Climate Change-related Stressors Research Articles

Climate challenges for fish larvae: Interactive multi-stressor effects impair acclimation potential of Atlantic herring larvae

Fish early life stages are particularly vulnerable and heavily affected by changing environmental factors. The interactive effects of multiple climate change-related stressors on fish larvae remain, however, largely underexplored. As rising temperatures can increase the abundance and virulence of bacteria, we investigated the combination of a spring heat wave and bacterial exposure on the development of Atlantic herring larvae (Clupea harengus). Eggs and larvae of Western Baltic Spring-spawners were reared at a normal and high temperature ramp and exposed to Vibrio alginolyticus and V. anguillarum, respectively. Subsequently, mRNA and miRNA transcriptomes, microbiota composition, growth and survival were assessed. Both high temperature and V. alginolyticus exposure induced a major downregulation of gene expression likely impeding larval cell proliferation. In contrast, interactive effects of elevated temperature and V. alginolyticus resulted in minimal gene expression changes, indicating an impaired plastic response, which may cause cellular damage reducing survival in later larval stages. The heat wave alone or in combination with V. alginolyticus induced a notable shift in miRNA expression leading to the down- but also upregulation of predicted target genes. Moreover, both increased temperature and the Vibrio exposures significantly altered the larval microbiota composition, with warming reducing microbial richness and diversity. The outcomes of this study highlight the high sensitivity of herring early life stages towards multiple climate change-related stressors. Our results indicate that interactive effects of rapidly changing environmental factors may exceed the larval stress threshold impairing essential acclimation responses, which may contribute to the ongoing recruitment decline of Western Baltic Spring-Spawning herring.

Integrated Multi-Biomarker Responses of Juvenile Zebra Seabream (Diplodus cervinus) to Warming and Acidification Conditions

The impacts of climate change-related stressors are becoming more noticeable in the ocean, particularly in coastal marine ecosystems. Yet limited information still exists on the physiological state and ecological resilience of marine fish species, especially during their early life stages (i.e., larvae and juveniles). The present study investigated the effects of chronic exposure to seawater warming (OW; ΔT = +4 °C) and acidification (OA; ΔpH = −0.3 pH units, equivalent to pCO2~1000 µatm), acting alone or combined (OWA), on juvenile zebra seabream (Diplodus cervinus) physiological resilience, considering distinct levels of biological organization (i.e., biochemical, cell, organ and individual levels). After 60 days of exposure, both stressors, in isolation or combination, significantly decreased specific growth rate (−11% in OW, −42% in OA and −49% in OWA) and leukocyte counts (from −29% in OA and OWA up to −37% in OW) in relation to the control treatment. In addition, a decreased Fulton’s condition index (K) was observed under warming and acidification in combination (−35% in OWA). At the cell level, OW, OA and OWA triggered different biomarker responses in D. cervinus (i.e., up-regulation, down-regulation, or absence of significant effect). In general, the results are suggestive of an antagonistic effect when warming and acidification are combined. OWA yielded the highest integrated biomarker response (IBR) index value in the whole organism, muscle, brain and gills of D. cervinus juveniles, therefore suggesting that the effects of these stressors are more severe when they act together. The distinct patterns observed in each stress scenario highlight the importance of carrying out further studies adjusted to the specificities of different regions, i.e., accounting not only for the type and degree of severity of environmental stressors already felt and/or projected for that specific area, but also the physiological plasticity of species that inhabit a particular ecosystem. The gathered knowledge will allow one to determine the vulnerability of particular marine species and geographic areas and, most importantly, to draw up effective and tailor-made conservation strategies to overcome climate change impacts.

Perception of Climate Change Vulnerability and its Impact on Sexual and Reproductive Health and Rights in Khutiya and Banganga River Basins.

