Vulnerable Ecosystems Research Articles

Functional diversity and metabolic response in benthic communities along an ocean acidification gradient

Altered ocean chemistry caused by ocean acidification (OA) is expected to have negative repercussions at different levels of the ecological hierarchy, starting from the individual and scaling up to the community and ultimately to the ecosystem level. Understanding the effects of OA on benthic organisms is of primary importance given their relevant ecological role in maintaining marine ecosystem functioning. The use of functional traits represents an effective technique to investigate how species adapt to altered environmental conditions and can be used to predict changes in the resilience of communities faced with stresses associated with climate change. Artificial supports were deployed for 1-y along a natural pH gradient in the shallow hydrothermal systems of the Bottaro crater near Panarea (Aeolian Archipelago, southern Tyrrhenian Sea), to explore changes in functional traits and metabolic rates of benthic communities and the repercussions in terms of functional diversity. Changes in community composition due to OA were accompanied by modifications in functional diversity. Altered conditions led to higher oxygen consumption in the acidified site and the selection of species with the functional traits needed to withstand OA. Calcification rate and reproduction were found to be the traits most affected by pH variations. A reduction in a community's functional evenness could potentially reduce its resilience to further environmental or anthropogenic stressors. These findings highlight the ability of the ecosystem to respond to climate change and provide insights into the modifications that can be expected given the predicted future pCO2 scenarios. Understanding the impact of climate change on functional diversity and thus on community functioning and stability is crucial if we are to predict changes in ecosystem vulnerability, especially in a context where OA occurs in combination with other environmental changes and anthropogenic stressors.

Community science for assessing the vulnerability of freshwater ecosystems: Water quality monitoring, restoration, and outreach by young naturalists in Nova Scotia, Canada.

Community science models that complement formal scientific investigations are valuable tools for addressing gaps in knowledge and engaging the community. Freshwater quality monitoring and vulnerability assessment, for example, are essential for conserving freshwater ecosystems, but often suffer from limited resources. While municipal programs focus on priority areas, community-based models can improve overall coverage both spatially and temporally. As an example of how community science initiatives centered on freshwater ecosystems enhance monitoring capacity, we present the case of the Young Naturalists Club (YNC) in Nova Scotia, Canada. The YNC's Nature Guardians program involves youth aged 10-14 in water monitoring, restoration, and outreach activities within Shubie Park, in Dartmouth, Nova Scotia. Between 2018 and 2021 the Nature Guardians collected water monitoring data at multiple park locations, and shared findings with city authorities and the Atlantic Water Network. In response to high bacteria counts, and concerns over nutrient influxes, the group's 2021-2023 restoration efforts have aimed to improve water quality, focusing on native plantings and outreach signage. This type of community-based monitoring offers several advantages, including local site selection based on community concerns, the potential for low-cost long-term monitoring, and community engagement. While a community-based monitoring model presents certain challenges including data standardization and verification, it offers a broader reach and can produce high-quality data when appropriate protocols are followed. This case underscores the potential of a community-based water quality monitoring approach and highlights the potential for community science to augment existing assessment structures, ultimately contributing to more resilient and sustainable freshwater ecosystems.

Drivers of Gully Erosion and its Socio-economic and Environmental Effects in a Tropical Semi-arid Environment

Gully erosion is a form of severe land degradation, which is more pronounced in semi-arid and arid environments due to their vulnerable ecosystems. Establishing the causes and effects of gully erosion is therefore fundamental in policy formulation and resource allocation for up-scaling context-specific gully mitigation and rehabilitation measures. Thus, this study aimed at assessing the causes and effects of gully erosion in semi-arid region, in the North-West part of Kenya. A cross-sectional survey, field measurements, laboratory analysis, focus group discussions and key informants’ interviews were used to collect data on drivers and effects of gully erosion. Descriptive statistics and content analysis were used to analyze the data. From the findings, 60 % of the respondents reported deforestation as the main driver of gully erosion. Further, 37 and 34 % of the respondents reported surface runoff and steep slopes, respectively, as major drivers of gully erosion. Soils in the region had a high dispersion ratio, with values of between 0.3 and 0.9, making them highly erodible. About 66 and 55 % of the respondents reported that the major effects of gully erosion were reduction in arable land size and death of livestock due to fatal falls, respectively. Approximately 14 ha of arable land and 1,483,600 Mg of sediment have been lost to gully erosion at the rate of about 2,410 Mg ha-1 over a period of 45 years. The average growth rate and density of gullies in the study site stood at 154 Mg ha-1 yr-1 and 0.7 km km-2, respectively. Four people and about 100 cattle had died due to fatal falls into the deep gullies. Thus, there is an urgent need to rehabilitate existing gullies while mitigating occurrence of new gullies in the study area. This would convert existing badlands into hotspots of biodiversity.

