Detritivorous Species Research Articles

Bird richness at Sítio do Sol in Cabreúva, State of São Paulo, Brazil

The Atlantic Forest biome has suffered great devastation but still possesses a vast biological and endemic richness, making its preservation essential. The Atlantic Forest fragments located in the interior of the state of São Paulo have not been studied as much as other areas, mainly in the municipality of Cabreúva. Therefore, this study aimed to characterize the bird richness of the Sítio do Sol property, in Cabreúva, São Paulo. The study was carried out from August 2021 to September 2022, covering seasonality. The findings revealed that 193 species were registered, distributed among 52 families, and 23 orders, with a predominance of the Passeriformes order and the Tyrannidae family. The most observed trophic guild among species was insectivorous, accounting for 78 (41%) species, followed by omnivorous with 59 (31%) species, carnivorous 18 (9%), frugivorous 16 (8%), granivorous 12 (6%), nectarivorous 8 (4%), and detritivorous species 2 (1%), with lower richness. This study is one of the few bird surveys carried out in the municipality of Cabreúva and indicates that even in small forest fragments, there is a considerable species richness. Developing more fauna surveys and management plans for the species present in the area is important to preserve these birds.

Heavy Minerals Distribution and Provenance in Modern Beach and Fluvial Sands of the Betic Cordillera, Southern Spain

This study uses heavy detrital minerals to determine actualistic fluvial and beach sand provenance across the Betic Cordillera (Spain), along the coast from Almeria to Marbella. The Betic Cordillera, primarily composed of metamorphic rocks to the east, supply an assemblage dominated by almandine and graphite, with a longshore dispersal from Almeria to Malaga. Buergerite and hypersthene indicate the provenance of calcalkaline lavas east of Cabo de Gata. The western part of the Betic Cordillera, which comprises the Ronda Peridotite Complex, supplies a chromite and diopside assemblage, with a dispersal from Marbella to Algeciras. Considering these mineralogical suites, the effects of source rock compositions and weathering are evaluated. The heavy mineral species mirror the mineralogy of the source rocks of local outcrops and wider source terranes. The fluvial heavy mineral suites do not differ significantly from those in the beaches except for some unstable species. Unstable species such as olivine, pyroxene, and amphibole do not show evidence of loss because of elevated topography and semiarid climate, which do not affect heavy minerals. This contribution also evaluates the potential of some heavy detrital species as ideal pathfinders in searching for diamonds.

Biomagnification of persistent organic pollutants (POPs) in detritivorous, phytophagous, and predatory invertebrates: How POPs enter terrestrial food web?

Invertebrates are primary contributors to fluxes of nutrients, energy, and contaminants in terrestrial food webs, but the trophodynamic of contaminants in invertebrate food chains is not fully understood. In this study, occurrence and biomagnification of persistent organic pollutants (POPs) were assessed in detritivorous, phytophagous, and predatory invertebrate food chains. Detritivorous species (earthworm and dung beetle) have higher concentrations of POPs than other species. Different composition patterns and biomagnification factors (BMFs) of POPs were observed for invertebrate species. Negative correlations were found between BMFs and log KOW of POPs for detritivorous and most phytophagous species. In contrast, parabolic relationships between BMFs and log KOW were observed in snails and predatory species, possibly attributed to the efficient digestion and absorption of diet and POPs for them. Bioenergetic characteristics are indicative of the biomagnification potential of POPs in terrestrial wildlife, as suggested by the significant and positive correlation between basal metabolic rates (BMRs) and BMFs of BDE 153 for invertebrates, amphibians, reptiles, birds, and mammals. The estimations of dietary exposure suggest that the terrestrial predators, especially feeding on the underground invertebrates, could be exposed to high level POPs from invertebrates.

