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Los Estados realizan cambios en sus regulaciones impositivas para fortalecer sus políticas de crecimiento país. Uno de los aspectos fundamentales para el crecimiento sostenible es la inversión en capital humano. La recaudación de tributos es un instrumento eficaz para responder a las necesidades sociales de un país, por ello en el Paraguay se ha estudiado la aplicación de la Reforma Tributaria de la Ley 6380/2019 a los efectos de seguir potenciando el volumen de recaudación y para reorientar los fondos en la salud, la educación, infraestrura y potenciar el capital humano en todas sus formas. El objetivo del presente estudio es analizar los cambios de la política impositiva propuesta por la Subsecretaría de Estado de Tributación - SET en base a la Ley 6380/2019 de Modernización y Simplificación tributaria. La investigación fue bibliográfica y documental. Se recurrió a fuentes de información primaria, secundaria y terciaria a los efectos de recopilar y sustraer datos relevantes. Se investigó en archivos de plataformas del Gobierno Nacional, se analizó materiales bibliográficos provistos por los profesionales del área de contabilidad y se recurrió a redacciones de medios de prensa para garantizar una información suficiente y actualizada. El resultado de la investigación demostró la alta participación de los impuestos indirectos en la economía tributaria y la necesidad que existe de una mayor equidad fiscal.

Droughts, or severe reductions of water flow, are expected to become more frequent and intense in rivers in many regions under the ongoing climate change scenario. It is therefore important to understand stream ecosystem functioning under drought conditions. We performed a meta-analysis of studies addressing drought effects on litter decomposition in streams (50 studies contributing 261 effect sizes) to quantify overall drought effects on this key ecosystem process and to identify the main moderators controlling these effects. Drought reduced litter decomposition by 43% overall, which can impact energy and matter fluxes along heterotrophic food webs. The magnitude of drought effects on litter decomposition depended on the type of drought (natural drought > human-induced drought), type of decomposer community (microbes + macroinvertebrates > microbes) under natural drought, climate (warm and humid > temperate and Mediterranean) under human-induced drought, and on litter identity. The magnitude of drought effects on litter decomposition also increased with the severity of the drought. The effects of ongoing climate change will likely be strongest in streams with abundant shredders undergoing natural drought, especially if the streams become temporary. The composition of the riparian vegetation may modulate the magnitude of drought effects on litter decomposition, which may have management applications. Open access funding provided by FCT|FCCN (b-on). This study was financed by the Portuguese Foundation for Science and Technology (FCT) through the research project STREAMECO (SFRH/BD/140761/2018) and the strategic projects UIDP/04292/2020 and UIDB/04292/2020 granted to MARE and project LA/P/0069/2020 granted to the Associate Laboratory ARNET, and by the Basque Government (IT1471-22). VF was financially supported by the FCT (CEECIND/02484/2018).

Litter decomposition is an ecosystem process that allows energy and nutrients transfer from dead plant matter into detrital food webs. Several studies revealed that leaf litter decomposition rates differ across biomes, but the reasons for these differences are not yet clear. Here, we test the role of several leaf litter physical and chemical characteristics as predictors of decomposition rates and whether life forms (evergreen vs. deciduous) differ in decomposition rates. Leaves from dominant riparian trees were collected in four ecoregions (temperate deciduous forest, subtropical seasonal semideciduous forest, tropical Cerrado and subtropical dense ombrophylous forest) and their physical and chemical characteristics were measured. We then determined leaf litter decomposition, colonization by aquatic hyphomycetes and macroinvertebrates in a same stream (i.e., under the same environmental conditions), and consumption rates by shredders under laboratory conditions. Deciduous and evergreen tree species did not differ in the measured litter characteristics, but deciduous leaves decompose faster than evergreens. Leaf litter from tree species from the four ecoregions differed in their physical and chemical characteristics. Litter from temperate deciduous species decomposed faster than litter from the other three ecoregions, generally supported higher aquatic hyphomycete species richness and sporulation rates and higher consumption rates by shredders. There were significant negative correlations between litter decomposition and associated biotic variables and litter initial lignin concentration and lignin:N ratio. We conclude that lignin concentration and lignin:N ratio are important predictors of litter decomposition, although other unmeasured parameters such as micronutrients may also play important roles in this key ecosystem process.