Temperature regime of the cold period in the Arctic zone of Yakutia for 1960–2022

Changes in the Arctic have global consequences. An increase in air temperature and a change in the cold period can affect vulnerable ecosystems with a permafrost lithogenic base in the Yakutia Arctic region. In this study, we specified the dates of the beginning and end of the cold period in spring and autumn for two multi-year periods (1961–1990 and 1991–2022) of the northwestern and northeastern parts of the Arctic zone in Yakutia. We calculated the temperature difference and rate of change (C°/10 years) for 1960–2022. We used meteorological series according to the “RIHMI-WDC” data: st. Olenek (Oleneksky ulus), st. Zhigansk (Zhigansky) st. Chokurdakh (Allaikhovsky) and st. Srednekolymsk (Srednekolymsky). For the period 1991–2022 in the northwestern part of the Arctic zone in Yakutia, a reduction in the cold period was observed due to an earlier onset in spring (May: 4 days at Olenek station and 6 days at Zhigansk station) and in the northeastern part-later autumn (September: 3 days at Chokurdakh and Srednekolymsk stations). The results of our study indicate that in April, the difference in the average air temperature between 1961 and 1990 and 1991–2022 at all stations is higher than in October. The only exception is the information obtained according to st. Chokurdakh (October–2.6°C, April–2.1°C). The rate of change in air temperature (°С/10 years) for the period 1960–2022 at the beginning of the cold period (October), it manifested itself to a greater extent in the northeast of Yakutia (Srednekolymsk station – 0.7 °C/10 years, Chokurdakh –°C/10 years). In the middle (January – 1.1 °С/10 years) and the end (April – 1.0 °С/10 years) of the cold period, the maximum rate of air temperature change was noted in the north-west of Yakutia according to the data of st. Olenek.This study is necessary for the verification and selection of representative climate models, the analysis of the spatiotemporal variability of the cold period, and the forecasting and contribution to the overall dispersion of soil temperature.

Mapping alien and native forest dynamics in Chile using Earth observation time series analysis

Chile is a global biodiversity hotspot and hosts a large proportion of the southern hemisphere’s temperate forests. The Chilean Valdivian temperate forest is a vulnerable ecosystem containing a highly ecologically valuable species assemblage. Productive forest plantations have involved deforestation of, and alien species introduction into, this ecosystem. This process has already severely impacted the western part of Chile (the Coastal Range) and is now occurring in the eastern part (the Andes), with forestry plantations promoted by government subsidies between 1974 and 2012. Archive Landsat satellite imagery classification and Google Earth Engine are used to assess land cover change over a 31-year period with a focus on alien species (Pinaceae and Eucalyptus spp.) spread and native (Nothofagus spp. and Araucaria araucana) deforestation. Results show a clear land cover pattern based on elevation: a higher altitude, relatively undisturbed area dominated by native forest (the Andes), and a lower altitude area where most human activity and related land covers are located (the valley area). The valley is highly dynamic because of constant land cover change due to forestry. Overall, Araucaria araucana cover has decreased over the study period, while Nothofagus spp. has remained relatively stable. Alien Pinaceae has decreased, while Eucalyptus spp. has remained stable. However, the results indicate that change analysis over long periods conceal dynamism. For example, Eucalyptus spp. sharply decreased between the 1980s and the 1990s and surged afterwards. Also, even though Nothofagus spp. cover dominates throughout the study period, change analysis shows a high degree of change in the valley area, indicating newly established Nothofagus spp. patches. Over the study period, long rotation Pinaceae plantations for timber have given way to shorter rotation forestry (alien Eucalyptus spp., native Nothofagus spp.) for pulp and local uses resulting from discontinuation of forest subsidies. In the absence of subsidies, only large-scale plantations can engage in long rotation forestry, as smallholders need the more stable income provided by shorter rotation forestry. Although higher elevations (the Andes) are dominated by native forest, several abandoned alien forest plantations may be the source of biological invasion. In addition, native forest degradation as a result of Araucaria araucana loss and shrub encroachment is occurring. Earth observation methods are key for forest and alien species monitoring and landscape management. They can enhance traditional, ground-based forest surveys and provide continuous and even retrospective monitoring of forest change thanks to the wide availability of current and historical satellite data.