Trophic Fish Structure Along the Beaches of The Brazilian Amazon River

Purpose: This study analyzes fish communities' diet and trophic structure on beaches along the Amazon River. Methods: 41 beaches were studied, and fish were collected with 12x3m trawl nets and 5mm mesh between nodes. The stomachs were analyzed using the frequency of occurrence and points method. The dietary index was calculated using the preponderance index (PI). Using IP values, the following trophic categories were established: detritivore, hematophagous, herbivorous, benthic invertivore, pelagic invertivore, terrestrial invertivore, scavenger, and piscivore. Species richness and abundance of fish in trophic categories were related to the longitudinal variation of the sampled sites through linear regression 1,166 stomachs from 119 species were analyzed. Results and discussion: The abundance and richness of detritivore species and the richness of scavengers showed a negative relationship throughout the floodplain, while the number of aquatic invertivore species showed a positive relationship. Implications of the research: The existing differences in beach water quality create a longitudinal conductivity gradient, transparency, and suspended material, gradually altering the environment and composition of the ichthyofauna and the trophic structure along the Amazon River. Originality/value: Ecological studies relating the trophic structure of fish to a large-scale longitudinal gradient are scarce in the Amazon River floodplain, which makes this article an essential piece for better understanding Amazonian systems by characterizing the trophic structure of fish from beaches in a longitudinal gradient of the Amazon River in Brazilian territory.

The gut microbiome mediates adaptation to scarce food in Coleoptera.

Beetles are ubiquitous cave invertebrates worldwide that adapted to scarce subterranean resources when they colonized caves. Here, we investigated the potential role of gut microbiota in the adaptation of beetles to caves from different climatic regions of the Carpathians. The beetles' microbiota was host-specific, reflecting phylogenetic and nutritional adaptation. The microbial community structure further resolved conspecific beetles by caves suggesting microbiota-host coevolution and influences by local environmental factors. The detritivore species hosted a variety of bacteria known to decompose and ferment organic matter, suggesting turnover and host cooperative digestion of the sedimentary microbiota and allochthonous-derived nutrients. The cave Carabidae, with strong mandibula, adapted to predation and scavenging of animal and plant remains, had distinct microbiota dominated by symbiotic lineages Spiroplasma or Wolbachia. All beetles had relatively high levels of fermentative Carnobacterium and Vagococcus involved in lipid accumulation and a reduction of metabolic activity, and both features characterize adaptation to caves.

Agricultural land use weakens the relationship between biodiversity and ecosystem functioning

Leaf litter decomposition is a significant ecosystem process for streams' energy provisioning, while species‐specific decomposition rates often form a continuum from slow to fast decomposing species allowing for resources' availability to stream consumers over a longer time period after leaf fall. Leaf litter mixtures in streams typically comprise leaf species varying in their traits, allowing for litter diversity effects on decomposition. At the same time, agricultural land use, habitat characteristics, water quality and invertebrate composition modulate leaf litter decomposition. To identify leaf litter diversity effects and disentangle the roles of agricultural intensity, habitat characteristics, water quality and invertebrate composition for leaf litter processing in streams, we quantified leaf litter decomposition of three leaf species covering a gradient from slow to fast decomposing species, tested either individually or as a three‐species mixture. The study was conducted over 21 days across 18 streams with a gradient of agricultural intensity (percent agricultural land use) in their catchments. We found leaf litter diversity effects in terms of complementarity under low to intermediate agricultural intensity, given that slow decomposing leaf species decomposed almost twice as fast in the three‐species mixture compared to the observations on individual leaf species. This leaf litter diversity effect decreased with increasing agricultural intensity, suggesting that agriculture weakens the biodiversity–ecosystem functioning relationship. However, pathways by which agriculture affected decomposition differed between single‐species and mixed‐species scenarios. For the single‐species scenario, negative effects of agriculture appeared to be mediated through effects on the proportion of sensitive detritivore species and altered habitat characteristics. For the mixed‐species scenario, altered water quality negatively affected the proportion of sensitive detritivore species, in turn reducing the diversity effect on functioning. Our results suggest that the weakened biodiversity–ecosystem functioning relationship under increasing agricultural intensity might be a significant factor threatening carbon cycling and food web integrity in streams.

Macro and microplastic intake in seafood variates by the marine organism's feeding behaviour: Is it a concern to human health?

