Interactions In Ecosystems Research Articles

Active and passive organic carbon fluxes during a bloom in the Southern Ocean (South Georgia)

The Controls Over Mesopelagic Interior Carbon Storage (COMICS) cruise DY086 took place aboard the RRS Discovery in the South Atlantic during November and December, 2017. Physical, chemical, biogeochemical and biological data were collected during three visits to ocean observatory station P3, off the coast of South Georgia, during an austral spring bloom. A diverse range of equipment including CTD-rosette, Acoustic Doppler Current Profiler (ADCP), net deployments, marine snow catchers (MSCs), Stand Alone Pump System (SAPS) and PELAGRA Sediment Traps were used to produce a comprehensive, high-quality dataset. The data can provide excellent insight into regional biological carbon pump (BCP) processes; it is recommended for use by observational scientists and modellers to enhance understanding of ecosystem interactions relating to mesopelagic carbon storage.

Growth Allocation Shifts in the Invasive Hydrilla verticillata Under Interspecific Competition with Native Submerged Macrophytes

Communities with high native species diversity tend to be less susceptible to the establishment of invasive species, especially in studies that test their local impact. This study investigated the impact of competition between native submerged aquatic macrophytes (SAMs) (Egeria najas and Egeria densa) and the exotic Hydrilla verticillata, recognized for its invasive potential in aquatic ecosystems, through a mesocosm experiment conducted over six months. Two treatments were evaluated: the intraspecific competition of H. verticillata and an interspecific competition involving all three species. The plants were cultivated under controlled conditions, with the foliar and subterranean biomass being monitored to analyze resource allocation patterns. The results showed that, under interspecific competition, the mean foliar biomass of H. verticillata was significantly higher compared to the intraspecific treatment, while the subterranean biomass was reduced in the presence of native species. We conclude that native species alter the biomass allocation pattern of the invader, favoring foliar structures over subterranean ones. Among the mechanisms of invasiveness, differential resource allocation represents an important strategy for the adaptation and competitiveness of invasive species influenced by environmental factors and resource competition. These findings contribute to the understanding of competitive interactions in aquatic ecosystems and have implications for the management and control of invasive species, highlighting the importance of promoting native diversity to mitigate invasibility. Future studies should investigate the impacts of reduced subterranean structures on the persistence and spread of submerged invasive species.

Predation by Coleps sp. (Ciliophora, Prostomatea) on polyps of Hydra (Cnidaria, Hydrozoa)

The present study reveals a novel predator-prey interaction in freshwater ecosystems: that of a free-living protozoan, Coleps sp., and polyps of the genus Hydra. Despite the common perception that larger body size confers competitive advantages, this finding shows that a large number of small-sized phagotrophic organisms, Coleps sp., attack Hydra polyps in groups, first attack their tentacles, and then gradually consuming the entire polyps. This finding was observed in Hydra vulgaris and Hydra sinensis specimens collected in freshwater bodies in São Paulo, Brazil. This discovery challenges traditional notions of size-based competitiveness and demonstrates that Coleps sp. can overcome the defensive barrier of hydra's cnidocytes. The study highlights the adaptability of Coleps sp. in its ability to prey not only on other protozoans, but also on multicellular organisms such as hydras. This suggests an even more complex predation dynamic that could have significant implications for the structure of freshwater zooplankton communities. This work provides a basis for future research into the ecological importance of “minor” predators such as Coleps sp. in regulating aquatic communities and underscores the need for more detailed studies to better understand the interactions between Hydra and Coleps sp., and how these relationships affect zooplankton populations and the overall dynamics of aquatic ecosystems.

A Review of Studies on the Effects of Anthropogenic Disturbances on Plant–Soil–Microorganism Interactions in Grassland Ecosystems: Based on Grazing and Tourism Perspectives