Nepal is one of the most vulnerable countries to climate change. The drivers of climate risk include its topography, ecological diversity, climatic variability, natural resource dependency, under-development, and socioeconomic vulnerabilities. Climate change affects women and girls in unique ways. Research conducted in Asia Pacific region highlight negative sexual and reproductive health outcomes from climate change-related stressors such as droughts, floods, and air pollution, factors also linked to decreased SRH services utilization, increased maternal mortality rates, and repercussions on women's mental health. This is a mixed methods study conducted in two river basins including household surveys with 384 females ages 18-49, 12 focus group discussions, and 22 key informant interviews. We conducted descriptive and thematic analysis. More than half relied on agriculture for income (66%). Despite one-third being heads of households, land ownership was low (13%). Climate change perceptions included rising temperatures (88%), increased heat wave (70%), drying water source (99%), and delayed monsoons (83%), impacting agriculture and increasing women's workload (61%) due to displacement and male migration. 64% reported disturbances in antenatal and postnatal care visits . Inaccessible healthcare facilities during the rainy season increased maternal mortality risks. Heavy river flooding hindered female community health volunteers access leading to childbirth complications. 82% of women feared being unable to protect their children post-climate events. Moreover, 21% of women faced gender-based violence during or after climate disasters. Our findings suggest clear impacts of climate change on women and the communities. Thus, climate adaptation efforts must be designed to address the unique impacts of the crisis on women and girls, making space for their increased participation and leadership.

Signals and Machinery for Mycorrhizae and Cereal and Oilseed Interactions towards Improved Tolerance to Environmental Stresses.

In the quest for sustainable agricultural practices, there arises an urgent need for alternative solutions to mineral fertilizers and pesticides, aiming to diminish the environmental footprint of farming. Arbuscular mycorrhizal fungi (AMF) emerge as a promising avenue, bestowing plants with heightened nutrient absorption capabilities while alleviating plant stress. Cereal and oilseed crops benefit from this association in a number of ways, including improved growth fitness, nutrient uptake, and tolerance to environmental stresses. Understanding the molecular mechanisms shaping the impact of AMF on these crops offers encouraging prospects for a more efficient use of these beneficial microorganisms to mitigate climate change-related stressors on plant functioning and productivity. An increased number of studies highlighted the boosting effect of AMF on grain and oil crops' tolerance to (a)biotic stresses while limited ones investigated the molecular aspects orchestrating the different involved mechanisms. This review gives an extensive overview of the different strategies initiated by mycorrhizal cereal and oilseed plants to manage the deleterious effects of environmental stress. We also discuss the molecular drivers and mechanistic concepts to unveil the molecular machinery triggered by AMF to alleviate the tolerance of these crops to stressors.

Lophelia reefs off North and West Africa–Comparing environment and health

The health status of cold-water coral reefs on the West African coast was investigated with the main objective of obtaining knowledge of the adaptive capacity of Lophelia pertusa to environmental stressors. Three coral sites were studied, in Northern Morocco, in the Morocco/Mauritania region (both in 2020) and, in the Ghana and Ivory coast region (visited in 2012, 2017, and 2019). Area cover of live colonies, explored through underwater videos, was used as an indicator of reef health and compared with the environmental variables: reef position, depth, water mass, temperature, dissolved oxygen concentration (DO), carbonate chemistry (pH, aragonite saturation (ΩAr), macronutrients and particles (visual). For a broader picture of the adaptations presented by Lophelia our results were compared with reefs in contrasting environments. Off Ghana and Mauritania healthy reefs (i.e., having areas with more than 20 % cover of live colonies) were found to reside at DO concentrations between 1.1 and 1.6 ml L−1, in corrosive waters (pH 7.7 and ΩAr 1.0) with high nutrient concentrations. By contrast, the reefs off the North of Morocco, sitting in well-oxygenated waters with oversaturated ΩAr, had no or few live colonies. Our findings together with data from other studies show that Lophelia has a wide tolerance to hypoxia and acidification, and that in relation to climate change increased temperature and silting could pose more serious threats. These findings highlight the importance of continued studies of Lophelia reefs in contrasting environmental conditions to better understand their adaptation potential to climate change-related stressors.

