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Aim Location Time Period Major Taxa Studied Methods Results Main Conclusions The relationship between body size and trophic position (BS–TP) typically exhibits a positive correlation in aquatic foodwebs, but the strength of this relationship is contingent on ecosystem type and climate. Different hypotheses have been proposed to elucidate climate and ecosystem type effects on the BS–TP relationship for ray‐finned fish. However, our understanding of whether such a relationship evolved in a correlated fashion, spanning various climates and ecosystem types, remains limited.Temperate and tropical marine and freshwater ecosystems.Present to millions of years ago.Ray‐finned fish.We used a phylogenetic tree and TP and BS data of more than a thousand freshwater and marine ray‐finned fishes, from distinct climates and ecosystems, to investigate patterns on macroevolutionary time scales of the evolutionary correlation of BS and TP. As part of our investigation, we also ran analyses excluding herbivores and detritivores from the dataset, then further focusing solely on carnivores.We found distinct patterns of the BS–TP evolutionary correlation for different climates and ecosystems. The evolutionary correlation between BS and TP was significant for all ecosystem type–climate combinations, except for tropical freshwater ecosystems. The results remained consistent even after accounting for phylogenetic uncertainty and when excluding herbivores and detritivores from the analysis.We found a weaker evolutionary correlation between BS and TP in tropical freshwater ecosystems. These findings are consistent with the stronger BS–TP relationship between extant taxa in temperate climates compared to the tropics, illustrating how evolutionary dynamics might have influenced the trophic structure of fish and contributed to shaping macroecological patterns of the BS–TP relationship. Our findings suggest that limitations that hinder evolutionary integration between BS and TP might be primarily attributed to energetic constraints imposed by temperature and the availability of C‐rich food resources at the base of the foodweb. [ABSTRACT FROM AUTHOR]

The diversity effect on decomposition, through the litter-mixing effects plays a central role in determining the nutrient and carbon dynamics in ecosystems. However, the litter-mixing effects are centered on a leaf litter perspective. Important aspects related to intraspecific interaction and biomass concentration are rarely evaluated, even though they could be essential to determine the litter decomposition dynamics. To our knowledge, we introduced a new perspective to evaluate whether and how the interaction between flower and leaf litter affects the occurrence, direction, and magnitude of litter-mixing effects in terrestrial and aquatic ecosystems. We performed laboratory experiments using flower and leaf litter from the yellow trumpet tree Tabebuia aurea (Silva Manso) Benth. and Hook. f. ex. S. Moore as a model. To obtain realistic results, we manipulated various scenarios of flower : leaf litter biomass proportion and measured 13 functional traits. Litter-mixing effects were consistent in both aquatic and terrestrial environments, with faster decomposition of both litter types in mixtures compared to their monocultures (synergistic effects). Litter-mixing effects were stronger in the terrestrial environment and at higher flower : leaf litter biomass proportions. Our results indicate that synergistic outcomes are mainly associated with complementary effects. Flower litter had a higher concentration of labile C compounds, N, P, and K and lower lignin concentrations, representing a labile litter, while leaf litter had a higher concentration of lignin, Ca, Mg, and Na, representing a refractory litter. Our results demonstrate the importance of litter-mixing effects between flower and leaf litter via complementary effects. These results shed light on the secondary consequences of flower litter on decomposition, suggesting that species with high reproductive investment in flower biomass may play an important role in the nutrient and carbon recycling of diverse plant communities, exerting a pivotal role in biogeochemical dynamics. [ABSTRACT FROM AUTHOR]