As the most widely distributed and largest terrestrial ecosystem in the world, grasslands play an important role in supporting global livestock production and maintaining ecosystem services. In light of the accelerated global socio-economic development and sustained population growth, grassland ecosystems are increasingly subjected to anthropogenic disturbances. However, there is a paucity of research examining the impact of such disturbances on plant–soil–microorganism interactions in grassland systems, particularly from the perspectives of grazing and tourism. Accordingly, this study presents a comprehensive analysis of the impacts of anthropogenic disturbance on grassland ecosystems over the past two decades, employing a dual perspective of grazing and tourism and utilizing econometric analysis of the existing literature through software such as CiteSpace. The results of this study demonstrate the following: (1) The current research focus is primarily concentrated in the fields of ecology and environmental sciences, particularly on the topics of plant diversity, abundance, and diversity, as well as the intensity of grazing. These areas may represent key development direction of future research. (2) The impact of anthropogenic disturbances on grassland ecosystems is primarily associated with grazing activities. Moderate grazing disturbances can facilitate the healthy development of grassland ecosystems. However, the intermediate disturbance hypothesis (IDH) may not fully account for the effects of grazing intensity on grassland ecology. At present, there is still a paucity of systematic research to determine the ecological indicators of grassland under a dual-disturbance scenario. It is recommended that future research be carried out to investigate the compound effects of trampling by tourism activities on plant–soil–microorganism interactions in grassland ecosystems. (3) The mutual feedback mechanism may represent a potential mechanism by which anthropogenic disturbances affect the coupled relationship between the plant, soil, and microbial systems in grassland ecosystems. Furthermore, the interaction among these three systems has the potential to exert direct or indirect impacts on the structure and function of grassland ecosystems in the context of disturbances. The present study aims to provide an overview of the structure and function of grassland ecosystems under anthropogenic disturbances. The objective is to identify a balance between the rational use of grassland and ecological protection under anthropogenic disturbance and to provide scientific reference for the sustainable use of grassland worldwide.

Matrix Differential Equation Modeling Of Sex Ratio Change And Multivariable Effect Analysis Of Ecosystem

Adequacy of food supply has a significant effect on the sex ratio of juvenile sea lampreys, which also adjusts to changes in the external environment, influenced by resource availability, position in the food web, and ecological niche. Therefore, it is necessary to pay attention to the effects of changes in sea lampreys' sex ratio on ecosystem interactions. In this paper, we constructed an ecosystem model. We comprehensively analysed the impacts of sea lamprey's sex ratio changes on the ecosystem from the four dimensions of the logistic equation of the population dynamics model, the sex ratio model, the food web model, and the spatio-temporal model1,2,3. The study showed that the sea lampreys population showed adaptability to changes in the environment4 , and its population was affected by ecological niche and resource utilisation; incubation temperature had a significant effect on the sex ratio; the sea lampreys played an important role in the balance between predators and prey; and showed adaptability to the gradient of the environment, suggesting that spatial heterogeneity exists in the ecosystem. The comprehensive assessment showed that the multilevel impacts of the sea lampreys on ecosystems included the regulation of population dynamics, the maintenance of food web balance and adaptation to changes in the environment, thus playing an important role in the stability and functioning of ecosystems.

Restoration of degraded seagrass meadows: Effects of plant growth-promoting rhizobacteria (PGPR) inoculation on Zostera marina growth, rhizosphere microbiome and ecosystem functionality

The utilization of plant growth-promoting rhizobacteria (PGPR) holds great promise for the restoration of damaged terrestrial plant ecosystems. However, there is a significant knowledge gap regarding the application of PGPR in rehabilitating aquatic ecosystems. In this study, we conducted a mesocosm experiment to investigate the effects of Raoultella ornithinolytica F65, Pantoea cypripedii G84, Klebsiella variicola G85, Novosphingobium profundi G86, and Klebsiella pneumoniae I109 on eelgrass (Zostera marina L.), which is a crucial marine angiosperm. The application of these strains resulted in a significant increase in the new leaf area of eelgrass, with improvements of 55.4%, 14.4%, 39.1%, 20.6%, and 55.7% observed, respectively. Moreover, PGPR inoculation enhanced shoot biomass, rhizome elongation, leaf carbon and nitrogen content, as well as photosynthetic pigments. Furthermore, it stimulated enzymatic activities within the rhizosphere soil and positively influenced its physicochemical properties. The Illumina Miseq sequencing results revealed a positive shift in the bacterial community, leading to an enrichment of functional groups associated with nitrogen fixation and degradation of aromatic compounds. These findings underscore the significant potential of PGPR as a transformative tool for enhancing seagrass growth and survival, offering innovative strategies for the restoration of degraded seagrass meadows. This research not only advances our understanding of microbial-plant interactions in aquatic ecosystems but contributes to the broader goals of ecosystem revitalization and biodiversity conservation.

