Ecosystem Research Articles

Elevational patterns of soil organic carbon and its fractions in tropical seasonal rainforests in karst peak-cluster depression region.

Karst ecosystems, especially tropical karst forests, are crucial to the global carbon cycle. In mountainous and hilly areas, elevation-related changes in environment and vegetation often lead to shifts in the accumulation and decomposition of soil organic carbon (SOC). However, the elevational patterns and influencing variables of SOC and its fractions in tropical karst forest ecosystems remain largely unexplored. Here, we analyzed the elevational patterns of SOC and its fractions in the topsoil and subsoil in the tropical seasonal rainforests within typical peak-cluster depression region of Southwest China. Our results indicated that the SOC content was highest at 400 m asl, which was significantly higher than that at 200 m asl (p < 0.05). Overall, SOC content demonstrated an increasing trend with rising elevation. Additionally, SOC content was significantly higher in the topsoil compared to the subsoil (p < 0.05). The majority of SOC fractions exhibited an increase with elevation but decrease with soil depth. Notably, only water-soluble organic carbon (WSOC) displayed a decrease with elevation. Meanwhile, recalcitrant organic carbon (ROC, 54.27%), particulate organic carbon (POC, 30.19%), and easily oxidizable organic carbon (EOC, 16.95%) were the main SOC fractions. Labile organic carbon (LOC) in the karst forest soil was predominantly composed of EOC and POC. Correlation analysis unveiled significant positive correlations between SOC and certain fractions with elevation, soil total nitrogen, and exchangeable magnesium. Conversely, significant negative correlations were observed with soil bulk density (SBD), soil total phosphorus, and litter phosphorus (Litter P). Redundancy analysis indicated that elevation, SBD, and Litter P were the main environmental variables influencing shifts in SOC and its fractions. Structural equation models showed that SOC was primarily directly impacted by soil properties but indirectly impacted by elevation. ROC was mainly associated with the direct effects of soil properties and litterfall, although elevation exerted a substantial impact through indirect pathways. Moreover, LOC was predominantly influenced by the direct impact of soil properties. Therefore, this study demonstrates that SOC and its fractions are strongly influenced by elevation in karst peak-cluster depression regions and have important implications for forest management and sustainable ecosystem development in these regions.

From planning to implementation: a multi-stakeholder partnership for managing plant invasions in tropical island ecosystems

From planning to implementation: a multi-stakeholder partnership for managing plant invasions in tropical island ecosystems

Detection of Hydrological Alteration and soil erosion in a conserved tropical sub-humid ecosystem of Ethiopia

Soil erosion poses a significant challenge in the sub-humid Ethiopian highlands, yet research on the long-term effectiveness of soil and water conservation (SWC) practices in this region using pre- and post-conservation approaches remains limited. This study addresses this knowledge gap by evaluating the impact of SWC practices on water balance and soil erosion in the Debre Mawi watershed. The study covers two-period analyses: pre-conservation (2010–2014) and post-conservation (2015–2022) using the Soil and Water Assessment Tool (SWAT) to simulate hydrological water balance. Hydrological changes were assessed with the Indicators of Hydrological Alteration (IHA) software. Spatial and weekly sediment distribution were also computed. Results showed the SWAT effectively simulated stream flow, though sediment yield estimation was less accurate. The data demonstrated a reduction in surface runoff by 18% and a decrease in sediment yield by 75%. Conversely, evapotranspiration and groundwater storage experienced increases of 13% and 34%, respectively. The decrease in runoff and sediment can be attributed to the implementation of SWC structures with infiltration furrows, which are presently filled with sediment. Moreover, the expansion of eucalyptus tree acreage may deplete soil water during dry periods, thereby prolonging the time needed for the soil to become saturated and produce runoff, but the impact has yet to be quantified. The IHA analysis confirmed a decrease in mean annual flow from 0.06 m3/s to 0.02 m3/s, and sediment concentration decreased from 831.2 mg/l to 285 mg/l between the pre-and post-conservation periods. The study detected that soil erosion is higher than the allowable limits recommended for Ethiopia even after implementing SWCPs. Additionally, sediment transport reduced after the first three weeks due to improved ground cover and soil stability, although significant amounts were recorded until the end of the rainy season, primarily from gullies. The study found significant hydrological alterations in flow and sediment dynamics following the implementation of SWC practices, particularly pronounced in the early years post-conservation (2015–2018). However, the effectiveness of SWC practices diminished over time, with conditions beginning to revert to pre-conservation levels after 10 years. This suggests that these techniques (infiltration furrows) may be unsuitable for sub-humid watersheds, or that they require improved design and major maintenance beyond the third year. This study offers valuable insights into the dynamics of SWC interventions, underscoring the importance of integrating agronomic practices with SWC efforts to sustain long-term soil and water conservation in Ethiopia's sub-humid highlands. Future research should explore the hydrological effects of eucalyptus expansion and refine SWC practices suited to these unique conditions.