Seafood is considered one of the healthiest sources of food intake for humans, mainly because of its high protein content. However, oceans are among the most polluted environments, and microplastics have been widely reported to be ingested, absorbed or bioaccumulated by marine organisms. The different feeding behaviour may contribute to infer the amounts of microplastic particles accidently intake by marine organisms. We investigated the putative levels of microplastics in different edible species of fish, molluscs, and crustaceans. Plastic fragments larger than 200 μm were detected in the digestive tract of 277 out of 390 specimens (71.5 ± 22.2%) of the 26 different species analysed. There was no evidence of microplastic translocation or bioaccumulation in the muscle tissue of fish, molluscs, and crustaceans. Organisms with carnivorous feeding habits had the highest prevalence of plastic ingestion (79 ± 9.4%), followed by planktivorous species (74 ± 15.5%), and detritivorous species (38 ± 36.9%), suggesting a transfer through the food chain. Moreover, we found evidence that species with less selective feeding habits may be the most affected by the ingestion of large microplastic particles. Our results provide further evidence to the ubiquitous presence of microplastics in marine organisms representing a direct threat to marine wildlife, and to human health with potential consequences for future generations according to the One Health initiatives approach.

An Analysis of Microplastics Ingested by the Mediterranean Detritivore Holothuria tubulosa (Echinodermata: Holothuroidea) Sheds Light on Patterns of Contaminant Distribution in Different Marine Areas

Microplastic pollution constitutes a serious environmental problem that requires more effective scientific research to describe its potential impacts on marine fauna. The interaction between microplastics and marine biota can have significant negative effects through the trophic chain, up to human health. To date, several steps forward have been made in our understanding of this phenomenon; however, large knowledge gaps still exist for several taxa and areas. In particular, the pattern of spatial and temporal distribution of microplastics in marine sediments and their interaction with benthic detritivore species still needs to be addressed. The Mediterranean Sea is one of the most impacted areas of the world, and its biota is deeply affected by microplastic pollution. To investigate the effects of the presence of microplastics in the sediments in this area, the echinoderm Holothuria tubulosa was chosen as a model species, and specimens were collected along the Salento peninsula in Apulia, Southern Italy. This peculiar geographic area extends between two ecoregions of the Mediterranean Sea, the Northern Ionian and the Southern Adriatic seas, characterized by peculiar and distinct currents and submarine topologies, resulting in a complex and dynamic ecosystem affected by seasonal fluctuations that make the Salento peninsula an interesting natural laboratory for predictions of future dispersion events on a wider scale. Microplastics were analyzed by investigating the gut contents of H. tubulosa individuals, and the SEM/EDX method was used to confirm the plastic material extracted. Results revealed microplastics in all the specimens analyzed and with a homogeneous pattern of distribution in time and some differences in space, suggesting that the presence of this anthropogenic material is constant throughout the year and its quantity is only slightly affected by the level of conservation and management strategies characterizing the sampling sites.

Evaluation of the use of Ancistrus brevipinnis (Loricariidae) as a bioindicator of water quality in the Ilha river, RS, Brazil

The use of fish as bioindicators of the effect of contaminants in the aquatic environment is usual. However, detritivorous species are less used for environmental monitoring. Thus, the aim of this study was to evaluate the use of Ancistrus brevipinnis as a potential bioindicator of water quality of the Ilha River, RS (southern Brazil) and compared to the result obtained for a routine species (Bryconamericus iheringii). For this purpose, the condition factor (CF), the presence of morphological changes in the gills and the quantification of metals in different tissues of the specimens collected in three sites of the Ilha River were evaluated. A homogeneity in the distribution of data was observed in the CF for the species B. iheringii, whereas the specimens of A. brevipinnis showed an oscillation in the distribution of data of the CF. Histological analysis showed greater sensitivity of B. iheringii in reproducing characteristics of the environment in its gill lamellae, which was not observed in A. brevipinnis. Conversely, Cr quantification was higher in the intestine samples of A. brevipinnis at all sites and in all collections due to its feeding behavior. The data reinforce the use of water column species as Bryconamericus iheringii for environmental monitoring, even if they do not reflect the whole aquatic ecosystem. Further studies evaluating other tissues and biomarkers, such as the gastrointestinal tract, may assist in describing the use of species more related to sediment.

