Trophic Guilds Research Articles

Responses of trophic fish guilds upstream and downstream of the Balbina dam, Central Amazon, Northern Brazil

Abstract This study compared the diversity, richness, abundance, and biomass of fish collected in three environments in the Central Amazon: (1) the reservoir of the Balbina hydroelectric dam; (2) the Uatumã River downstream of the dam; and (3) the Abacate River. Through the analysis of food resources, we determined the fish trophic guilds for each environment. We hypothesized that the undisturbed environment of the Abacate River would present the highest values of diversity, richness, abundance, and biomass, followed by the Uatumã River and the reservoir, and that there would be significant differences among the trophic guilds among the three environments. The highest taxonomic richness was observed for the Uatumã River, followed by the Abacate River and the reservoir. There was no statistical difference in the species richness of the trophic guilds among the three sampled sites, but the three areas differed in abundance. The highest value of guild biomass was observed for the Uatumã River, followed by the reservoir and the Abacate River. Characteristics of the Uatumã and Abacate River systems, such as size, greater complexity and heterogeneity of habitats, and flood regime, may be the cause of the greater species richness in these rivers, compared to the reservoir.

Impact of vereda dryness on the insect herbivore diversity in adjacent cerrado areas in Brazilian Protected Areas

Unravelling the factors that influence plant-insect interactions remains a fundamental concern in terrestrial ecology. In the present study, we evaluated the impact of varying degrees of drying on cerrado areas adjacent to veredas on the species richness, abundance and composition of the insect herbivore fauna. Additionally, we examined differences in these impacts between various guilds (chewing and sucker insects) and developmental stages (adult and immature insects). The research has been performed in study areas located in three Protected Areas in Brazil. In total, we recorded 106 species of herbivorous insects across five orders (Coleoptera, Hemiptera, Hymenoptera, Lepidoptera, and Orthoptera). Hemiptera and Coleoptera stood out as the orders with the highest species diversity and individual numbers. Among the families, Cicadellidae and Curculionidae exhibited the highest richness in species and abundance of individuals. We found that richness of herbivorous insects was higher in wet zones (20.2 ± 6.5) of the veredas compared to dry zones (12.3 ± 7.5), as well as the abundance of herbivorous insects was higher in wet zones (49.4 ± 25.5) than in the dry zones (15.8 ± 7.9). Whithin insect guilds, the abundance of chewing insects was higher in wet zones (34.0 ± 13.6) than in dry zones (16.3 ± 14.8), but this difference was not observed for the diversity of sucking insects. Regarding developmental stage, immature insects exhibited higher species richness in wet zones (10.4 ± 5.0) compared to dry zones (5.3 ± 2.1), while adult insect diversity did not show differences between the studied zones. Furthermore, the species composition of herbivorous insects, various trophic guilds (chewers and suckers) and developmental stages (adults and immature insect) did not significantly differ among the zones studied within the veredas. According to our findings, herbivorous insects exhibit a preference for wet environments, which provide better conditions and higher-quality food resources for development and reproduction.

Dams and agricultural lands affect energy sources and the trophic position of fish in a floodplain

Abstract Landscape change caused by hydropower dam construction and invasion of agriculture in the riparian zone has been a catalyst for alterations in fish food web dynamics. The objectives of this study were to investigate the trophic state and land use of three rivers, one directly impacted by a dam; the trophic structure of four fish species of four trophic guilds; and the relationship between the trophic state and land use with trophic structure. We found a greater total allochthonous contribution in the dam-regulated river in contrast to its tributaries, along with less natural cover in the riparian zone, but a high percentage of natural vegetation on the islands. Additionally, we observed greater contribution of the riverine sources for all three rivers, independent of the trophic state and natural cover of the river. The trophic position was greater for the fish in the river in a protected area and lower in the rivers with a high percentage of agropastoral activities in the riparian areas. These findings show the importance of the conservation of the riverine zones mainly in dam-regulated rivers, because this vegetation provides the main energy source by fish.