Sharks and their relatives: can their past help predict their future?

Elasmobranchs (i.e., sharks, skates, and rays) have survived five mass extinction events and changed relatively little throughout their ~450-million-year evolutionary history. Therefore, elasmobranchs may provide critical evolutionary perspectives on how species and populations can elicit phenotypic plasticity and adaptation responses to climate change. Unfortunately, despite their roles as critical apex- and meso-predators, most elasmobranch species are considered to be highly vulnerable to the impacts of fisheries exploitation and climate change, which is compounded by their K-selected life history strategies. Furthermore, the future of elasmobranchs is uncertain at best in the face of anthropogenic climate change because there have only been a handful of studies that have directly investigated the effects of climate change related stressors. Phenotypic plasticity in response to climate change, specifically ocean warming, may be a species’ best chance of resilience given the expedited rate of environmental change. However, despite extensive research on plasticity within and across generations in teleost fishes, there remains a knowledge gap for elasmobranch species, owing to their extended life spans and delayed sexual maturity. Here, we present four case studies on different elasmobranch species to lend perspectives on the capacity for phenotypic plasticity within the context of ocean warming. Furthermore, we discuss potential research avenues and modern technologies that may enable future investigations to empirically explore the capacity for phenotypic plasticity in elasmobranchs.

Coping with climate change: The role of climate related stressors in affecting the mental health of young people in Mexico.

Young people today are predicted to experience more climate change related stressors and harms than the previous generation, yet they are often excluded from climate research, policy, and advocacy. Increasingly, this exposure is associated with experience of common mental health disorders (CMD). The VoCes-19 study collected surveys from 168,407 young people across Mexico (ages 15-24 years) through an innovative online platform, collecting information on various characteristics including CMD and experience of recent climate harms. Logistic regression models were fit to explore characteristics associated with CMD. Structural equation models were fit to explore pathways between exposure, feeling of concern about climate change, and a sense of agency (meaning the respondent felt they could help address the climate crisis) and how these relate to CMD. Of the respondents, 42% (n = 50,682) were categorized as experiencing CMD, higher among those who experienced a climate stressor (51%, n = 4,808) vs those not experiencing climate stressors (41%, n = 43,872). Adjusting for key demographic characteristics, exposure to any climate event increased the odds of CMD by 50% (Odd Ratio = 1.57; 95% Confidence Interval (CI) 1.49, 1.64), highest for heatwaves. Specific climate impacts such as housing damage, loss of or inability to work, damage to family business, leaving school and physical health affected were adversely related to CMD, though for different climate hazards. More concern and less agency were related to CMD through different pathways, particularly for those exposed to recent events. Future research regarding the cumulative exposures to climate change, not just acute events but as an ongoing crisis, and various pathways that influence the mental health and well-being of young people must be clearly understood to develop programs and policies to protect the next generation.

Direct and indirect impacts of ocean acidification and warming on algae-herbivore interactions in intertidal habitats

Anthropogenically induced global climate change has caused profound impacts in the world ocean. Climate change related stressors, like ocean acidification (OA) and warming (OW) can affect physiological performance of marine species. However, studies evaluating the impacts of these stressors on algae-herbivore interactions have been much more scarce. We approached this issue by assessing the combined impacts of OA and OW on the physiological energetics of the herbivorous snail Tegula atra, and whether this snail is affected indirectly by changes in biochemical composition of the kelp Lessonia spicata, in response to OA and OW. Our results show that OA and OW induce changes in kelp biochemical composition and palatability (organic matter, phenolic content), which in turn affect snails' feeding behaviour and energy balance. Nutritional quality of food plays a key role on grazers' physiological energetics and can define the stability of trophic interactions in rapidly changing environments such as intertidal communities.