Distinct resource utilization by introduced man-made grouper hybrid: an overlooked anthropogenic impact from a longstanding religious practice

AbstractAnthropogenic activities, such as the introduction of non-native aquaculture species, have significantly altered trophic interactions in marine ecosystems. The hybrid grouper (TGGG), an aquaculture product originating from an artificial F1 crossbreed between Epinephelus fuscoguttatus and E. lanceolatus, has been released into the wild through religious activities, raising concerns about the ecological implications of this man-made species. With its carnivorous diet and large body size inherited from the parental species, TGGG could pose significant impacts to the marine ecosystem. Yet, little is known about the diet composition of TGGG upon release into the natural environment as well as its dietary overlap or partitioning with closely related species. Here, we deployed gut content DNA metabarcoding to determine the prey richness and dietary niche of wild-caught TGGG and compared it to four native grouper species (Epinephelus awoara, E. bleekeri, E. coioides and E. quoyanus). Our results indicate that the TGGG exhibited five unique prey taxa, with teleosts being the predominant prey, followed by crustaceans and cephalopods. Notably, the TGGG displayed a significantly lower mean number of prey taxa compared to the other groupers, suggesting a distinct diet composition that may reflect a transition in feeding behaviour. This study provides a comprehensive analysis with high taxonomic resolution on the diet of artificial hybrids in the wild, indicating the potential for successful establishment if release events persist. Finally, these findings provide new insights into how local trophic dynamics are impacted by the under-investigated release of animals through religious practices.

Strategies for enriching targeted sulfate-reducing bacteria and revealing their microbial interactions in anaerobic digestion ecosystems

Deciphering relationships between sulfate-reducing bacteria (SRB) and other microorganisms is crucial for stable operation of anaerobic digestion systems when treating sulfate-containing wastewater. However, few studies have differentiated the incomplete oxidizing SRB (IO-SRB) and complete oxidizing SRB (CO-SRB) in anaerobic digestion ecosystems. Four ethanol-fed bioreactors were operated under two operational modes (sequencing batch reactor, SBR; and continuous-flow reactor, CFR) and two chemical oxygen demand (COD) to sulfate ratios (1 and 2) to systematically explore strategies for enriching IO-SRB and/or CO-SRB and their microbial interactions with other microorganisms. Compared to SBRs, CFRs could enhance sulfate removal and demonstrated higher microbial activities in sulfate and ethanol degradation. IO-SRB competed with ethanol oxidizing bacteria in all reactors, and IO-SRB's contribution to ethanol degradation increased from 62.9 %-67.1 % to 69.0 %-82.1 % as the COD/sulfate ratio decreased from 2 to 1. Moreover, CO-SRB competed acetotrophic methanogens exclusively in CFRs, as CO-SRB could not be efficiently enriched in SBRs. Low COD/sulfate ratios facilitated the enrichment of Desulfococcus (CO-SRB), and the CFR operational mode further strengthened its enrichment. Additionally, hydrogenotrophic SRB outperformed hydrogenotrophic methanogens in all four reactors. In general, IO-SRB and CO-SRB possessed distinct microbial interactions with methanogens, with potential syntrophic relationships between IO-SRB and acetotrophic methanogens while competitive relationships between CO-SRB and acetotrophic methanogens.

Haemoparasite infection risk in multi-host avian system: an integrated analysis.

Avian blood parasites play a crucial role in wildlife health and ecosystem dynamics, exhibiting heterogeneous spatial distribution influenced by various factors. Although factors underlying heterogeneity in infection with blood parasites have been explored in many avian hosts, their importance in the context of host species and the parasite taxon remains poorly understood, particularly in cohabiting host species. Using next-generation sequencing for parasite screening, we investigate the association between Haemoproteus, Plasmodium and Trypanosoma infections in relation to individual parameters, host densities and landscape features in 3 cavity-nesting passerines: great tit (Parus major), blue tit (Cyanistes caeruleus) and collared flycatcher (Ficedula albicollis) in a highly fragmented forest habitat. Overall, Haemoproteus infections predominated, followed by Plasmodium and Trypanosoma, with great tits most and collared flycatchers least parasitized. There were no common patterns across host species in the probability of infection with locally transmitted parasites from each genus. Specifically, in all cases, the effect of particular parameters, if present, was observed only in 1 host species. Body condition influenced Haemoproteus and Plasmodium infections differently in tits. Host density, whether own species or all pooled, explained Haemoproteus infections in great tits and collared flycatchers, and Plasmodium in great tits. Landscape metrics, such as moisture index and distance to coast edge and pastures, affected infection probability in specific host–parasite combinations. Relative risk maps revealed infection risk gradients, but spatial variation repeatability over time was low. Our study highlights the complex dynamics of avian blood parasites in multi-host systems, shedding light on host–parasite interactions in natural ecosystems.