Coral Community Composition Linked to Hypoxia Exposure.

Tropical reef ecosystems are strongly influenced by the composition of coral species, but the factors influencing coral diversity and distributions are not fully understood. Here we demonstrate that large variations in the relative abundance of three major coral species across adjacent Caribbean reef sites are strongly related to their different low O2 tolerances. In laboratory experiments designed to mimic reef conditions, the cumulative effect of repeated nightly low O2 drove coral bleaching and mortality, with limited modulation by temperature. After four nights of repeated low O2, species responses also varied widely, from > 50% bleaching in Acropora cervicornis to no discernable sensitivity of Porites furcata. A simple metric of hypoxic pressure that combines these experimentally derived species sensitivities with high-resolution field data accurately predicts the observed relative abundance of species across three reefs. Only the well-oxygenated reef supported the framework-building hypoxia-sensitive Acropora cervicornis, while the hypoxia-tolerant weedy species Porites furcata was dominant on the most frequently O2-deplete reef. Physiological exclusion of acroporids from these O2-deplete reefs underscores the need for hypoxia management to reduce extirpation risk.

Interaction Between Climate Change Scenarios and Biological Invasion Reveals Complex Cascading Effects in Freshwater Ecosystems.

Climate change often facilitates biological invasions, leading to potential interactive impacts of these global drivers on freshwater ecosystems. Although climatic mitigation efforts may reduce the magnitude of these interactive impacts, we are still missing experimental evidence for such effects under multiple climate change scenarios within a multi-trophic framework. To address this knowledge gap, we experimentally compared the independent and interactive effects of two climate change scenarios (mitigation and business-as-usual) and biological invasion on the biomass of major freshwater trophic groups (phytoplankton, zooplankton, periphyton, macroinvertebrates, and a native macrophyte) and the decomposition rate of allochthonous material. Among the independent effects, we found that the business-as-usual climate treatment resulted in lower native macrophyte biomass and higher periphyton biomass compared to the climatic baseline and mitigation treatments. This indicates the potential of climate change to alter the relative dominance of different freshwater producers and demonstrates that climate mitigation efforts can counteract these effects. Biological invasion alone increased the biomass of chironomids, a dominant macroinvertebrate group in tropical freshwater ecosystems, demonstrating a compensatory effect on climate change. Climate change and biological invasion interactively reduced the decomposition rate of allochthonous detritus, likely mediated by the feeding preference of abundant chironomids for periphytic algae associated with the presence of non-native macrophytes. We concluded that (i) climatic mitigation can maintain climate baseline conditions in freshwater ecosystems, and (ii) the interactive effects between future climate scenarios and biological invasion are related to complex cascading interactions among trophic groups on ecosystem processes.

