Changes In Community Structure Research Articles

Inter-annual variability in the phytoplankton abundance and community structure of a tropical monsoonal estuary in response to variable monsoonal patterns

The study elucidates the inter-annual and seasonal variability in the phytoplankton abundance and community structure concurrent to variable rainfall patterns in Chettuva, a tropical monsoonal estuary along the southwest coast of India. The phytoplankton community exhibited statistically significant inter-annual variation with a 1.2-fold increase in abundance (av. 19.44 ×104cellsL-1) in 2021 in comparison with 2019 (av. 15.30 ×104cellsL-1). A total of 87 phytoplankton species were observed during the study, among which Bacillariophyceae dominated with 52 species, followed by Dinophyceae (20 species), and to a lesser extent by Chlorophyceae (11 species) and Cyanophyceae (2 species). Phytoplankton community structure also showed variation, with 71 species contributing to the diversity in 2021 and 62 species in 2019. Though Bacillariophycea dominated during both years, the community was more diverse in 2021comparatively a more saline year Biddulphia sp. Coscinodiscus sp., Cyclotella striata, Melosira sulcata, Pleurosigma sp., and Skeletonema costatum were the diatoms common to both the years, though with varied abundance. Dinophyceae did not show a conspicuous change in community structure in both years, with mostly the same species contributing to the total phytoplankton population but showed slight variation in abundance. Cyanophycea was observed exclusively during the year 2021. The abundance and community structure of the species varied from year to year, but they also changed seasonally, with lower numbers observed during the monsoon compared to the post-monsoon period in both years. CCA analysis identified two groups of phytoplankton assemblages in relation to the prevailing environmental conditions. The Group I species preferred lower temperature and salinity and elevated nutrient concentrations and they dominated during the monsoon season. Group II species preferred high saline well oxygenated, nutrient-poor waters and they dominated during the post-monsoon. Furthermore, the trophic state index analysis indicated mesotrophic conditions during the monsoon, while eutrophic conditions were observed in the post-monsoon period.

Diversity of Orchid in Abies nephrolepis Nature Reserve in Shanxi, China.

Abies nephrolepis Nature Reserve has complex habitats and rich species diversity but lacks systematic ecological surveys. We focused on Orchid in Abies nephrolepis Nature Reserve, investigated and analyzed Orchid diversity and changes in community structure according to the characteristics of the alpine valleys in the study area, in terms of altitude gradient and habitat type, using the sample line method and the quadrat method. The results showed that 11 genera and 13 species of Orchidaceae were found in the survey, among which the species richness of Malaxis monophyllos was the highest, Neottia puberula was the second highest, and the species richness of Tulotis ussuriensis was the lowest, and the species with relative plurality ≥ 10% were Malaxis monophyllos (51.69%), Neottia puberula (14.77%), and Cypripedium guttatum (11.15%). The results of diversity analysis showed that Orchidaceae species were rich and the diversity index were the highest in the middle altitude area of 1950-2250 m; the distribution of Orchidaceae in the low altitude area was obviously clustered, and the similarity with the high altitude area was low. With the increase in altitude, the number of species showed an increase and then a decrease, showing a single-peak state, which was in line with the theory of "Intermediate altitude expansion hypothesis". The species and number of Orchidaceae in different habitats of Abies nephrolepis Nature Reserve also varied considerably, with Shannon-Wiener diversity index being the highest in EV4 (Abies nephrolepis + Picea meyeri + Picea wilsonii + Larix gmelinii var. principis-rupprechtii-Lonicera hispida-Carex lanceolata community) and EV5, and the smallest in EV1 habitats, Pielow evenness index being the highest in EV5 habitats and the lowest in EV1 habitats, and Simpson's index being the highest in EV5 habitats and the lowest in EV1 habitats. This study provides a scientific basis for strengthening regional monitoring of species diversity and protecting biodiversity.

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.