Feeding ecology of two wild sympatric canids in protected areas of northeastern Argentina

AbstractThe role of mesocarnivores in wildlife communities tends to be overlooked, which has led to a large gap in natural history knowledge. In northeastern Argentina, two mesocarnivore foxes, Cerdocyon thous and Lycalopex gymnocercus, live in sympatry in noncompetitive coexistence. Their feeding habits have been studied in many occasions; however, the studies related to trophic variability in a wider spatial scale remain scarce. In this study, we aimed to analyze how the diet of these foxes varies in three protected areas in Argentina: the Mburucuyá National Park (MNP), the “San Nicolás Portal” (SN), and the Natural Reserve Rincón de Santa María (RSM). We collected fecal samples in each area, identified them using thin layer chromatography at species level, and classified the found feeding items to obtained two parameters: occurrence and relative frequency. Furthermore, we compared the diet of the two species in each site and between sites using chi‐square and estimated trophic niche breadth and overlap between the species. We found that both species consumed different food categories, with variable frequencies across study sites. We observed that in each area, the foxes differed in diet composition. However, we found no differences between the diet compositions of C. thous and L. gymnocercus, showing high niche overlap in each site. Here, we show the plasticity of both fox species in changing their diets even with small geographical variation. Both species can coexist even with a high diet overlap, possibly explained by their noncompetitive coexistence which may occur due to the current changes in the ecosystem interactions, or partitioning may exist but on a smaller niche level.

Microfluidics for studying the deep underground biosphere: from applications to fundamentals.

In this review, selected examples are presented to demonstrate how microfluidic approaches can be utilized for investigating microbial life from deep geological environments, both from practical and fundamental perspectives. Beginning with the definition of the deep underground biosphere and the conventional experimental techniques employed for these studies, the use of microfluidic systems for accessing critical parameters of deep life in geological environments at the microscale is subsequently addressed (high pressure, high temperature, low volume). Microfluidics can simulate a range of environmental conditions on a chip, enabling rapid and comprehensive studies of microbial behavior and interactions in subsurface ecosystems, such as simulations of porous systems, interactions among microbes/microbes/minerals, and gradient cultivation. Transparent microreactors allow real-time, noninvasive analysis of microbial activities (microscopy, Raman spectroscopy, FTIR microspectroscopy, etc.), providing detailed insights into biogeochemical processes and facilitating pore-scale analysis. Finally, the current challenges and opportunities to expand the use of microfluidic methodologies for studying and monitoring the deep biosphere in real time under deep underground conditions are discussed.

Is the response of plant root systems to precipitation primarily driven by the rhizosphere soil?

BackgroundChanges in precipitation alter soil moisture, thereby affecting the aboveground and belowground ecological processes. However, it remains unclear whether plant root systems alter these effects through rhizospheric processes. In this study, a precipitation control experiment was conducted in the alpine grassland of northern Tibet to simulate precipitation changes with a 50% decrease and 50% increase in precipitation. Nutrient and microbial biomass, root traits, and survival strategies in the rhizosphere and bulk soils of the dominant plant, Stipa purpurea, were analyzed for alterations under precipitation changes.ResultsIncreased precipitation (IP) significantly decreased the rhizosphere soil total phosphorus and bulk soil ammonium nitrogen and increased the rhizosphere soil total potassium. Decreasing precipitation (DP) significantly increased the rhizosphere soil total potassium and decreased the bulk soil total potassium. DP significantly reduced microbial biomass carbon, nitrogen and phosphorus in rhizosphere soil, while IP significantly increased the bulk soil MBC:MBP, soil C:P imbalance, and soil N:P imbalance. Along the PC1 axis, where the contribution of the traits was relatively large, it was possible to define the root economic spectrum. The root system of Stipa purpurea from the DP treatment was distributed on the conservative side of the economic spectrum, whereas that from the control and IP treatments were clustered on the acquisition side.ConclusionsIncreasing and decreasing precipitation mainly affected the contents of total phosphorus and total potassium in rhizosphere soil and the contents of ammonium nitrogen and total potassium in bulk soil of Stipa purpurea. The microbial biomass carbon, nitrogen and phosphorus were mainly affected by a decrease in precipitation. Decreasing precipitation significantly reduced microbial biomass carbon, nitrogen and phosphorus, but the rhizosphere MBC:MBN, MBC:MBP and MBN:MBP remained stable under the change of precipitation. Increasing precipitation exacerbated the C:P imbalance and N:P imbalance in bulk soil, and increased the demand for phosphorus by bulk microorganisms. Increased precipitation promoted root access to resources. The root system of Stipa purpurea in the context of precipitation changes was driven by rhizosphere nutrients and bulk microorganisms. This study is important for revealing plant–microbe–soil interactions in terrestrial ecosystems.