Physiological-dependent alterations on transcriptomic and proteomic patterns of the single and combined temperature and salinity-exposed hybrid grouper, Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂

Global warming and the changes in environmental conditions such as temperature and salinity may affect the health of marine species. However, the underlying mechanisms remain poorly characterized. The objectives of the present study were to examine the liver transcriptome and proteome of the marine species, hybrid grouper (E. fuscoguttatus ♀ × E. lanceolatus ♂), to assess which physiological pathways are modulated by exposure to climate change-related stressors, how the responses vary with exposure duration, and whether they represent adaptive or maladaptive changes. To answer these questions, the hybrid grouper was subjected to single stressors (elevated temperatures, reduced salinity) or stressor combinations for 3 or 14 days. As endpoints, we examined changes in body and organ growth, liver histopathology, lipid accumulation, and alterations of the liver transcriptome and proteome. The results demonstrated that the elevated temperature resulted in reduced body weight and a reduced liver-somatic index after a 14-day exposure. The spleen-somatic index was significantly decreased compared to controls after 3-day treatment. At the transcriptomic level, the pathways with the greatest numbers of differentially expressed genes at day 3 of exposure were immune-related in all treatment groups. After 14 days of exposure, the transcriptomic and proteomic analyses showed that metabolic and protective processes became activated. The increased lipid droplet accumulation in the hepatocytes is corroborated by the transcriptomic/proteomic findings which show alterations in the pathways of lipid metabolism and fatty acid oxidation. While these changes may represent adaptive responses, the increase of hepatic lipid accumulation despite an overall loss of liver and body weight may represent a maladaptive process. Overall, the physiological responses of the hybrid grouper showed a clear time dependency, and they were partly stressor-specific, with the low salinity treatment separating from the treatments with elevated temperature. When both stressors were combined, the temperature effect dominated the salinity effect.

Extreme conditions reduce hatching success of green turtles (Chelonia mydas L.) at Karan Island, the major nesting site in the Arabian Gulf

Survival in the early life stages is a major factor determining the growth and stability of wildlife populations. For sea turtles, nest location must provide favorable conditions to support embryonic development. Hatching success and incubation environment of green turtle eggs were examined in July 2019 at Karan Island, a major nesting site for the species in the Arabian Gulf. Mean hatching success averaged at 38.8 % (range = 2.5–75.0 %, n = 14). Eggs that suffered early embryonic death (EED) and late embryonic death (LED) represented 19.8 % (range: 3.3–64.2 %) and 41.4 % (range: 4.8–92.6 %) of the clutch on average, respectively. Nest sand was either coarse (0.5–1 mm: mean 44.8 %, range = 30.4–56.9 % by dry weight, n = 14) or medium (0.25–0.5 mm: mean 33.6 %, range = 12.0–45.5 % by dry weight, n = 14). Mean sand moisture (4.0 %, range = 3.2–4.9 %, n = 14) was at the lower margin for successful development. Hatching success was significantly higher in clutches with sand salinity <1500 EC.uS/cm (n = 5) than those above 2500 EC.uS/cm (n = 5). Mean clutch temperatures at 1200 h increased by an average of 5.4 °C during the 50-d post-oviposition from 31.2 °C to 36.6 °C. Embryos experienced lethally high temperatures in addition to impacts of other environmental factors (salinity, moisture, sand grain size), which was related to reduced hatching success. Conservation initiatives must consider the synergistic influence of the above parameters in formulating strategies to improve the overall resilience of the green turtle population in the Arabian Gulf to anthropogenic and climate change-related stressors.