Climate and soil stressed elevation patterns of plant species to determine the aboveground biomass distributions in a valley-type Savanna.

Extreme environments such as prolonged high temperatures and droughts can cause vulnerability of vegetation ecosystems. The dry-hot valleys of Southwestern China, known for their extremely high annual temperature, lack of water, and unique non-zonal "hot island" habitat in the global temperate zone, provide exceptional sites for studying how plant adapts to the prolonged dry and hot environment. However, the specific local biotic-environment relationships in these regions remain incompletely elucidated. The study aims to evaluate how valley-type Savanna vegetation species and their communities adapt to long-term drought and high-temperature stress environments. The study investigated the changes in species diversity and communities' aboveground biomass of a valley-type Savanna vegetation along an elevation gradient of Yuanmou dry-hot valley in Jinsha River basin, southwest China. Subsequently, a general linear model was utilized to simulate the distribution pattern of species diversities and their constituent biomass along theelevation gradient. Finally, the RDA and VPH mothed were used to evaluate the impacts and contributions of environmental factors or variables on the patterns. The field survey reveals an altitudinal gradient effect on the valley-type Savanna, with a dominant species of shrubs and herbs plants distribution below an elevation of 1700m, and a significant positive relationship between the SR, Shannon-Wiener, Simpson, and Pielou indices and altitudes. Relatively, the community aboveground biomass did not increase significantly with elevation, which was mainly due to a decreased biomass of herbaceous plants along the elevation. Different regulators of shrub-herbaceous plant species and their functional groups made different elevation patterns of species diversity and aboveground biomass in valley-type Savannas. Herbaceous plants are responsible for maintaining species diversity and ensuring stability in the aboveground biomass of the vegetation. However, the influence of shrubs on aboveground biomass became more pronounced as environmental conditions varied along the altitudinal gradient. Furthermore, species diversity was mainly influenced by soil and climatic environmental factors, whereas community biomass was mainly regulated by plant species or functional groups. The study demonstrates that the spatial pattern of valley-type Savanna was formed as a result of different environmental responses and the productive capacity of retained plant species or functional groups to climate-soil factors, highlighting the value of the Yuanmou dry-hot Valley as a microcosm for exploring the intricate interactions between vegetation evolution and changes in environmental factors.

Urea fertilization increased CO2 and CH4 emissions by enhancing C-cycling genes in semi-arid grasslands

Global climate change is predicted to increase exogenous N input into terrestrial ecosystems, leading to significant changes in soil C-cycling. However, it remains largely unknown how these changes affect soil C-cycling, especially in semi-arid grasslands, which are one of the most vulnerable ecosystems. Here, based on a 3-year field study involving N additions (0, 25, 50, and 100 kg ha−1 yr−1 of urea) in a semi-arid grassland on the Loess Plateau, we investigated the impact of urea fertilization on plant characteristics, soil properties, CO2 and CH4 emissions, and microbial C cycling genes. The compositions of genes involved in C cycling, including C fixation, degradation, methanogenesis, and methane oxidation, were determined using metagenomics analysis. We found that N enrichment increased both above- and belowground biomasses and soil organic C content, but this positive effect was weakened when excessive N was input (N100). N enrichment also altered the C-cycling processes by modifying C-cycle-related genes, specifically stimulating the Calvin cycle C-fixation process, which led to an increase in the relative abundance of cbbS, prkB, and cbbL genes. However, it had no significant effect on the Reductive citrate cycle and 3-hydroxypropionate bi-cycle. N enrichment led to higher soil CO2 and CH4 emissions compared to treatments without added N. This increase showed significant correlations with C degradation genes (bglA, per, and lpo), methanogenesis genes (mch, ftr, and mcr), methane oxidation genes (pmoA, pmoB, and pmoC), and the abundance of microbial taxa harboring these genes. Microbial C-cycling genes were primarily influenced by N-induced changes in soil properties. Specifically, reduced soil pH largely explained the alterations in methane metabolism, while elevated available N levels were mainly responsible for the shift in C fixation and C degradation genes. Our results suggest that soil N enrichment enhances microbial C-cycling processes and soil CO2 and CH4 emissions in semi-arid ecosystems, which contributes to more accurate predictions of ecosystem C-cycling under future climate change.

