Structure Of Biological Communities Research Articles

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, and made available to the photic region via upwelling processes, consequently triggering changes in the biological community structure and biogeochemical processes.

Taxonomic, functional, and phylogenetic diversity of anuran assemblages across habitats and seasons in a Neotropical savanna

AbstractDifferences between habitats and seasonal changes in climate are some of the main factors responsible for shaping diversity patterns and biological community structures. In this context, anurans are considered excellent models for ecological studies due to their high sensitivity to environmental changes. This study analyzed how differences between open and forested formations and seasonality influence the taxonomic, functional, and phylogenetic diversity of anuran assemblages in an area of Neotropical savanna. Parameters of taxonomic (species richness—SR), functional (functional diversity—SES.FD, functional dispersion—FDis, and functional redundancy—FR), and phylogenetic diversity (phylogenetic species variability—PSV and phylogenetic species richness—PSR) were used to quantify spatiotemporal changes in the anuran assemblages. Sampling was carried out over 15 months, using pitfall traps and active searches. In total, we recorded 598 individuals belonging to 21 species and seven families. Species composition, SR, and PSR differed between habitats and seasons, the latter two being higher in open formations during the rainy season. SES.FD differed seasonally and was higher in the dry season. FDis, FR, and PSV did not differ between treatments. Anurans from forested formations were functionally and phylogenetically clustered during the rainy season, while those from open formations were functionally clustered during the same season. Habitat type and seasonal variation were important in determining the taxonomic, functional, and phylogenetic diversity of the anuran assemblages. However, changes in climate and land use are expected to negatively impact the ecological and evolutionary diversity of these organisms in the Cerrado, reinforcing the importance of conservation policies and actions.Abstract in Portuguese is available with online material.

Spatial structure and potential processes linking fish and benthic communities in a protected reef ecosystem in SE Brazil

Top-down and bottom-up processes can mediate the structuring of biological communities. Several studies have provided separate support for those processes in pelagic and benthic compartments of reef systems but studies focusing on whole-reef processes are less common. Here, we sampled 3 ‘reef compartments’ in the Alcatrazes Archipelago in Southeastern Brazil: benthic cover of colonial organisms, solitary organisms, and reef fish (i.e. pelagic) to identify the groups responsible for spatial community structure among reefs. A dynamic mosaic structure best defines the assemblages of each compartment, with substantial changes observed among sites over 2 consecutive years and at 2 depth strata, separated by a sharp thermocline. Changes in benthic cover of colonial organisms are largely due to the extent of the blooming of Sargassum canopies, algal turfs, and the zoanthid Palythoa caribaeorum. Solitary organisms show a consistent monotonic change in the abundance of sea urchins, ascidians, and snails. Fish assemblage structure differed among reefs; however, we observed that large invertivore fish tended to concentrate in warmer water above the thermocline and small fish of different feeding habits were found in deeper and colder water in all reefs. We observed a potential strong link between the reefscape and solitary organisms, with a negative relationship between the abundance of urchins and the cover of Sargassum spp. suggesting top-down control. A second link is indicated by a positive relationship between low-lying cover composed of articulated turf and P. caribaeorum and larger invertivorous fish, suggesting bottom-up control through the provision of favorable foraging grounds.

Tree of life metabarcoding can serve as a biotic benchmark for shifting baselines in urbanized estuaries