Nutrient dynamics and biogeochemical processes at the Polar front of Indian sector of the Southern Ocean: Influence of Circumpolar deep water intrusion

The Circumpolar Deep water (CDW) is one of the largest water masses in the Southern Ocean. The cross-frontal flow of the CDW is a vital mode of redistribution and transport of heat, salts, nutrients, etc. in the ocean. The present study aims to understand the role of the CDW intrusion on nutrient dynamics and biogeochemical processes at the Polar frontal region. The study noted a patch of high nutrients layer at ∼300-400 m in the Polar Front-II, underlying the dicothermal layer or the temperature minimum layer. This high nutrient patch was attributed to the intrusion of the CDW at the Polar front, influencing the physico-chemical processes in the water column. It was evident that, the density gradient, stratification and overall, the combined effect of physico-chemical and biological factors as a consequence of intrusion of the CDW contributed to the formation of the high nitrate patch at the Polar Front-II. Even though, the CDW intrusion did not significantly impact the photic layer dynamics during this study, the possible barrier effect during austral summer contribute to the formation of the high nitrate layer. This feature may be responsible for trapping nutrients in the subsurface due to stratification, made available to the photic region via upwelling processes, consequently triggering changes in the biological community structure and biogeochemical processes.

Responses of various organic carbon pools to elevated temperatures in soils

Soil organic carbon (SOC) and its composition may be vulnerable to the effects of microbial degradation and various environmental stresses. Hitherto, the responses of various SOC pools to warming have rarely been explored. In this study, an incubation experiment was performed with top soils (0–20 cm) from Alfisol and Ultisol at three temperatures (15, 30 and 45 °C). Warming significantly decreased the contents of SOC, particulate organic carbon (POC), mineral associated organic carbon (MAOC) and iron bound organic carbon (Fe–OC) to different degrees. However, the proportion of MAOC and Fe–OC to SOC increased by 3.6–13.3 % and 3.8–7.3 %, respectively, with rising temperature, suggesting that the temperature response of MAOC and especially Fe-OC mineralization is lower than other SOC pools. From the analysis of the Fe-OC structure by various spectroscopic techniques, it was found that elevated temperature increased the proportion of aromatic C but decreased that of aliphatic C to Fe-OC. Soil pH, identified as the most important environmental variable for controlling Fe-OC chemical structure by Mantel test, exhibited a significant negative correlation with aliphatic Fe-OC and positive correlation with aromatic Fe-OC. Synchrotron radiation–based Fourier transform infrared (SR–FTIR) spectroscopy affirmed the higher binding strength of aromatic C with Fe oxides than aliphatic C in both soils. In addition, elevated temperature induced the increase and decrease of K-strategy bacteria and r-strategy bacteria, respectively, indicating warming slowed the bacterial growth, which could produce less necromass carbon for the association of Fe oxides and caused the decrease in Fe-OC. In summary, warming-induced changes in pH and microbial community structure can lead to a decrease in Fe-OC content, whereas the increased proportions confirmed that Fe-OC remains the most stable OC pool facing with short-term soil warming. These findings are helpful for better understanding the importance of soil minerals, especially Fe oxides, in the regulation of soil C sequestration under the context of climate change.

Variation in Community Structure and Abundance of Fish in Simple Structured Shallow Sandy Habitats

ABSTRACTSandy beaches and their surf zones characterise many of the world's open coastlines. They are important breeding, nursery and feeding areas for many species of fish. Despite the commonness and importance of sandy beach surf zones, the dynamics, space occupancy and diversity patterns of residing fish is in many places poorly understood. The aim of this study was to (1) characterise the fish community structure in 11 simple structured sandy surf zones of the northern Baltic Sea and (2) relate variation in fish abundance and community structure to a set of chosen abiotic variables. Using beach seine, weekly or biweekly sampling was conducted at fixed sites at 10 occasions throughout a summer season. A total of 60,006 fish individuals belonging to 20 species were recorded. Changes in abundance and community structure were mainly driven by the variation of only five species reflecting species‐specific recruitment patterns and different spatial responses to abiotic variables. Dominating groups were Gasterosteidae, Ammodytidae and Gobiidae that together formed 86% of the total adult fish catches. Larval numbers were completely dominated by Gobiidae. Multivariate analyses indicated species‐specific responses to measured environmental variables, most important being a combination of wave exposure, beach slope, bottom roughness, and temperature. The present study shows that changes in fish abundance on simple structured sandy sublittoral beaches in the northern Baltic Sea are large over the course of a breeding season. It also reveals that variation in adult and juvenile fish are driven by a set of abiotic factors that influence on the fish assemblage structure through mainly species‐specific, rather than through generic responses. Unravelling the degree to which the sandy shore fish community vary in the northern Baltic Sea will help in managing coastal environments that are increasingly being threatened by many anthropogenic stressors.