The diversity effect on decomposition, through the litter-mixing effects, plays a central role in determining the nutrient and carbon dynamics in ecosystems. However, the litter-mixing effects are centered on a leaf litter perspective. Important aspects related to intraspecific interaction and biomass concentration are rarely evaluated, even though they could be essential to determine the litter decomposition dynamics. Here, we introduced a new perspective to evaluate whether and how the interaction between flower and leaf litter affects the occurrence, direction, and magnitude of litter-mixing effects in terrestrial and aquatic ecosystems. We performed laboratory experiments using flower and leaf litter from the yellow trumpet tree Tabebuia aurea (Silva Manso) Benth. & Hook. f. ex. S. Moore as a model. To obtain realistic results and a mechanistic understanding, we used different scenarios of flower:leaf litter biomass proportion and measured 13 functional traits, respectively. Litter-mixing effects were consistent in both aquatic and terrestrial environments, with faster decomposition of both litter types in mixtures compared to their monocultures (synergistic effects). Litter-mixing effects were stronger in the terrestrial environment and higher flower:leaf litter biomass proportion. Our results indicate that synergistic results are mainly associated with complementary effects. Flower litter had a higher concentration of nutrients important to decomposition, such as N, P, K, and water-holding capacity, while leaf litter had a higher concentration of Ca, Mg, and Na. To our knowledge, this is the first study to demonstrate the importance of litter-mixing effects between flower and leaf litter. This result sheds light on the secondary consequences of flower litter on decomposition, suggesting that species with high reproductive investment in flower biomass may play an important role in the nutrient and carbon recycling of diverse plant communities, exerting a pivotal role in biogeochemical dynamics. [ABSTRACT FROM AUTHOR]

The diversity effect on decomposition, through the litter-mixing effects, plays a central role in determining the nutrient and carbon dynamics in ecosystems. However, the litter-mixing effects are centered on a leaf litter perspective. Important aspects related to intraspecific interaction and biomass concentration are rarely evaluated, even though they could be essential to determine the litter decomposition dynamics. Here, we introduced a new perspective to evaluate whether and how the interaction between flower and leaf litter affects the occurrence, direction, and magnitude of litter-mixing effects in terrestrial and aquatic ecosystems. We performed laboratory experiments using flower and leaf litter from the yellow trumpet tree Tabebuia aurea (Silva Manso) Benth. & Hook. f. ex. S. Moore as a model. To obtain realistic results and a mechanistic understanding, we used different scenarios of flower:leaf litter biomass proportion and measured 13 functional traits, respectively. Litter-mixing effects were consistent in both aquatic and terrestrial environments, with faster decomposition of both litter types in mixtures compared to their monocultures (synergistic effects). Litter-mixing effects were stronger in the terrestrial environment and higher flower:leaf litter biomass proportion. Our results indicate that synergistic results are mainly associated with complementary effects. Flower litter had a higher concentration of nutrients important to decomposition, such as N, P, K, and water-holding capacity, while leaf litter had a higher concentration of Ca, Mg, and Na. To our knowledge, this is the first study to demonstrate the importance of litter-mixing effects between flower and leaf litter. This result sheds light on the secondary consequences of flower litter on decomposition, suggesting that species with high reproductive investment in flower biomass may play an important role in the nutrient and carbon recycling of diverse plant communities, exerting a pivotal role in biogeochemical dynamics. [ABSTRACT FROM AUTHOR]

Riparian forests provide abundant plant litter – mostly in the form of dead leaves (hereafter litter) – for both forest soils and adjacent stream ecosystems, supporting terrestrial and aquatic detritus‐based food webs. Although the fate of litter is predominantly dependent on its chemical and physical traits, there is limited availability of data on those traits over large spatial scales or empirical comparisons of traits across tropical biomes. We filled this gap by exploring the differences and similarities of nine litter traits and their dependence on phylogenetics for 68 plant species from riparian forests across three continental‐scale, South American biomes: Amazon, Atlantic Forest and Cerrado. All three biomes produced litter with similar percentages of carbon (C) and phosphorus (P), C:P mass ratios, specific leaf area and toughness. However, litter from the driest biome (Cerrado) was better defended chemically (higher phenolic content) and had lower nutritional quality (higher C:nitrogen [N] mass ratio) but showed lower nutritional limitation (lower N:P mass ratio) than litter from more humid biomes. We found no phylogenetic signal for traits after constructing a phylogenetic tree across all biomes, suggesting that trait differences across biomes were environmentally determined. However, a strong phylogenetic signal was observed for P in the Atlantic Forest, which indicates that closely related species have similar %P in that biome. Our findings suggest that litter from more humid biomes was higher in nitrogen, although more phosphorus‐limited, than litter produced in drier climates such as that of the Cerrado biome. [ABSTRACT FROM AUTHOR]