Definitions and scope of the mental health burden of global climate change

IntroductionClimate change is increasing the frequency of extreme weather events – such as heatwaves, droughts, floods, and wildfires – and undermining the mental health and wellbeing of global populations, but the dimensions and scope of this burden remain under-studied.ObjectivesTo identify the distinct but overlapping mental health domains that are being impacted by climate change-related stressors and how these domains relate to and interact with one another.MethodsA narrative synthesis of conceptual and empirical studies of climate change and mental health.ResultsWe find strong empirical evidence that climate change is already harming mental health across multiple mental health domains, including through increased rates of psychiatric disorders (e.g., PTSD, depression, anxiety), sub-clinical psychological distress, harmful substance use, self-harm/suicidal behaviors, and worry about the observed and anticipated impacts of climate change. Most of the mental health burden is likely to occur in the form of sub-clinical symptoms, including lowered resilience and subjective well-being, while negative psychological states (e.g., eco-anxiety) are likely to constitute a smaller proportion of the overall burden. We argue that the mental health burden can be helpfully conceptualised within a dual-continuum model that considers the presence/absence of psychiatric diagnosis on the one hand, and high/low psychosocial wellbeing on the other.Image:ConclusionsClimate change is already harming the mental health of global populations across multiple functional domains. Defining and tracking the scope of this growing burden is essential so that effective preventive and adaptive action can be taken.Disclosure of InterestNone Declared

Mucilage-induced necrosis reveals cellular oxidative stress in the Mediterranean gorgonian Paramuricea clavata

The red gorgonian Paramuricea clavata is a fundamental ecosystem engineer of coralligenous biocenosis in the Mediterranean Sea, where it plays crucial ecological functions and enhances the habitat biodiversity. However, this species is strongly endangered due to climate change-related stressors such as mucilage events, which have increased in recent decades causing extensive damage and mortality, but whose impacts at the molecular and cellular levels are still unexplored. In this study, different cellular stress biomarkers were analyzed in mucilage-colonized P. clavata specimens living in the Portofino Marine Protected Area (Ligurian Sea, Italy), in order to elucidate the cellular pathways affected by mucilage and the cellular defense mechanisms adopted. Within these colonies, portions of healthy tissue located at different distances from mucilage-induced necrosis were considered. Our results showed that mucilage affected the cellular oxidative status and impaired lipid cell membranes of the whole P. clavata colony. Indeed, an increase in the superoxide dismutase (SOD) and glutathione reductase (GR) enzymatic activity and in the level of lipid peroxidation (LPO) was detected in colonies showing mucilage-induced necrotic tissues compared to healthy ones. In particular, fragments sampled just next to the necrotic tissue displayed the highest levels of SOD and LPO, indicating that harmful oxidative damage was in progress, especially in portions neighboring the mucilage colonization. In this context, the up-regulation of the antioxidant mechanisms might represent a defense and a barrier from hypoxic or anoxic conditions created by mucilage overgrowth or by the invasion of toxic organisms embedded in the mucilaginous aggregates. On the contrary, the cellular protein homeostasis, analyzed by the expression of the 60-kDa Heat shock protein (Hsp60), was not altered by the mucilage. This analysis contributes to provide new insights into the cellular and molecular response of gorgonians to a stress source whose effects are likely to worsen in a climate change scenario.

Climate change and substance use disorders – do we understand the risks?

IntroductionClimate change is increasing the frequency and intensity of severe heatwaves, storms, floods, droughts, and wildfires. These events cause widespread economic and social disruption and are undermining population health worldwide. Despite a growing literature on how climate change threatens mental health, its influence on harmful substance use has not been systematically addressed.ObjectivesWe propose an explanatory framework explicating the plausible links between climate change-related stressors and an increase in harmful substance use.MethodsWe critically review and synthesise literature documenting the pathways, processes and mechanisms linking climate change to increased substance use vulnerability.ResultsSeveral plausible pathways link climate change to increased risk of harmful substance use worldwide. These include: (1) anxiety about the impacts of unchecked climate change, (2) destabilisation of psychosocial and economic support systems, (3) increasing rates of mental disorders, and (4) increased physical health burden. Children may face disproportionate risk due to their vulnerability to both mental disorders and substance use, particularly during adolescence. We argue that a developmental life-course perspective situated within a broader ‘systems thinking’ approach provides a coherent framework for understanding how climate change is aggravating the multiple, persistent, interacting risks that influence harmful substance use pathways.ConclusionsClimate change is already undermining health and wellbeing of global populations. By inference, it is also aggravating pathway to harmful substance use. This is a critical psychosocial problem for individuals and communities alike. Conceptual and methodological work is urgently needed so that effective adaptive and preventive action can be taken.DisclosureNo significant relationships.