The effect of urbanization on species composition and trophic guilds of bats (Mammalia, Chiroptera) in the Brazilian Savanna.

Urban environments present less environmental heterogeneity in relation to the natural ones, affecting the biodiversity of bats and the ecological processes in which they participate. In this way, we will identify how urbanization influences the structure of bat communities in the municipality of Goiânia, Goiás, Brazil. We compared species composition, guilds and bat richness in a gradient that crossed urban, semi-urban and natural areas in the municipality of Goiânia, contained in the Cerrado biome. We captured a total of 775 bats of 16 species distributed in three families. Urban areas had a higher species abundance, while semi-urban areas had a higher species richness. The three types of environments have different compositions, the urban one being more homogeneous, the fauna in these areas is composed of generalist species, which benefit from this process. The diversity present in semi-urban areas is a consequence of the intersection between urban and natural fauna, which is why urban expansion needs to occur in a planned manner to minimize the impacts of this process and ensure the maintenance of biodiversity.

Impact of pesticides on the arthropofauna associated with potato (Solanum tuberosum) cultivation in Cusco-Peru

The impact of several pesticides on the diversity of arthropofauna associated with commercial potato cultivation was evaluated in Mollepata, province of Anta in Cusco-Peru, to determine which trophic guilds (TG) are affected. The treatments were fipronil, propineb and conventional (rotation of several pesticides). Thirty-five pitfall traps were placed in each treatment with the purpose of collecting the arthropofauna in potatoes. Five applications of the corresponding treatment were carried out and a total of five check-ups were carried out with a frequency of fourteen days. The most abundant families were Hemiptera: Cicadellidae (19.82%), Coleoptera: Chrysomelidae (16.33%) and Diptera: Sciaridae (11.92%). Propineb was the treatment that presented, at the family level, the largest total number of individuals. For the entire study, at the level of TG, the decreasing sequence of the total number of families was: phytophagous with 30 families (32.97%); predators 23 families (26.37%); detritivores 20 families (21.98%); parasitoids 10 families (9.89%); pollinators six families (6.59%) and finally omnivorous with two families (2.20%). Propineb presented the highest values of the total number of individuals in phytophages and parasitoids. On the other hand, alpha diversity indices did not present differences between treatments for omnivores, detritivores, pollinators and predators. The beta diversity indices were variable, generally obtaining greater similarity between the fipronil and conventional treatment. The phytophagous and parasitoid TGs were those that presented the most differentiated values when evaluating the effect of pesticides on soil arthropofauna based on alpha diversity indices.

Linking ecological characteristics with fish diversity, assemblage patterns and feeding guilds, and GIS applications along the temporal and spatial gradients in a large subtropical reservoir, India, for sustainable management

Abstract The objective of the investigation was to explore the abundance, composition, and diversity patterns of the fish fauna along the temporal and spatial scale and study the influence of environmental parameters on the fish assemblage in the Rihand reservoir, a large sub-tropical Indian reservoir in India. On the temporal scale, the highest abundance was recorded in the summer season and the lowest in the monsoon season, while on the spatial scale, the highest abundance was recorded from the riverine and the minimum from the lacustrine zone. The highest species richness and diversity were recorded from the riverine zone followed by the transitional and lacustrine zones, respectively. The analysis of the variance of fish abundance revealed insignificant differences between the riverine and the transitional zones. The trophic guild analysis indicated the dominance of carnivores. The output of canonical correspondence analysis depicted the significant influence of the physico-chemical traits on the abundance of fish species. The transparency and specific conductivity were found to be the most critical factors affecting fish assemblages in the Rihand reservoir. This study generated important baseline ecological information that would be useful for the monitoring, conservation, and management of the reservoir ecosystem.

