in the Santa Fe River watershed in north‐central Florida, USA where a gradient in DOC quantity and quality is caused by varying surface water‐groundwater exchange. The watershed is underlain by the karstic Floridan aquifer, which is confined in the headwaters and contains terrigenous recalcitrant DOC, while the unconfined lower reaches contain protein‐like labile DOC substrates. Where extensive surface water‐groundwater exchange occurs at the boundary between the confined and unconfined aquifer, incomplete denitrification raises N2O concentration to 6.1 μg N‐N2O L−1, approximately 20 times greater than the concentration expected from equilibration with atmospheric N2O. These elevated concentrations create average local fluxes reaching ∼950 μg N‐N2O m−2 hr−1 within the mixing zone. Summation of spatially explicit emission estimates for upstream, mixing zone, and downstream river sections yield a total average emission rate of ∼3,758 kg N‐N2O yr−1. Despite having the smallest surface area across the river transect (∼8%), emissions from the mixing zone account for 26% of the total river emission rate. These findings highlight the potential contributions from karst landscapes to N2O cycling caused by varying redox conditions during surface water‐groundwater exchange, which creates hotspots of N2O production and emissions.

Integrating hydrological connectivity and zooplankton composition in Arctic ponds and lakes

Abstract Arctic landscapes are characterised by their numerous ponds and lakes. With increased climate warming and consequent changes in hydrological connectivity, the ecology of many of these waterbodies is expected to change. We sampled 13 ponds and 22 lakes for zooplankton and various limnological and physical environmental variables in the vicinity of Cambridge Bay, Nunavut (69.1169° N, 105.0597° W), with the aim of testing how well the degree of hydrological connectivity explained patterns in species composition and abundance and contributed to crustacean production. Ponds were hydrologically isolated while the lakes were arranged in four lake chains and ranged from the headwaters to highly inter‐connected lakes receiving water from one to 768 upstream lakes. In all sites combined, 77 zooplankton species were found, including 56 rotifers, six copepods, 11 cladocerans, two fairy shrimp species, a mysid, and a tadpole shrimp. We show that the zooplankton communities differed between hydrologically isolated (ponds) and connected (lakes) systems, with 17 species unique to ponds and 20 to lakes. Furthermore, the communities were more similar within lake chains and hence in lakes closer to each other. In ponds, distances between waterbodies had no impact on community similarity. Zooplankton abundance was higher in lakes (255 ind/L) than in ponds (65 ind/L) due to the higher number of rotifers that accounted for nearly 80% of the zooplankton abundance in lakes. In ponds, rotifers, cladocerans, and copepods were equally abundant. In terms of biomass, cladocerans represented 65% of total biomass in all waterbodies except for a chain of deep lakes that had abundant fish communities. In these lakes, cladoceran abundance and biomass were low and probably limited by fish predation. Zooplankton production was higher in ponds (4.6 mgC m−3 day−1) than in lakes (1.7 mgC m−3 day−1), and within lakes was lowest in the chain composed of large lakes (1.3 mgC m−3 day−1). The high production in ponds was closely linked to high zooplankton biomass and further explained by high gross primary production supported by relatively high nutrient concentrations in these shallow systems. Our study emphasises that hydrological connectivity is key to shaping zooplankton communities, although fish presence also appears to affect them. It shows that isolated ponds (that currently account for c83% of all waterbodies on southern Victoria Island) are hotspots of aquatic biological productivity that probably play an essential role in Arctic freshwater landscapes. Finally, our study provides critical baseline information on the current composition of Arctic zooplankton communities important for estimating climate change impacts.

Seasonal dynamics of a glycan-degrading flavobacterial genus in a tidally mixed coastal temperate habitat.