Urbanization of estuaries drastically changed existing shorelines and bathymetric contours, in turn modifying habitat for marine foundational species that host critical biodiversity. And yet we lack approaches to characterize a significant fraction of the biota that inhabit these ecosystems on time scales that align with rates of urbanization. Environmental DNA (or eDNA) metabarcoding that combines multiple assays targeting a broad range of taxonomic groups can provide a solution, but we need to determine whether the biological communities it detects ally with different habitats in these changing aquatic environments. In this study, we tested whether tree of life metabarcoding (ToL-metabarcoding) data extracted from filtered seawater samples correlated with four known geomorphic habitat zones across a heavily urbanized estuary (Sydney Harbour, Australia). Using this method, we substantially expanded our knowledge on the composition and spatial distribution of marine biodiversity across the tree of life in Sydney Harbour, particularly for organisms where existing records are sparse. Excluding terrestrial DNA inputs, we identified significant effects of both distance from the mouth of Sydney Harbour and geomorphic zone on biological community structure in the ToL-metabarcoding dataset (entire community), as well as in each of the taxonomic subgroups that we considered (fish, macroinvertebrates, algae and aquatic plants, bacteria). This effect appeared to be driven by taxa as a collective versus a few individual taxa, with each taxon explaining no more than 0.62% of the variation between geomorphic zones. Similarly, taxonomic richness was significantly higher within geomorphic zones with large sample sizes, but also decreased by 1% with each additional kilometer from the estuary mouth, a result consistent with a reduction in tidal inputs and available habitat in upper catchments. Based on these results, we suggest that ToL-metabarcoding can be used to benchmark biological monitoring in other urbanized estuaries globally, and in Sydney Harbour at future time points based on detection of bioindicators across the tree of life. We also suggest that robust biotic snapshots can be archived following extensive curation of taxonomic assignments that incorporates ecological affinities, supported by records from relevant and regional biodiversity repositories.

Структура и динамика гидробиоценозов (фитоперифитон, зоопланктон, зообентос) рек Карельского побережья Белого моря.

This paper summarizes the results of the studies of biota structural organization and dynamics of small rivers of the Karelian White Sea coast. The chemical features and the structure of biological communities in the watercourses were investigated. Analysis of the species composition, abundance and biomass of phytoperiphyton, zooplankton, and zoobenthos was carried out. Variations in the structure of aquatic communities primarily are due to specific hydrographic and hydrological characteristics of river stretches. The paper discusses the main principles of the changes in a structure and functioning of hydrobiont communities in rivers. The trophic status of the rivers, their saprobiological state, and the significance of individual communities and biotic indices for bioindication of the ecological state of the rivers,are estimated. We concluded that the consideration of three groups of organisms enables a more comprehensive and reliable monitoring than the assessment based on a single group.

Distinct structure, assembly, and gene expression of microplankton in two Arctic estuaries with varied terrestrial inputs

The Laptev Sea is a major Marginal Sea in the Western Arctic Ocean. The Arctic amplification brought by global warming influences the hydrological properties of rivers passing through the permafrost zone, which would alter the biological community structure at continental margin. In this study, the structure, assembly, and gene expression of planktonic microbial communities in two estuaries (Protoka Ularovskaya River Estuary, PURE; Lena River Estuary, LRE) of Laptev Sea were examined to investigate the environmental effects of polar rivers. PURE and LRE exhibited distinct environmental characteristics: low temperature and high salinity for PURE, and high temperature and low salinity for LRE, influenced by runoff size. Salinity more closely influenced microbial communities in LRE, with freshwater species playing a significant role in community composition. The findings revealed differences between two estuaries in community composition and diversity. Prokaryotes and microeukaryotes had shown different assembly patterns in response to habitat changes caused by terrestrial freshwater input. Furthermore, compared with the PURE, the co-occurrence and inter-domain network of the LRE, which was more affected by terrestrial input, was more complex and stable. Functional gene prediction revealed a higher gene expression of methane metabolism in LRE than in PURE, particularly those related to methane oxidation, and this conclusion could help better explore the impact of global warming on the methane cycle in the Arctic Marginal Seas. This study explored the increased freshwater runoffs under the background of global warming dramatically affect Arctic microplankton communities from community structure, assembly and gene expression aspects.