Constructed wetland coupled microbial fuel cell (CW-MFC) with Phragmites australis planted for hexavalent chromium removal and electricity generation

Hexavalent chromium (Cr(VI)) in aqueous solution is characterized by strong mobility, high solubility, and significant biological toxicity. In this study, four constructed wetland combined with microbial fuel cell (CW-MFC) systems were established to explore the changes in electricity generation, water purification, and microbial community structure under the influence of plant, bioelectrochemical, and Cr(VI) stress. The planted CW-MFC (total Cr: 97.5 %, Cr(VI): 99.2 %) and non-planted CW-MFC (total Cr: 95.3 %, Cr(VI): 97.3 %) showed significantly higher Cr removal efficiency than open circuit CW-MFC (total Cr: 86.9 %, Cr(VI): 84.8 %). The presence of plants and Cr(VI) increased the average voltage and power density of CW-MFC. Additionally, plants, bioelectrochemistry, and Cr(VI) improved COD removal and significantly enhanced the abundance and diversity of microorganisms in the system during long-term domestication. The Cr(VI)-reducing bacterium Exiguobacterium was least abundant in non-Cr(VI) containing CW-MFC system. The abundance of the electrochemically active bacteria (EAB) Geobacter increased under bioelectrochemistry and Cr(VI).

Antibacterial periodontal ligament stem cells enhance periodontal regeneration and regulate the oral microbiome

BackgroundThe transplantation of periodontal ligament stem cells (PDLSCs) has been shown to enhance periodontal regeneration in animal models and clinical trials. However, it is not known whether PDLSCs are antibacterial and whether this affects oral microbiota and periodontal regeneration.MethodsWe isolated human PDLSCs from periodontal ligament of extracted teeth. Rats’ periodontal fenestration defects were prepared, and treated with PDLSC injections (Cell group), using saline injections (Saline group) as the control. The oral microbiota was explored by 16 S rDNA sequencing and compared with that before surgery (PRE group). The antibacterial property of PDLSCs and its underlying mechanism were tested in vitro.ResultsMicrobiome analyses reveal a decreased biodiversity, a changed community structure, and downregulated community functions of the oral microbiome in the Saline group. PDLSCs injections enhance periodontal regeneration, reverse the decrease in diversity, and increase the abundance of non-pathogenic bacterial Bifidobacterium sp. and Lactobacillus sp., making the oral microbiome similar to that of the PRE group. In vitro, PDLSCs inhibit the growth of Staphylococcus aureus, Escherichia coli, and Fusobacterium nucleatum. The main mechanism of action is postulated to involve production of the cationic antimicrobial peptide LL-37.ConclusionsOur findings reveal that PDLSC injections enhance periodontal regeneration and regulate the oral microbiome to foster an oral cavity microenvironment conducive to symbiotic microbiota associated with health.

Use of long-term underwater camera surveillance to assess the effects of the largest Amazonian hydroelectric dam on fish communities