Investigating the role of the ERF104 gene in stress tolerance in model plant Arabidopsis suecica using CRISPR

ETHYLENE RESPOSNE FACTORS are highly conserved genes that have been found to be involved in stress‐related hormone signaling in plants. When these genes are over‐expressed, they can have negative impacts on plant health, leading to inhibited growth and leaf senescence under stressful conditions. Could knocking down the function of an ERF improve plant response in the face of climate change related stressors such as soil salinity? A CRISPR gene knockdown will be performed on ETHYLENE RESPONSE FACTOR 104 in Arabidopsis suecica. A. suecica is an allopolyploid plant which has shown differential expression of ERF104 in genetically different accessions. A CRISPR gene knockout of ERF104 will be performed on two different accessions of A. suecica, which will then be genotyped to look for signs of genetic mutation. Phenotypic observations of mutation will also be performed as the plants grow and are exposed to stressful conditions. Upon successful completion of the experiment, I expect to see that the ERF104gene is no longer being overexpressed in A. suecica, which should result in the plant showing fewer signs of stress when grown on salinity plates.

Spatial Distribution, Diversity, and Activity of Microbial Phototrophs in the Baltic Sea

Microbial plankton is essential for ocean biogeochemistry. As part of the prokaryotic phototrophic microbial community, both oxygenic phototrophs (OP) and anoxygenic phototrophs (AP) are widely distributed in the ocean and may play a significant role in carbon flow and oxygen production. However, comparative studies of microbial OP and AP have received very little attention, even though their different roles might be important in various marine environments, especially in oxygen minimum zones (OMZ). We explored the spatial distribution of the microbial community in the Baltic Sea, including an OMZ region, with a particular focus on the distribution and activity of OP and AP. We used 16S rRNA amplicon sequencing in combination with a qPCR-based quantification of photosynthesis marker genes. We found that specific bacterial groups dominated surface and intermediate depths, the OMZ, and deep waters, respectively. Salinity, temperature, oxygen, and depth were significant factors explaining the microbial community composition and distribution. A high diversity of OP and AP was observed, including OP-Chlorophyta, Diatoms, Cyanobacteria and Cryptomonads, and AP-Proteobacteria and Chloroflexota. OP were more abundant at most stations compared to AP. OP showed high photosynthetic activity and more photosynthesis activity in higher temperature and upper waters, while AP photosynthesis cannot be detected in most stations. Both, cyanobacterial and eukaryotic OP preferred to live in higher temperature and upper waters, but Cyanobacteria also preferred to live in oxic water while the whole OP community showed preference to live in higher salinity area. However, AP did not show any significant hydrochemical preference but prefer to live with OP community. The Baltic Sea is exposed to multiple climate change related stressors, such as warming, decreasing salinity, and deoxygenation. This study contributes to understanding and interpretation of how microbial community, especially phototrophic groups, might shift in their distribution and activity in a changing ocean like the Baltic Sea.