Non-native nitrogen-fixing Acacia species have been invading riparian ecosystems worldwide, potentially threatening stream communities that strongly depend on allochthonous litter. We examined the effects of the invasion of native deciduous temperate forests by Acacia species on litter decomposition and associated fungal decomposers in streams. Litter of native (Alnus glutinosa and Quercus robur) and invasive (Acacia melanoxylon) species were enclosed in fine-mesh bags and immersed in three native and three invaded streams, for 14–98 days. Litter decomposition rates, fungal biomass, and aquatic hyphomycete sporulation rates were higher in invaded than in native streams, likely due to the higher water nitrogen concentration found in invaded streams. Alnus glutinosa litter had higher aquatic hyphomycete sporulation rates and species richness, and higher decomposition rates, probably because they were soft and nitrogen rich. Quercus robur litter also had high aquatic hyphomycete sporulation rates but lower decomposition rates than Al. glutinosa, probably due to high polyphenol concentration and carbon:nitrogen ratio. Acacia melanoxylon litter had lower aquatic hyphomycete sporulation rates and species richness, and lower decomposition rates, most likely because it was very tough. Thus, litter decomposition rates varied in the order: Al. glutinosa > Q. robur > Ac. melanoxylon. The aquatic hyphomycete community structure strongly differed between native and invaded streams, and among litter species, suggesting that microbes were sensitive to water nitrogen concentration and litter characteristics. Overall, increases in water nitrogen concentration and alterations in litter characteristics promoted by the invasion of native riparian forests by Acacia species may affect the activity and community structure of microbial decomposers, and instream litter decomposition, thus altering the functioning of stream ecosystems.

Plant litter is the major source of energy and nutrients in stream ecosystems and its decomposition is vital for ecosystem nutrient cycling and functioning. Invertebrates are key contributors to instream litter decomposition, yet quantification of their effects and drivers at the global scale remains lacking. Here, we systematically synthesized data comprising 2707 observations from 141 studies of stream litter decomposition to assess the contribution and drivers of invertebrates to the decomposition process across the globe. We found that (1) the presence of invertebrates enhanced instream litter decomposition globally by an average of 74%; (2) initial litter quality and stream water physicochemical properties were equal drivers of invertebrate effects on litter decomposition, while invertebrate effects on litter decomposition were not affected by climatic region, mesh size of coarse-mesh bags or mycorrhizal association of plants providing leaf litter; and (3) the contribution of invertebrates to litter decomposition was greatest during the early stages of litter mass loss (0-20%). Our results, besides quantitatively synthesizing the global pattern of invertebrate contribution to instream litter decomposition, highlight the most significant effects of invertebrates on litter decomposition at early rather than middle or late decomposition stages, providing support for the inclusion of invertebrates in global dynamic models of litter decomposition in streams to explore mechanisms and impacts of terrestrial, aquatic, and atmospheric carbon fluxes. ispartof: BIOLOGICAL REVIEWS vol:97 issue:6 pages:2023-2038 ispartof: location:England status: published

The invasion of native riparian forests by exotic tree species can lead to profound changes in the ecological integrity of freshwater ecosystems. We assessed litter decomposition of native (Alnus glutinosa and Quercus robur) and invasive (Acacia melanoxylon and Acacia dealbata) tree species, and associated microbial activity and community structure, after being immersed for conditioning in 3 reference and 3 “invaded” streams in Serra da Lousa (central Portugal) and used in microcosms simulating stream conditions. Litter decomposition differed among species, in the order: Al. glutinosa > Q. robur > (Ac. melanoxylon ~ Ac. dealbata). Alnus glutinosa litter decomposed faster probably because it was soft and had high nitrogen concentration for decomposers. Quercus robur litter decomposed slower most likely because it was tough and had high polyphenol and low nitrogen concentrations. Acacia melanoxylon litter was the toughest and had a thick cuticle that likely acted as a physical barrier for microbial colonization. In Ac. dealbata, the small-sized leaflets and high lignin concentration may have limited microbial litter decomposition. Litter decomposition was faster in “invaded” streams, probably because they were N-limited and increases in nitrogen concentration in water, promoted by Acacia species invasion, stimulated microbial activity on litter. The aquatic hyphomycete community structure differed among litter species and between stream types, further suggesting that microbes were sensitive to litter characteristics and water nutrient concentrations. Overall, the invasion of native riparian forests by Acacia species may affect microbial decomposer activity, thus altering important stream ecosystem processes, such as litter decomposition and nutrient cycles.