Coastal marine habitats constitute hotspots of primary productivity. In temperate regions, this is due both to massive phytoplankton blooms and dense colonisation by macroalgae that mostly store carbon as glycans, contributing substantially to local and global carbon sequestration. Because they control carbon and energy fluxes, algae-degrading microorganisms are crucial for coastal ecosystem functions. Environmental surveys revealed consistent seasonal dynamics of alga-associated bacterial assemblages, yet resolving what factors regulate the in situ abundance, growth rate and ecological functions of individual taxa remains a challenge. Here, we specifically investigated the seasonal dynamics of abundance and activity for a well-known alga-degrading marine flavobacterial genus in a tidally mixed coastal habitat of the Western English Channel. We show that members of the genus Zobellia are a stable, low-abundance component of healthy macroalgal microbiota and can also colonise particles in the water column. This genus undergoes recurring seasonal variations with higher abundances in winter, significantly associated to biotic and abiotic variables. Zobellia can become a dominant part of bacterial communities on decaying macroalgae, showing a strong activity and high estimated in situ growth rates. These results provide insights into the seasonal dynamics and environmental constraints driving natural populations of alga-degrading bacteria that influence coastal carbon cycling.

Life cycle assessment of fermentative production of lactic acid from bread waste based on process modelling using pinch technology

Bread waste (BW), a rich source of fermentable carbohydrates, has the potential to be a sustainable feedstock for the production of lactic acid (LA). In our previous work, the LA concentration of 155.4 g/L was achieved from BW via enzymatic hydrolysis, which was followed by a techno-economic analysis of the bioprocess. This work evaluates the relative environmental performance of two scenarios - neutral and low pH fermentation processes for polymer-grade LA production from BW using a cradle-to-gate life cycle assessment (LCA). The LCA was based on an industrial-scale biorefinery process handling 100 metric tons BW per day modelled using Aspen Plus. The LCA results depicted that wastewater from anaerobic digestion (AD) (42.3–51 %) and cooling water utility (34.6–39.5 %), majorly from esterification, were the critical environmental hotspots for LA production. Low pH fermentation yielded the best results compared to neutral pH fermentation, with 11.4–11.5 % reduction in the overall environmental footprint. Moreover, process integration by pinch technology, which enhanced thermal efficiency and heat recovery within the process, led to a further reduction in the impacts by 7.2–7.34 %. Scenario and sensitivity analyses depicted that substituting ultrapure water with completely softened water and sustainable management of AD wastewater could further improve the environmental performance of the processes.

Evaluating environmental, economic, and social aspects of an intensive pig production farm in the south of Brazil: a case study

PurposeThe objective of this work was to quantify and understand the impacts of intensive pig production at family-farm level. A case study from the west of Santa Catarina State was used to identify adverse issues (hotspots) of pig production by integrating the assessment of the environmental, economic, and social aspects of the system. The quantitative and qualitative indicators calculated can guide and support the decision-making processes for a variety of stakeholders and actors.MethodsThe environmental performance of the pig production system was assessed from cradle-to-farm gate using environmental Life Cycle Assessment methodology set out in ISO 14040 (ISO 2006a). The functional unit (FU) was 1 kg of Liveweight (kg-LW). The structure of the Life Cycle Sustainability Assessment (LCSA) was based on Neugebauer et al. (J Clean Prod 102:165–176, 2015) and Chen and Holden (J Clean Prod 172:1169–1179, 2018), who proposed a tiered framework to evaluate the impacts on the environmental, social, and financial aspects of a product. The economic dimension or Life Cycle Cost (Hunkeler et al. in Environmental life cycle costing. Crc Press, London, 2008) focused on farm-level activities. The social impact was calculated based on the UNEP/SETAC (2009) guidelines.Results and discussionThe environmental performance of the finishing pig production was slightly lower than reference value for climate impacts, acidification, and eutrophication. The economic impacts tended to be positive, reflecting the efforts of the farmer and employee to maintain high productivity and reduce the number of pig losses in comparison with the reference values. However, this effort did not result in greater profitability, causing low farm income. The impacts of low profitability were not transferred to the employee since the wage were above the reference value. There is a need for more education for small farmers, which is known to have a positive correlation with the adoption of new technologies, thus reducing adverse environmental and social impacts and increasing economic return.ConclusionsThe interaction of social and economic factors suggests it is unlikely that the farm can achieve better environmental performance. The limited economic return and low level of education have a negative impact on the farmer’s capacity to adopt new technologies to improve environmental outcomes. The use of LCSA, based on a consistent model across the three aspects of sustainability, made it possible to understand the interaction of these factors.