Highland forest dynamics across equatorial East Africa during the end of the African humid period

Tropical mountain ecosystems hold immense ecological and economic importance, yet they face disproportionate risks from shifting tropical climates. For example, present-day montane vegetation of East Africa is characterized by different plant species that grow in and are restricted to certain elevations due to environmental tolerances. As climate changes and temperature/rainfall zones move on mountains, these species must rapidly adjust their ranges or risk extinction.Paleoenvironmental records offer valuable insights into past climate and ecosystem dynamics, aiding predictions for ongoing climate change impacts. In particular, warming and wetting in tropical East Africa during the mid-Holocene resulted in both lowland and highland forest expansion. However, the relative impacts of rainfall and temperature change on montane ecosystems along with the influence of lowland forest expansion on montane communities is not completely understood. We use fossil pollen to study the vegetation changes in two lakes at different altitudes in the Rwenzori Mountains, Uganda: Lake Mahoma (Montane Forest belt) and Upper Kachope Lake (Afroalpine belt). Further, using the newly relaunched African Pollen Database and recent temperature reconstructions, we provide a regional synthesis of vegetation changes in the Rwenzori and then compare this with changes observed from other equatorial East African montane sites (particularly Mt Kenya).In the early to mid-Holocene in the Rwenzori Mountains, trees common today in lowland forests dominated, driven largely by warmer temperatures. After 4000 years ago (4ka), Afromontane forest trees along with grasses progressively replaced lowland trees. Not all sites experienced identical transitions. For instance, at Lake Rutundu on Mt Kenya at the same elevation as Lake Mahoma, bamboo expansion preceded Afromontane forest growth, likely influenced by variations in fire. Variance partitioning indicates that each site responded differently to changes in temperature and rainfall. Therefore, these site-specific ecological responses underscore the importance of considering biogeographic legacies as management strategies are developed, despite similarities in modern ecology.

Elevational and Seasonal Patterns of Plant-Hummingbird Interactions in a High Tropical Mountain.

Tropical mountain ecosystems harbor diverse biological communities, making them valuable models for exploring the factors that shape ecological interactions along environmental gradients. We investigated the spatial and temporal drivers of plant-hummingbird interaction networks across three forest types (pine-oak, fir, and subalpine) along a tropical high mountain gradient in western Mexico (2400 to 3700 m.a.s.l.). We measured species abundance, diversity, morphology, and interaction frequencies. Plant diversity metrics significantly declined in the highest elevation subalpine forest, whereas hummingbird diversity remained consistent across elevations. Interaction networks were similarly nested across elevations, but they were more specialized in the subalpine forest, where lower plant species richness and higher floral abundance led to greater resource partitioning among hummingbirds. Plant-hummingbird networks were larger and less specialized during the dry season, driven by greater species diversity and abundance. Species turnover explained network variation along the elevational gradient, while interaction rewiring and the arrival of migratory hummingbirds explained changes between seasons. Phenological overlap was the most important driver of the observed variation in interaction frequencies across elevations and seasons. Flower abundance had a minor influence on interaction frequencies at low- and mid-elevation networks, and hummingbird abundance was significant for dry- and rainy-season networks. Morphological matching was significant in the low-elevation forest and in the dry season. Plant phylogenetic relatedness had negligible effects on interaction patterns, but hummingbird phylogeny influenced feeding preferences in high-elevation and rainy-season networks. Our findings highlight the role of species turnover, interaction rewiring, and phenological overlap in structuring plant-hummingbird networks, with specific effects of abundance, morphology, and phylogeny varying with elevation and season. High-elevation ecosystems play a crucial role as reservoirs of floral resources for both resident and migratory hummingbirds during resource-scarce periods, emphasizing their importance in maintaining biodiversity in tropical mountain gradients.

Influence of Mini Warm Pool Extent on Phytoplankton Productivity and Export in the Arabian Sea