Shredders play a crucial role in litter decomposition in streams. However, in oceanic islands, many streams have low shredder density and richness, and microbes seem to be the main litter decomposers. Here, we evaluate the effects of shredders and aquatic hyphomycetes on litter decomposition in insular streams. Three leaf species differing in physical and chemical characteristics, Alnus glutinosa, Clethra arborea, and Cryptomeria japonica, were enclosed in bags of coarse and fine mesh to allow and avoid macroinvertebrate access to the litter, respectively, and incubated in six streams along a gradient of Limnephilus atlanticus (Trichoptera) density in Sao Miguel Island. In streams with higher L. atlanticus density, leaf mass loss was higher in coarse than fine mesh bags. However, no difference in litter mass loss was found between bag types in streams with no L. atlanticus, despite the presence of other shredder taxa. These results suggest that when L. atlanticus are present at relatively high densities, they significantly contribute to litter decomposition, while litter decomposition is mainly driven by microbes when L. atlanticus density is low, or they are absent. Moreover, litter decomposition depends on litter quality, with leaves with high nutrient concentration and low concentration of secondary compounds being preferred by shredders.

Human impacts, particularly nutrient pollution and land-use change, have caused significant declines in the quality and quantity of freshwater resources. Most global assessments have concentrated on species diversity and composition, but effects on the multifunctionality of streams and rivers remain unclear. Here, we analyse the most comprehensive compilation of stream ecosystem functions to date to provide an overview of the responses of nutrient uptake, leaf litter decomposition, ecosystem productivity, and food web complexity to six globally pervasive human stressors. We show that human stressors inhibited ecosystem functioning for most stressor-function pairs. Nitrate uptake efficiency was most affected and was inhibited by 347% due to agriculture. However, concomitant negative and positive effects were common even within a given stressor-function pair. Some part of this variability in effect direction could be explained by the structural heterogeneity of the landscape and latitudinal position of the streams. Ranking human stressors by their absolute effects on ecosystem multifunctionality revealed significant effects for all studied stressors, with wastewater effluents (194%), agriculture (148%), and urban land use (137%) having the strongest effects. Our results demonstrate that we are at risk of losing the functional backbone of streams and rivers if human stressors persist in contemporary intensity, and that freshwaters are losing critical ecosystem services that humans rely on. We advocate for more studies on the effects of multiple stressors on ecosystem multifunctionality to improve the functional understanding of human impacts. Finally, freshwater management must shift its focus toward an ecological function-based approach and needs to develop strategies for maintaining or restoring ecosystem functioning of streams and rivers. Generalitat de Catalunya, Grant/Award Number: 2017SGR0976; Portuguese Foundation for Science and Technology, Grant/Award Number: CEEIND/02484/2018 and UIDP/04292/2020

Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter. Key Points • Nitrogen (N) and phosphorus (P) immobilization was measured on organic matter (cotton) in 100 rivers and riparian zones representing 11 biomes • Elevated temperature in riparian zones and phosphate in rivers increased immobilization, and consequently accelerated decomposition • N and P immobilization was strongly linked by microbial stoichiometry despite widely varied surface-water nutrient ratios Plain Language Summary Bacteria and fungi contribute to the breakdown of leaf litter in rivers and floodplains. To break down leaf litter, these microbes need the nutrients nitrogen and phosphorus (P), and microbes can get nutrients either from the leaf litter itself or from the environment. Most leaf litter has low nutrient content and microbes must rely on the environment to supply nutrients. We studied microbial nutrient uptake from the environment during litter breakdown to determine whether it varies predictably across the globe and how it is influenced by changing climate and nutrient pollution. In 100 rivers and floodplains in 11 of Earth's major biomes we placed small strips of cotton as stand-ins for leaf litter. Nutrient uptake was consistently greater on cotton strips that were submerged in the river compared to cotton on the floodplain. For microbes in the river, nutrient uptake was faster in instances where there was more P in the water. For microbes in the floodplain, nutrient uptake was faster where temperatures were warmer. Faster nutrient uptake by microbes was linked with faster cotton breakdown in rivers and floodplains. Our study shows that climate change and nutrient pollution can alter the activity of microbes in rivers and floodplains.