Species distribution is a combination of ecological, historical, stochastic, and evolutionary mechanisms, and is a process that has been severely impacted by anthropogenic activities. Freshwater zooplankton is adequate to assess that combination because it groups cosmopolitan and endemic species. We hypothesized that the spatial distribution of Diaphanosoma species is defined by a complex interaction between factors such as spatial limitation, limitation of environmental conditions, and ecological conditions. We georeferenced the occurrence of Diaphanosoma in Brazil to study the potential distribution of the species, preference of ecoregions, environmental features associated with Diaphanosoma, and their co-occurring patterns. Five species of Diaphanosoma are widely distributed in Brazil. D. spinulosum and D. birgei were widely distributed while D. fluviatile and D. polyspina had a more restricted distribution. The occurrences of Diaphanosoma species were shown to have an association with factors such as the total concentrations of nitrogen and phosphorus, pH and, temperature, except in the case of the D. brevireme. Our results show that geographic, environmental, and biotic filters can drive the spatial distribution of species of the genus Diaphanosoma. Therefore, the distribution and spatial occurrence of these species depend on dispersal capacity and spatial restrictions, suitability of the abiotic environment, and ecological interactions. [ABSTRACT FROM AUTHOR]

The home-field advantage (HFA) hypothesis establishes that plant litter decomposes faster at 'home' sites than in 'away' sites due to more specialized decomposers acting at home sites. This hypothesis has predominantly been tested through 'yes or no' transplanting experiments, where the litter decomposition of a focal species is quantified near and away from their conspecifics. Herein, we evaluated the occurrence and magnitude of home-field effects on the leaf litter decomposition of Myrcia ramuliflora (O.Berg) N. Silveira (Myrtaceae) along a natural gradient of conspecific litterfall input and also if home-field effects are affected by litter and soil traits. Litter decomposition of M. ramuliflora was assessed through litterbags placed in 39 plots in a tropical heath vegetation over a period of 12 months. We also characterized abiotic factors, litter layer traits, and litter diversity. Our results indicated the occurrence of positive (i.e. Home-field advantage) and negative (i.e. Home-field disadvantage) effects in more than half of the plots. Positive and negative effects occurred in a similar frequency and magnitude. Among all predictors tested, only the community weighted mean C/N ratio of the litterfall input was associated with home-field effects. Our results reinforce the lack of generality for home-field effects found in the literature and thus challenge the understanding of litter-decomposer interaction in tropical ecosystems. [ABSTRACT FROM AUTHOR]