A multi-tissues comparison of biomarkers in Serrasalmus rhombeus (Teleostei: Serrasalmidae) and Prochilodus nigricans (Teleostei: Prochilodontidae) from two Amazonian rivers with distinct levels of pollution

Aquatic ecosystems are often exposed to a complex mixture of pollutants that can have a negative influence on the health of the resident organisms. In this context, it is crucial to understand the biological responses of the different organisms that inhabit impacted areas to identify biomonitors that are representative of alterations in the local biota. In the present study, two fish, Serrasalmus rhombeus (red-eyed piranha) and Prochilodus nigricans (curimatã) were assessed as potential biomonitors for Amazonian rivers. A total of 121 fish of these two species were collected during the dry season from two rivers representing different extremes of pollution. One site was the Xingu River, which has low level of pollution, while the other was the Itacaiunas River, which is impacted by high levels pollution from multiple sources. Two exposure biomarkers (glutathione S-transferase activity and total antioxidant capacity) and one effect biomarker (lipid peroxidation) were evaluated in samples of both species extracted from various types of tissues (brain, liver, gills and muscle). The results of the analyses indicated the occurrence of both species-specific and tissue-specific responses. The responses of the biomarkers of the detritivorous species, P. nigricans, were more significant than those of the apex predator, S. rhombeus. In addition, the P. nigricans specimens from the polluted (Itacaiunas) river presented marked suppression of the responses related to the detoxification and antioxidant defences, which resulted in more significant oxidative damage (lipoperoxidation) in comparison with the less polluted (Xingu) river. These findings indicate that P. nigricans is the more sensitive of the two species and would thus be the better choice as a biomonitor for environmental monitoring. The results of the present study also indicate that a more integrated approach to the assessment of the response of biochemical biomarkers, including the analysis of a range of different types of tissue should be adopted to guarantee the robustness of analyses of environmental quality.

Modelling the population dynamics of an exploited, tropical fish species playing a fundamental role in aquatic ecosystems

AbstractThe coporo, Prochilodus mariae, plays a fundamental role in aquatic ecosystems as a detritivorous species facilitating the flow of carbon to the rest of the ecosystem's food web. It is also one of the most exploited freshwater fish species. Fishing, pollution and environmental changes in the Orinoquia region of Colombia have considerably reduced its population size. We analysed the population dynamics of P. mariae during an annual river cycle, including extreme drought and flood scenarios, by means of a mathematical model and simulations. The model we propose is novel because it relates biological, ecological and environmental factors to the population dynamics, including reproduction, growth in size and biomass of fish, recruitment, predation, fishing mortality and river flow. The proposed mathematical model apparently gives an approximate description of the population dynamics of P. mariae for 2010 because a good fit of the model to the catch data of the species of that year was obtained. The simulations showed that the first 3 months of the year are crucial for the species because this is when it is most affected by a combination of fishing, biological factors which increase natural mortality (e.g. upstream migration and predation) and environmental factors (e.g. low river flow). Hypothetical scenarios show that local extinction could occur if fishing were to increase and river flow were to decrease.

Microplastic pollution in the food web: observation of ingestion by the talitrid amphipod Cryptorchestia garbinii on the shores of Lake Garda

Plastic pollution in the environment has become a much-discussed issue worldwide. In recent decades, the contamination of all environments has become increasingly evident, in particular, that of water is highly concerning. Ingestion by different animal species under natural conditions has also been demonstrated. Among these is the Talitrid Amphipod Cryptorchestia garbinii, which lives on the banks of the internal waterways and lakes’ shorelines. As detritivores species, it is very exposed to microplastics that can be ingested, probably mistaking them for food. Aiming to highlight the microplastic ingestion and the role of this species as an entry point for the food web, we analyzed 80 specimens from 4 sites along the shores of Garda Lake, one of the first lakes in Italy to be studied for this type of contamination. The microplastics ingested were observed and quantified through the Nile Red staining method. We were able to verify the presence of ingested microplastics in all the samples analyzed and, therefore, in the food web. This species could serve as valuable natural models of plastic exposure. Microplastic sentinel species can be used as a proxy for environmental exposure and ecosystem monitoring tools to quantify and assess the impacts of microplastic contamination.

