Global Change Scenarios Research Articles

Vulnerability assessment of the pink shrimp small-scale fishery to climate change in southwestern Atlantic brackish coastal lagoons (Uruguay)

Assessing vulnerability using semi-quantitative approaches provide an opportunity to analyze conditions of exposure, sensitivity and adaptive capacity of socio-ecological systems concerning climate change drivers and anthropogenic factors. We assessed the vulnerability of the small-scale pink shrimp fishery of Castillos and Rocha lagoons, two coastal Uruguayan ecosystems of the southwest Atlantic, considering social factors and climate change drivers which affect atmospheric-oceanographic conditions regionally and locally. Using a risk approach, we evaluated the ecological system's exposure to environmental drivers. Then we estimated the sensitivity and adaptive capacity of fishers and the local community (social system). High vulnerability found for this fishery results from a combination of large-scale environmental drivers impacting the ecological system, and social factors causing high sensitivity and low adaptive capacity of the social system. High risk level with adverse ecosystem effects triggered by climate change drivers acting on the distribution of this migratory crustacean in the southwest Atlantic region could promote adverse consequences on harvest duration and shrimp catch levels in the Uruguayan coastal lagoons. Fishers and their communities showed high sensitivity to a set of (demographic, economic, governance, cultural and technological) factors. The social system of both lagoons showed a low adaptive capacity to prevent social impacts or to mitigate climate change hazards. A broad set of social indicators was identified in Rocha lagoon to enhance fishers and community resilience, while the indicator set was narrower in Castillos lagoon. Lastly, weak governance, dormant fisheries laws, non-compliance of fisheries regulations and lack of climate early warning monitoring hamper the adaptability of these small-scale fisher communities under global change scenarios. Comparative evaluation of spatial, environmental and social settings between lagoons can offer lessons for upscaling the assessment and adaptation measures to other small-scale fisheries regionally and globally.

Assessing the vulnerability of endangered and endemic brooding sea urchin Cassidulus mitis in response to climate change: Impacts on larvae and settlers in the southwestern Atlantic

Echinoderms play important roles in marine ecosystems and exhibit high sensitivity to environmental changes. The echinoid Cassidulus mitis has been considered an endangered species due to its restricted geographic distribution and unique reproductive behavior, with an epibenthic lecithotrophic larva and offspring brooded among the female spines during initial development until the settler stage. We studied the effects of low salinities (30 and 26) and high temperatures (27 and 31 °C) on the early development of C. mitis in a predicted scenario of global climate change through four parameters: 1. survival and 2. chronology of larval development, and 3. survival and 4. growth of settlers. Both larvae and settlers of C. mitis can survive under these scenarios, probably due to the lecithotrophic and epibenthic larval characteristics and developmental strategies of this species. However, all experimental conditions affected at least one of the initial developmental studied parameters of C. mitis, potentially compromising the species' viability in a scenario of climate change.

Effect of the seasonal precipitation regime on shrub litter decomposition in a subtropical forest

Changes in the seasonal precipitation regime induced by global climate change may alter moisture and the dynamics of related microbes and enzymes, thereby significantly affecting forest litter decomposition; however, the specific mechanisms remain unclear. Hence, a precipitation manipulation experiment including the treatments of control (CK), decreased precipitation in the dry season with extremely increased precipitation in the wet season (IE) and decreased precipitation in the dry season with proportionally increased precipitation in the wet season (IP) was performed from October 2020 to October 2021 in a subtropical evergreen broad-leaved forest in China. The moisture, chemical properties, microbial biomass, enzyme activity, and decomposition rates of two dominant shrub species foliar litter, Phyllostachys violascens and Alangium chinense, were measured at six stages during the dry and wet seasons. The results showed that both IE and IP significantly increased the litter decomposition rates (more than 2.0% for P. violascens and more than 4.7% for A. chinense, respectively), while the effects of IE were the most significant, which was mainly related to the precipitation availability and the frequency of dry-wet cycle. Furthermore, the IE and IP increased the wet season’s contribution to the annual total decomposition regardless of litter species, and more significant effects were also observed in IE. Additionally, the results of structural equation model indicated that the seasonal precipitation regime could regulate the decomposition process directly by changing moisture and the contents of elements and refractory substances, as well as indirectly by influencing the related microbial biomass and enzyme activity. These results deepen the understanding of the biogeochemical cycle in forest ecosystems under the global climate change scenarios.