New Functionalities and Regional/National Use Cases of the Anomaly Hotspots of Agricultural Production (ASAP) Platform

The Anomaly hotSpots of Agricultural Production (ASAP) Decision Support System was launched operationally in 2017 for providing timely early warning information on agricultural production based on Earth Observation and agro-climatic data in an open and easy to use online platform. Over the last three years, the system has seen several methodological improvements related to the input indicators and to system functionalities. These include: an improved dataset of rainfall estimates for Africa; a new satellite indicator of biomass optimised for near-real-time monitoring; an indicator of crop and rangeland water stress derived from a water balance accounting scheme; the inclusion of seasonal precipitation forecasts; national and sub-national crop calendars adapted to ASAP phenology; and a new interface for the visualisation and analysis of high spatial resolution Sentinel and Landsat data. In parallel to these technical improvements, stakeholders and users uptake was consolidated through the set up of regionally adapted versions of the ASAP system for Eastern Africa in partnership with the Intergovernmental Authority on Development (IGAD) Climate Prediction and Applications Centre (ICPAC), for North Africa with the Observatoire du Sahara et du Sahel (OSS), and through the collaboration with the Angolan National Institute of Meteorology and Geophysics (INAMET), that used the ASAP system to inform about agricultural drought. Finally, ASAP indicators have been used as inputs for quantitative crop yield forecasting with machine learning at the province level for Algeria’s 2021 and 2022 winter crop seasons that were affected by drought.

Assessment of badland susceptibility and its governing factors using a random forest approach. Application to the Upper Llobregat River Basin and Catalonia (Spain)

Badlands are considered hotspots of sediment production, contributing to large fractions of the sediment budget of catchments and river basins. The erosion rates of these areas can exceed 100 t ha−1 y−1, leading to significant environmental and economic impacts. This research aims to assess badland susceptibility and the relevance of its governing factors at different spatial scales using the well-known machine learning approach random forest (RF). The Upper Llobregat River Basin (ULRB, approx. 500 km2) and Catalonia (approx. 32,000 km2) have been selected as study areas. Previous studies stated that the RF approach is successful at making predictions for the same area where it has been trained, but the results of testing it in a different area remains unexplored. This work aims to evaluate the feasibility of upscaling to the large region of Catalonia a RF model trained in the small ULRB area. Two badland datasets of both small and large regions and a total of eleven governing factors have been used to determine the areas susceptible to badlands. Models performance has been analyzed through three different evaluation metrics: overall accuracy, kappa coefficient and area under receiver operating characteristic curve (AUC). The outcomes of this work confirmed that RF is a powerful tool for badland susceptibility analysis, specially when predictions are made in the same scale and spatial context where the model has been trained. Upscaling a RF model defined in the ULRB to the large area of Catalonia has been possible, but improved results have been obtained when the training of the models has directly been performed in the large region. Our final RF modelling results have facilitated the development of a large scale (32,000 km2) Badland Susceptibility Map for the full extension of Catalonia with a predictive overall accuracy of 97%, which strongly emphasizes lithology and Normalized Difference Vegetation Index (NDVI) as the main conditioning factors of badland distribution.