Unraveling the relationship between plant species and physicochemical properties on rhizosphere and rhizoplane fungal communities in alpine wet meadows

BackgroundWet meadows, a type of wetland, are impacted by significant climate fluctuation and human activity, impacting soil microorganisms that play an essential role in ecosystem processes. Understanding the underlying ecological mechanisms and processes of wet meadows depends on the fungal communities associated with the plant roots. We used Illumina MiSeq profiling for amplicon sequencing to determine how environmental factors and elevation affect the fungal communities of the rhizosphere and rhizoplane related to three plant species, Cremanthodium ellisii, Cremanthodium lineare, and Caltha scaposa, in alpine wet meadows.ResultsThe phyla Ascomycota and Basidiomycota dominated the rhizosphere (54.5% and 20.9%) and rhizoplane (51.6% and 36.4%), while the predominant fungal genera in the rhizosphere and rhizoplane were Unclassified fungi, Unclassified Ascomycota, Pseudeurotium, Tetracladium, Vishniacozyma, Rhodotorula, Cadophora, and Penicillium. Mantel test and network analysis revealed that the soil water content (SWC), soil organic carbon (SOC), and total nitrogen (TN) were the primary drivers of fungal communities. However, the influence of microbial biomass C (MBC), pH, microbial biomass N (MBN), and elevation varied. Stochastic assembly processes were dominant in both rhizosphere and rhizoplane fungal communities. FUNGuild functional prediction revealed site-specific variation in the trophic level and guild of plant-root-associated fungal communities. The rhizosphere contained 58.5% saprotrophs, 11.7% pathotrophs, and 12.6% symbiotrophs. In addition, 60.4% of the observed OTUs were arbuscular mycorrhizae, 13.2% were endophytes, 20.9% were ectomycorrhizae, and 1.09% were orchid mycorrhizae. The rhizoplane comprised 51.3% of OTUs linked with saprotrophs, 13.9% with pathotrophs, and 7.92% with symbiotrophs. Moreover, 36.1% of OTUs represented arbuscular mycorrhizae, 25.0% were endophytes, 30.6% were ectomycorrhizae, and 2.77% were ascribed to orchid mycorrhizae in the rhizoplane. The abundance of saprotrophs and pathotrophs in the rhizosphere was highest in C. ellisii at SI and SIII, while symbiotrophs were highest in C. lineare at SIII. Similar variations among the plant species and sites were observed in the fungal functional groups (guilds).ConclusionsIt was concluded that although root compartments significantly influenced the fungal communities in the rhizosphere and rhizoplane, environmental factors and plant types exhibited distinct effects. This study explains how physicochemical properties, plant species, and sites can alter the overall structure and functional repertoire of fungal communities in alpine wet meadows.Graphical

Stream food webs in tropical mountains rely on allochthonous carbon regardless of land use

The relative importance of allochthonous and autochthonous carbon (C) as sources of energy for tropical stream food webs remains an open question. Allochthonous C might be the main energy source for small and shaded forest streams, while autochthonous C is more likely to fuel food webs draining land uses with less dense vegetation. We studied food webs in cloud forest streams draining watersheds with forests, coffee plantations, and pastures. Our goal was to assess the effects of those land uses on the C source and structure of stream food webs. The study took place in tropical montane streams in La Antigua Watershed, in eastern Mexico. We selected three streams per land use and sampled biofilm and leaf litter as the main food resources, and macroinvertebrates and aquatic vertebrates from different trophic guilds. Samples were analyzed for δ13C and δ15N isotopes. Using a Bayesian mixing model, we estimated the proportional assimilation of autochthonous and allochthonous carbon by each guild. We found that consumers were mostly using allochthonous C in all streams, regardless of watershed land use. Our findings indicate that montane cloud forest streams are dominated by allochthony even in watersheds dominated by pastures. Abundant precipitation in this life zone might facilitate the movement of allochthonous C into streams. While food webs of streams from coffee plantations and pastures also rely on allochthonous resources, other impacts do result in important changes in stream functioning.

Saproxylic beetles' morphological traits and higher trophic guilds indicate boreal forest naturalness.