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We utilized laboratory microcosms to evaluate the effects of a benthic sediment bioturbator (Heteromastus similis; Polychaeta; conveyor-belt deposit feeder) on vertical distributions of C[H.sub.4] in sediment and net C[H.sub.4] fluxes across sediment-water-air interfaces. The effect of H. similis on sediment C[H.sub.4] concentration ([C[H.sub.4]]) varied depending on sediment depth and was strongest at higher animal densities. In comparison with defaunated controls, microcosms with the highest density of H. similis exhibited an increase in [C[H.sub.4]] of 3.7-fold, on average, at the sediment surface (0-2 cm), but these concentrations decreased by ~2-fold in deeper sediment layers (2-8 cm). However, irrespective of sediment depth, the density of H. similis resulted in an overall nonlinear reduction of bulk sediment [C[H.sub.4]]. Most of the observed C[H.sub.4] losses from the sediment were due to C[H.sub.4] oxidation, but the bioturbatory activities of H. similis also promoted significant increases in [C[H.sub.4]] in both the water column and the microcosm headspace. These results suggest that benthic invertebrates can mediate C[H.sub.4] turnover between compartments in aquatic ecosystems, with further consequences for the coupling between benthic-pelagic food chains via the methanotrophic-mediated microbial loop, as well as increase C[H.sub.4] emissions to the atmosphere. Des microcosmes de laboratoire nous ont servi a evaluer les effets d'un perturbateur biologique des sediments benthiques (Heteromastus similis; polychete qui se nourrit de sediments par convoyage) sur la repartition verticale de C[H.sub.4] dans le sediment et les flux nets de C[H.sub.4] a travers les interfaces sediment-eau-air. L'effet d'H. similis sur les concentrations de C[H.sub.4] ([C[H.sub.4]]) varie en fonction de la profondeur du sediment et est maximal aux plus fortes densites d'animaux. En comparaison des temoins sans animaux, les microcosmes avec les densites les plus elevees d'H. similis montrent une augmentation de [C[H.sub.4]] de 3,7 fois en moyenne a la surface des sediments (0-2 cm), mais ces concentration diminuent de ~2 fois dans les couches plus profondes de sediment (2-8 cm). Cependant, quelle que soit la profondeur des sediments, la densite d'H. similis cause une reduction generale non lineaire du [C[H.sub.4]] du sediment global. La plupart des pertes de C[H.sub.4] observees dans les sediments sont dues a l'oxydation de C[H.sub.4]; cependant, les activites de perturbation biologique d'H. similis provoquent aussi des augmentations significatives de [C[H.sub.4]], tant dans la colonne d'eau que dans l'espace de tete du microcosme. Ces resultats laissent croire que les invertebres benthiques peuvent servir d'agents dans le circulation du C[H.sub.4] entre les compartiments des ecosystemes aquatiques, avec des consequences additionnelles sur le couplage des chaines alimentaires benthique et pelagique par l'intermediaire de la boucle microbienne methanotrophique, ainsi que sur l'accroissement des emissions de C[H.sub.4] vers l'atmosphere. [Traduit par la Redaction], Introduction Inland aquatic ecosystems such as wetlands, rice fields, and shallow lakes are major sources of the C[H.sub.4] that is released into the atmosphere (Bartlett and Harriss 1993; Whiting and [...]

GLO:69VH/01jul21:bes21890-fig-0002.jpg PHOTO (COLOR): . gl Photo 2: Clumps of E. spectabile arranged along a rocky outcrop in the Brazil's semiarid Caatinga region. The rupicolous bromeliad I Encholirium spectabile i acts as a key species for biodiversity in rocky outcrops of Brazil's semiarid Caatinga biome. GLO:69VH/01jul21:bes21890-fig-0004.jpg PHOTO (COLOR): . gl Photo 4: The bat (Lonchophylla mordax) approaching the inflorescence of E. spectabile to feed on the nectar of the flowers. [Extracted from the article]

Bromeliads provide habitat and food resources for various organisms. Besides the nectar and pollen, the leaf and fruit tissues of these plants supply food for various animal groups. Among the groups that feed on bromeliads, herbivores are the ones that cause the most damage to these plants; among such organisms, some are well known, such as butterfly and moth caterpillars. Here we will describe some of the ecological relationships between the butterflies Strymon serapio and moths Castnia invaria in association with the rupicolous habitat-forming bromeliad Encholirium spectabile. In rocky outcrops of the Brazilian Semiarid Caatinga, S. serapio caterpillars were frequently observed in the blooms of E. spectabile and adults in the leaves, as well as adults of C. invaria. However, in C. invaria the larvae develop inside the bromeliads. Adults of both species were associated with E. spectabile throughout the year in the study area. We observed S. serapio eggs and larvae mainly during the beginning of the dry season, and the eggs of C. invaria, occur mainly during the rainy season. Regarding the daily activity period, the two species show diurnal habits. Caterpillars of S. serapio develop mutualistic relations with ants of the genus Crematogaster in the blooms of E. spectabile. This is the first record for this kind of ant-butterfly interactions taking place in Encholirum bromeliads, although they have already been cited for other species of Bromeliaceae. The record of these interactions in E. spectabile suggests that these bromeliads are relevant for local biodiversity, also regarding interactions with species of commercial interest, which use the E. spectabile as a host plant.. [ABSTRACT FROM AUTHOR]