Coping and Adapting to Climate Change in Australia: Yoga Perspectives

Scientists caution against ignoring human-induced climate change and related health repercussions, with a growing body of literature highlighting the mental health effects of climate change and the importance of understanding coping and adaptation strategies. Less is known, however, about sustainable personal practices fortifying mental health in the context of climate change. The present study sought to investigate how long-term yoga practitioners (yoga therapists or yoga teachers) in Australia with a lived experience of climate change-related events are coping and adapting. The aim was to better understand participants' reports of climate change-related experiences and how yoga influences their mental health and choices in the face of climate change. Eleven in-depth telephone interviews were conducted and analyzed using an interpretive phenomenological methodology. Participants reported that their ongoing relationship with yoga influences how they cope with climate change-related stressors and their being-in-the-world, and how concern for all life bolsters their responses to climate change. The results illustrate the part yoga may play in supporting long-term practitioners to prepare for, cope with, and respond to climate change events and impacts. Offering inclusive, interdisciplinary yoga therapy and community-based networks fostering ethical living and response flexibility may prove beneficial not only for the mental health and coping ability of participants, but for the planet.

Land-dependent marine species face climate-driven impacts on land and at sea

Land-dependent marine species are a unique guild of species whose life histories rely on both land and sea. This group is exposed to climate change-related stressors 2-fold, as climate change impacts likely occur at different velocities across land and sea habitat, leading to a greater probability of evolutionary traps. Thus, it is difficult to assess vulnerability and subsequently manage these populations in response to climate change. Without consideration of the factors unique to land-dependent marine species, current vulnerability assessment frameworks may fall short when evaluating climate impacts on these species. We identified commonalities in climate-related threats across taxa and geographic regions, highlighting the specific life history strategies that may be better suited to adapt to the changing climate. Accordingly, we suggest 3 considerations for assessing the vulnerability of land-dependent marine species: (1) degree of specialization, (2) intraspecies population-level differences, and (3) non-climate stressors. Where possible, we suggest how the exclusion of this information in management and conservation planning may lead to less successful outcomes. Potential compounding impacts of multiple stressors puts this group at particular risk of population collapse when losing land and/or sea habitat and functionality. Each of these considerations should be included when assessing vulnerabilities to climate change, as well as in effective and proactive management responses.

A unified model for high resolution mapping of global lake (>1 ha) clarity using Landsat imagery data

Lake clarity, usually measured by Secchi disc depth (SDD), is a reliable proxy of lakes trophic status due to its close link with total suspended matter, chlorophyll-a, and nutrients. Trained with in-situ measured SDD and match-up Landsat images, we established various regression models to estimate SDD for global lakes. We selected a unified model which demonstrated good spatiotemporal transferability, and has potential to map SDD in different years with good quality of Landsat top-of-atmosphere (TOA) images embedded in Google Earth Engine (GEE). The unified model was successfully calibrated (n = 3586 data points, R2 = 0.84, MAPE = 29.8%) against SDD measured in 2235 lakes across the world, and the validation (n = 1779, R2 = 0.76, MAPE = 38.8%) also exhibited stable performance. The unified model was tuned to historical SDD measurements coincident with different Landsat sensors (L5-TM, L7-ETM+, L8-OLI) launched over the past four decades (1984–2020), thus confirming its temporal stability. Global SDD was mapped using GEE with OLI TOA products mainly acquired in 2019 to examine the spatial variation of lake water clarity (lake surface area ≥ 1 ha) all over the world. Worldwide, lake water clarity averaged 3.13 ± 1.71 m in 2019, but exhibited remarkable spatial variability due to catchment hydrological and landscape settings, lake morphology, elevation and anthropogenic impact. Inland waters in Europe (4.18 ± 1.82 m) and North America (3.84 ± 1.77 m) had the highest clarity due to greater water depth combined with less human disturbance in the high latitude regions. Lakes in South America (2.50 ± 2.33 m), Asia (2.44 ± 1.63 m) and Africa (2.36 ± 0.72 m) displayed intermediate clarity. Lakes in Oceania (1.97 ± 1.48 m) exhibited the lowest clarity for all continents except Antarctica. Further, we used the mapped SDD to evaluate water trophic status using the Carlson trophic state index. Our results indicate that, in 2019, about 63.6% of the lake areas and 47.8% of total lake numbers (2,219,627/4,646,056) were oligotrophic for global lakes, while about 23.6% areal percent and 37.1% of lake numbers are eutrophic mostly as a result of their being located in agricultural and urban-dominated drainage basins. This study, for the first time, provides water clarity information for lakes with area ≥ 1 ha all over the world with 30-m resolution and facilitates the understanding of the water clarity relevant to TSM (r = 0.95), Chl-a (r = 0.73), total phosphorus (r = 0.75), total nitrogen (r = 0.60), which could further provide water clarity data and technical support for trophic level evaluations as well. This unified model could serve as a powerful research tool for long-term monitoring of aquatic ecosystems and assessing their resilience to anthropogenic disturbance and climate change-related stressors.