Effects of climate change on gilthead seabream aquaculture in the Mediterranean

Aquaculture of gilthead seabream, arguably the most important finfish aquaculture species in the Mediterranean, faces changing environmental conditions due to faster-than-average climate change in the region. We utilize physiological modelling to estimate effects of moderate and severe climate change on key indices of aquaculture production for all coastal regions of the Mediterranean. Two publicly available global climate change scenarios with daily sea temperature projections serve as forcing for the physiological model during two-year farming cycles representing: (i) reference period starting in 2021, (ii) mid-term effects starting in 2051, and (iii) long-term effects starting in 2091.We investigate effects of climate change by analyzing changes in time for fish to reach a market size, feed conversion ratio at the market size, and the weight of the fish and the associated feed conversion ratio after two years of farming. Additionally, we track the number of days with sea water temperatures equal to or greater than 28 °C during the two-year period, when gilthead seabream starts experiencing temperature stress. Time to market size generally decreases with climate change from the initial average of 450 days for the reference period by up to 36%. Feed conversion ratio at market size does not appreciably change with climate change, but it does change for the two-year culturing period for up to 10 %, primarily due to faster growth in warmer sea water, and the correspondingly greater weight achieved over the two-year growth cycle.While the outlook for aquaculture is positive in the mid-term, some indicators show a negative trend in the long-term. The long-term effects of climate change will be greatest in the currently most productive farming regions of the Mediterranean: Levantine, Aegean, and Adriatic seas, and coastal waters of Tunisia. Our analysis focuses on basin-level features, but we provide geospatially referenced simulation results that can be used to analyze effects of climate change in a particular region of interest.

Effects of Climate Change on Soil Organic Matter C and H Isotope Composition in a Mediterranean Savannah (Dehesa): An Assessment Using Py-CSIA.

Dehesas are Mediterranean agro-sylvo-pastoral systems sensitive to climate change. Extreme climate conditions forecasted for Mediterranean areas may change soil C turnover, which is of relevance for soil biogeochemistry modeling. The effect of climate change on soil organic matter (SOM) is investigated in a field experiment mimicking environmental conditions of global change scenarios (soil temperature increase, +2-3 °C, W; rainfall exclusion, 30%, D; a combination of both, W+D). Pyrolysis-compound-specific isotope analysis (Py-CSIA) is used for C and H isotope characterization of SOM compounds and to forecast trends exerted by the induced climate shift. After 2.5 years, significant δ13C and δ2H isotopic enrichments were detected. Observed short- and mid-chain n-alkane δ13C shifts point to an increased microbial SOM reworking in the W treatment; a 2H enrichment of up to 40‰ of lignin methoxyphenols was found when combining W+D treatments under the tree canopy, probably related to H fractionation due to increased soil water evapotranspiration. Our findings indicate that the effect of the tree canopy drives SOM dynamics in dehesas and that, in the short term, foreseen climate change scenarios will exert changes in the SOM dynamics comprising the biogeochemical C and H cycles.

Response of soil microbial community structure, carbon and nitrogen cycling to drying and rewetting

Global change scenarios predict that precipitation regimes will become more variable in many parts of the world, extending drought periods and increasing rainfall intensity. Under these conditions, soil microbial community composition will likely change in ways that have implications for microbially-mediated nutrient cycling. Understanding these responses is key to predicting consequential changes in ecosystem functions. A 30 day incubation experiment was used to investigate the response of microbial community structure to three different soil moisture treatments, namely, constantly moist (CM), constantly dry (CD), and drying-rewetting (DRW), in soils of three different land condition types (Remnant, Restored, and Old-field) from Para Woodlands Nature Reserve, South Australia. Soil respiration and inorganic N transformations were approximately the same across soils, despite fundamental differences in physicochemical properties, vegetation communities, and land-use history. Soil microbial community structure changed in response to the different soil moisture treatments; responses of taxa was divergent among soils. These results demonstrate that changes to soil moisture regimes under climate projections will almost certainly have consequences for soil microbial communities and C and N dynamics. The results highlight the need for further research to understand the mechanisms driving divergent responses to soil moisture, particularly in areas of different land-use types.