Forests contribute to numerous ecosystem functions and services and contain a large proportion of terrestrial biodiversity, but they are being negatively impaced by anthropogenic activities. Forests that have never been clear-cut and have old growth characteristics, termed "near-natural," often harbor different and richer species assemblages than managed forests. Alternative management strategies may be able to balance the needs of biodiversity with the demands of forestry, but evaluation efforts are limited by the challenges of measuring biodiversity. Species richness is frequently used as a simple measure of biodiversity, but research indicates that it may not adequately capture community-level changes. Alternatively, trait-based measures of biodiversity may prove to be useful, but research is lacking. In this paper, we use a large dataset that includes 339 obligate saproxylic beetle species collected over a decade in the boreal region throughout southern Norway to: (1) establish if there is a difference in beetle community composition between near-natural and managed forests; and (2) determine which measures of beetle biodiversity best indicate forest naturalness. We arranged the sites in an ordination space and tested for differences in community composition between these forest types. We also tested different measures of biodiversity to determine which were the most predictive of forest naturalness. We found a clear difference in community composition between near-natural and managed forests. Additionally, three measures of biodiversity were most predictive of forest naturalness: proportional abundance of predators, community weighted mean (CWM) of wing length, and CWM of body roundness. The probability that a forest was near-natural increased with the proportional abundance of predators but decreased with CWM wing length and body roundness. Although species richness was higher in near-natural forests, the effect was not significant. Overall, our findings underscore the conservation value of near-natural forests and highlight the potential of several measures of biodiversity for determining forest quality.

Macroecological constraints on species' ‘movement profiles’: Body mass does not explain it all

AbstractAimAnimals couple habitats by three types of movement: dispersal, migration, and foraging, which dynamically link populations, communities, and ecosystems. Across these types, movement distances tend to correlate with each other, potentially reflecting allometric scaling with body mass, but ecological and evolutionary species' traits may constrain movement distances and weaken these correlations. Here, we investigate multivariate “movement profiles” to better understand patterns in movement across movement types, with the aim of improving predictions in ecology from populations to ecosystems.LocationGlobal.Time period1945–2019.Major taxa studiedVertebrates.MethodsWe synthesized distances of all three movement types (dispersal, migration, and foraging) across 300+ vertebrate species and investigated how the relationships between movement types and body mass were modified by evolutionary history and trophic guild.ResultsWe found that the strength of relationships between movement types and body mass varied among taxa and trophic guilds, for example, strongly positive for mammals but weak for birds, or positive across trophic guilds for foraging and dispersal but not migration. Notably, movement profiles interacted with the effects of shared evolutionary history and trophic guild to diminish covariance between movement types.Main conclusionsOverall, we find that movement types with distinct ecological consequences (foraging, migration) are often correlated, although some species seem able to overcome biomechanical, evolutionary, and metabolic constraints by reducing correlations among movement types. This integrative assessment of movement can improve ecological prediction by allowing estimation of unobserved movement distances for parameterization of models based on estimation of other movement types.

Spatial distribution and daily activity patterns of three carnivore species in temperate grasslands of southern Brazil and northern Uruguay

In the temperate grasslands of southern Brazil and northern Uruguay, three species of mesopredators have similar size, are in the same guild, and they seem to tolerate anthropogenic modifications. Sympatric species from the same trophic guild tend to divide resources both spatially and temporally to facilitate coexistence. The aim of this study was to determine the patterns of the periods of daily activity and habitat use through different detection and occupancy models, of Cerdocyon thous (crab-eating fox), Lycalopex gymnocercus (pampas fox) and Leopardus geoffroyi (geoffroy's cat) in the mosaic of landscapes of anthropic domain in the Uruguayan Savanna ecoregion, through camera trap records. A total of 66 cameras were installed, divided into the 3 main environments, with a distance of 2 km between each camera to maintain the independence of the records, achieving a real sampling effort of 4,756 trap nights. The three mesocarnivores considered in this study were predominantly nocturnal. Cerdocyon thous presented a vesperal-nocturnal activity pattern, being sunset the moment of highest activity, in contrast, L. gymnocercus presented highest activity at sunrise, being crepuscular-nocturnal. These opposite daily activity patterns among foxes species have not been recorded in other regions. With respect to L. geoffroyi, these specie presented a mostly nocturnal activity pattern. Regarding the use of habitats by the species after applying different models, the highest probability of detection and occupation of C. thous and L. geoffroyi was in the native forest environment and for L. gymnocercus was the natural grassland. Even the preference of L. geoffroyi for the native forest environment, these species presented a certain degree of adaptability for habitats with alterations produced by agricultural activities. The results obtained represent a very important contribution to the region in which this study was carried out, as well as allowing us to compare the results with other studies with these species in other regions.