Environmental heterogeneity caused by large-scale cultivation of Pyropia haitanensis shapes multi-group biodiversity distribution in coastal areas

The response of marine biodiversity to mariculture has long been a research focus in marine ecology. However, the effects of seaweed cultivation on biological community assembly are poorly understood, especially in diverse communities with distinct ecological characteristics. In this study, we used environmental DNA metabarcoding to investigate the spatial distribution patterns of bacterial, protistan, and metazoan diversity, aiming to reveal the mechanisms of community assembly in the Pyropia haitanensis cultivation zone along the Fujian coast, China. We found that, compared with the biological communities in control zones, those in P. haitanensis cultivation zones exhibited stronger geographic distance-decay patterns and displayed more complex and stable network structures. Deterministic processes (environmental selection) played a more important role in the assembly of bacterial, protistan, and metazoan communities in P. haitanensis cultivation zones, especially metazoan communities. Variance partitioning analysis showed that environmental variables made greater contributions to the diversity of the three types of communities within the P. haitanensis cultivation zones than in the control zones. Partial least squares path modeling analysis identified nitrate‑nitrogen (NO3-N), pH, particulate organic carbon (POC), and dissolved organic carbon (DOC) as the key environmental variables affecting biodiversity. Overall, the environmental heterogeneity caused by the large-scale cultivation of P. haitanensis could be the crucial factor influencing the composition and structure of various biological communities. Our results highlight the importance of the responses of multi-group organisms to the cultivation of seaweed, and provide insights into the coexistence patterns of biodiversity at the spatial scale.

The Impact of Fishing Ban Policy on Marine Ecological Environment

This study aims to explore the impact of implementing fishing moratorium policies on the marine ecological environment in the Bohai Sea region. The marine environment in this area has been long degraded, primarily due to excessive fishing and pollution. This study focuses on the before and after effects of the fishing moratorium policy on the marine ecological environment. Research methods include literature review and data analysis, analyzing the marine environmental conditions in the region prior to the implementation of the fishing moratorium policy. The results show that implementing the fishing moratorium policy can effectively restore the marine ecological environment, enhance species diversity, and stabilize the structure of marine biological communities. Additionally, the fishing moratorium policy provides guarantee for the sustainable utilization of fishery resources. However, there are still some issues in the implementation process of the fishing moratorium policy, such as reduction in fishermen's income and decline in fishery output. Future research needs to further explore how to optimize the fishing moratorium policy and balance marine ecological protection with the economic interests of fishermen. In conclusion, the impact of implementing fishing moratorium policies in the Bohai Sea region on the marine ecological environment is significant but still requires further improvement and optimization.

Spatial, Geographical, Climatic, and Edaphic Influences on Moss Community Structure: A Case Study from Qinhuangdao, China

In the realms of ecology and biogeography, the interaction between biodiversity and environmental factors is a critical area of research. This intersection highlights how biological communities, especially among groups like bryophytes, are influenced and shaped by their surrounding environmental conditions. This study presents a pioneering investigation into the diversity and community structure of mosses in Qinhuangdao, Hubei Province, China, a region marked by its diverse topography and climate. Employing extensive field surveys across 30 plots, we gathered and analyzed the relationship between moss species distribution and environmental variables, including topographical, climatic, and soil factors. Utilizing a range of analytical techniques, such as cluster analysis, canonical correspondence analysis (CCA), and partial least squares path modeling (PLS-PM), we characterized the intricate relationships between moss biodiversity and environmental gradients. The research has documented 84 species distributed among 36 genera and 13 families. Solar radiation has a great impact on moss diversity. There were significant differences between Form. Entodon compressus and Form. Plagiobryum demissum. Climate has a great impact on the community structure of mosses. Geographical factors were also identified as key secondary influences, affecting moss community structures both directly and indirectly by creating suitable microenvironments and influencing climate and soil properties. Additionally, the study highlights the indirect impact of spatial factors on these environmental variables, which in turn shape the structure of biological communities. The findings indicate that the annual temperature range is a key factor influencing the distribution and formation of moss community structures. The findings provide new insights into the ecological adaptation of mosses in diverse environmental settings and lay a crucial foundation for biodiversity conservation and ecosystem management in the Qinhuangdao area.