Distribution Pattern of Mangrove Fish Communities in China.

Mangroves are among the most productive marine and coastal ecosystems and play an important role in maintaining the stability and diversity of fish communities. To explore the structure of mangrove fish communities in China, we compiled previous studies, monographs, and two databases on 54 mangrove areas published in the past 30 years. Mangrove fish communities in China comprised Osteichthys (597 species) and Chondrichthyes (14 species), representing 611 species in 344 genera, 117 families, and 28 orders. Perciformes were the predominant taxon, with 350 species in 52 families, accounting for 57% of the total species richness. Reef fish accounted for 29.62%. With regard to feeding groups, there were 328 carnivorous species (53.68%), 214 omnivorous species (35.02%), 41 herbivorous species (6.71%), and 28 detritivores species (4.58%). Classified by body size, 57.61% were small-sized, 24.22% medium-sized, and 18.17% were large-sized fishes. A total of 5.23% (32 species) of these mangrove fish are currently on IUCN red lists, i.e., 2 species are critically endangered, 4 are endangered, 12 are vulnerable, and 14 are near threatened. Cluster analyses shows that Chinese mangroves fish were divided into two categories, i.e., coastal mangrove and island mangrove type. This is closely related to the distribution of reef fish. Moreover, the number of fish species showed a strong positive correlation with mangrove area, but not with latitude. The main reasons may be the subtropical and tropical geographic locations, as well as the characteristics of the South China Sea and the Taiwan Warm Current. The size and integrity of mangrove area are crucial to the local ecosystems; thus, protecting and restoring mangroves is of great significance to large-scale ecosystem-stability and local biodiversity.

Dam cascade in run‐of‐river systems promotes homogenisation of fish functional traits in a plateau river

AbstractImpoundments caused by dams are often responsible for intense changes in physical, chemical, geomorphological and hydrological characteristics of rivers, and are one of the main causes in global freshwater biodiversity declines. When these changes derive from multiple cascading dams, the cumulative effect can amplify, causing more pronounced consequences than each individual reservoir, which may affect, among other factors, the biotic and functional conditions of fish fauna. We aim to evaluate the impact of dam cascades on fish functional diversity by applying trait‐based analysis. We evaluate the functional attributes (functional indices and community‐weighted means of trait values) and environmental variables at 11 sites, which encompassed different segments affected by the hydroelectric plants (transition, reservoir, reduced discharge section and tributary) in the Antas River Basin dam cascade system located in southern Brazil. The spatial differences of the functional indices (richness, evenness, divergence, dispersion and diversity) as well as the weighted averages of each functional trait were tested through analysis of variance. The most affected functional characteristics were those related to habitat exploration by detritivorous species, especially the use of food resources and body shape, as well as the type of swimming movement. These traits were more representative at the most downstream site of the complex. Thus, our results suggest that the cascade of dams acts in the functional homogenisation of the ichthyofauna in the intermediate stretches, mainly reflecting physical changes in habitat.

Metal bioaccumulation in fish from the Araguari River (Amazon biome) and human health risks from fish consumption.

Recently, high concentrations of metals have been found in the waters from sampling sites located in the Araguari River lower section. These metals can be bioaccumulated by fish, but also biomagnified, representing a potential risk through human consumption. Here, we aimed to (1) determine the metal concentrations in muscle samples from fish; (2) evaluate bioaccumulation of metals in muscle tissue of fish species with different feeding behaviors; and (3) investigate the risks of single metals, as well as mixture of metals, to human fish consumption. Eleven fish species were sampled (3 carnivorous, 5 omnivorous, and 3 detritivorous). In four fish species, Cd and Pb concentrations exceeded the Brazilian maximum limits (MLs) for human consumption. Individually, Pb and Cd concentrations in the muscle of these fish indicate risks to human health. When considering the mixture of metals, the consumption of all fish species represents risks. The highest risks implicate detritivorous species. For all fish species evaluated, the estimated daily intake (EDI) of Hg shows values above its reference dose (RfD). Our results suggest the need to establish an environmental monitoring program that aims to preserve environmental quality, biodiversity, and human health. It is also necessary to develop actions that aim to educate Amazonian populations on safe fish preparation and consumption.