From friends to foes: fungi could be emerging marine sponge pathogens under global change scenarios.

Global change, experienced in the form of ocean warming and pollution by man-made goods and xenobiotics, is rapidly affecting reef ecosystems and could have devastating consequences for marine ecology. Due to their critical role in regulating marine food webs and trophic connections, sponges are an essential model for studying and forecasting the impact of global change on reef ecosystems. Microbes are regarded as major contributors to the health and survival of sponges in marine environments. While most culture-independent studies on sponge microbiome composition to date have focused on prokaryotic diversity, the importance of fungi in holobiont behavior has been largely overlooked. Studies focusing on the biology of sponge fungi are uncommon. Thus, our current understanding is quite limited regarding the interactions and “crosstalk” between sponges and their associated fungi. Anthropogenic activities and climate change may reveal sponge-associated fungi as novel emerging pathogens. Global change scenarios could trigger the expression of fungal virulence genes and unearth new opportunistic pathogens, posing a risk to the health of sponges and severely damaging reef ecosystems. Although ambitious, this hypothesis has not yet been proven. Here we also postulate as a pioneering hypothesis that manipulating sponge-associated fungal communities may be a new strategy to cope with the threats posed to sponge health by pathogens and pollutants. Additionally, we anticipate that sponge-derived fungi might be used as novel sponge health promoters and beneficial members of the resident sponge microbiome in order to increase the sponge's resistance to opportunistic fungal infections under a scenario of global change.

Global change scenarios in coastal river deltas and their sustainable development implications

Deltas play a critical role in the ambition to achieve global sustainable development given their relatively large shares in population and productive croplands, as well as their precarious low-lying position between upstream river basin development and rising seas. The large pressures on these systems risk undermining the persistence of delta societies, economies, and ecosystems. We analyse possible future development in 49 deltas around the globe under the Shared Socio-economic and Representative Concentration Pathways until 2100. Population density, urban fraction, and total and irrigated cropland fraction are three to twelve times greater in these deltas, on average, than in the rest of the world. Maximum river water discharges are projected to increase by 11–33 % and river sediment discharges are projected to decrease 26–37 % on average, depending on the scenario. Regional sea-level rise reaches almost 1.0 m by 2100 for certain deltas in the worst-case scenario, increasing to almost 2.0 m of relative rise considering land subsidence. Extreme sea levels could be much higher still—reaching over 4.0 m by 2100 for six of the 49 deltas analysed. Socio-economic conditions to support adaptation are the weakest among deltas with the greatest pressures, compounding the challenge of sustainable development. Asian and African deltas stand out as having heightened socio-economic challenges—huge population and land use pressures in most Asian deltas and the Nile delta; low capacity for adaptation in most African deltas and the Irrawaddy delta. Although, deltas in other parts of the world are not immune from these and other pressures, either. Because of unique pressures and processes operating in deltas, as in other “hotspots” such as small islands, mountains, and semi-arid areas, we recommend greater consideration and conceptualisation of environmental processes in global sustainable development agendas and in the Integrated Assessment Models used to guide global policy.

Northern shrimp from multiple origins show similar sensitivity to global change drivers, but different cellular energetic capacity.

Species with a wide distribution can experience significant regional variation in environmental conditions, to which they can acclimatize or adapt. Consequently, the geographic origin of an organism can influence its responses to environmental changes, and therefore its sensitivity to combined global change drivers. This study aimed at determining the physiological responses of the northern shrimp, Pandalus borealis, at different levels of biological organization and from four different geographic origins, exposed to elevated temperature and low pH to define its sensitivity to future ocean warming and acidification. Shrimp sampled within the northwest Atlantic were exposed for 30days to combinations of three temperature (2, 6 or 10°C) and two pH levels (7.75 or 7.40). Survival, metabolic rates, whole-organism aerobic performance and cellular energetic capacity were assessed at the end of the exposure. Our results show that shrimp survival was negatively affected by temperature above 6°C and low pH, regardless of their origin. Additionally, shrimp from different origins show overall similar whole-organism performances: aerobic scope increasing with increasing temperature and decreasing with decreasing pH. Finally, the stability of aerobic metabolism appears to be related to cellular adjustments specific to shrimp origin. Our results show that the level of intraspecific variation differs among levels of biological organization: different cellular capacities lead to similar individual performances. Thus, the sensitivity of the northern shrimp to ocean warming and acidification is overall comparable among origins. Nonetheless, shrimp vulnerability to predicted global change scenarios for 2100 could differ among origins owing to different regional environmental conditions.