Fish assemblage structure related to habitat heterogeneity in rocky reefs in the Mexican Pacific coast

Abstract One of the major paradigms in ecology is the understanding of processes and patterns related to the structure of biological communities. Reef ecosystems, with their high productivity, habitat heterogeneity, and fish diversity provide a model for studying these processes. We sampled four sites three times during the season associated with the California Current and two times associated with the North Equatorial Current using video-transects on the coast of Zihuatanejo, Guerrero, Mexico to determine the relationship between the habitat characteristics and the structure of the fish assemblage. We recorded a total of 26 families and 54 species and estimated fish richness and abundance. In addition to measuring local water variables such as temperature (°C), salinity (PPT), pH and dissolved oxygen (O2%), we determined habitat heterogeneity by processing photographs of the substrate and calculated rugosity using the tape chain. Oxygen and temperature were the variables associated to sea water conditions that differentiated the sampled sites. The fish community structure presented high correlations with temperature, salinity, and dissolved oxygen, followed by the heterogeneity components such as rugosity and substrate diversity. Our results showed that seasonal changes in water conditions and physical components in the coast of Zihuatanejo promotes changes in the fish community.

Biological nitrogen fixation, diversity and community structure of diazotrophs in two mosses in 25 temperate forests.

Many moss species are associated with nitrogen (N)-fixing bacteria (diazotrophs) that support the N supply of mosses. Our knowledge relates primarily to pristine ecosystems with low atmospheric N input, but knowledge of biological N fixation (BNF) and diazotrophic communities in mosses in temperate forests with high N deposition is limited. We measured BNF rates using the direct stable isotope method and studied the total and potentially active diazotrophic communities in two abundant mosses, Brachythecium rutabulum and Hypnum cupressiforme, both growing on lying deadwood trunks in 25 temperate forest sites. BNF rates in both mosses were similar to those observed in moss species of pristine ecosystems. H. cupressiforme fixed three times more N2 and exhibited lower diazotrophic richness than B. rutabulum. Frankia was the most prominent diazotroph followed by cyanobacteria Nostoc. Manganese, iron, and molybdenum contents in mosses were positively correlated with BNF and diazotrophic communities. Frankia maintained high BNF rates in H. cupressiforme and B. rutabulum even under high chronic N deposition in Central European forests. Moss N concentration and 15 N abundance indicate a rather minor contribution of BNF to the N nutrition of these mosses.

On the De Novo Emergence of Ecological Interactions during Evolutionary Diversification: A Conceptual Framework and Experimental Test.

AbstractEcological interactions are crucial to the structure and function of biological communities, but we lack a causal understanding of the forces shaping their emergence during evolutionary diversification. Here we provide a conceptual framework linking different modes of diversification (e.g., ecological diversification), which depend on environmental characteristics, to the evolution of different forms of ecological interactions (e.g., resource partitioning) in asexual lineages. We tested the framework by examining the net interactions in communities of Pseudomonas aeruginosa produced via experimental evolution in nutritionally simple (SIM) or complex (COM) environments by contrasting the productivity and competitive fitness of whole evolved communities relative to their component isolates. As expected, we found that nutritional complexity drove the evolution of communities with net positive interactions whereas SIM communities had similar performance as their component isolates. A follow-up experiment revealed that high fitness in two COM communities was driven by rare variants (frequency <0.1%) that antagonized PA14, the ancestral strain and common competitor used in fitness assays. Our study suggests that the evolution of de novo ecological interactions in asexual lineages is predictable at a broad scale from environmental conditions. Further, our work demonstrates that rare variants can disproportionately impact the function of relatively simple microbial communities.