Species identity and the functioning of ecosystems: the role of detritivore traits and trophic interactions in connecting of multiple ecosystem responses

Ecosystems world‐wide experience changes in species composition in response to natural and anthropogenic changes in environmental conditions. Research to date has greatly improved our understanding of how species affect focal ecosystem functions. However, because measurements of multiple ecosystem functions have not been consistently justified for any given trophic group, it is unclear whether interpretations of research syntheses adequately reflect the contributions of consumers to ecosystems. Using model communities assembled in experimental microcosms, we examined the relationship between four numerically dominant detritivore species and six ecosystem functions that underpin fundamental aspects of carbon and nitrogen cycling above‐ and below‐ground. We tested whether ecosystem responses to changes in detritivore identity depended upon species trait dissimilarity, food web compartment (aboveground, belowground, mixed) or number of responses considered (one to six). We found little influence of detritivore species identity on brown (i.e. soil‐based) processes. Only one of four detritivore species uniquely influenced decomposition, and detritivore species did not vary in their influence on soil nitrogen pools (NO3− and NH4+), or root biomass. However, changes in detritivore identity influenced multiple aboveground ecosystem functions. That is, by serving as prey, ecosystem engineers and occasionally also as herbivores as well as detritivores, these species altered the strength of aboveground predator–herbivore interactions and plant–shoot biomass. Yet, dissimilarity of detritivore functional traits was not associated with dissimilarity of ecosystem functioning. These results serve as an important reminder that consumers influence ecosystem processes via multiple energy channels and that food web interactions set important context for consumer‐mediated effects on multiple ecosystem functions. Given that species are being lost, gained and redistributed at unprecedented rates, we can anticipate that changes in species identity will have additional ecosystem consequences beyond those predicted by species' primary functional role.

Species identity drives ecosystem function in a subsidy-dependent coastal ecosystem.

Declines in species diversity carry profound implications for ecosystem functioning. Communities of primary producers and consumers interact on evolutionary as well as ecological time scales, shaping complex relationships between biodiversity and ecosystem functioning. In subsidized ecosystems, resource inputs are independent of consumer actions, offering a simplified view of the relationship between species diversity and function for higher trophic levels. With food webs supported by substantial but variable inputs of detritus from adjacent marine ecosystems, sandy beaches are classic examples of subsidized ecosystems. We investigated effects of consumer species diversity and identity on a key ecological function, consumption of kelp wrack from nearshore giant kelp (Macrocystis pyrifera) forests. We assessed effects of species richness on kelp consumption by experimentally manipulating richness of six common species of invertebrate detritivores in laboratory mesocosms and conducting field assays of kelp consumption on beaches. Consumer richness had no effect on kelp consumption in the field and a slight negative effect in laboratory experiments. Kelp consumption was most strongly affected by the species composition of the detritivore community. Species identity and body size of intertidal detritivores drove variation in kelp consumption rates in both experiments and field assays. Our results provide further evidence that species traits, rather than richness per se, influence ecosystem function most, particularly in detrital-based food webs with high functional redundancy across species. On sandy beaches, where biodiversity is threatened by rising sea levels and expanding development, our findings suggest that loss of large-bodied consumer species could disproportionally impact ecosystem function.