The increase in the construction of mega dams in tropical basins is considered a threat to freshwater fish diversity. Although difficult to detect in conventional monitoring programs, rheophilic species and those reliant on shallow habitats comprise a large proportion of fish diversity in tropical basins and are among the most sensitive species to hydropower impacts. We used Baited Remote Underwater Video (BRUV), an innovative, non-invasive sampling technique, to record the impacts caused by Belo Monte, the third largest hydropower project in the world, on fishes inhabiting fast waters in the Xingu River. BRUV were set in a river stretch of ~ 240 km for 7 years, 2 before and 5 after the Belo Monte operation. We explored the spatial and temporal variation in fish diversity (α, β, and γ) and abundance (MaxN) using generalized additive models. We also investigated the variation of environmental variables and tested how much information we gained by including them in the diversity and abundance models. Belo Monte altered the flow regime, water characteristics, and fishery yield in the Xingu, resulting in changes in the fish community structure. Temporally, we observed sharp declines in α diversity and abundance, far exceeding those from a previous study conducted with more conventional sampling methods (i.e., catch-based) in the region. γ-diversity was also significantly reduced, but we observed a non-expected increase in β diversity over time. The latter may be associated with a reduction in river connectivity and an increase in environmental heterogeneity among river sectors. Unexpected signs of recovery in diversity metrics were observed in the last years of monitoring, which may be associated with the maintenance of flow levels higher than those previously planned. These results showed that BRUV can be a useful and sensitive tool to monitor the impacts of dams and other enterprises on fish fauna from clear-water rivers. Moreover, this study enhances our comprehension of the temporal variations in freshwater fish diversity metrics and discusses the prevalent assumption that a linear continuum in fish-structure damage associated with dam impoundments may exhibit temporal non-linearity.

High-frequency study of megafaunal communities on whale bone, wood and carbonate in hypoxic Barkley Canyon

Organic-rich whale bones and wood falls occur widely in the deep sea and support diverse faunal communities, contributing to seafloor habitat diversity. Changes in community structure through succession on deep-sea bone/wood substrates are modulated by ecosystem engineers, i.e., bone-eating Osedax annelids, and wood-boring Xylophaga bivalves. Here, we use a comparative experimental approach and Ocean Networks Canada’s (ONC) cabled observatory in hypoxic Barkley Canyon to study, at high temporal resolution, colonization and succession on whale-bone, Douglas fir wood, and control carbonate rock over 8.3 mo. Experimental substrates were similar in size and mounted on PVC plates near the seafloor at 890 m depth and monitored by high-definition video camera for 5-min intervals every 6-12 h over a period of 8.3 mo. A broad range of seafloor and sea-surface environmental variables were also monitored at this site over the 8.3 mo to account for environmental variability and food input. Following loss of the high-definition camera, substrates were surveyed approximately annually with lower resolution ROV video for an additional 8.5 y. We find that megafaunal abundances, species diversity, and community structure varied substantially over 8.3 mo on each substrate, with markedly different patterns on whale bones due to the development of extensive white bacterial mats. A combination of seafloor and sea surface variables explained < 35% of bone/wood community variation. Bone-eating Osedax annelids failed to colonize whale bones even after 9.2 years, and boring Xylophaga bivalves colonized the wood at much lower rates than in better oxygenated deep-sea locations. Species diversity on whale-bone and wood substrates appeared to be substantially reduced due to the absence of ecosystem engineers and the low oxygen concentrations. We hypothesize that Osedax/Xylophaga colonization, bone/wood degradation, and bone/wood community development may be limited by oxygen concentrations of 0.22 - 0.33 ml.l on the NE Pacific margin, and that OMZ expansion due to climate change will reduce whale-bone and wood degradation, and the contribution of whale falls and wood falls to beta diversity, on the NE Pacific margin.

Structure and long-term changes of polychaete communities of the Varanger fjord in 2003 and 2019

Long-term changes in species composition, production indicators, and structure of polychaete communities for the period of 2003 and 2019 in the Russian part of the Varanger fjord (Barents Sea) were shown. The connection of such changes with climate factors and the influence of the red king crab are considered. The changes in species composition, structure, and production characteristics of polychaetes in the Russian part of the Varanger fjord (Barents Sea) in 2003 and 2019 are shown. The linkage between these changes and the climatic factor, as well as the influence of the introduced red king crab Paralithodes camtschaticus (Tilesius, 1815), is discussed. The results demonstrate an increase in the quantitative characteristics of polychaete Spiochaetopterus typicus M. Sars, 1856, indicating a decrease in pressure from the king crab on bottom communities. The biodiversity indices indicate the absence of negative changes in the settlements of polychaetes in the Varanger fjord during the studied period.