Aims: We evaluated the relative importance that biodiversity factors, abiotic conditions, and vegetation structure have on monthly leaf litter production. We tested if biodiversity drives leaf litter production through the increase in species richness or community‐weighted mean traits regardless of the influence of other biodiversity factors that reflect species niche differentiation, such as phylogenetic and functional diversities. We also tested if precipitation imposes greater influence on the production than any asynchronous effects between species that result from temporal niche partitioning. Location: Seasonal heath vegetation that covers white‐sand coastal areas in northeastern Brazil. Methods: We conducted an observational study across 41 25‐m2 permanent plots to sample leaf litter production of the vegetation during 18 months from January 2016 to June 2017 at monthly intervals. We used structural equation modeling in combination with linear mixed models to test the above‐mentioned hypotheses. Results: Our study encompassed 22 focal species. Species richness was the only biodiversity factor to influence leaf litter production, although its effect was weak, suggesting that the chance of including high‐yielding species by increasing richness enhances the production regardless of the degree of species niche complementarity through functional and phylogenetical dissimilarities. We also observed a major control of precipitation on leaf litter production, as well as a lack of interaction between species richness and its temporal dynamic of production, demonstrating the key role of climate‐mediated controls. Conclusion: We believe that plant diversity loses importance for ecosystem functioning in ecological contexts where the entire community responds similarly to abiotic pressures, particularly if the ecosystem process is marked by strong temporal dynamics. Our study provided empirical support for this line of reasoning since the seasonal heath vegetation responded mostly to rainfall seasonality. [ABSTRACT FROM AUTHOR]

Assessing zooplankton biodiversity is essential to support freshwater management/conservation programs. Here, we investigated the zooplankton community structure from 180 shallow lakes in northeastern Brazil and analyzed them according to biome (Atlantic Forest or Caatinga), the origin of ecosystems (natural or man-made lakes), and habitat type (pelagic or littoral). Additionally, we provided an updated list of zooplankton species. We registered 227 species (137 Rotifera, 65 Cladocera, 25 Copepoda). The most common species of each major group among all lakes were the cladoceran Ceriodaphina cornuta, the rotifers Brachionus havanaensis and Lecane bulla, and the copepod Termocyclops decipiens. Species related to aquatic vegetation, as the Lecanidae rotifers and phytophilous cladocerans, were more frequent along Atlantic Forest biome and natural lakes. On the other hand, species that are bioindicators of eutrophic waters were more common at the Caatinga biome and man-made lakes. Atlantic Forest and Caatinga biomes had similar species richness, but different community compositions for all zooplankton groups, reinforcing the Caatinga significance for the Brazilian aquatic biodiversity. The type of habitat was the most important factor structuring species richness, with higher richness in the littoral region when compared to the pelagic. A result of many unique species of Cladocera and Rotifera associated with the aquatic vegetation were observed. The findings demonstrated that conservation/management plans cannot generalize zooplankton species distribution across different biomes, origins and even within a single lake, between the pelagic and littoral zones. This study provided a zooplankton species list from 180 lakes in northeastern Brazil and showed that species distribution, richness and composition vary according to biome (Atlantic Forest or Caatinga), the lake origin (natural or man-made lakes), and the lake habitat (pelagic or littoral). [ABSTRACT FROM AUTHOR]

The energetic demand of consumers increases with body size and temperature. This implies that energetic constraints may limit the trophic position of larger consumers, which is expected to be lower in tropical than in temperate regions to compensate for energy limitation. Using a global dataset of 3635 marine and freshwater ray‐finned fish species, we addressed if and how climate affects the fish body size–trophic position relationship in both freshwater and marine ecosystems, while controlling for the effects of taxonomic affiliation. We observed significant fish body size–trophic position relationships for different ecosystems. However, only in freshwater systems larger tropical fish presented a significantly lower trophic position than their temperate counterparts. Climate did not affect the fish body size–trophic position relationship in marine systems. Our results suggest that larger tropical freshwater fish may compensate for higher energetic constraints feeding at lower trophic positions, compared to their temperate counterparts of similar body size. The lower latitudinal temperature range in marine ecosystems and/or their larger ecosystem size may attenuate and/or compensate for the energy limitation of larger marine fish. Based on our results, temperature may determine macroecological patterns of aquatic food webs, but its effect is contingent on ecosystem type. We suggest that freshwater ecosystems may be more sensitive to warming‐induced alterations in food web topology and food chain length than marine ecosystems. [ABSTRACT FROM AUTHOR]