Projected Changes in Spawning Ground Distribution of Mature Albacore Tuna in the Indian Ocean under Various Global Climate Change Scenarios

The present study utilised a geometric mean model in which sea surface temperature, oxygen, and sea surface salinity were used to predict the effects of climate change on the habitats of mature albacore tuna in the Indian Ocean under multiple representative concentration pathway (RCP) scenarios. Data pertaining to the albacore tuna fishing conducted by Taiwanese longline fisheries during the October–March period in 1998–2016 were analysed. The fishery data comprised fishing location (latitude and longitude), fishing effort (number of hooks used), number of catches, fishing time (month and year), and fish weight. Nominal catch per unit effort data were standardised to mitigate the potential effects of temporal and spatial factors in causing bias and overestimation. The Habitat Suitability Index (HSI) scores of potential habitats for mature albacore in the Indian Ocean are predicted to change considerably in response to varying levels of predicted climate change. Under projected warm climate conditions (RCP 8.5), the stratification of water is predicted to cause low HSI areas to expand and potential habitats for mature albacore to shift southward by 2100. The findings derived from these mature albacore habitat forecasts can contribute to the evaluation of potential hazards and feasible adaptation measures for albacore fishery resources in the context of climate change. The distribution trends pertaining to potential habitats for mature albacore should be used with caution and can provide resource stakeholders with guidance for decision-making.

Different facets of the same niche: Integrating citizen science and scientific survey data to predict biological invasion risk under multiple global change drivers.

Citizen science initiatives have been increasingly used by researchers as a source of occurrence data to model the distribution of alien species. Since citizen science presence-only data suffer from some fundamental issues, efforts have been made to combine these data with those provided by scientifically structured surveys. Surprisingly, only a few studies proposing data integration evaluated the contribution of this process to the effective sampling of species' environmental niches and, consequently, its effect on model predictions on new time intervals. We relied on niche overlap analyses, machine learning classification algorithms and ecological niche models to compare the ability of data from citizen science and scientific surveys, along with their integration, in capturing the realized niche of 13 invasive alien species in Italy. Moreover, we assessed differences in current and future invasion risk predicted by each data set under multiple global change scenarios. We showed that data from citizen science and scientific surveys captured similar species niches though highlighting exclusive portions associated with clearly identifiable environmental conditions. In terrestrial species, citizen science data granted the highest gain in environmental space to the pooled niches, determining an increased future biological invasion risk. A few aquatic species modelled at the regional scale reported a net loss in the pooled niches compared to their scientific survey niches, suggesting that citizen science data may also lead to contraction in pooled niches. For these species, models predicted a lower future biological invasion risk. These findings indicate that citizen science data may represent a valuable contribution to predicting future spread of invasive alien species, especially within national-scale programmes. At the same time, citizen science data collected on species poorly known to citizen scientists, or in strictly local contexts, may strongly affect the niche quantification of these taxa and the prediction of their future biological invasion risk.