Eutrophication weakens the positive biodiversity–productivity relationship of benthic diatoms in plateau lakes

Context Freshwater primary productivity is threatened by the decline in biodiversity associated with nutrient enrichment, but there is still uncertainty about how the biodiversity and productivity relationship (BPR) varies with the trophic states. Aims We aimed to examine the variation of benthic diatom BPRs in three plateau lakes with different trophic states and their underlying driving mechanisms. Methods We examined the relationship between diatom taxonomic and functional diversity, niche width, and niche overlap with productivity. Key results The taxonomic and functional diversity, niche width and productivity of benthic diatoms were highest in the mesotrophic lake. The benthic diatom BPRs were linear and positive, with the slope of BPRs being the lowest in eutrophic lake. Motile, non-attached and small-sized diatoms were dominant in eutrophic lake. Nutrient concentrations indirectly affected primary productivity by influencing algal community structure, niche width and biodiversity change. Conclusions Diatom productivity and diversity showed a positive relationship, but nutrient enrichment weakened this relationship. By combining taxonomic and functional diversity indices, supplemented by niche analysis, we can further understand the variation of diatom productivity. Implications The results provide a basis for predicting the changes in BPRs of benthic diatoms in the littoral zone with different trophic states.

Diversity and Activity of Soil N2O-Reducing Bacteria Shaped by Urbanization.

Nitrous oxide (N2O) is a potent greenhouse gas with various production pathways. N2O reductase (N2OR) is the primary N2O sink, but the distribution of its gene clades, typically nosZI and atypically nosZII, along urbanization gradients remains poorly understood. Here we sampled soils from forests, parks, and farmland across eight provinces in eastern China, using high-throughput sequencing to distinguish between two N2O-reducing bacteria clades. A deterministic process mainly determined assemblies of the nosZI communities. Homogeneous selection drove nosZI deterministic processes, and both homogeneous and heterogeneous selection influenced nosZII. This suggests nosZII is more sensitive to environmental changes than nosZI, with significant changes in community structure over time or space. Ecosystems with stronger anthropogenic disturbance, such as urban areas, provide diverse ecological niches for N2O-reducing bacteria (especially nosZII) to adapt to environmental fluctuations. Structural equation modeling (SEM) and correlation analyses revealed that pH significantly influences the community composition of both N2O-reducing bacteria clades. This study underscores urbanization's impact on N2O-reducing bacteria in urban soils, highlighting the importance of nosZII and survival strategies. It offers novel insights into the role of atypical denitrifiers among N2O-reducing bacteria, underscoring their potential ecological importance in mitigating N2O emissions from urban soils.

Dry season irrigation promotes nutrient cycling by reorganizing Eucalyptus rhizosphere microbiome

In southern China, seasonal droughts and low soil phosphorus content constrain the productivity of Eucalyptus trees. To understand the rhizosphere microbiome response to the dry season, metagenomic sequencing analysis was used to investigate the 6-year-old Eucalyptus rhizosphere microbiome under four different irrigation and fertilization treatments. The results showed that irrigation and fertilization during the dry season significantly altered the composition of microbiome in the rhizosphere soil of Eucalyptus plantations. The soil physicochemical properties and enzyme activity explained 30.73 % and 29.75 % of the changes in bacterial and fungal community structure in Eucalyptus rhizosphere soil, respectively. Irrigation and fertilization during the dry season significantly altered the physicochemical properties of rhizosphere soil. Compared with the seasonal drought without fertilizer treatment (CK), the dry season irrigation with fertilizer treatment (WF) significantly increased the content of total nitrogen (46.34 %), available nitrogen (37.72 %), available phosphorus (440.9 %), and organic matter (35.34 %). Soil organic matter (OM), pH, and available phosphorus (AP) were key environmental factors influencing the microbial community composition. Moreover, irrigation and fertilization promoted carbon fixation and nitrogen and phosphorus mineralization, increasing soil OM content and the availability of inorganic nitrogen and phosphorus. Meanwhile, compared to the CK, the increase of acid phosphatase (16.81 %), invertase (146.89 %)and urease (59.45 %) in rhizosphere soil under irrigation (W) treatment further proves that dry season irrigation promote the soil carbon, nitrogen and phosphorus cycles. Irrigation and fertilization treatment alleviated the constraints of low phosphorus in southern China's soil, which promoted Eucalyptus productivity. In conclusion, we suggest implementing reasonable irrigation and fertilization strategies in the production practice of Eucalyptus and utilizing microbial resources to improve soil fertility and Eucalyptus productivity.