Durante um largo período, o efetivo impacto da guerra colonial na sociedade portuguesa foi acompanhado de um relativo silêncio institucional envolvendo a memória do conflito. À escassa abordagem pública do evento seguiu-se, nas duas últimas décadas, o crescimento de diferentes processos de memorialização do conflito, para os quais contribuiu decisivamente o trabalho de memória produzido por associações ou grupos mais ou menos formalizados de antigos combatentes. Este artigo analisa dois desses eixos memoriais: os monumentos evocativos da guerra e as representações mnemónicas do conflito no maior blogue português de antigos combatentes. Argumentaremos que apesar de estarem circunscritos às comunidades de recordação que os promovem e neles participam, influenciam e são influenciados pela memória pública dominante da guerra e contribuem para gerar momentos de sociabilidade e sentimentos de (auto)reconhecimento para esses grupos. For a long period of time, the effective impact of the colonial war on Portuguese society was accompanied by a relative institutional silence concerning the memory of the conflict. The scarce public approach to the event was followed, in the last two decades, by the growth of different processes of memorialization of the conflict, to which the memory work produced by more or less formalized associations or groups of former combatants contributed decisively. This article analyzes two of these memorial axes: the war memorials and the mnemonic representations of the conflict in the largest Portuguese blog of former combatants. We will argue that despite being circumscribed to the communities of remembrance that promote and participate in them, they influence and are influenced by the dominant public memory of the war and contribute to generate moments of sociability and feelings of (self)recognition for these groups. Pendant une longue période, l’impact effectif de la guerre coloniale sur la société portugaise s’est accompagné d’un relatif silence institutionnel concernant la mémoire du conflit. La rareté de l’approche publique de l’événement a été suivie, au cours des deux dernières décennies, par la croissance de différents processus de mémorisation du conflit, auxquels a contribué de manière décisive le travail de mémoire produit par des associations ou des groupes plus ou moins formalisés d’anciens combattants. Cet article analyse deux de ces axes mémoriels: les monuments de guerre et les représentations mnémoniques du conflit dans le plus grand blog portugais d’anciens combattants. Nous soutiendrons que, bien qu’ils soient circonscrits aux communautés du souvenir qui les promeuvent et y participent, ils influencent et sont influencés par la mémoire publique dominante de la guerre et contribuent à générer des moments de sociabilité et des sentiments d’(auto)reconnaissance pour ces groupes.

Mestrado em Educação Pré-Escolar e em Ensino do 1ºCiclo do Ensino Básico Submitted by Dina Rocha (dir.biblioteca@ipsantarem.pt) on 2021-12-27T11:52:34Z No. of bitstreams: 1 Relatório de Estágio_Verónica Alcobia.pdf: 4449407 bytes, checksum: ea2a776a9bf36256be0ef727ac0428cb (MD5) Made available in DSpace on 2021-12-27T11:52:34Z (GMT). No. of bitstreams: 1 Relatório de Estágio_Verónica Alcobia.pdf: 4449407 bytes, checksum: ea2a776a9bf36256be0ef727ac0428cb (MD5) Previous issue date: 2021-11-29 N/A

Leaf litter decomposition in streams is a fundamental ecosystem process that allows for the cycling of nutrients. The rate at which leaf litter decomposes is greatly controlled by its intrinsic characteristics. However, intraspecific variation in leaf litter characteristics poses a major challenge for large-scale studies aiming at identifying the environmental moderators of leaf litter decomposition. Thus, several standardized organic substrates have been proposed as surrogates for leaf litter. Tea bags were proposed as a standardized alternative to leaf litter for studies in soil and their use in aquatic ecosystems has been growing in recent years. It is therefore necessary to evaluate how tea is colonized and decomposed by aquatic microbial decomposers to assess its usefulness as a surrogate for leaf litter in litter decomposition studies. Here we compared the microbial colonization (based on the reproductive activity of aquatic hyphomycetes) and decomposition of green and rooibos teas and native alder leaf litter in two streams differing in environmental conditions. Colonization of green tea was lower than that of alder leaf litter, but their decomposition rates were similar. In contrast, colonization of rooibos tea was similar to that of alder leaf litter, but it decomposed 3–4 × slower. Results were consistent in both streams. Despite differences in magnitude, dynamics of microbial colonization and decomposition of tea were similar to those of alder leaf litter and were sensitive to substrate characteristics. Tea may be used as a surrogate for leaf litter in studies addressing microbial-driven leaf litter decomposition in streams.