Plausible maize planting distribution under future global change scenarios

ContextPopulation expansion has become a trend. To meet the growing demand for crops, the area required for planting crops will also increase in the future. Current research generally assumes that land suitable for crops will generally shrink under global change, which, together with the increased crop demand, poses challenges to food security. ObjectiveThe objective of this study is to access the global maize planting distribution by improving the crop distribution model with a special focus on both environmental and socioeconomic factors under the global change scenarios of SSP245 and SSP385. MethodsWe constructed a crop distribution model that considers both environmental and socioeconomic factors. The environmental factors include topography, soil, and climate variables, while socioeconomic factors include supply-demand balancing, planting inertia, trade, irrigation ratio, and yield progress variables. Through those two aspects, we conducted a comprehensive prediction for the maize planting distribution. Results and conclusionCompared with the statistics, the modelling results of most countries differ slightly from the statistical data (within 20%), which shows that the model has good performance. Based on the projections of the model, the predicted planting area under the SSP245 and SSP385 scenarios in the near-term (2016–2035) increases by 39.86% and 48.70%, and in the mid-term (2046–2065) increases by 56.17% and 75.73%, respectively. In addition, the maize planting zone has decreased in size in the United States, Mexico, northern Brazil, South Africa, and southern Europe. SignificanceOur study provided a comprehensive crop distribution model and projected the global maize planting distribution, emphasizing the importance of socioeconomic factors in crop distribution modelling. Our research could benefit agricultural risk and regional field management.

Warming exacerbates the impacts of ultraviolet radiation in temperate diatoms but alleviates the effect on polar species.

Under global change scenarios, the sea surface temperature is increasing steadily along with other changes to oceanic environments. Consequently, marine diatoms are influenced by multiple ocean global change drivers. We hypothesized that temperature rise mediates the responses of polar and temperate diatoms to UV radiation (UVR) to different extents, and exposed the temperate centric diatoms, Thalassiosira weissflogii and Skeletonema costatum, and a polar pennate diatom Entomoneis sp., to warming (+5°C) for 10 days, then performed short-term incubations under different radiation treatments with or without UVR. The effective quantum yields of the three diatoms were stable during exposure to PAR, but decreased when exposed to PAR + UVR, leading to significant UV-induced inhibition, which was 3% and 9%, respectively, for T. weissflogii and S. costatum under ambient temperature but increased to 12% and 17%, respectively, in the cells acclimated to the warming treatment. In contrast, UVR induced much higher inhibition, by about 45%, in the polar diatom Entomoneis sp. at ambient temperature, and the warming treatment alleviated the UV-induced inhibition, which dropped to 36%. The growth rates were significantly inhibited by UVR in S. costatum under the warming treatment and in Entomoneis sp. under ambient temperature, while there was no significant effect for T. weissflogii. Our results indicate that the polar diatom was more sensitive to UVR though warming could alleviate its impact, whereas the temperate diatoms were less sensitive to UVR but warming exacerbated its impacts, implying that diatoms living in different regions may exhibit differential responses to global changes.

Plant traits modulate grassland stability during drought and post‐drought periods

Abstract Grasslands are subject to climate change, such as severe drought, and an important aspect of their functioning is temporal stability in response to extreme climate events. Previous research has explored the impacts of extreme drought and post‐drought periods on grassland stability, yet the mechanistic pathways behind these changes have rarely been studied. Here, we implemented an experiment with 4 years of drought and 3 years of recovery to assess the effects of drought and post‐drought on the temporal stability of above‐ground net primary productivity (ANPP) and its underlying mechanisms. To do so, we measured community‐weighted mean (CWM) of six plant growth and nine seed traits, functional diversity, population stability and species asynchrony across two cold, semiarid grasslands in northern China. We also performed piecewise structural equation models (SEMs) to assess the relationships between ANPP stability and its underlying mechanisms and how drought and post‐drought periods alter the relative contribution of these mechanisms to ANPP stability. We found that temporal stability of ANPP was not reduced during drought due to grasses maintaining productivity, which compensated for increased variation of forb productivity. Moreover, ANPP recovered rapidly after drought, and both grasses and forbs contributed to community stability during the post‐drought period. Overall, ANPP stability decreased during the combined drought and post‐drought periods because of rapid changes in ANPP from drought to post‐drought. SEMs revealed that the temporal stability of ANPP during drought and post‐drought periods was modulated by functional diversity and community‐weighted mean traits directly and indirectly by altering species asynchrony and population stability. Specifically, the temporal stability of ANPP was positively correlated with functional divergence of plant communities. CWMs of seed traits (e.g. seed width and thickness), rather than plant growth traits (e.g. specific leaf area and leaf nutrient content), stabilized grassland ANPP. Productivity of plant communities with large and thick seeds was less sensitive to precipitation changes over time. These results emphasize the importance of considering both the functional trait distribution among species and seed traits of dominant species since their combined effects can stabilize ecosystem functions under global climate change scenarios. Read the free Plain Language Summary for this article on the Journal blog.