The Arabian Sea is a highly productive tropical ecosystem of the Indian Ocean that supports high fluxes of particulate organic carbon to the mesopelagic zone from two distinct periods of elevated biological productivity associated with the semiannual reversals of the monsoonal wind system. There are now strong indications that the Arabian Sea’s monsoonal wind patterns and hydrographic conditions are being impacted by long-term temperature increases, but the consequences of these changes on primary production and carbon export to the mesopelagic zone are unknown. This is especially true for the summer monsoon period when cloud cover obscures much of the Arabian Sea basin and therefore precludes remotely sensed ocean color measurements for estimating phytoplankton biomass and productivity. Here we overcome this limitation by using a database of bio-optical profiles from Biogeochemical Argo floats collected over the last decade to evaluate the impact of interannual temperature increases on Arabian Sea primary production and carbon export. We classify individual years of float observations based on the spatial extent of the Arabian Sea Mini Warm Pool that appears in the southeast Arabian Sea before the onset of the summer monsoon. This mini warm pool, which begins to build in winter and collapses with the onset of the summer monsoon in late spring, has gained considerable interest on account of its influence on the timing of the onset of the summer monsoon. We observed a 35 percent decrease in primary production during the summer monsoon phytoplankton bloom in strong warm pool years, and a 13 percent decrease in particle stocks in the upper mesopelagic zone following the peak of the bloom. Decreases in production and export were additionally accompanied by a decrease in average particle size, indicating a shift from larger cells like diatoms that appear from fertilization of the oligotrophic waters to smaller phytoplankton size classes in response to a deepening of the thermocline and increased stratification of the water column. These results suggest changes in phytoplankton community structure and further decreases in primary production and carbon export in the Arabian Sea in response to future warming.

Assessment of soil pollution in coastal landscapes of the Republic of Djibouti and ecological risks

Tropical ecosystems play an important role in the environment. Coastal areas are subjected to a wide range of impacts and pollution, which have drawn worldwide attention over the past few decades. Comprehensive studies of heavy metal content in soils worldwide are extremely important for assessing and predicting ecological risks. Very few studies have been devoted to a complete study of the physicochemical characteristics of soils, assessment of heavy metal accumulation in coastal zones along the Djibouti coast, and potential ecological risks. The study investigated the physico-chemical characteristics of soil, assessed the accumulation of heavy metals in coastal zones along the Djibouti coast, and analyzed the potential environmental risks associated with the presence of heavy metals in the studied soils. Analysis of heavy metals and trace elements in the soils of the coastal areas of Djibouti revealed that the levels of these elements are lower than in soils of the Red Sea coast and are in line with WHO and other international standards. All heavy metals in the soil of the studied area demonstrate low levels of potential ecological risk. The soils of the studied areas, overall, have not undergone significant heavy metal pollution and can be considered suitable for various types of use.

Carbon and nitrogen sources in tropical coastal lagoon food webs under variable hydrological conditions

Whilst the impact of continental and marine nutrient sources on the ecological functioning of coastal food webs is well investigated in temperate regions, tropical ecosystems remain less well understood, in particular coastal lagoons. In this study, the sources of carbon and nitrogen in a coastal lagoon system in the southeast of Madagascar are traced using stable isotopes of carbon (δ13C) and nitrogen (δ15N). Three interconnected coastal lagoons with different degree of river influence and eutrophication are investigated. Their food webs are assessed with respect to spatial and seasonal (wet and dry seasons) variations in lagoon water conditions, as well as with respect to the sources of nutrients and organic matters. Results show that river input is the main source of NO3−, and that NO3− supply is significantly higher during the wet season. In contrast, NH4+ is produced internally in the lagoon, and concentrations are higher during the dry season. A lower δ13C value observed in particulate organic matter (POM; proxy of phytoplankton) indicates terrestrial-riverine carbon inputs, which generally have low δ13C values. During the dry season, exceptionally high δ15N values of lagoon POM suggest the uptake of newly produced lagoon water NH4+ and/or the 15N enrichment of lagoon POM pool due to mineralization, resulting in 15N enrichment in consumers. Moreover, δ13C and δ15N values of consumers (fishes and invertebrates) reflect predominantly those of lagoon POM and sediment organic matter (SOM), suggesting that consumers primarily depend on lagoon POM and SOM as sources of carbon and nitrogen. The δ15N values in consumers further indicate that some species feed on more than one trophic level, suggesting flexible foraging strategy of consumers as a function of food source availability. This study demonstrates the roles of both river inflow and sediment in supplying carbon and nitrogen to a coastal lagoon food web, documenting the ecological implications of seasonal variations in lagoon hydrological conditions.