Responses of phenology to preseason drought and soil temperature for different land cover types on the Mongolian Plateau

Drought and heat caused major disturbance in nature by interfering with plant phenology, and can also alter the vulnerability and resilience of terrestrial ecosystems. Existing research on the Mongolian Plateau has primarily focused on studying the response of the start (SOS) and end (EOS) of the growing season to drought and heat variations. However, there is still a lack of comprehensive understanding regarding the coupled effects of drought and heat on phenology across different land cover types. In this study, we retrieved SOS and EOS based on 34-year (1982–2015) normalized difference vegetation index (NDVI) dataset from Global Inventory Modeling and Mapping Studies (GIMMS). Results showed that grasslands and the Gobi-Desert show rapid advancement in SOS, and forests presented the slowest advancement in SOS, but SOS in croplands were delayed. EOS across four land cover types advanced, with the Gobi-Desert showed the highest rate of advancement and forests the lowest. Using the Palmer Drought Severity Index (PDSI) and soil temperature as the indicators of drought and thermal conditions, the responses of SOS and EOS to these two climate variables were evaluated. The advanced SOS driven by lower drought severity was detected in forests, grasslands, croplands and the Gobi-Desert. The dominant response of EOS to drought severity was positive in croplands, grasslands and forests, except for the Gobi-Desert, where drought severity had negative effects on EOS. Compared with the daily average soil temperature (STmean), the daily maximum soil temperature (STmax, daytime), and the daily minimum soil temperature (STmin, nighttime), the daily diurnal soil temperature range (DSTR, where DSTR = STmax − STmin) between night and day were the most suitable indicators for assessing the response of SOS and EOS to soil temperature. Strong negative correlation between SOS and the preseason DSTR was pronounced in all land cover types on the Mongolian Plateau. However, EOS was negatively correlated with the preseason DSTR only in the Gobi-Desert. Last but not least, normalized sensitivity assessments reveal that the negative impacts of DSTR on SOS and EOS were the main controlling factors on the Mongolian Plateau phenology, followed by the couple negative effects of drought severity and DSTR.

Smallholder farmers' vulnerability to climate change and variability: Evidence from three agroecologies in the Upper Blue Nile, Ethiopia

This study delves into the profound impact of climate change on agriculture in Ethiopia, particularly the vulnerabilities faced by smallholder farmers and the resulting implications for poverty. Focusing on three distinct agroecologies, namely: highland, midland, and lowland zones. The study employed a robust methodology, combining a cross-sectional survey, spatial-temporal trend analysis using GIS, and the development of an overall vulnerability index through the balanced weighted average method. The study, encompassing 646 households, combines data from a variety of sources and analytical tools like the vulnerability index, ArcGIS 10.8, and ERDA's IMAGINE 2015. Utilizing the LVI-IPCC scale, the study shows that climate change is an immediate vulnerability in all agroecological zones. It identifies highland areas as the most sensitive and exposed regions, while lowland households are found to be the most vulnerable in terms of overall vulnerabilities. The research reveals specific challenges faced by communities, such as inadequate health facilities and insufficient food and water supplies in both highland and lowland agroecosystems. Additionally, our investigation has observed a significant alteration in land use practices, specifically the shift from communal grazing land to private cultivation and plantations, emphasizing eucalyptus. This alteration enhances the ecosystem's vulnerability to climate disturbances. The study suggests targeted interventions, such as advocating for sustainable land-use practices, afforestation, and adopting climate-smart agriculture practices. It is important to implement policy measures that prioritize conserving and restoring shrubland, grazing land, and natural forests to ensure both long-term socio-economic and ecosystem resilience. The study's nuanced insights are instrumental in understanding the diverse challenges posed by climate change in Ethiopian agriculture, supporting informed policymaking and sustainable interventions.