Stable phytoplankton community compositions in Lake Mead (Nevada-Arizona, USA) during two decades of severe drought

Lake Mead, a large reservoir on the Colorado River and a critical drinking water source for the southwestern United States, typically exhibits high water quality, characterized by low nutrient and chlorophyll-a concentrations. This stability persists despite the inflow of highly treated wastewater since the 1960s and significant water level declines since 2000, driven by the ongoing Megadrought and basin-wide consumptive use. Such environmental changes may alter phytoplankton communities, potentially leading to increased cyanobacteria abundance, which could negatively impact water quality and the aquatic ecosystem through harmful algal blooms and toxin production. Here we analyzed 17 years of phytoplankton community structure and chlorophyll-a concentrations in Lake Mead, alongside quantitative water quality data, including nutrients, temperature, and water clarity, to assess the effects of environmental changes on phytoplankton communities. Contrary to the hypothesis that cyanobacteria abundance would have increased throughout the reservoir, our results indicate that phytoplankton community structures have remained largely stable, except for shallow areas where increases in temperature or phosphorus levels were observed. Additionally, we evaluated machine learning models for predicting changes in phytoplankton community structures. While the models confidently predicted changes in total phytoplankton biovolume and chlorophyll-a concentrations within the input parameter boundaries, predictions of peak biovolume showed considerable uncertainty, emphasizing the importance of incorporating uncertainty analysis in forecasting and communicating results. This study underscores the current buffering capacity of large, oligotrophic reservoirs like Lake Mead to maintain stable phytoplankton communities despite environmental changes. However, it also highlights the potential for significant community shifts if this buffering capacity is exceeded.

A Metagenomics Pipeline to Characterize Self-Collected Vaginal Microbiome Samples.

Vaginitis is a widespread issue for women worldwide, yet current diagnostic tools are lacking. Bacterial vaginosis (BV) is the most prevalent type of vaginitis, found in 10-50% of reproductive-aged women. Current diagnostic methods for BV rely on clinical criteria, microscopy, or the detection of a few microbes by qPCR. However, many vaginal infections lack a single etiological agent and are characterized by changes in the vaginal microbiome community structure (e.g., BV is defined as a loss of protective lactobacilli resulting in an overgrowth of anaerobic bacteria). Shotgun metagenomic sequencing provides a comprehensive view of all the organisms present in the vaginal microbiome (VMB), allowing for a better understanding of all potential etiologies. Here, we describe a robust VMB metagenomics sequencing test with a sensitivity of 93.1%, a specificity of 90%, a negative predictive value of 93.4%, and a positive predictive value of 89.6% certified by Clinical Laboratory Improvement Amendments (CLIA), the College of American Pathologist (CAP), and the Clinical Laboratory Evaluation Program (CLEP). We sequenced over 7000 human vaginal samples with this pipeline and described general findings and comparisons to US census data.

Investigating Changes in the Soil Fungal Community Structure, Functions, and Network Stability with Prolonged Grafted Watermelon Cultivation

Investigating Changes in the Soil Fungal Community Structure, Functions, and Network Stability with Prolonged Grafted Watermelon Cultivation

Minimum area of primitive broad-leaved Korean pine forest community based on biomass