Zooming in the plastisphere: the ecological interface for phytoplankton-plastic interactions in aquatic ecosystems.

Phytoplankton is an essential resource in aquatic ecosystems, situated at the base of aquatic food webs. Plastic pollution can impact these organisms, potentially affecting the functioning of aquatic ecosystems. The interaction between plastics and phytoplankton is multifaceted: while microplastics can exert toxic effects on phytoplankton, plastics can also act as a substrate for colonisation. By reviewing the existing literature, this study aims to address pivotal questions concerning the intricate interplay among plastics and phytoplankton/phytobenthos and analyse impacts on fundamental ecosystem processes (e.g. primary production, nutrient cycling). This investigation spans both marine and freshwater ecosystems, examining diverse organisational levels from subcellular processes to entire ecosystems. The diverse chemical composition of plastics, along with their variable properties and role in forming the "plastisphere", underscores the complexity of their influences on aquatic environments. Morphological changes, alterations in metabolic processes, defence and stress responses, including homoaggregation and extracellular polysaccharide biosynthesis, represent adaptive strategies employed by phytoplankton to cope with plastic-induced stress. Plastics also serve as potential habitats for harmful algae and invasive species, thereby influencing biodiversity and environmental conditions. Processes affected by phytoplankton-plastic interaction can have cascading effects throughout the aquatic food web via altered bottom-up and top-down processes. This review emphasises that our understanding of how these multiple interactions compare in impact on natural processes is far from complete, and uncertainty persists regarding whether they drive significant alterations in ecological variables. A lack of comprehensive investigation poses a risk of overlooking fundamental aspects in addressing the environmental challenges associated with widespread plastic pollution.

Host trees partially explain the complex bacterial communities of two threatened saproxylic beetles.

Microorganisms are integral to ecosystem functioning and host adaptation, yet the understanding of microbiomes in diverse beetle taxa remains limited. We conducted a comprehensive study to investigate the microbial composition of two red flat bark beetle species, Cucujus haematodes and C. cinnaberinus, and assessed the influence of host taxonomic relatedness and host tree species on their microbiomes. We sampled 67 larvae of two Cucujus taxa taken from 11 host tree species. 16S rRNA V4 fragment sequencing revealed distinct microbial communities associated with each Cucujus species, with host tree species significantly influencing microbiome composition. Alpha and beta diversity metrics indicated significant differences between microbial communities in both beetle and host tree species. Principal component analysis indicated distinct clustering based on host tree species but not for beetle species. This overlap could be attributed to the similar ecology of both Cucujus species. The detection of various bacteria, among which some have already been reported in saproxylophagous beetles, suggests that the red flat bark beetles ingest the bacteria via foraging on other wood-dwelling invertebrates. Our findings show the complex interplay between host taxonomy, microhabitat and microbial composition in Cucujus, providing insights into their ecological roles and conservation implications. This research helps to fill the gap in understanding the microbial dynamics of saproxylic beetles, sheds light on factors shaping their microbiomes and highlights the importance of considering both host species and environmental conditions when studying insect-microbe interactions in forest ecosystems.

Monitoring bay-scale ecosystem changes in bivalve aquaculture embayments using flow cytometry.