Investigating the Long-Term Effects of Climate Change on Specific Vulnerable Ecosystem Such as Coral Reefs

Investigating the Long-Term Effects of Climate Change on Specific Vulnerable Ecosystem Such as Coral Reefs

Linking ecosystem pressures and marine macroinvertebrate ecosystem services in mangroves and seagrasses

African coastal ecosystems encompass high biodiversity that provides crucial ecosystem services (ES). However, the supply of these ES is threatened due to ecosystem degradation, which threatens human well-being and livelihoods. This study investigated the link between pressures and the ES provided by marine macroinvertebrates (MMIs) in mangroves and seagrasses. We assessed ecosystem condition (marine protected areas, MPAs), pressures, namely climate change (sea surface temperature and sea level), land-use and land-cover changes, overexploitation (mangrove deforestation and overfishing), and core MMI ES (provisioning, regulation, cultural). Our results revealed a low ratio of MPAs compared to the Aichi Target 11, emphasizing the need for a comprehensive conservation strategy. Sea temperature and level showed an increasing trend, indicating the vulnerability of coastal ecosystems to climate change. The decline in mangrove forest cover highlights the need to mitigate adverse effects of land-use change. The increasing number of artisanal fishery licences suggests increased pressure on MMIs, which can have severe consequences for local communities. MMI food production, particularly shrimp, and recreational fishing increased in the last 2 decades. Regulation services and cultural services related to research and education varied through time due to the limited availability of data. This information was used to develop an exploratory conceptual model illustrating the complex relationships among pressures, condition, MMI ES, and management goals for the sustainable use of marine resources and their connection with food security. Our findings underscore the importance of preserving MMI populations and habitats while addressing knowledge gaps to enhance the resilience of coastal ecosystems.

Interacting effects of fire and hydroclimate on oak and beech community prevalence in the southern Great Lakes region

Abstract Rising temperatures, increasing hydroclimate variability and intensifying disturbance regimes increase the risk of rapid ecosystem conversions. We can leverage multi‐proxy records of past ecosystem transformations to understand their causes and ecosystem vulnerability to rapid change. Prior to Euro‐American settlement, northern Indiana was a mosaic of prairie, oak‐dominated forests/woodlands and beech‐dominated hardwood forests. This heterogeneity, combined with well‐documented but poorly understood past beech population declines, make this region ideal for studying the drivers of ecosystem transformations. Here, we present a new record from Story Lake, IN, with proxies for vegetation composition (pollen), fire (charcoal) and beech intrinsic water use efficiency (δ13C of beech pollen; δ13Cbeech). Multiple proxies from the same core enable clear establishment of lead–lag relationships. Additionally, δ13Cbeech enables direct comparisons between beech population abundance and physiological responses to changing environments. We compare Story Lake to a nearby lake‐level reconstruction and to pollen records from nearby Pretty and Appleman Lakes and the distal Spicer Lake, to test hypotheses about synchrony and the spatial scale of governing processes. The 11.7 ka sediment record from Story Lake indicates multiple conversions between beech‐hardwood forest and oak forest/woodland. Beech pollen abundances rapidly increased between 7.5 and 7.1 ka, while oak declined. Oak abundances increased after 4.6 ka and remained high until 2.8 ka, indicating replacement of mesic forests by oak forest/woodland. At 2.8 ka, beech abundances rapidly increased, indicating mesic forest reestablishment. Beech and oak abundances correlate with charcoal accumulation rates but beech abundance is not correlated with δ13Cbeech. Fluctuations in beech abundances are synchronous among Story, Appleman and Pretty Lakes, but asynchronous between Story and Spicer Lakes, suggesting regulation by local‐scale vegetation‐fire‐climate feedbacks and secondarily by regional‐scale drivers. Holocene forest composition and fire dynamics appear to be closely co‐regulated and may be affected by local to regional climate variations. The importance of extrinsic drivers and positive/negative feedbacks changes over time, with higher ecoclimate sensitivity before 2.8 ka and greater resilience afterwards. Synthesis: Overall, oak‐ and beech‐dominated ecosystems were highly dynamic over the Holocene, with multiple ecosystem conversions driven by shifting interactions among vegetation, hydroclimate and fire regime.