Unveiling the Diversity and Ecological Roles of Macrofungi in Ayer Hitam Forest Reserve, Selangor, Malaysia

The biodiversity of macrofungi in remaining lowland dipterocarp forest in highly urbanization pressures is infrequently studied, even though their significant impact on the ecosystem of forested and non-forested habitats. Therefore, this research endeavours to unravel the diversity of macrofungi from different substrates in the Ayer Hitam Forest Reserve located in Selangor, Malaysia. Through a combination of field surveys, the study seeks to contribute valuable insights into the complex relationships between macrofungi and the surrounding habitats where macrofungal community structure was mainly influenced by substrate richness and microclimates. Sporocarps of macrofungi were collected from selected sites using opportunistic sampling methods. A total of 333 sporocarps were obtained and identified based on morphological and molecular analysis. Basidiomycota prevailed in the Ayer Hitam Forest Reserve where 27 species belonging to 14 families were successfully identified. Saprophytic fungi (22 species, 81.5%) dominated the areas, and a small number of mycorrhizal (1 species, 3.7%) and parasitic (4 species, 14.8%) fungi were found. Based on species diversity, order Polyporales is the highest occurrence species in the sampling areas with a Shannon-Weiner Index value of 2.103 and Simpson Index value of 0.954, Evenness Index value of 0.601, making it the most abundant order containing Microporus species, The findings are expected to enhance our knowledge of the biodiversity of macrofungi from different substrates in Ayer Hitam Forest Reserve, which can lead to conservation efforts and promote the ecological significance of macrofungi in tropical forest ecosystems.

A descriptive study of the biometrics of the stingless bee Lepidotrigona flavibasis in northern Thailand

Stingless bees play a crucial role in tropical and subtropical ecosystems, contributing significantly to biodiversity and pollination services. The species Lepidotrigona flavibasis (Cockerell 1929) (Apidae: Meliponini), found in Southeast Asia, has attracted attention for its unique nesting habits and valuable honey production. The objective of this study was to compare colony size and productivity between different nesting cavities. Twelve colonies of L. flavibasis were collected in Chiang Mai province, Thailand, to study biometrical data. Six colonies were housed in hollowed logs, previously occupied by Apis cerana, and six in bamboo cavities. The colony ages ranged from 8 months to 5 years. This study found that log cavity colonies had larger populations and more brood cells than bamboo cavity colonies. Results show that log cavity colonies had an average number of workers (3,842.6 ± 2036), drones (288.2 ± 511), brood cells (5,914.5 ± 3026), honey pots (290.5 ± 210), and pollen pots (96.8 ± 90). The bamboo cavity colonies were found to have an average number of workers (1,628.2 ± 575), drones (64 ± 58), brood cells (2,333.7 ± 1875), honey pots (127.3 ± 95), and pollen pots (94.8 ± 57). Overall, the log cavity colonies demonstrated greater colony size and productivity regarding adult bees and brood.

Ediacaran-type non-mineralized tube-dwelling organisms persisted into the early Cambrian (Terreneuvian) in Baltica

The Ediacaran taxon Conotubus hemiannulatus has been discovered in the Terreneuvian blue clays of Estonia. Alongside Conotubus, Gaojiashania-like tubes are also found in these clays. These tubes are fully compressed and pyritized. The well-developed peristomes of Conotubus might have provided stability if the living worm was partially buried in the soft sea floor, suggesting that Conotubus was a sessile suspension feeder. The presence of the archaic Conotubus hemiannulatus in the Fortunian of Estonia indicates that the tube morphology of some cloudinids did not change between the Ediacaran and the Terreneuvian. The existence of these old-fashioned cloudinids in the Terreneuvian suggests either that the early Cambrian ecosystem in Baltica was not significantly different from that of the Ediacaran, or that cloudinids with organic tubes were more resilient to ecological changes than previously thought. Most Terreneuvian faunas originate from lower latitudes, whereas Baltica, during the Terreneuvian, was located at middle-high latitudes and experienced a cold climate. We hypothesize that the cold climate zone ecosystem was more archaic in the Fortunian than the tropical ecosystem, providing a final refuge for the Ediacaran non-mineralized tubicolous organisms. The increased competition pressure from diverse modern animals in the tropics could have driven Ediacaran-type non-mineralized tubicolous organisms to seek refuge in the colder regions of the ocean, where the competition from more advanced animals was less intense.