River Ecosystem Health Assessment in Rapid Urbanization Regions (Shenzhen, China) under the Guidance of Bioremediation Objectives

As a coastal city with rapid urbanization and high-intensity human activities, Shenzhen, China has carried out a series of comprehensive treatments for water pollution control and ecological restoration in recent years. However, the restoration effect is mainly reflected in the improvement of water quality and riparian landscape, and there is still a big gap in reaching the river’s ecological restoration goals. Therefore, it is necessary to make a full investigation and evaluation of river aquatic systems that focuses on the restoration of aquatic communities and ecosystem health. We surveyed forty-seven sampling sites in nine basins to investigate water quality and aquatic organisms (algae and macroinvertebrates) during the low-water period in 2019. Under the guidance of the EU Water Framework Directive (WFD), the urban river ecosystem health assessment system, with a total of twenty indicators from six criteria layers, was established. We addressed the bioremediation objectives in this system and aquatic organism indicators as high-weight characteristic indicators. The results showed that the degradation of the river ecosystem in Shenzhen is serious, which is mainly reflected in the simple structure of the aquatic biological community and the low biodiversity. Only one “healthy” sample site, accounting for 2% of the total sampling sites; six sites of “sub-health” level, accounting for 13%; twenty-four “poor” sample points, accounting for 51%; sixteen “extremely poor” sample points, accounting for 34%. From the perspective of spatial distribution, the river ecological status of Daya Bay Basin and Dapeng Bay Basin is good, which is at the level of “health” to “sub-health”; the Guanlan River Basin, Maozhou River Basin, Shenzhen River Basin, Shenzhen Bay Basin, Pingshan River Basin, and most of the Longgang River Basin are of “poor to extremely poor” grade; the Pearl Estuary basin is of “extremely poor” grade. This assessment system can be used as an effective tool to monitor the ecological health status, especially the enhancement of biodiversity and ecosystem function of rivers. Moreover, it could provide important decision-making guidance for river management affected by high-intensity human activities.

Exploring Biomarker Signatures in Glaciovolcanic Environments: Implications for the Search for Life on Mars

Glaciovolcanic systems, where hydrothermal heat interacts with ice, offer favorable conditions for life by providing liquid water, nutrients, and physicochemical gradients (Cousins and Crawford 2011). Despite significant climate change, evidence for glaciovolcanism is widespread through Mars’ history. Such sites may have offered refugia for life after Mars lost much of its surface water, representing some of the most recent habitable areas and promising sites to recover biomarkers. We examined a terrestrial glaciovolcanic site to study the indigenous biological community structure, the supporting physicochemical parameters, and the distribution of biomarkers within the geologic context. The insights will help refine Mars exploration of analogous sites. Method: We studied a partially subglacial hydrothermal area at the summit of the active Kverkfjöll volcano, Iceland. The heated ground has created a large ice-damned meltwater lake with shoreline hot springs, thermal streams, and mud pots of variable activity. We collected water and sediment samples aseptically across the breadth of features, including the lake (surface &amp; depth). Samples were kept at -4°C. Environmental parameters were measured at each sample site. Sediment samples were split for mineralogical and organic analysis. Mineralogy was measured by X-ray Diffraction. Organic samples were freeze-dried and extracted with a Bligh &amp; Dyer method (Bligh and Dyer 1959). Extracts were divided into hydrocarbons, neutral lipids, glycolipids, and phospholipid fatty acids (PLFA) with hexane, dichloromethane, acetone, and methanol. Gas Chromatography/Mass Spectrometry was used to analyze hydrocarbons and PLFA as fatty acid methyl esters. Results: Environmental: Fluids ranged from acidic to alkaline (pH 3-9), low to high temperature (8-87°C), and severely dysoxic to oxic (0.5-5 mg/L dissolved O). Mineralogy comprised a dioctahedral swelling clay, heulandite, and minor quartz, anatase, and pyrite. The assemblage suggests argillic-grade alteration at 100-140°C (Fulignati 2020), confirming that the glaciovolcanic conditions were within theoretical boundaries for life (&amp;lt;150°C (Merino et al. 2019)), and formed minerals capable of protecting organic matter (e.g., swelling clay). Lipids: PLFA are essential components of cell membranes and degrade rapidly upon cell death. PLFA profiles thus provide insight into the composition and distribution of the viable community. Results revealed a diversity of PLFA with low molecular weights and several bacterial-diagnostic structures, indicating an active prokaryote-dominated biosphere. Molecular patterns correlated (p&amp;lt;0.05) with pH, temperature, and oxygen, suggesting homeoviscous adaptations or community composition variations. In either case, microbes demonstrate adaptability to extreme conditions in glaciovolcanic settings. Hydrocarbons are inert and used as molecular fossils. We detected multiple patterns attributable to microbial biosynthesis, including abundant C17 (straight and branched) diagnostic of cyanobacteria; high concentrations of short-chain n-alkane/alkene doublets (&amp;lt;C22) with an even carbon preference (CPI&amp;lt;1) indicating diverse microbial input; and a narrow unresolved complex mixture with elution parameters characteristic of microbial heterotrophy (Finkel et al. 2023). The pattern of even-numbered alkane/alkene pairs has been scarcely reported and offers insight into rare hydrocarbon distributions. Interestingly, the hydrocarbon and PLFA patterns do not align. Thus, PLFA are not a significant source of hydrocarbons here and we suggest direct microbial synthesis dominates. Implications of this hypothesis will be discussed in the context of palaeobiological reconstruction. Conclusion: Our site provides an array of physicochemical niches for diverse life modes and a mineral assemblage amenable to organic preservation. Analogous sites on Mars should be explored, but more work is needed to understand preservation biases of hydrocarbon sources and the implications for interpretation.