Trophic transfer patterns of arsenic in freshwater ecosystem layers in arsenic-endemic Ganges Delta and its potential human health risk.

Arsenic (As) is a toxic environmental contaminant with global public health concern. In aquatic ecosystems, the quantification of total As is restricted chiefly to the individual organisms. The present study has quantified the total As in different trophic layers (sediment-water-phytoplankton-periphyton-zooplankton-fish-gastropod-hydrophytes) of lentic freshwater ecosystems. As transfer pathways quantifying the transmission rate across trophic-level compartmental route were delineated using a novel model-based approach along with its potential contamination risk to humans. Lentic water bodies from Indo-Gangetic region, acore area of groundwater As, were selected for the present investigation. The study revealed that among the lower biota, zooplankton were the highest accumulator of total As (5554-11,564µgkg-1) with magnification (rate = 1.129) of the metalloid, followed by phytoplankton (2579-6865µgkg-1) and periphytic biofilm (1075 to 4382µgkg -1). Muscle tissue of zooplanktivore Labeo catla is found to store higher As (80-115µgkg-1 w.w.) compared to bottom-dwelling omnivore Cirrhinus mrigala (58-92µgkg-1 w.w.). Whereas, Amblypharyngodon mola has accumulated higher As (203-319µgkg-1 w.w.) than Puntius sophore (30-98µgkg-1 w.w.) that raised further concern. The hepatic concentration indicated arsenic-mediated stress based on As stress index (threshold value = 1). Mrigal and Mola showed significant biomagnification among fishes while biodiminution was observed in Catla, Bata, Rohu and Punti. All the studied fishes were under the arsenic mediated stress. In the 'sediment-water-periphytic biofilm-gastropod' compartment, the direct grazing accumulation was higher (rate = 0.618) than the indirect path (rate = 0.587). Stems of edible freshwater macrophytes accumulated lesser As (32-190µgkg-1 d.w.) than roots (292-946µgkg-1 d.w.) and leaves (62-231µgkg-1 d.w.). The target cancer risk (TCR) revealed a greater concern for adults consuming edible macrophyte regularly. Similarly, the varied level of target hazard quotient and TCR for adults consuming fishes from these waterbodies further speculated significant health concerns. The trophic transfer rate of environmental As in soil-water-biota level at an increasing trophic guild and consumer risk analysis have been unravelled for the first time in the Indo-Gangetic plains, which will be helpful for the strategic mitigation of As contamination.

Effect of environmental drivers of fish assemblage and diversity patterns in temporal scale in Mongra Reservoir: A case study from one of the tributaries of Mahanadi Basin, Central India