Bay-scale empirical evaluations of how bivalve aquaculture alters plankton composition, and subsequently ecological functioning and higher trophic levels, are lacking. Temporal, inter- and within-bay variation in hydrodynamic, environmental, and aquaculture pressure complicate plankton monitoring design to detect bay-scale changes and inform aquaculture ecosystem interactions. Here, we used flow cytometry to investigate spatio-temporal variations in bacteria and phytoplankton (< 20 μm) composition in four bivalve aquaculture embayments. We observed higher abundances of bacteria and phytoplankton in shallow embayments that experienced greater freshwater and nutrient inputs. Depleted nutrient conditions may have led to the dominance of picophytoplankton cells, which showed strong within-bay variation as a function of riverine vs marine influence and nutrient availability. Although environmental forcings appeared to be a strong driver of spatio-temporal trends, results showed that bivalve aquaculture may reduce near-lease phytoplankton abundance and favor bacterial growth. We discuss confounding environmental factors that must be accounted for when interpreting aquaculture effects such as grazing, benthic-pelagic coupling processes, and microbial biogeochemical cycling. Conclusions provide guidance on sampling considerations using flow cytometry in aquaculture sites based on embayment geomorphology and hydrodynamics.

Insights into the occurrence of phylosymbiosis and co-phylogeny in the holobionts of octocorals from the Mediterranean Sea and Red Sea

BackgroundCorals are the foundational species of coral reefs and coralligenous ecosystems. Their success has been linked to symbioses with microorganisms, and a coral host and its symbionts are therefore considered a single entity, called the holobiont. This suggests that there may be evolutionary links between corals and their microbiomes. While there is evidence of phylosymbiosis in scleractinian hexacorals, little is known about the holobionts of Alcyonacean octocorals.Results16S rRNA gene amplicon sequencing revealed differences in the diversity and composition of bacterial communities associated with octocorals collected from the mesophotic zones of the Mediterranean and Red Seas. The low diversity and consistent dominance of Endozoicomonadaceae and/or Spirochaetaceae in the bacterial communities of Mediterranean octocorals suggest that these corals may have a shared evolutionary history with their microbiota. Phylosymbiotic signals were indeed detected and cophylogeny in associations between several bacterial strains, particularly those belonging to Endozoicomonadaceae or Spirochaetaceae, and coral species were identified. Conversely, phylosymbiotic patterns were not evident in Red Sea octocorals, likely due to the high bacterial taxonomic diversity in their microbiota, but cophylogeny in associations between certain coral and bacterial species was observed. Noteworthy were the associations with Endozoicomonadaceae, suggesting a plausible evolutionary link that warrants further investigations to uncover potential underlying patterns.ConclusionsOverall, our findings emphasize the importance of Endozoicomonadaceae and Spirochaetaceae in coral symbiosis and the significance of exploring host-microbiome interactions in mesophotic ecosystems for a comprehensive understanding of coral-microbiome evolutionary history.

Soil Physical Properties Affect Herbivory of Lampronadata cristata in a Cork Oak Forest.

Studies have reported the important role of soil properties in regulating insect herbivory under controlled conditions or at relatively large scales. However, whether fine-scale variation of soil properties affects insect herbivory under natural conditions in forests is still unclear. We selected a ca. 300 ha Quercus variabilis forest area where the leaf damage was mainly caused by Lampronadata cristata (Lepidoptera: Notodontidae) and set 200 10 × 10 m plots within the area. We examined insect herbivory (percent leaf area damaged) on Q. variabilis and correlated it to soil properties and tree characteristics. Insect herbivory decreased with soil sand percentage and bulk density and increased with DBH and tree height. Effects of soil sand percentage and bulk density on insect herbivory were partly mediated by DBH and tree height. Our results indicated that soil physical properties may have significant effects on insect herbivory by directly influencing insect herbivores that need to complete their life cycle in the soil, or by indirectly affecting insect herbivores through influencing DBH and tree height which reflects the total leaf biomass available to the insect herbivore. This study may help to understand the complex relationship between soil and plant-insect interactions in forest ecosystems.