Early warning signals of grassland ecosystem degradation: A case study from the northeast Qinghai-Tibetan Plateau

As a typical vulnerable ecosystem, alpine steppes can be subject to nonlinear accelerations in degradation, once tipping points are reached or exceeded, and thus far more effort and investment will be needed, to reverse the degraded status of such ecosystems, if effective preventive measures or interventions are not adopted sufficiently early. Thus, detecting early warning signals of tipping events is extremely important for ecosystem protection and recovery, but remains highly challenging. For alpine steppes, coverage or biomass loss and species invasion are both key transitions. Using multi-source data, including ground surveys and remote sensing images with different resolutions, we tried to screen and identify potential early-warning signals for alpine grassland degradation events and analyze their efficacy. The results showed that the degradation levels derived from spatial heterogeneity information combined with a vegetation index were reliable, as was verified by ground surveys, and could illustrate the degradation process of a grassland ecosystem. Six common early-warning signals (variance, skewness, and autocorrelation, from both the spatial and temporal domains) were tested according to degradation degree, and spatial autocorrelation and temporal autocorrelation had the best performances, as they could indicate different degradation levels, and the change trends of temporal autocorrelation could provide early-warning functions. A waved change of spatial variance could reflect a vegetation growth dynamic that might indicate species invasion. In this study, the threshold values of spatial and temporal autocorrelation were 0.7 and 0.2, respectively, and from these, the thresholds of vegetation coverage and biomass were then obtained. However, these signals and thresholds had some limitations during application. These findings provide insights into better understanding of the alpine grassland degradation process, and contribute to a better management approach for vulnerable ecosystems using early-warning methods.

Non-native ants are breaking down biogeographic boundaries and homogenizing community assemblages

As geographic distance increases, species assemblages become more distinct, defining global biogeographic realms with abrupt biogeographic boundaries. Yet, it remains largely unknown to what extent these realms may change because of human-mediated dispersal of species. Focusing on the distributions of 309 non-native ant species, we show that historical biogeographic patterns have already broken down into tropical versus non-tropical regions. Importantly, we demonstrate that these profound changes are not limited to the distribution patterns of non-native ants but fundamentally alter biogeographic boundaries of all ant biodiversity (13,774 species). In total, 52% of ant assemblages have become more similar, supporting a global trend of biotic homogenization. Strikingly, this trend was strongest on islands and in the tropics, which harbor some of the most vulnerable ecosystems. Overall, we show that the pervasive anthropogenic impacts on biodiversity override biogeographic patterns resulting from millions of years of evolution, and disproportionally affect particular regions.

Deterministic assembly of grassland soil microbial communities driven by climate warming amplifies soil carbon loss

Perturbations in soil microbial communities caused by climate warming are expected to have a strong impact on biodiversity and future climate–carbon (C) feedback, especially in vulnerable habitats that are highly sensitive to environmental change. Here, we investigate the impact of four-year experimental warming on soil microbes and C cycling in the Loess Hilly Region of China. The results showed that warming led to soil C loss, mainly from labile C, and this C loss is associated with microbial response. Warming significantly decreased soil bacterial diversity and altered its community structure, especially increasing the abundance of heat-tolerant microorganisms, but had no effect on fungi. Warming also significantly increased the relative importance of homogeneous selection and decreased “drift” of bacterial and fungal communities. Moreover, warming decreased bacterial network stability but increased fungal network stability. Notably, the magnitude of soil C loss was significantly and positively correlated with differences in bacterial community characteristics under ambient and warming conditions, including diversity, composition, network stability, and community assembly. This result suggests that microbial responses to warming may amplify soil C loss. Combined, these results provide insights into soil microbial responses and C feedback in vulnerable ecosystems under climate warming scenarios.