Temperature and salinity trends in the northern limit of the Canary Current Upwelling System

Thermohaline time series are crucial for detecting and quantifying abiotic changes in the marine environment, and even more so in the present global change scenario. This is particularly relevant for the Ría the Vigo and its adjacent shelf, a highly productive ecosystem at the northern limit of the Canary Current Upwelling System (CanCUS). This study analyses a 34-year time series (1987–2020) of Conductivity-Temperature-Depth (CTD) casts, the longest series available to date in the region. Long-term trends, shifts, and seasonal variability of temperature and salinity were assessed and investigated in relation to regional meteorological variability and basin-scale atmospheric teleconnection indices. Generalized Additive Models (GAM) allowed us to determine that monthly thermohaline variability can be largely explained by regional meteo-climatic variability, mainly upwelling index and river discharge. Trends and shifts in some teleconnection patterns, especially the East Atlantic (EA) pattern, may also be related to both the shift in salinity in 2013 and its long-term decrease below 50 m depth. Despite the current global warming context, no statistically significant trend was observed for either the upwelling index or temperature. The spatial analysis of sea surface temperature trends suggests that our study area has been responding to climate change differently from other surrounding near-shore areas, as the Finisterre Cape or the southern Bay of Biscay. Overall, this study highlights the importance of long-term observations to elucidate the impact of climate change in the northern limit of the CanCUS and encourages caution when extrapolating conclusions from ecosystem studies on a regional scale.

Climate forcing on estuarine zooplanktonic production

Estuaries are among the most valuable aquatic systems in the world and resolving how there are impacted by climate change is fundamental to their management under global change scenarios. In this study, a ten-year time series (2003−2013) of zooplankton in an estuarine area (Mondego estuary, Portugal) is used to determine the impact of climate variability on estuarine zooplanktonic secondary production. For that, a trend analysis of seasonal zooplankton production was applied and their link with large-scale, regional, and local environment was tested by Distance-based multivariate multiple regression (DistLM). The annual integrated production of zooplankton varied between 34.27 mg C m−3 (2003) and 179.804 mg C m−3 (2013). Results showed that estuarine and marine zooplanktonic production increased in the estuary, mostly during summer/autumn and spring/summer, respectively. Local and regional environmental forcing drove copepod production in the estuary, with large-scale regime shifts affecting both directly and indirectly.

Plant pathogenesis: Towardmultidimensional understanding of the microbiome.

Single pathogen-targeted disease management measure has shown drawbacks in field efficacy under the scenario of global change. An in-depth understanding of plant pathogenesis will provide a promising solution but faces the challenges of the emerging paradigm involving the plant microbiome. While the beneficial impact of the plant microbiome is well characterized, their potential role in facilitating pathological processes has so far remained largely overlooked. To address these unsolved controversies and emerging challenges, we hereby highlight the pathobiome, the disease-assisting portion hidden in the plant microbiome, in the plant pathogenesis paradigm. We review the detrimental actions mediated by the pathobiome at multiple scales and further discuss hownatural and human triggers result in the prevalence of the plant pathobiome, which would probably provide a clue to the mitigation of plant disease epidemics. Collectively, the article would advance the current insight into plant pathogenesis and also pave a new way to cope with the upward trends of plant disease by designing the pathobiome-targeted measure.