Unraveling Community Potential Interactions by Environmental DNA in the Hong Kong Coastal Waters

ABSTRACTTraditional approaches for studying potential interactions in marine ecosystems often struggle to fully capture all taxa in a community, especially rare species. This issue is particularly challenging in coastal waters with high biodiversity and spatiotemporal dynamics. In this study, we employed environmental DNA (eDNA) metabarcoding, utilizing multiple marker genes, to comprehensively investigate interspecific interactions across various domains in the subtropical coastal waters of Hong Kong. The southern and eastern regions of Hong Kong waters exhibit distinct environmental seasonality, and our investigation focused on comparing the potential interaction networks and the keystone taxa between these two regions. The putative species interaction networks across various groups (i.e., bacteria, protists, and metazoans) were revealed by using weighted correlation network analysis (WGCNA). Our results showed that primary consumers, mainly dinoflagellates and ciliates, were the dominant actors within the interaction networks, although their distributions varied between the two regions. Bacterial taxa from the Pseudomonadota groups primarily constituted saprobes in the southern region, while exhibiting an even distribution in the eastern region. The interaction network in the southern region was larger but less stable compared to the eastern region. This could be attributed to the stronger responses of keystone taxa to environmental variations and the relatively higher number of connectors (e.g., Akashiwo and Protoperidinium within Dinophyceae) in the eastern region. Our findings highlight the versatility of eDNA metabarcoding for studying potential species interactions, providing critical insights into ecosystem structure and stability, and offering suggestions for marine biodiversity conservation.

Driving mechanism of land use and landscape pattern to phytoplankton and zooplankton community and their trophic interactions in river ecosystems

The trophic interactions between phytoplankton and zooplankton communities are essential for maintaining river ecosystem integrity and health. However, the driving mechanisms of land use and landscape patterns (LULP) affecting their trophic interactions are not fully understood. Therefore, the research objective of this study was to reveal the driving mechanisms of LULP on the interaction of phytoplankton with zooplankton through remote sensing interpretation of LULP in different buffer scales (500 m, 1000 m, 1500 m, and catchment), combined with water environment factors and plankton community structures analyzed. Results showed that LULP had the most significant effect on the phytoplankton and the zooplankton community structure at 500 and 1500 m buffer scales, respectively. Construction land (CON) and edge density (ED) most influenced phytoplankton and zooplankton community structure and their influence mechanisms were identified, i.e., CON increased the species (S) of phytoplankton by increasing the concentration of NO3-N in river water at the 500 m buffer scale. ED reduced the biological density (BD) of zooplankton by decreasing the concentration of heavy metal (HM) in river water at the 1500 m buffer scale. The water area (WAT) and ED showed the most significant influence on plankton interaction. Three pathways were found to explain their influence mechanisms, i.e., ED decreased the BD or Shannon-Weiner index (H’) of zooplankton by increasing the dissolved oxygen (DO) to enhance BD of phytoplankton in river water at the 1500 m buffer scale; the WAT increased the BD of phytoplankton by increasing water temperature to reduce the H' of zooplankton at the 500 m buffer. These findings have implications for effective ecological planning of future human activities in the stream domain and maintaining river ecosystem health.

Co-Occurrence Patterns Do Not Predict Mutualistic Interactions Between Plant and Butterfly Species.

Biotic interactions are crucial for determining the structure and dynamics of communities; however, direct measurement of these interactions can be challenging in terms of time and resources, especially when numerous species are involved. Inferring species interactions from species co-occurrence patterns is increasingly being used; however, recent studies have highlighted some limitations. To our knowledge, no attempt has been made to test the accuracy of the existing methods for detecting mutualistic interactions in terrestrial ecosystems. In this study, we compiled two literature-based, long-term datasets of interactions between butterflies and herbaceous plant species in two regions of Germany and compared them with observational abundance and presence/absence data collected within a year in the same regions. We tested how well the species associations generated by three different co-occurrence analysis methods matched those of empirically measured mutualistic associations using sensitivity and specificity analyses and compared the strength of associations. We also checked whether flower abundance data (instead of plant abundance data) increased the accuracy of the co-occurrence models and validated our results using empirical flower visitation data. The results revealed that, although all methods exhibited low sensitivity, our implementation of the Relative Interaction Intensity index with pairwise null models performed the best, followed by the probabilistic method and Spearman's rank correlation method. However, empirical data showed a significant number of interactions that were not detected using co-occurrence methods. Incorporating flower abundance data did not improve sensitivity but enhanced specificity in one region. Further analysis demonstrated incongruence between the predicted co-occurrence associations and actual interaction strengths, with many pairs exhibiting high interaction strength but low co-occurrence or vice versa. These findings underscore the complexity of ecological dynamics and highlight the limitations of current co-occurrence methods for accurately capturing species interactions.