Based on the survey data of nine primitive broad-leaved Korean pine forest plots ranging from 1 to 10.4 ha in Heilongjiang Province, this study used the moving window method and GIS technology to analyze the variation characteristics of the spatial distribution pattern of forest biomass in each plot. We explored the minimum area that can reflect the structural and functional characteristics of the primitive broad-leaved Korean pine forest, and used computer simulation random sampling method to verify the accuracy of the minimum area. The results showed that: (1) Through the analysis of the spatial distribution raster map of biomass deviation in the plots at various scales of 10 − 100 m, there is a minimum area (0.64 ha) for the critical range of biomass density variation in the primitive broad-leaved Korean pine forest. This minimum area based on biomass density can indirectly reflect the comprehensive characteristics of productivity level per unit area, structure, function, and environmental quality of the primitive broad-leaved Korean pine forest community. (2) Using computer simulation random sampling, it was found that only by sampling in a specific plot larger than or equal to the minimum area can equivalent or similar results be achieved as random sampling within the plot, indicating that the minimum area determined by the moving window method is accurate. (3) The minimum area determined in this paper is an excellent indicator reflecting the complexity of community structure, which can be used for comparing changes in community structure and function before and after external disturbances, and has a good evaluation effect. This minimum area can also be used as a basis for scientific and reasonable setting of plot size in the investigation and monitoring work of broad-leaved Korean pine forests in this region, thereby achieving the goals of improving work efficiency and saving work costs.

The microbiome of bioreactors containing mass-cultivated marine diatoms for industrial carbon capture and utilization

Marine microalgae are a promising innovation platform for carbon capture and utilization (CCU) biotechnologies to mitigate industrial greenhouse gas emissions. However, industrial-scale cultivation of algal mono-cultures is challenging and often unscalable. Non-axenic microalgae in large semi-open photobioreactors lead to the co-cultivation of diverse microbial communities. There is limited knowledge about the “bioreactor ecology” involving microalgae interacting with the microbiome and its subsequent impact on process stability and productivity. In this study, we describe the semi-continuous industrial mass cultivation of the cold-adapted marine diatom, Porosira glacialis UiT201, by investigating the prokaryotic and microeukaryotic (phytoplankton and heterotrophic protist) communities. Data were collected in two consecutive time series experiments, representing the initiation and operation of an industrial-scale CCU photobioreactor (300,000 L). The first experiment experienced a culture “crash” of the focal strain after 39 days, while the second culture remained stable and “healthy” for 60 days. The results highlight that this mass cultivation system represents a unique industrial marine microbial ecosystem. The succession of the prokaryotic community was primarily driven by species replacement, indicating turnover due to selective bioreactor conditions and/or biological interactions. Nonetheless, the bioreactor consistently harbors a recurring and abundant core microbiome, suggesting that the closely associated bacterial community is influenced by microalgae-specific properties and can endure a dynamic and variable environment. The observed culture collapse of P. glacialis coincided with changes in the core microbiome structure and different environmental growth conditions compared to the stable and “healthy” experiment. These findings imply that cohabiting microbial taxa within industrial microalgae cultivation likely play a critical role in stabilizing the conversion of industrial CO2 into marine biomass, and changes in community structure serve as an indicator of process stability.

Local and regional processes drive distance decay in structure in a spatial multilayer plant-pollinator network.

Understanding spatial variation in species distribution and community structure is at the core of community ecology. Nevertheless, the effect of distance on metacommunity structure remains little studied. We examine how plant-pollinator community structure changes across geographical distances at a regional scale and disentangle its underlying local and regional processes. We use a multilayer network to represent linked plant-pollinator communities as a metacommunity in the Canary Islands. We used modularity (i.e. the extent to which the community is partitioned into groups of densely interacting species) to quantify distance decay in structure across space. In multilayer modularity, the same species can belong to different modules in different communities, and modules can span communities. This enabled quantifying how similarity in module composition varied with distance between islands. We developed three null models, each controlling for a separate component of the multilayer network, to disentangle the role of species turnover, interaction rewiring and local factors in driving distance decay in structure. We found a pattern of distance decay in structure, indicating that islands tended to share fewer modules with increasing distance. Species turnover (but not interaction rewiring) was the primary regional process triggering distance decay in structure. Local interaction structure also played an essential role in determining the structure similarity of communities at a regional scale. Therefore, local factors that determine species interactions occurring at a local scale drive distance decay in structure at a regional scale. Our work highlights the interplay between local and regional processes underlying community structure. The methodology, and specifically the null models, we developed provides a general framework for linking communities in space and testing different hypotheses regarding the factors generating spatial structure.