A core question involving both plant physiology and community ecology is whether traits from different organs are coordinated across species, beyond pairwise trait correlations. The strength of within-community trait coordination has been hypothesized to increase along gradients of environmental harshness, due to the cost of adopting ecological strategies out of the viable niche space supported by the abiotic conditions. We evaluated the strength of trait relationship and coordination in a stressful environment using 21 leaf and stem traits of 21 deciduous and evergreen woody species from a heath vegetation growing on coastal sandy plain in northeastern South America. The study region faces marked dry season, high soil salinity and acidity, and poor nutritional conditions. Results from multiple factor analyses supported two weak and independent axes of trait coordination, which accounted for 25%-29% of the trait variance using phylogenetically independent contrasts. Trait correlations on the multiple factor analyses main axis fit well with the global plant economic spectrum, with species investing in small leaves and dense stems as opposed to species with softer stems and large leaves. The species' positions on the main functional axis corresponded to the competitor-stress-tolerant side of Grime's CSR triangle of plant strategies. The weak degree of trait coordination displayed by the heath vegetation species contradicted our expectation of high trait coordination in stressful environmental habitats. The distinct biogeographic origins of the species occurring in the study region and the prevalence of a regional environmental filter coupled with local homogeneous conditions could account for prevalence of trait independence we observed. [ABSTRACT FROM AUTHOR]

Despite the general acknowledgment of the role of niche and stochastic process in community dynamics, the role of species relative abundances according to both perspectives may have different effects regarding coexistence patterns. In this study, we explore a minimum probabilistic stochastic model to determine the relationship of populations relative and total abundances with species chances to outcompete each other and their persistence in time (i.e., unstable coexistence). Our model is focused on the effects drift (i.e., random sampling of recruitment) under different scenarios of selection (i.e., fitness differences between species). Our results show that taking into account the stochasticity in demographic properties and conservation of individuals in closed communities (zero-sum assumption), initial population abundance can strongly influence species chances to outcompete each other, despite fitness inequalities between populations, and also, influence the period of coexistence of these species in a particular time interval. Systems carrying capacity can have an important role in species coexistence by exacerbating fitness inequalities and affecting the size of the period of coexistence. Overall, the simple stochastic formulation used in this study demonstrated that populations initial abundances could act as an equalizing mechanism, reducing fitness inequalities, which can favor species coexistence and even make less fitted species to be more likely to outcompete better-fitted species, and thus to dominate ecological communities in the absence of niche mechanisms. Although our model is restricted to a pair of interacting species, and overall conclusions are already predicted by the Neutral Theory of Biodiversity, our main objective was to derive a model that can explicitly show the functional relationship between population densities and community mono-dominance odds. Overall, our study provides a straightforward understanding of how a stochastic process (i.e., drift) may affect the expected outcome based on species selection (i.e., fitness inequalities among species) and the resulting outcome regarding unstable coexistence among species. [ABSTRACT FROM AUTHOR]

The mere presence of predators (i.e., predation risk) can alter consumer physiology by restricting food intake and inducing stress, which can ultimately affect prey-mediated ecosystem processes such as nutrient cycling. However, many environmental factors, including conspecific density, can mediate the perception of risk by prey. Prey conspecific density has been defined as a fundamental feature that modulates perceived risk. In this study, we tested the effects of predation risk on prey nutrient stoichiometry (body and excretion). Using a constant predation risk, we also tested the effects of varying conspecific densities on prey responses to predation risk. To answer these questions, we conducted a mesocosm experiment using caged predators ( Belostoma sp.), and small bullfrog tadpoles ( Lithobates catesbeianus) as prey. We found that L. catesbeianus tadpoles adjust their body nutrient stoichiometry in response to predation risk, which is affected by conspecific density. We also found that the prey exhibited strong morphological responses to predation risk (i.e., an increase in tail muscle mass), which were positively correlated to body nitrogen content. Thus, we pose the notion that in risky situations, adaptive phenotypic responses rather than behavioral ones might partially explain why prey might have a higher nitrogen content under predation risk. In addition, the interactive roles of conspecific density and predation risk, which might result in reduced perceived risk and physiological restrictions in prey, also affected how prey stoichiometry responded to the fear of predation. [ABSTRACT FROM AUTHOR]