Implications of transient methane flux on associated biological communities in high-arctic seep habitats, Storbanken, Norwegian Barents Sea

The continental margins of the Arctic Ocean basin contain methane seeps, where transient fluxes of seafloor methane are released due to the thermal dissociation of gas hydrates. An increase in shallow methane seeps identified over the past decade, potentially due to enhanced warming of the Arctic Ocean bottom water and associated destabilization of hydrate structure. Biological communities associated with methane release east of Svalbard in the Barents Sea (Storbanken Crater site, 76° 46.7′N, 35° 43.5′E, depths between 120 m–300 m depths) were investigated using towed camera imagery and ship-based platforms during a 2017 CAGE17-2 cruise on the RV Helmer Hanssen. We analyzed relationships among methane flux data, seafloor habitat characteristics, and biological community structure (i.e., presence and distribution of megafauna and expression of microbial mats) from a total of 14 surveys (6827 images and 40 multicore sediment cores) within the Storbanken Crater area and compared it to 2015 data. Unlike seep expressions at deeper sites (∼1200 m) in the Norwegian margin region, no seep-endemic, chemosynthetic-associated megafaunal species were observed at the shallow surveyed sites and all sites hosted similarly diverse communities of non-seep species, including commercially important fish and crustaceans. Methane concentrations did not markedly differ between the crater and non-crater sites. Rates of methane gas advection through sediments (in the form of flares) were relatively low and concentration of methane was even lower in porewater samples at the crater site. We present the first evidence of methane flare flux and intermittent microbial mat distribution with associated folliculinid ciliates, which suggests a long history of methane emissions and a transient seep environment in spatial and temporal flux. Together, this study presents a critical baseline on the temporal release of arctic methane and benthic biological communities to initiate temporal studies that identify future changes and predict the impact of climate change.