Moss biocrusts buffer soil CO2 effluxes in a subtropical karst ecosystem

Biocrusts, specialized communities comprised of mosses, lichens, cyanobacteria, fungi, and bacteria occurring on the ground surface, are famous as ecological engineers on Earth, but less is understood in humid karst areas, where they are often widespread and provide important ecosystem services. To better understand how biocrusts affect soil carbon cycles, we performed an in situ study monitoring net soil exchange (NSE) of CO2, soil respiration (Rs), soil temperature and moisture, and determined soil nutrient contents and carbon-related enzyme activities over three different microcosms (soils covered by moss biocrusts, soils deprived of biocrust-forming mosses, and bare soils) in a subtropical karst ecosystem in southwest China. The results showed that, in comparison with bare soils, moss biocrusts increased Rs by 40% but decreased NSE by 49% and the temperature sensitivity of Rs by 35%. However, disturbance to moss biocrusts decreased Rs by 26% but increased NSE by 104% and the temperature sensitivity of Rs by 93%. Although moss biocrusts increased the content of soil organic carbon and total nitrogen and the activity of β-glucosidase, this effect was reversed by disturbance to moss biocrusts. While Rs was significantly correlated with soil temperature and moisture, the effect of moss biocrusts on Rs was partly explained by soil organic carbon, total nitrogen, and β-glucosidase. Overall, this study adds to the scarce number of experiments characterizing biocrust ecology in humid karst ecosystems and calls for management efforts to protect and restore biocrusts to buffer soil CO2 emissions under global change scenarios.

Distribution and Activity of Sulfur-Metabolizing Bacteria along the Temperature Gradient in Phototrophic Mats of the Chilean Hot Spring Porcelana.

In terrestrial hot springs, some members of the microbial mat community utilize sulfur chemical species for reduction and oxidization metabolism. In this study, the diversity and activity of sulfur-metabolizing bacteria were evaluated along a temperature gradient (48-69 °C) in non-acidic phototrophic mats of the Porcelana hot spring (Northern Patagonia, Chile) using complementary meta-omic methodologies and specific amplification of the aprA (APS reductase) and soxB (thiosulfohydrolase) genes. Overall, the key players in sulfur metabolism varied mostly in abundance along the temperature gradient, which is relevant for evaluating the possible implications of microorganisms associated with sulfur cycling under the current global climate change scenario. Our results strongly suggest that sulfate reduction occurs throughout the whole temperature gradient, being supported by different taxa depending on temperature. Assimilative sulfate reduction is the most relevant pathway in terms of taxonomic abundance and activity, whereas the sulfur-oxidizing system (Sox) is likely to be more diverse at low rather than at high temperatures. Members of the phylum Chloroflexota showed higher sulfur cycle-related transcriptional activity at 66 °C, with a potential contribution to sulfate reduction and oxidation to thiosulfate. In contrast, at the lowest temperature (48 °C), Burkholderiales and Acetobacterales (both Pseudomonadota, also known as Proteobacteria) showed a higher contribution to dissimilative sulfate reduction/oxidation as well as to thiosulfate metabolism. Cyanobacteriota and Planctomycetota were especially active in assimilatory sulfate reduction. Analysis of the aprA and soxB genes pointed to members of the order Burkholderiales (Gammaproteobacteria) as the most dominant and active along the temperature gradient for these genes. Changes in the diversity and activity of different sulfur-metabolizing bacteria in photoautotrophic microbial mats along a temperature gradient revealed their important role in hot spring environments, especially the main primary producers (Chloroflexota/Cyanobacteriota) and diazotrophs (Cyanobacteriota), showing that carbon, nitrogen, and sulfur cycles are highly linked in these extreme systems.

Deep-Water Dynamics along the 2012–2020 Observations on the Continental Margin of the Southern Adriatic Sea (Mediterranean Sea)

This work presents the results of long-term deep-water observations carried out in the southwestern Adriatic margin. Hydrodynamics and thermohaline measurements were carried out in the last 100 m of the water column using two long-term moorings placed at two different locations along the western sector of the Adriatic continental margin (open slope vs. submarine canyon). The observations, carried out over a period of almost 10 years, made it possible to define the intra- and interannual deep-water dynamics, which are mainly influenced by the passage of cold, dense water. The hydrodynamic field is influenced by seasonal behavior and varies from year to year, with no clear temporal trend or periodicity. Thermohaline properties follow hydrodynamics but also show a climatological trend toward higher temperatures and salinity. The combination and variability of preconditioning factors explains the interannual variability in dense water passage at the mooring sites triggering the formation of dense water in the northern Adriatic. The impulsive nature of the dense water flow, which is difficult to capture with sporadic oceanographic surveys, and its linkage with the large-scale atmospheric circulation make continuous monitoring essential to answer open questions about cascading processes and deep-water dynamics under a global change scenario.