Evaluating the vulnerability of coralligenous epifauna to macroalgal invasions

Abstract This work constitutes the first comprehensive study of the epifaunal response to biological invasions in coralligenous habitats, which are one of the main hotspots of biodiversity in the Mediterranean. The epifaunal community inhabiting the invasive macroalga Rugulopteryx okamurae and other dominant sessile hosts on coralligenous habitats (i.e. the sponge Spongia lamella, the gorgonian Paramuricea clavata, and the macroalga Sphaerococcus coronopifolius) was characterized. A total of 137 taxa were found. There was a lack of functional equivalence between macroalgal species (both native and invasive) and sessile invertebrates. Despite the absence of significant differences in mean density values and number of species per replicate among host species, epifaunal composition on gorgonians and sponges differed significantly from that on both macroalgae. Epifaunal assemblages, especially those inhabiting macroalgal species, were dominated by generalist detritivorous species that can inhabit different hosts, while specialized interactions between mobile epifauna and sessile hosts were observed almost exclusively on sessile invertebrates. Moreover, epifaunal community associated with invertebrate hosts showed higher spatial heterogeneity in comparison with native and invasive macroalgae. A competitive displacement of native hosts by the spreading of R. okamurae on coralligenous habitats would likely result in a biotic impoverishment in terms of overall number of species and a taxonomical and functional homogenization of the epifaunal community. Specialist species with a heterogeneous distribution could be gradually replaced by a spatially homogeneous assemblage dominated by generalist species.

Litter decomposition can be reduced by pesticide effects on detritivores and decomposers: Implications for tropical stream functioning

Understanding which factors affect the process of leaf litter decomposition is crucial if we are to predict changes in the functioning of stream ecosystems as a result of human activities. One major activity with known consequences on streams is agriculture, which is of particular concern in tropical regions, where forests are being rapidly replaced by crops. While pesticides are potential drivers of reduced decomposition rates observed in agricultural tropical streams, their specific effects on the performance of decomposers and detritivores are mostly unknown. We used a microcosm experiment to examine the individual and joint effects of an insecticide (chlorpyrifos) and a fungicide (chlorothalonil) on survival and growth of detritivores (Anchytarsus, Hyalella and Lepidostoma), aquatic hyphomycetes (AH) sporulation rate, taxon richness, assemblage structure, and leaf litter decomposition rates. Our results revealed detrimental effects on detritivore survival (which were mostly due to the insecticide and strongest for Hyalella), changes in AH assemblage structure, and reduced sporulation rate, taxon richness and microbial decomposition (mostly in response to the fungicide). Total decomposition was reduced especially when the pesticides were combined, suggesting that they operated differently and their effects were additive. Importantly, effects on decomposition were greater for single-species detritivore treatments than for the 3-species mixture, indicating that detritivore species loss may exacerbate the consequences of pesticides of stream ecosystem functioning.

Fish tissues for biomonitoring toxic and essential trace elements in the Lower Amazon

Brazilian soils can have high concentrations of toxic elements, mainly mercury (Hg) and arsenic (As), metals also associated with anthropogenic activities (e.g. intensive agriculture, mining, deforestation and hydroelectric plants). This can lead to large amounts of these elements reaching and/or being mobilized in the aquatic ecosystem, which constitutes a serious threat to the environment and to the health of local populations. Thus, we evaluate the feasibility of analyzing the tissues of freshwater fish species for monitoring toxic and trace element accumulation within the aquatic ecosystem in the Lower Amazon, Brazil. Two fish species were considered: Cichla temensis (Tucunaré), a carnivorous species, and Pterygoplichthys pardalis (Acari), a detritivorous species. Samples of liver and muscle from both species were evaluated in relation to their potential use for biomonitoring purposes. The study findings clearly demonstrate the value these fish species and tissues, particularly liver, for biomonitoring toxic and trace element concentrations in the aquatic environment across the study region. While Tucunaré liver proved the best option for biomonitoring elements that accumulate through the food chain (e.g. Hg), Acari liver better reflected elements that typically accumulate in the sediments (e.g. As). Moreover, the trace element profiles, determined using chemometric (multivariate) techniques, differed greatly in specimens from waters in the Andean mountain range (sampling sites located in the main course of the Amazon River) with high sediment concentrations, and in specimens from the Guyana and Brazilian shields (Porto Trombetas on the Trombetas River and Itaituba on the Tapajós River). The findings also indicate that deposition of elements in freshwater fish in this area is mainly associated with the geological origin of the soils and that large amounts of toxic elements can reach the aquatic ecosystem due to anthropogenic activities, thereby posing a serious danger to the environment and the health of the riverside communities.