Arbuscular mycorrhizal fungi reduce N2O emissions from degraded residue patches

Nitrous oxide (N2O) is a potent greenhouse gas, and agricultural soils represent a major anthropogenic source. Crop residues provide nutrients for plants but also act as hotspots of N2O production. The hyphae of arbuscular mycorrhizal fungi (AMF) could proliferate in organic patches, utilize released N from the organic patches, and potentially mitigate N2O emissions. However, the effect of AMF on N2O emissions in degraded residue patches and the possible microbial mechanism remain uncertain. Here, a mesocosm experiment was conducted to investigate the impact of AMF (Funneliformis mosseae) inoculation on N2O emissions, availabilities of carbon and nitrogen, extracellular enzyme activities, and the abundance of key N-cycling genes in degraded residue patches. Our results showed that AMF hyphae significantly reduced N2O emissions from degraded residue patches. Quantitative PCR analysis of key functional genes involved in N2O production (amoA, nirK, nirS) and consumption (nosZ) showed that AMF significantly reduced the abundance of the bacterial amoA and nirS genes. NH4+, NO3−, total dissolved nitrogen (TDN), total nitrogen (TN), and dissolved organic carbon (DOC) contents decreased drastically in the presence of AMF. In addition, the activities of all tested extracellular enzymes were significantly decreased by AMF and positively correlated with DOC content. Multiple stepwise regression analysis demonstrated that the abundance of the nirS gene primarily influenced N2O emissions and was positively correlated with DOC content in degraded residue patches. Our findings indicate that AMF suppressed N2O producers, particularly nirS-type denitrifiers, by slowing down the release of C and N from degraded residues, thereby leading to a cascade effect on the decrease of N2O emissions. This study provides a promising approach to mitigate N2O emissions by enhancing AMF in the agroecosystems.

Deconstruction of tropospheric chemical reactivity using aircraft measurements: the Atmospheric Tomography Mission (ATom) data

Abstract. The NASA Atmospheric Tomography Mission (ATom) completed four seasonal deployments (August 2016, February 2017, October 2017, May 2018), each with regular 0.2–12 km profiling by transecting the remote Pacific Ocean and Atlantic Ocean basins. Additional data were also acquired for the Southern Ocean, the Arctic basin, and two flights over Antarctica. ATom in situ measurements provide a near-complete chemical characterization of the ∼ 140 000 10 s (80 m by 2 km) air parcels measured along the flight path. This paper presents the Modeling Data Stream (MDS), a continuous gap-filled record of the 10 s parcels containing the chemical species needed to initialize a gas-phase chemistry model for the budgets of tropospheric ozone and methane. Global 3D models have been used to calculate the Reactivity Data Stream (RDS), which is comprised of the chemical reactivities (production and loss) for methane, ozone, and carbon monoxide, through 24 h integration of the 10 s parcels. These parcels accurately sample tropospheric heterogeneity and allow us to partially deconstruct the spatial scales and variability that define tropospheric chemistry from composition to reactions. This paper provides a first look at and analysis of the up-to-date MDS and RDS data including all four deployments (Prather et al., 2023, https://doi.org/10.7280/D1B12H). ATom's regular profiling of the ocean basins allows for weighted averages to build probability densities for the key species and reactivities presented here. These statistics provide climatological metrics for global chemistry models, e.g., the large-scale pattern of ozone and methane loss in the lower troposphere and the more sporadic hotspots of ozone production in the upper troposphere. The profiling curtains of reactivity also identify meteorologically variable and hence deployment-specific hotspots of photochemical activity. Added calculations of the sensitivities of the production and loss terms relative to each species emphasize the few dominant species that control the ozone and methane budgets and whose statistical patterns should be key model–measurement metrics. From the sensitivities, we also derive linearized lifetimes of ozone and methane on a parcel-by-parcel basis and average over the basins, providing an observational basis for these previously model-only diagnostics. We had found that most model differences in the ozone and methane budgets are caused by the models calculating different climatologies for the key species such as O3, CO, H2O, NOx, CH4, and T, and thus these ATom measurements make a substantial contribution to the understanding of model differences and even identifying model errors in global tropospheric chemistry.

Understanding ozone episodes during the TRACER-AQ campaign in Houston, Texas: The role of transport and ozone production sensitivity to precursors