Tests of the biodiversity and ecosystem functioning (BEF) relationship have focused little attention on the importance of interactions between species diversity and other attributes of ecological communities such as community biomass. Moreover, BEF research has been mainly derived from studies measuring a single ecosystem process that often represents resource consumption within a given habitat. Focus on single processes has prevented us from exploring the characteristics of ecosystem processes that can be critical in helping us to identify how novel pathways throughout BEF mechanisms may operate. Here, we investigated whether and how the effects of biodiversity mediated by non-trophic interactions among benthic bioturbator species vary according to community biomass and ecosystem processes. We hypothesized that (1) bioturbator biomass and species richness interact to affect the rates of benthic nutrient regeneration [dissolved inorganic nitrogen (DIN) and total dissolved phosphorus (TDP)] and consequently bacterioplankton production (BP) and that (2) the complementarity effects of diversity will be stronger on BP than on nutrient regeneration because the former represents a more integrative process that can be mediated by multivariate nutrient complementarity. We show that the effects of bioturbator diversity on nutrient regeneration increased BP via multivariate nutrient complementarity. Consistent with our prediction, the complementarity effects were significantly stronger on BP than on DIN and TDP. The effects of the biomassspecies richness interaction on complementarity varied among the individual processes, but the aggregated measures of complementarity over all ecosystem processes were significantly higher at the highest community biomass level. Our results suggest that the complementarity effects of biodiversity can be stronger on more integrative ecosystem processes, which integrate subsidiary "simpler" processes, via multivariate complementarity. In addition, reductions in community biomass may decrease the strength of interspecific interactions so that the enhanced effects of biodiversity on ecosystem processes can disappear well before species become extinct. [ABSTRACT FROM AUTHOR]

Abstract: Conservation planning and biodiversity monitoring rely exclusively on the use of surrogate groups. However, the effectiveness of these groups in representing unknown biodiversity is rarely tested. These tests can be based on cross-taxon concordance (or congruence) analysis. In a second step, the main mechanisms underlying concordance can be investigated. Here, we evaluated the relative influence of local environmental factors and spatial processes on the patterns of beta-diversity exhibited by phytoplankton, zooplankton and benthic invertebrates and the strength of assemblage concordance among these assemblages in 38 upland Amazonian lakes (northern Brazil) over four years. Zooplankton and benthic invertebrates responded exclusively to environmental variables. These results are in accordance with the expected under the species sorting model, where local factors are the main mechanisms shaping assemblage structure. In general, patterns of concordance between the assemblages were weak and varied through time, indicating that the use of surrogates in freshwater ecosystems may be a flawed approach. [Copyright &y& Elsevier]

Understanding the effects of predators and resources on primary producers has been a major focus of interest in ecology. Within this context, the trophic cascade concept especially concerning the pelagic zone of lakes has been the focus of the majority of these studies. However, littoral food webs could be especially interesting because base trophic levels may be strongly regulated by consumers and prone to be light limited. In this study, the availability of nutrients and light and the presence of an omnivorous fish (Hyphessobrycon bifasciatus) were manipulated in enclosures placed in a humic coastal lagoon (Cabiu' nas Lagoon, Macae' - RJ) to evaluate the individual and interactive effects of resource availability (nutrients and light) and food web configuration on the biomass and stoichiometry of periphyton and benthic grazers. Our findings suggest that light and nutrients interact to determine periphyton biomass and stoichiometry, which propagates to the consumer level. We observed a positive effect of the availability of nutrients on periphytic biomass and grazers' biomass, as well as a reduction of periphytic C:N:P ratios and an increase of grazers' N and P content. Low light availability constrained the propagation of nutrient effects on periphyton biomass and induced higher periphytic C:N:P ratios. The effects of fish presence strongly interacted with resource availability. In general, a positive effect of fish presence was observed for the total biomass of periphyton and grazer's biomass, especially with high resource availability, but the opposite was found for periphytic autotrophic biomass. Fish also had a significant effect on periphyton stoichiometry, but no effect was observed on grazers' stoichiometric ratios. In summary, we observed that the indirect effect of fish predation on periphyton biomass might be dependent on multiple resources and periphyton nutrient stoichiometric variation can affect consumers' stoichiometry. [ABSTRACT FROM AUTHOR]