Fatty-acid based assessment of benthic food-web responses to multiple stressors in a large river system

Rivers are often exposed to multiple stressors, such as nutrients and contaminants, whose impacts on the river food webs may not be distinguished by sole assessment of biological community structures. We examined the benthic algal assemblages and the fatty acids (FA) of benthic macroinvertebrates in the lower Athabasca River in Canada, aiming to assess the changes in algal support and nutritional quality of the benthic food web in response to cumulative exposure to natural bitumen, municipal sewage discharge (hereafter, “sewage”), and oil sands mining (“mining”). Data show that the decline in water quality (increases in nutrient concentrations and total suspended solids) was associated with decreases in benthic diatom abundance, and was driven mainly by sewage-induced nutrient enrichment. Responses in nutritional quality of benthic macroinvertebrates, indicated by their polyunsaturated FA (PUFA) concentrations, were taxon- and stressor-specific. Nutritional quality of the larval dragonfly predator, Ophiogomphus, decreased nonlinearly with decreasing benthic diatom abundance and was lowest at the sewage-affected sites, although exposure to natural bitumen also resulted in reduced Ophiogomphus PUFA concentrations. In contrast, the PUFA concentrations of mayfly grazers/collector-gatherers were not affected by natural bitumen exposure, and were higher at the sewage and sewage+mining sites. The PUFA concentrations of the shredder Pteronarcys larvae did not change with cumulative exposure to the stressors. Sediment metal and polycyclic aromatic compound concentrations were not associated with the macroinvertebrate FA changes. Overall, we provide evidence that sewage induced reduction in trophic support by PUFA-rich diatoms, and was the predominant driver of the observed changes in FA composition and nutritional quality of the benthic macroinvertebrates. Fatty-acid metrics are useful to untangle effects of concurrent stressors, but the assessment outcomes depend on the functional feeding guilds used. A food-web perspective using multiple trophic levels and feeding guilds supports a more holistic assessment of the stressor impacts.

Coral reef pinnacles act as ecological magnets for the abundance, diversity and biomass of predatory fishes

Predation is a key ecological process regulating the structure and diversity of biological communities, yet predators do not exist homogeneously in nature. Coral reefs possess diverse assemblages of predatory fishes, the distribution and abundance of which is well documented for coastal and emergent reefs. However, for remote, isolated and submerged reefs, such as those found on pinnacles and seamounts, our understanding of predatory fish communities is limited. These features are ubiquitous in the world’s oceans and frequently targeted by fishers for their presumed fish aggregation properties. Here we describe communities of predatory fishes on a series of pinnacle reefs and contrast these to regional coastal and offshore emergent reefs. Pinnacles supported 2-4× higher abundance, biomass and diversity of predatory fishes compared to emergent reefs. They also supported unique communities, with 32 out of the 63 predator species in our study found only on pinnacle reefs. For species found on all 3 reef types, all were most abundant on pinnacles and the 6 taxa driving differences in community structure were most abundant on pinnacles. Together, our results show that predatory fishes are strongly attracted to pinnacles, although the mechanisms are still unclear. Prioritising the selection of these small ecological magnets in conservation planning would be an effective approach to target the protection of regional reef fish biodiversity.

New Perspectives in Sustainable Aquaculture

The strong growth of the aquaculture industry can represent a serious threat to aquatic ecosystems and requires the development of new strategies to control and minimize the impact of such activities on the structure and function of biological communities [...]

Daily responses of the planktonic food web to environmental dynamics in the vegetated littoral zone of a large shallow lake