This study investigated transport pathways and photochemical formation responsible for ozone exceedances during the September 2021 deployment of the Tracking Aerosol Convection Interactions ExpeRiment/Air Quality (TRACER-AQ) campaign in Houston, Texas. We focused on two ozone episodes, September 6th–September 11th (“Episode 1”) and September 23rd–September 26th (“Episode 2”), when the maximum daily eight-hour average (MDA8) ozone at surface monitors exceeded 70 ppbv. Long-range transport patterns of air masses during these episodes were from the central/northern US. High-resolution (4 km resolution) trajectory analysis with FLEXible PARTicle (FLEXPART) dispersion model revealed local recirculation of air masses and the accumulation of pollutants across Houston contribute to the ozone exceedances. Comprehensive Air Quality Model with extensions (CAMx) driven by 1.33-km resolution meteorology from the Weather Research and Forecast (WRF) tool simulated elevated ozone production rates during ozone episodes across the Houston metropolitan area, with ozone production hotspots mostly over Houston city and industrial districts of the Houston Ship Channel (HSC). The regional increase in ozone production rates was due to the transport of VOC-rich air masses (via northerly flows) that brought ozone precursors to the region, which ultimately caused a transition in the ozone formation tendency from generally VOC-limited to NOx-limited conditions. However, the city of Houston and the HSC remained in a VOC-limited regime because of local NOx emissions that, to some extent, preponderated the impact of transported VOCs. While approximately 37 % of the elevated ozone production was attributed to local photochemistry, the remaining ∼63 % increase in ozone production was due to the transported ozone to the region during episodes, bringing ozone to the Houston region and contributing to ozone exceedances. The outcomes of this study illustrated the synergy between transport and ozone production, both long-range and local scale, which resulted in ozone exceedances in Houston.

Holistic and integrated life cycle sustainability assessment of prospective biomass to liquid production in Germany

As a part of the developing bioeconomy, liquid biofuels may play an important role for transportation due to the hope for a sustainable drop-in alternative to substitute fossil fuels and maintaining existing economic infrastructures. In this case study we applied Holistic and Integrated Life Cycle Sustainability Assessment to a prospective technical concept for the production of biofuels from wood residues, sorghum and straw via gasification and Fischer-Tropsch synthesis located in the German federal state Brandenburg. Through this quantitative and qualitative sustainability assessment we identified synergies and hot-spots of biofuel production on a detailed and aggregated level, as well as compare the impacts to fossil fuels and other alternative transport systems. 99 social, ecological and economic indicator results addressing 14 out of 17 SDGs show contributions but also sustainability risks of such biofuels for the SDGs. The total substitution factor of impacts (f = 21.38) for all indicators of biofuels compared to fossil fuels indicates significantly higher impacts of biofuels production, in particular for land (SDG 15, f = 30.43), water (SDG 14, f = 125.57), consumption and production patterns (SDG 12, f = 54.11), low energy efficiency and maintaining problematic global supply chains and working conditions. However, the impacts on climate can be lower (SDG 13, f = 0.42), if residual heat is effectively and efficiently used. Comparing the transportation systems and use phases of fuels, all types of car-based individual transportation including fossil fuels (f = 6.50), biofuels (f = 9.16) and electric drive (f = 6.46) had significant higher impacts than transportation by train. Besides technological downsides, such as the high energy demand, biofuels may play a minor role for specific applications with no other alternative energy technologies in the future. In conclusion, it is very questionable whether such liquid biofuels are a suitable drop-in solution to substitute fossil fuels in a significant quantity. In a final discussion we referred to the necessary societal-ecological transformation with structural changes of production, consumption, political economy and global supply chains. In the future, Holistic and Integrated Life Cycle Sustainability Assessment will be further improved by closing indicator and database gaps, including a cost analysis and direct stakeholder participation, as well as absolute sustainability assessments on how much biofuel production is sustainable.

Plastispheres as hotspots of microbially-driven methylmercury production in paddy soils

Microplastics (MPs) as emerging contaminants have accumulated extensively in agricultural ecosystems and are known to exert important effects on biogeochemical processes. However, how MPs in paddy soils influence the conversion of mercury (Hg) to neurotoxic methylmercury (MeHg) remains poorly understood. Here, we evaluated the effects of MPs on Hg methylation and associated microbial communities in microcosms using two typical paddy soils in China (i.e., yellow and red soils). Results showed that the addition of MPs significantly increased MeHg production in both soils, which could be related to higher Hg methylation potential in the plastisphere than in the bulk soil. We found significant divergences in the community composition of Hg methylators between the plastisphere and the bulk soil. In addition, the plastisphere had higher proportions of Geobacterales in the yellow soil and Methanomicrobia in the red soil compared with the bulk soil, respectively; and plastisphere also had more densely connected microbial groups between non-Hg methylators and Hg methylators. These microbiota in the plastisphere are different from those in the bulk soil, which could partially account for their distinct MeHg production ability. Our findings suggest plastisphere as a unique biotope for MeHg production and provide new insights into the environment risks of MP accumulation in agricultural soils.