Abstract: Human activities are exposing freshwater ecosystems to a wide range of stressors, whose direct and indirect effects can be alleviated or exacerbated through interactive effects with dynamic environmental drivers. This study used long-term data from two Neotropical lacustrine freshwater systems (Batata Lake, an Amazonian floodplain lake and Imboassica lagoon, an Atlantic coastal lagoon) subjected to different kinds of environmental fluctuations (i.e., flood pulse and sandbar opening) and anthropogenic impacts (i.e., siltation and eutrophication). Our objective was to determine whether the effects of human perturbations are contingent on modifications of important biotic and abiotic characteristics through environmental variability. For both ecosystems, environmental variability consistently interacted with anthropogenic perturbations to alter most of the variables analyzed, such as nutrient dynamics, chlorophyll-a concentration, zooplankton and benthic invertebrate species richness, and temporal community stability, which indicates that interactive effects between environmental variability and anthropogenic perturbations may impact a myriad of ecosystem properties. Furthermore, the nature of these interactive effects was highly dependent on the variable considered and on the ecosystem analyzed. For example, at Imboassica lagoon, sandbar openings interacted synergistically with trophic state to increase the phosphorus concentration in the water column. At Batata Lake, flooding generally alleviated the negative effects of siltation on species richness by both diluting inorganic suspended material concentration and by promoting local recruitment from the regional species pool. Such results indicate that our ability to understand and predict the outcome of anthropogenic impacts on inland aquatic systems can be hampered if we consider human stressors as “static” phenomena disconnected from dynamic interactions with major local environmental drivers. [Copyright &y& Elsevier]

We utilized laboratory microcosms to evaluate the effects of a benthic sediment bioturbator (Heteromastus similis; Polychaeta; conveyor-belt deposit feeder) on vertical distributions of CH4 in sediment and net CH4 fluxes across sediment–water–air interfaces. The effect of H. similis on sediment CH4 concentration ([CH4]) varied depending on sediment depth and was strongest at higher animal densities. In comparison with defaunated controls, microcosms with the highest density of H. similis exhibited an increase in [CH4] of 3.7-fold, on average, at the sediment surface (0–2 cm), but these concentrations decreased by ~2-fold in deeper sediment layers (2–8 cm). However, irrespective of sediment depth, the density of H. similis resulted in an overall nonlinear reduction of bulk sediment [CH4]. Most of the observed CH4 losses from the sediment were due to CH4 oxidation, but the bioturbatory activities of H. similis also promoted significant increases in [CH4] in both the water column and the microcosm headspace. These results suggest that benthic invertebrates can mediate CH4 turnover between compartments in aquatic ecosystems, with further consequences for the coupling between benthic–pelagic food chains via the methanotrophic-mediated microbial loop, as well as increase CH4 emissions to the atmosphere. [ABSTRACT FROM AUTHOR]

Abstract: We performed a field experiment in a tropical humic coastal lagoon to evaluate periphyton biomass accrual and metabolism on three different substrates (1) plastic ribbons, (2) green and (3) senescent leaves of the emergent macrophyte Typha domingensis) over 30 days. The contribution of autotrophic biomass decreased as total biomass increased over the time. Mean periphytic ash free dry weight ranged from 0.8 to 5.6mgcm−2, but periphyton chlorophyll a concentrations presented shorter amplitudes, which oscillated from 0.12 to 0.44μgcm−2 throughout the experiment. Periphyton metabolism was overall heterotrophic on all substrates, especially on senescent leaves. Our data show that substrate type influenced both biomass accrual and periphyton net productivity and respiration rates throughout periphyton development and highlighted the dominance of heterotrophic metabolism. The periphyton respiration may be subsidized by both water- and substrate-derived allochthonous energy pathways, shedding light on the role of periphytic assemblages to the carbon cycling, as a source of CO2 to the system. [Copyright &y& Elsevier]