Enhanced global carbon cycle sensitivity to tropical temperature linked to internal climate variability.

The sensitivity of atmospheric CO2 growth rate to tropical temperature (γT) has almost doubled between 1959 and 2011, a trend that has been linked to increasing drought in the tropics. However, γT has declined since then. Understanding whether these variations in γT reflect forced changes or internal climate variability in the carbon cycle is crucial for future climate projections. We show that doubling sensitivity events can arise in simulations by Earth system models with perturbed initial conditions but are likely explained by internal climate variability. We show that the doubling sensitivity event is associated with the occurrence of a few, but very strong, El Niño events, such as 1982/83 and 1997/98. Such extreme events result in concurrent carbon release by tropical and extratropical ecosystems, increasing the variance of the global land carbon sink and its apparent sensitivity to tropical temperature. Our results imply that the doubling sensitivity does not necessarily indicate a change in carbon cycle response to climate change.

Geography and ecology structure diversification in Ziziphus Mill. (Rhamnaceae)

Understanding the processes responsible for creating and preserving biodiversity within tropical ecosystems is essential for gaining deeper insights into the history, dynamics, and resilience of these environments. We investigated the biogeography and evolution of Ziziphus Mill. (Rhamnaceae), a genus of c.50 species found in all major tropical biomes and across Africa, Asia and Australasia to evaluate how ecology and geography structures its diversification, and their associations with functional traits. We used consistency and retention indices, as well as the delta statistic to test for phylogenetic signal in ecology, geography and functional traits. We constructed a time-calibrated phylogeny using BEAST, followed by the reconstruction of biome and geographical affinities in BioGeoBEARS, and ancestral functional trait evolution using phytools and ape. At a global scale, geography structures Ziziphus’ diversification more than ecology, as evidenced by higher phylogenetic signal in retention indices and the delta statistic. Multiple ecological switches among biomes are associated with dispersal events, which structure Ziziphus’ diversification at smaller scales. Biogeographic estimation suggests that Ziziphus evolved out of closed biomes in Asia during the Oligocene. Long distance dispersal from Asia to Africa resulted in the occupation of two novel biomes, the expanding tropical grassy biome and the desertic biome. Geographic transitions across continents that retain the same biome are fewer but are demonstrated by a dispersal from the closed biome in Asia to the same ecological setting in Australia. In keeping with the younger age of the savanna biome and the Pliocene radiation of geoxylic species, the youngest species in Ziziphus are mostly found in open biomes, and the youngest habit is geoxylic. Leaf hair appears to confer advantages across biomes whilst being a synapomorphy for open and desertic clades. One of two evolutions back into closed biomes is associated with the development of the liana habit. We inferred the most complete phylogeny for Ziziphus to date. Ziziphus originated in closed biomes in Asia in the Oligocene. At a global scale, geography structures diversification more than ecology (biome preference) in Ziziphus. Biome shifts are frequently associated with long distance dispersal events. Shifts in growth form are frequently associated with biome shifts.

Coevolutionary dynamics in tropical peat ecosystems: A case study of Sumatra peatlands biosphere reserve