AbstractInfluence of seasonal variations in environmental parameters on fish assemblage and species diversity patterns was studied in a tropical reservoir of Central India during March 2021 to February 2022. A total of 41 species belonging to 7 orders, 15 families and 29 genera were recorded with highest diversity during post‐monsoon season compared to the pre‐monsoon season and monsoon season. The fish abundance similarity between the monsoon and post‐monsoon reached a maximum of 89%. Seasonal variations in the mean species abundance, Simpson dominance index, Shannon diversity index, Pielou's evenness index and Margalef's richness index were determined. One‐way ANOVA revealed a significant difference (P < 0.05) at the temporal scale. There was a significant seasonal difference in species abundance (P = 0.0006) and evenness index (P = 0.02) among the diversity indices. During the study period, three ‘vulnerable’ species, three ‘near threatened’ species and two ‘endangered’ species were caught. Carnivore dominance was evident throughout the year in the trophic guild of fishes. The Pearson correlation test revealed that water pH, dissolved oxygen, sediment organic carbon and clay percentage were positively correlated to all four diversity indices. Simpson and Margalef species richness diversity indices were positively correlated to sediment pH. Fish abundance was positively associated with sediment pH, silt, phosphorus and nitrogen content. Canonical correspondence analysis was used to investigate the relationships between fish assemblages and environmental conditions. Among the 19 physicochemical parameters, nine (dissolved oxygen, total dissolved solids, conductivity, transparency, hardness, phosphate and chlorophyll‐a, sediment nitrogen and phosphorus) characteristics were shown to be statistically significant (P < 0.05) in determining fish diversity. Dissolved oxygen, total dissolved solids, conductivity, transparency, hardness, phosphate and chlorophyll‐a of water and sediment nitrogen and phosphorus qualities were the key factors for the species abundance. The reservoir boasts a diverse fish population that allows multi‐species fishing and generates revenue for numerous local fishers. Fish habitats should be protected in order to maintain diversity and long‐term ecological benefits.

New interactive functional indicator approach for river health assessment in an Asian temperate river: Comprehensive analysis of water chemistry, physical habitat, land use, and the biological disturbance of invasive alien species

Elucidating the responses of aquatic communities to environmental (e.g., chemical, habitat, and flow regime) and biological disturbances is essential to the maintenance and restoration of healthy ecosystems. This study investigated the interactions between environmental and biological disturbance factors and functional indicators of ecological health in 99 sampling sites along a temperate river. Variance tests and multivariate statistical tools, such as non-metric multidimensional scaling (NMDS) and generalized linear models (GLMs), were employed to evaluate the responses of functional indicator guilds and ecological river health to various in-stream chemical, physical, habitat, and land-use pattern factors along with the biological impact of invasive alien species (IAS). Variance testing revealed significant variation (χ2 > 6.2 and p < 0.05) in common species abundance and ecological functional guilds among spatial groups according to chemical pollution levels, land-use intensity, and land-use patterns. NMDS analysis and GLMs based on trophic, habitat, and tolerance guilds, and the results of the multi-metric index of biological integrity for fish, indicated statistically significant patterns in response to environmental disturbance, particularly chemical degradation associated with nutrient (nitrogen and phosphorus) enrichment and organic pollution, loss of gravel and cobble substrates, and intensified agricultural land use. The spatial pattern of IAS abundance was also significantly correlated with the alteration in fish community structures. This study underscores the often-unnoticed impact of high IAS abundance on river health, and its interactions with chemical and physical degradation resulting from agricultural and urban land uses. In summary, this study highlights the importance of addressing multiple environmental and biological disturbances to maintain and conserve the health of river systems.

Biological invasions alter the structure of a tropical freshwater food web.

Biological invasions are expected to alter food web structure, but there are limited empirical data directly comparing invaded versus uninvaded food webs, particularly in species-rich, tropical systems. We characterize for the first time the food web of Lake Gatun-a diverse and highly invaded tropical freshwater lake within the Panama Canal. We used stable isotope analysis to reconstruct the trophic structure of the fish community of Lake Gatun and to compare it to that of a minimally invaded reference lake, Lake Bayano. We found significant differences between the trophic structures of these two Neotropical lakes, notably that Lake Gatun's fish community was characterized by a longer food chain, greater isotopic diversity, a broader range of trophic positions and body sizes, and shifts in the isotopic positions of several native taxa relative to Lake Bayano. The degree of isotopic overlap between native and non-native trophic guilds in Lake Gatun was variable, with herbivores exhibiting the lowest (20%-29%) overlap and carnivores the greatest (81%-100%). Overall, our results provide some of the first empirical evidence for the ways in which multiple introduced and native species may partition isotopic space in a species-rich tropical freshwater food web.

Metabarcoding reveals that mixed forests mitigate negative effects of non-native trees on canopy arthropod diversity.