Sources and pathways of halomethoxybenzenes in northern Baltic estuaries

IntroductionThousands of halogenated natural products (HNPs) are generated in the ocean and on land. A subset of these, halomethoxybenzenes (HMBs), are released from both natural and anthropogenic sources. Here we consider: 1. Brominated anisoles (BAs), transformation products of bromophenols. 2. Drosophilin A methyl ether (DAME: 1,2,4,5-tetrachloro-3,6-dimethoxybenzene), a secondary metabolite of terrestrial fungi. 3. Tetrachloroveratrole (TeCV: 1,2,3,4-tetrachloro-5,6-dimethoxybenzene), a lignin byproduct found in bleached kraft mill effluent. 4. Pentachloroanisole (PeCA), a metabolite of the wood preservative pentachlorophenol.MethodsWe examined several ecosystem compartments to determine sources and exchange processes for these HMBs: air, precipitation, rivers, forest fungi and litter, and water from northern Baltic estuaries and offshore. Samples were analyzed for HMBs by capillary gas chromatography – quadrupole mass spectrometry.Results and discussionAll four types of HMBs were found in air, and BAs, DAME and TeCV were also present in precipitation. BAs and DAME were common in rivers and estuaries, whereas TeCV was low and PeCA was below detection. DAME was identified in several species of fungi and in forest litter; TeCV was occasionally present, but BAs and PeCA were below detection. Concentrations of BAs were higher in estuaries than in rivers or offshore waters, showing that estuaries are hot spots for production. BAs were negatively or not correlated with chlorophyll-a, suggesting contribution by heterotrophic bacteria as well as known production by phytoplankton and macroalgae. DAME was negatively or not correlated with BAs and did not appear to be produced in the estuaries; fungi and forest litter containing fungal mycelia are suggested as sources. HMBs volatilize from sea and land, disperse through the atmosphere, and return via precipitation and rivers. Production and biogeochemical cycles are influenced by climate change and we suggest BAs and DAME for following partitioning and exchange processes.

Whale shark abundance forecast: The interannual hotspot effect

Abstract Each year, whale sharks (Rhincodon typus) aggregate in the northern Gulf of California at Bahia de los Angeles, a small coastal village that recently developed whale shark swimming as economic activity during the summer and autumn. Since the number of animals using the bay fluctuates annually, we aimed to predict it 1 month before each whale shark season. We based our modelling approach on the hypothesis that interannual warming conditions would spatially restrict whale shark habitats, triggering larger aggregations in areas that remain productive. We photo‐identified whale sharks while surface feeding in Bahia de los Angeles during a 13‐year period, which allowed us to estimate a local abundance index per year through mark–recapture techniques. Then, we fitted these abundances as a function of several competing model structures, based on means of sea surface temperature and chlorophyll‐a, as well as their interannual anomalies from the linear trend, during spring, within the best‐known range of the species in the northern Gulf of California. The results of the ecological model showed that whale sharks visit Bahia de los Angeles in larger numbers during extreme warming conditions, with relatively high surface chlorophyll‐a concentrations, which was especially evident during the 2014–2016 northeast Pacific Marine Heatwave and El Niño. Presumably, the overall reduction in surface productivity associated with these events forced whale sharks to restrict their summer–autumn habitat to productivity hotspots, including Bahia de los Angeles. Our model allowed us to predict the number of animals visiting the site before each season starts, which has crucial proactive management implications, such as allowing authorities to regulate the ecotourism effort dynamically to reduce the probability of ship strikes and/or excessive stress to the animals. We propose an abundance baseline from the prediction for neutral interannual conditions. Synthesis and applications. We recommend local authorities apply the model described in this study during the late spring of each year to obtain predictions of the upcoming whale shark abundance and establish the maximum ecotourism effort allowed accordingly.