Adaptive livelihood strategies among small-scale fishing households to climate change-related stressors in Central Coast Vietnam

PurposeThis paper aims to examine adaptive livelihood strategies used by small-scale fishing households in the two coastal communities in Central Vietnam under the context of climate change-related stressors.Design/methodology/approachField data were collected through mixed quantitative and qualitative methods including a review of secondary data, key-informant interviews, group discussions and household surveys with 300 sampled fishing households. The qualitative data support the analysis and discussion of quantitative data.FindingsThe results showed local households’ perception of the presence and influence of multiple non-climate and climate stressors on their fishery-based livelihoods in terms of employment and income in many ways. The affected households exerted to develop a diversity of adaptation methods within and out of fishing to sustain their livelihoods and cover a deficit in household income. The household socio-demographic characteristics particularly education, labour force, fishing equipment and social support played significant importance in characterising the categories of adaptation strategies among the survey households. The role of local governments in creating an enabling environment for local-level adaptation, as well as protecting marine and coastal ecosystems was rather limited despite their recognized importance.Originality/valueThe paper provides an empirical case of how small-scale fishing households in coastal communities in Central Vietnam are adapting to climate-related stressors. It suggests policy should promote livelihood diversification opportunities and address household-level constraints for adaptation. Fisheries management plan is urgently needed to control illegal fishing activities for sustainable use of coastal and marine fishery resources and the appropriate mechanism is important to stretch local governments’ resources for better supporting local-level adaptation.

Exposure time modulates the effects of climate change-related stressors on fertile sporophytes and early-life stage performance of a habitat-forming kelp species

Understanding the impact of increases in pCO2 (OA) and extreme changes in temperature on marine organisms is critical to predicting how they will cope with climate change. We evaluated the effects of OA as well as warming and cooling trend temperature on early reproductive traits of Lessonia trabeculata, a bio-engineer kelp species. Sori discs were maintained for an exposure time (ET) of 3 (T3) and 7 (T7) days to one of two contrasting pCO2 levels (450 and 1100 μatm). In addition, at each pCO2 level, they were subjected to three temperature treatments: 15 °C (control), 10 °C (cool) and 19 °C (warm). Subsequently, we compared sorus photosynthetic performance (Fv/Fm), the number of meiospores released (MR) and their germination rate (GR) after 48 h of settlement, with values obtained from sori discs not exposed (DNE) to the treatments. The Fv/Fm measured for DNE was lower than at T3 and T7 at 10 and 15 °C but not at 19 °C. Regardless of temperature, we found no significant differences between MR measured at T0 and T3. MR at T7 was significantly lower at 19 °C than at 10 and 15 °C. We found only a significant reduction in MR in response to elevated pCO2 at T3. The GR of meiospores released by DNE and then maintained for 48 h to 19 °C decreased significantly by ~33% when compared with those maintained for the same time at 10 and 15 °C. A similar, but more drastic reduction (~54%) in the GR was found in meiospores released by sori discs exposed for T3 and maintained for 48 h to 19 °C. We suggest that OA and warming trend will threaten the early establishment of this species with further consequences for the functioning of the associated ecosystem.