Nitrogen loss in coastal sediments driven by anaerobic ammonium oxidation coupled to microbial reduction of Mn(IV)-oxide

Coastal sediments play a central role in regulating the amount of land-derived reactive nitrogen (Nr) entering the ocean, and their importance becomes crucial in vulnerable ecosystems threatened by anthropogenic activities. Sedimentary denitrification has been identified as the main sink of Nr in marine environments, while anaerobic ammonium oxidation with nitrite (anammox) has also been pointed out as a key player in controlling the nitrogen pool in these locations. Collected evidence in the present work indicates that the microbial biota in coastal sediments from Baja California (northwestern Mexico) has the potential to drive anaerobic ammonium oxidation linked to Mn(IV) reduction (manganammox). Unamended sediment showed ammonification, but addition of vernadite (δMnO2 with nano-crystal size ∼15 Å) as terminal electron acceptor fueled simultaneous ammonium oxidation (up to ∼400 μM of ammonium removed) and production of Mn(II) with a ratio ∆[Mn(II)]/∆[NH4+] of 1.8, which is very close to the stoichiometric value of manganammox (1.5). Additional incubations spiked with external ammonium also showed concomitant ammonium oxidation and Mn(II) production, accounting for ∼30 % of the oxidized ammonium. Tracer analysis revealed that the nitrogen loss associated with manganammox was 4.2 ± 0.4 μg 30N2/g-day, which is 17-fold higher than that related to the feammox process (anaerobic ammonium oxidation linked to Fe(III) reduction, 0.24 ± 0.02 μg 30N2/g-day). Taxonomic characterization based on 16S rRNA gene sequencing revealed the existence of several clades belonging to Desulfobacterota as potential microorganisms catalyzing the manganammox process. These findings suggest that manganammox has the potential to be an additional Nr sink in coastal environments, whose contribution to total Nr losses remains to be evaluated.

Towards invasion ecology for subterranean ecosystems

Invasive alien species (IAS) are widely recognized as a major threat to ecosystems globally. Despite the growing interest and research effort on biological invasions, the impact of IAS on both terrestrial and aquatic subterranean habitats remains considerably under-studied in comparison to other environments. The Convention on Biological Diversity (CBD) has established global targets to mitigate the impacts of IAS, emphasizing the need for countries, organizations, and the scientific community to identify gaps in knowledge, monitoring, and management strategies for IAS. To this end, we mapped knowledge gaps in biological invasions of subterranean habitats that emerged from the first systematic surveys of the available information. We suggest that there are five main gaps restricting our ability to understand and tackle biological invasions in subterranean ecosystems. Given the vulnerability of subterranean ecosystems and the lack of attention they have received in conservation policies, it is crucial to increase research emphasis on IAS. This opinion paper aims to stimulate such efforts and contribute to the preservation of these ecosystems.

Sustainable solid waste management challenges in hill cities of developing Countries: Insights from eastern Himalayan smart cities of Sikkim, India

Rapid urbanization and the growing tourism industry in the Himalayan region have raised significant concerns about the sustainable handling and management of solid waste in the area. This concern is particularly pronounced in the unique and vulnerable ecosystem of cities nestled in the eastern Indian Himalayas, where geography, ecology, and socio-economic factors converge to create distinctive challenges. This study undertakes a thorough investigation of solid waste management practices and challenges in two smart cities nestled in the eastern Himalayan region of India, specifically Gangtok and Namchi. The primary objective was to unveil the complex challenges confronting these cities by conducting an in-depth exploration of waste management practices. This comprehensive investigation was achieved through the collection of samples, conducting surveys within each ward of the cities, and performing physicochemical characterization analyses. The study also proposes a solution-oriented approach leveraging life cycle analysis. Despite the Himalayan backdrop, waste generation varies significantly, with Gangtok producing substantially more waste (50 tons per day (TPD)) compared to Namchi (4.6 TPD). Both cities excel in waste collection, but Gangtok leads in proactive treatment, with 22% (11 TPD) undergoing composting and recycling. However, shared challenges at riverside disposal sites, including overfilled dumpsites and leachate contamination, pose potential environmental hazards amid the Himalayan allure. Organic waste predominates at 40.9% and 40.01% in both cities, indicating composting potential. Plastic closely at 22.25% (Namchi) and 22.65% (Gangtok) was way above the global (12 %) and national (8.4 %) average respectively, emphasizing the urgency of plastic waste reduction strategy. The 16.95% cardboard in Gangtok highlights potential commerce-related waste. The study also highlights the importance of comprehensive policies for informal sector well-being. The lifecycle assessment of Namchi and Gangtok reveals significant methane emissions (99%) from waste anaerobic decomposition potentially due to poor source segregation. Implementing a futuristic waste strategy reduces emissions by 38% in Namchi and 40% in Gangtok, through biogas utilization and renewable energy adoption. The findings advocate for citizen engagement, improved collection, targeted campaigns, and circular economy principles. To ensure sustainability and resilience in waste management within mountain regions, tailored strategies such as material recycling facilities, community engagement initiatives, and landfill diversion mandates should integrate ecological, socioeconomic, and logistical considerations, fostering awareness and participation among communities.