Tropical peat swamp is an essential ecosystem experiencing increased degradation over the past few decades. Therefore, this study used the social-ecological system (SES) perspective to explain the complex relationship between humans and nature in the Sumatran Peatlands Biosphere Reserve. The peat swamp forest has experienced a significant decline, followed by a significant increase in oil palm and forest plantations in areas designated for peat protection. Human systems have evolved to become complex and hierarchical, constituting individuals, groups, organizations, and institutions. Studies on SES conducted in the tropical peatlands of Asia have yet to address the co-evolutionary processes occurring in this region, which could illustrate the dynamic relationship between humans and nature. This study highlights the co-evolutionary processes occurring in the tropical peatland biosphere reserve and provides insights into their sustainability trajectory. Moreover, the coevolution process shows that biosphere reserve is shifting toward an unsustainable path. This is indicated by ongoing degradation in three zones and a lack of a comprehensive framework for landscape-scale water management. Implementing landscape-scale water management is essential to sustain the capacity of peatlands social-ecological systems facing disturbances, and it is important to maintain biodiversity. In addition, exploring alternative development pathways can help alter these trajectories toward sustainability.

Taxonomic Diversity and Interannual Variation of Fish in the Lagoon of Meiji Reef (Mischief Reef), South China Sea.

Coral reef fish are important groups of coral reefs, which have great economic and ecological value. Meiji Reef is a representative tropical semi-enclosed atoll in the South China Sea, with rich fish resources. Based on the data from hand-fishing, line-fishing, and gillnet surveys of fish in Meiji Reef from 1998 to 2018, this study summarized the fish species list of Meiji Reef and analyzed the species composition, inclusion index at the taxonomic level (TINCL), genus-family diversity index (G-F index), average taxonomic distinctness index (Δ+), and variation in taxonomic distinctness (Λ+) and their changes. The results revealed that from 1998 to 2018, there were 166 reef-dwelling fish species on Meiji Reef, belonging to 69 genera, 33 families, and 11 orders, of which 128 species were from 20 families of Perciformes, accounting for 77.10% of the total cataloged species. Regarding the dependence of fish on coral reefs, there were 155 reef-dependent species or resident species (accounting for 93.37%) and 11 reef-independent species or wandering species (accounting for 6.63%). The TINCL of the order, families, and genus of fish in Meiji Reef were very high. The genus diversity index (G index), family diversity index (F index), and G-F index of fish in Meiji Reef were very high, and the G index of fish in Meiji Reef in 1998-1999 was higher than that in 2016-2018. The Δ+ and Λ+ values of fish in Meiji Reef from 1998 to 2018 were 56.1 and 148.5, respectively. Compared with 1998-1999, Δ+ and Λ+ of fish increased during 2016-2018, reflecting that the relatives of fish in Meiji Reef became further distant, and the uniformity of taxonomic relationships among species decreased. The research findings indicated that fish exhibited a high taxonomic diversity in Meiji Reef; however, it also revealed significant fluctuations in the fish diversity of Meiji Reef over an extended period, emphasizing the urgent need for timely protection measures. This investigation significantly contributes to our comprehension of the intricate dynamics governing fish species within Meiji Reef and holds broader implications for biodiversity conservation in tropical marine ecosystems.

Strangler fig–host tree associations: Insights into the ecology and management of tropical urban green spaces

Societal Impact StatementThe strangler fig is known for its hemiepiphytic growth form and conspicuous strangling behavior in the tropics worldwide. It also plays an important role in providing ecological functions in tropical urban ecosystems. This study reveals strangler figs tend to colonize large trees with suitable microsites in a large tropical botanical garden and cause some negative effects on their hosts. We advocate balanced management strategies considering ecological functions, potential risks, and overall values of stranglers and their hosts. These results provide a scientific basis for us to develop better practices for plant management in urban green spaces (especially botanical gardens with high plant biodiversity) in tropical urban ecosystems.Summary Strangler figs colonize trees in tropical cities, which contribute to a unique urban ecology and enrich local ecological functions. Understanding ecological associations between strangler figs and their host trees can improve green space management in tropical urban ecosystems. We investigated 9282 trees growing in the Xishuangbanna Tropical Botanical Garden and then analyzed the diversity, characteristics, and network of strangler figs and their host trees. We found 13 strangler fig species (319 individuals) widely colonized 67 host species, with palm hosts bearing 52% of all strangler individuals. Strangler figs had a high colonization rate in large trees with appropriate microsites (e.g., persistent palm petioles and the fork of mature trees with rough trunks). Leaf nitrogen and phosphorus content of hosts decreased significantly after strangler figs' aerial roots had entered the ground. The strangler–host network was characterized by relatively high specialization and low nestedness, and simulated management of strangler figs on large hosts and palm hosts could simplify the strangler–host network. Strangler fig colonization can be managed. Planting trees with large diameters at breast height and rough bark can increase the colonization of stranglers, while cutting off aerial roots can inhibit their establishment. The epiphytic stage is the best time to manage strangler figs. We recommend taking into consideration the trade‐offs among ecological functioning, human safety, and the multifaceted value of strangler figs and their host trees and thereby implementing comprehensive management strategies tailored to different contexts for improving green space management in the tropics.