Averting climate change-induced forest diebacks increasingly relies on tree species planted outside of their natural range and on the addition of non-native tree species to mixed-species forests. However, the consequences of such changes for associated biodiversity remain poorly understood, especially for the forest canopy as a largely understudied forest stratum. Here, we used flight interception traps and a metabarcoding approach to study the taxonomic and functional (trophic guilds) composition and taxon richness of canopy arthropods. We sampled 15 monospecific and mixed stands of native European beech, native Norway spruce-planted outside its natural range-and non-native Douglas fir in northwest Germany. We found that the diversity of arthropods was lower in non-native Douglas fir compared with native beech stands. Taxon richness of herbivores was reduced by both conifer species. Other functional guilds, however, were not affected by stand type. Arthropod composition differed strongly between native broadleaved beech and monospecific coniferous (native spruce or non-native Douglas fir) stands, with less pronounced differences between the native and non-native conifers. Beech-conifer mixtures consistently hosted intermediate arthropod diversity and community composition compared with the respective monospecific stands. Moreover, arthropod diversity had a positive relationship with the number of canopy microhabitats. Our study shows that considering arthropod taxa of multiple functional groups reveals the multifaceted impact of non-native tree species on forest canopy arthropod communities. Contrasting with previous studies that primarily focused on the forest floor, we found that native beech hosts a rich diversity of arthropods, compared with lower diversity and distinct communities in economically attractive, and especially in non-native, conifers with few canopy microhabitats. Broadleaf-conifer mixtures did not perform better than native beech stands, but mitigated the negative effects of conifers, making such mixtures a compromise to foster both forest-associated diversity and economic yield.

Empirical measurements of ammonium excretion in kelp forest fishes: Effects of body size, taxonomy and trophic guild

Fishes and other consumers excrete metabolic waste products, including dissolved nutrients rich in nitrogen, which is an essential nutrient for primary production. Relatively little is known about the magnitude and variability of nutrients excreted by fishes in kelp forest ecosystems and whether consumer-derived nutrients are important for supporting kelp productivity. In this study, the supply of ammonium (NH4+) excreted by the dominant fishes (30 species representing ∼85% of total fish biomass) was investigated on nearshore rocky reefs in California. Using rapid field incubations, the amount of excreted dissolved ammonium was measured as a function of body size (n = 460 individuals) and predictive models were developed relating mass to excretion rates at the family-level. Mass-specific excretion rates ranged from 0.08 to 3.45 μmol·g−1·hr−1, and per capita ammonium excretion rates ranged from 5.9 to 2765 μmol·individual·hr−1. Ammonium excretion scaled with fish body mass to the ¾ power, as predicted by the metabolic theory of ecology; mass-specific excretion rates were higher in smaller fishes, but larger fishes contributed more ammonium per individual. When controlling for body size, ammonium excretion rates were greatest among surfperch (Embiotocidae), damselfish (Pomacentridae), and wrasses (Labridae), and the general trophic groups of planktivores and micro-carnivores. When body size differences were considered, the greatest mean excretion rates per individual were observed in larger-bodied species, such as California Sheephead (Semicossyphus pulcher) and Lingcod (Ophiodon elongatus). Empirical estimates of nutrient excretion by fishes, among the first measured in temperate kelp forests, were consistent with those in other aquatic systems. Ultimately, empirically derived excretion rates are the first step to quantifying the relative importance of consumers to nutrient cycling in kelp forest ecosystems.