GENETIC DISTANCE REVEALS SYNONYMY AND NEW FISH SPECIES IN BALIKESİR STREAMS, TÜRKİYE

The Mediterranean-Aegean region play a significant role in the context of conserving biodiversity. The protection of endemic and local species becomes attainable only with a thorough understanding of their biology. Specifically, aquatic species dwelling in inland waters may be more vulnerable due to the irregular composition of their habitats, characterized by natural barriers. It becomes imperative to initiate the conservation process by identifying the fauna and flora of ecosystems, thereby facilitating the development of comprehensive conservation plans. In this context, the primary objective of the present study is to identify freshwater fish species inhabiting Madra and Havran Streams in Balıkesir, Türkiye using the DNA barcoding method. The procedure involves DNA isolation through the Chelex protocol, followed by the amplification of the mitochondrial CO1 region using various primer combinations. The results obtained from the gene sequences of 29 individuals in total provide valuable information on species diversity, genetic relationships, and variations. This research emphasizes the importance of DNA barcoding as a valuable tool for species identification, genetic exploration, and conservation plans. The acquired outcomes establish a foundation for the effective management of aquatic biodiversity, particularly within these vulnerable ecosystems.

Carbon emissions, wastewater treatment and aquatic ecosystems

As a nexus of environmental pollution, fossil fuel consumption and the global warming, carbon emissions are critical in China's long-term environmental strategies. In the water cycle, carbon is released during wastewater discharge, wastewater treatment, and subsequent changes in aquatic ecosystems. To gain a comprehensive understanding of this entire process, we investigate the intricate connections using balanced panel data from 261 prefecture-level cities in China spanning the period from 2000 to 2020. Each sample is quantified using 48 features derived from hydrosphere, biosphere, anthroposphere, atmosphere, pedosphere and lithosphere. This paper contributes to the relevant studies in the following ways: Firstly, to analyze the basic interaction within the water cycle, we utilize Structural Equation Modeling (SEM). Our results indicate a weak linear relationship between wastewater treatment and carbon emissions. We also substantiate the crucial role of the aquatic ecosystems in carbon fixation. Secondly, in order to comprehend the intricate interactions within the Earth system, we employ eight machine learning models to predict carbon emissions. We observe that extremely randomized trees (ET) exhibit the highest predictive accuracy among these models. Thirdly, in interpreting the ET model, we utilize Explainable artificial intelligence (XAI) techniques, including Shapley Additive Explanations (SHAP) and Accumulated Local Effects (ALE). Our 3D-SHAP analysis reveals heterogeneity in the emission effects of wastewater treatment across different sub-groups, indicating that emissions are especially sensitive to increased wastewater treatment in agricultural and tourism cities. Furthermore, 3D-SHAP analysis of the aquatic ecosystems exhibits a series of spikes, signifying that aquatic plants will abruptly lose their carbon storage ability once the degradation of the aquatic ecosystems exceeds a certain threshold. Finally, our ALE evaluation, depicting the dispersion tendency of feature importance, identifies the uncertainty of wastewater carbon release in agricultural and tourism cities, while also affirming the vulnerability of the aquatic ecosystems.