Littoral zones are the most productive areas of shallow lakes and make important contributions to energy transfer to higher trophic levels in aquatic ecosystems. Great habitat heterogeneity characterizes the littoral ecosystems, often encompassing macrophyte covered areas that provide microhabitats with diverse structural complexity, and several effects over the structure and function of biological communities. The effects of macrophytes on trophic interactions are more complex in subtropical lakes than in temperate lakes. The relationships between planktonic food web components and the effects of a highly dynamic environment in structuring plankton communities were studied in a large subtropical shallow lake. The study was conducted for twenty-five consecutive days in the summer of 2016 at two sites (Station 1 and Station 2) in the well-developed littoral zone of Lake Mangueira hosting different plant life forms. Strong spatial variation between sampling stations was evidenced in the density of most of the communities, with the highest means of bacterioplankton, phytoplankton, and ciliates density being recorded at the station surrounded mainly by submerged macrophytes (Station 1). These plants particularly modify microhabitat complexity by increasing the availability and functional diversity of niches. Furthermore, submerged macrophytes tend to accumulate more periphyton biomass, a quality food resource for many consumers. Important grazing relationships, nutrient demands, and trophic structure were assessed through carbon biomass of the communities. Phytoplankton accounted for a greater proportion of the entire plankton community than bacteria, while zooplankton had low carbon biomass of crustaceans and a high dominance of ciliates and rotifers, with a greater grazing impact on bacterioplankton than on phytoplankton. According to RDA and multiple-regression analysis, nutrients and humic substances were the main predictors of variability in the littoral food web components over a short-sampling interval. The carbon biomass of bacteria and metazooplankton were both positively related to humic substances and nutrients at Station 1, as well as the biomass ratio of metazooplankton to phytoplankton and metazooplankton to ciliates. This suggests that humic substances have been metabolized by bacteria and transferred to higher trophic levels through predation. On the other hand, humic substances negatively affected the carbon biomass of bacteria and cyanobacteria at Station 2, suggesting a mostly refractory DOC around the emergent plants. Results indicate that despite the greater importance of bacterial biomass in the energy transfer through zooplankton predation, the efficiency of carbon transfer in algal and bacteria-based food webs was both very low. The effects of macrophytes on the quantity and/or quality of nutrients and substrates for bacteria uptake and phytoplankton requirements, explained the spatial variability of plankton food web components, even over the short distance between stations, as well as the inefficient microbial loop found in the littoral zone inhabited by macrophytes.

Biological Evaluation and Key Stress Factor Diagnosis of Compound Contaminated Soil Based on Environmental DNA

Healthy biological community composition and diversity are the basis for soil ecosystems to provide complete ecological functions and services. The current technical bottleneck in soil pollution control is the lack of systematic and comprehensive biodiversity indicators. In this study, the compound-polluted soil in an industrial park was taken as the object, and environmental DNA (eDNA)technology was used to monitor and analyze the composition of the biological community in the polluted soil. The environmental DNA-species sensitivity distribution (eDNA-SSD) method was constructed to diagnose the key stress factors and their ecological threshold. The results showed that:① compound pollution did not have a significant impact on the α-diversity of soil organisms in the park but led to changes in the composition of biological communities and dominant species with high relative abundance. The dominant groups in the polluted soil were Proteobacteria (25.54%), Ascomycota (15.65%), Actinobacteria (8.75%), and Chloroflexi (7.64%). ② Environmental factors accounted for 51.27% of the differences in soil biodistribution, and aniline, sulfate, petroleum hydrocarbon, and lead were the key stress factors for soil biomes. Among them, aniline had the most significant effect on the community distribution of bacteria (P=0.030), sulfate on fungi (P=0.025), and metazoans (P=0.032). ③ The ecological risk threshold (hazardous concentration for 5% of species, HC5) of pollutants with 95% species as the protection target showed a gradient decreasing trend of sulfate (470.00 mg·kg-1), petroleum hydrocarbon (17.00 mg·kg-1), lead (13.00 mg·kg-1), arsenic (6.20 mg·kg-1), 4-chloroaniline (0.16 mg·kg-1), and aniline (0.11 mg·kg-1). Nevertheless, the existing soil risk control value was significantly higher than the ecological risk value, indicating that the existing control standards targeting human health were not suitable for protecting soil health. The comprehensive pollution index showed that the soil pollution in the park was mostly mild pollution accompanied by heavy pollution at individual points. The biological evaluation method based on eDNA-SSD could achieve the comprehensive evaluation of composite pollution in the absence of the benchmark value of pollutants and at the same time better distinguish the differences in soil biological community structure and composition under different pollution levels (P=0.053). In conclusion, the environmental DNA soil biomonitoring and assessment method developed in this study has guiding significance and application value for soil ecosystem restoration assessment.