DNA metabarcoding reveals evidence of inter- and intra-guild predation by Scylla paramamosain in a marine ecosystem

IntroductionCrustacean predators exhibit diverse trophic interactions across various habitats in aquatic ecosystems. To assess their ecological roles, it is essential to understand their complete dietary spectrum. Recently, DNA-based techniques such as DNA metabarcoding and high-throughput sequencing have provided insights into trophic networks and their response to environmental drivers.MethodsIn this study, we used these methods to investigate the impact of salinity gradients on the trophic networks of mud crabs (Scylla paramamosain) in marine ecosystems.ResultsOur results revealed that mud crabs prey on a wide range of taxa, including crabs (other than the host species), fish, shrimps, and other prey factions. Salinity gradients had a significant influence on the specific prey items, such as high predation on Metapenaeus, and Trigonopterus species in high salinity sites. Notably, crabs exhibited a greater infestation of Portunion parasites in environments with high salinity levels, in contrast to environments with lower salinity levels. Ordination analysis showed that mud crabs adapt their diet according to environmental constraints.DiscussionFurthermore, the results indicate that mud crabs showed opportunistic predation behavior as they were observed preying on other Portunidae species sharing the same trophic guild. Overall, these findings demonstrate the dietary plasticity and associated parasite infestation of an important crustacean predator, and provide evidence that environmental changes may affect incidences of the associated parasites as well as the specific predator-prey interactions indirectly through fluctuations in marine ecosystems.

Edaphic Beetles (Insecta: Coleoptera) in Three Different Land Use Systems in the Eastern Amazon

Objective: The objective of this study was to evaluate edaphic beetles’ abundance, diversity indexes and composition dependence in different land-use systems (LUS) under tropical climate conditions. Method: We surveyed three different LUS such as primary forest fragment (FFP), agroforestry system (SAF) and conventional agricultural cultivation (CAC) in Eastern Amazon. The edaphic beetles were collected using pitfall traps, identified to the family taxonomic level and classified into trophic guilds (carnivore, detritivore, fungivore, and/or herbivore). Results and conclusion: All LUS showed strong dominance by Scarabaeidae and Staphylinidae families. The edaphic beetles community is influenced by the LUS, since the highest rates of abundance, average richness, diversity and evenness were found in the CAC. Edaphic beetles’ composition is dependent to natural vegetation, which accumulated richness is the greatest parameter related to natural vegetation. Research implications: No-tillage cultivation, with homogeneous vegetation formed by decayed plant material from the last culture cycle, can improve and preserve beetles’ detritivore trophic guild. Due to the edaphic beetles’ composition dependence to natural vegetation, is important to preserve forest fragments near altered landscapes to ensure better conditions for this organism’s reestablishment. Originality/value: Edaphic beetles have rarely been studied under different LUS with tropical conditions, particularly in the Eastern Amazon. Comprising these organisms distribution pattern after land-use changes is essential for ecological conservation implications.

Impact of forest disturbance on microarthropod communities depends on underlying ecological gradients and species traits.

Windstorms and salvage logging lead to huge soil disturbance in alpine spruce forests, potentially affecting soil-living arthropods. However, the impacts of forest loss and possible interactions with underlying ecological gradients on soil microarthropod communities remain little known, especially across different environmental conditions. Here we used DNA metabarcoding approach to study wind-induced disturbances on forest communities of springtails and soil mites. In particular, we aimed to test the effect of forest soil disturbance on the abundance, richness, species composition, and functional guilds of microarthropods. We sampled 29 pairs of windfall-forest sites across gradients of elevation, precipitation, aspect and slope, 2 years after a massive windstorm, named Vaia, which hit North-Eastern Italy in October 2018. Our results showed that wind-induced disturbances led to detrimental impacts on soil-living communities. Abundance of microarthropods decreased in windfalls, but with interacting effects with precipitation gradients. Operative Taxonomic Units (OTU) richness strongly decreased in post-disturbance sites, particularly affecting plant-feeder trophic guilds. Furthermore, species composition analyses revealed that communities occurring in post-disturbance sites were different to those in undisturbed forests (i.e., stands without wind damage). However, variables at different spatial scales played different roles depending on the considered taxon. Our study contributes to shed light on the impacts on important, but often neglected arthropod communities after windstorm in spruce forests. Effects of forest disturbance are often mediated by underlying large scale ecological gradients, such as precipitation and topography. Massive impacts of stronger and more frequent windstorms are expected to hit forests in the future; given the response we recorded, mediated by environmental features, forest managers need to take site-specific conservation measures.