Triple planetary crisis: why healthcare professionals should care.

Humanity currently faces an ecological crisis with devastating consequences to all living species. While climate change is estimated to lead to 250,000 extra deaths per year between 2030 and 2050, pollution is known to cause 9 million premature deaths: a figure much greater than the deaths caused by AIDS, tuberculosis and malaria combined. The healthcare sector is both burdened by, and contributes to, the impact of climate change and environmental degradation. Amidst glaring evidence of the interdependence of human health and the eco system, there is an urgent call for healthcare professionals to concern themselves with the triple planetary threat humanity currently faces. Without immediate mitigative measures, the future seems uncertain. Some healthcare systems at local, national and global levels have taken numerous initiatives to address, mitigate and adapt to these changes, however, these are not sufficient. A lack of awareness among healthcare professionals of the ecological crisis, its interconnectedness, and the role of healthcare in it, plays a significant role in the lack responsibility of healthcare professionals in this space. Therefore, this paper presents a discussion of the current landscape of the triple threat of climate change, loss of biodiversity, and pollution, while emphasising the contribution of healthcare professionals to it. Furthermore, interrelated concepts such as planetary health and eco-anxiety are briefly discussed. This perspective paper also presents several key prospective research areas that may lay the foundation for motivating healthcare professionals to play an active role in preventing and mitigating the ecological crises humanity currently faces.

Microplastic pollution in tropical coral reef ecosystems from the coastal South China Sea and their impacts on corals in situ

Coral reefs possess extremely high ecological value in tropical and subtropical waters worldwide. Microplastics as emerging and pervasive pollutants pose a great threat to the health of coral ecosystems. However, in situ studies on microplastics pollution and its impacts in coral ecosystems globally are limited. The occurrence characteristics of microplastics in the environment mediums and reef-dwelling organisms were investigated in coral reef areas from the southern Hainan Island, and the impacts of microplastics on corals in situ were evaluated in this study. Average microplastics abundance was 9.48 items L-1 in seawater, 190.00 items kg-1 in sediment, 0.36 items g-1 in coral, 1.50 items g-1 in shellfish, 0.48 items g-1 in fish gill, and 1.71 items g-1 in fish gastrointestinal tract. The prevalent microplastics in the above samples were characterized as being less than 1000 µm in size, fibrous, and transparent, with predominant polymer types as polyethylene terephthalate, polypropylene, polyethylene, and rayon. The microplastic enrichment capacity of different corals varied (Pocillopora >Acropora >Sinularia). Notably, microplastics were more abundant on the surface of corals compared to their interiors, with distinct characteristics observed, including larger-sized (>500 µm) and fiber-shaped polyethylene terephthalate microplastics on the surface and smaller-sized (20–200 µm) fragmented polyethylene microplastics within coral interiors. Furthermore, the investigation showed species-specific impacts of microplastics on corals in situ, including photosynthetic activity of photosymbionts and antioxidant and immune activities of corals. Furthermore, the ecological risks of microplastics were minor across most environmental media in the studied areas, with exceptions in the bottom seawater and surface sediment of YLW, which exhibited extreme and medium risk levels, respectively. Coral risk levels were generally medium, except for dangerous levels in DDH and high levels in LHT. The potential sources of microplastics in the marginal reefs of southern Hainan Island were primarily tourism, residential, and fishing activities.