[EN]Litter decomposition is an ecological process of key importance for forest headwater stream functioning, with repercussions for the global carbon cycle. The process is directly and indirectly mediated by microbial decomposers, mostly aquatic hyphomycetes, and influenced by environmental and biological factors such as water temperature and litter quality. These two factors are forecasted to change globally within the next few decades, in ways that may have contrasting effects on microbial-induced litter decomposition: while warming is expected to enhance microbial performance, the reduction in litter quality due to increased atmospheric carbon dioxide and community composition alteration may have the opposite outcome. We explored this issue through a microcosm experiment focused on early microbial-mediated litter decomposition under stream oligotrophic conditions, by simultaneously manipulating water temperature (10 degrees C and 15 degrees C) and litter quality (12 broadleaf plant species classified into 4 categories based on initial concentrations of nitrogen and tannins). We assessed potential changes in microbial-mediated litter decomposition and the performance of fungal decomposers (i.e., microbial respiration, biomass accrual, and sporulation rate) and species richness. We found stronger effects of litter quality, which enhanced the performance of microbial decomposers and decomposition rates, than temperature, which barely influenced any of the studied variables. Our results suggest that poorer litter quality associated with global change will have a major repercussion on stream ecosystem functioning. This study was financed by the Portuguese Foundation for Science and Technology (FCT), through the strategic projects UIDP/04292/2020 granted to MARE and start-up funds from the Donana Biological Station (EBD-CSIC) and Ikerbasque to LB. Financial support granted by the FCT to VF (IF/00129/2014, CEECIND/02484/2018) is also acknowledged. Special thanks to A. LandeiraDabarca and C. Grela-Docal for their assistance in field and laboratory work and to L. Barmuta, J. Chara, C. Colon-Gaud, M.O. Gessner, J.F. Goncalves Jr., B. McKie, R. Pearson, C. Swan, and C. Yule, among others, collaborators from GLoBE network, for collecting the plant litter.

Riparian forests are subjected to multiple disturbances, such as tree diseases caused by invasive pathogens, whose consequences on stream functioning are unknown. We assessed the impact of Phytophthora cinnamomi infection, and interactions with temperature, on microbial decomposition of Castanea sativa leaves. Leaves from healthy, symptomatic and highly symptomatic trees were incubated in the laboratory at 13 and 18 °C for 64 d. Infection significantly increased polyphenolic concentration and leaf toughness, reducing leaf decomposition and microbial respiration rates irrespective of temperature. Aquatic hyphomycete communities differed significantly in leaves from highly symptomatic trees. Fungal biomass was highest at 18 °C, irrespective of tree health status. None of the parameters were influenced by the tree health status × temperature interaction, suggesting that temperature rise may not synergistically increase the cross-ecosystem effects caused by P. cinnamomi in streams where litter decomposition is microbial-driven. Infection by P. cinnamomi alters the nutritional quality of leaves affecting the functioning of aquatic ecosystems.

The effects of mixing different leaf litter species on litter decomposition in streams have received considerable attention in recent years. However, contrasting results have been reported and the mechanisms behind the effects of litter diversity have been poorly examined. We compared the decomposition rates and associated fungi for two contrasting litter species, when incubated individually and in mixture, at two different current velocities. Coarse-mesh bags with alder litter individually, oak litter individually and with a mixture of both were incubated in a forest headwater stream over 32 days, under fast or slow current velocities. We determined litter decomposition rates, microbial oxygen consumption rates, and aquatic hyphomycete sporulation rates, species richness and community composition; litter species in the mixture were processed individually. Our results provided weak evidences for diversity effects on leaf litter decomposition. Generally, litter decomposition was unaffected by mixing contrasting litter species, with litter species in the mixture decomposing at the same rate as when incubated individually at both current velocities. The same pattern was observed for microbial variables. Decomposition rates and microbial colonization and activity depended primarily on the traits of the target litter species and were not affected by those of the companion species. However, litter-mixing effects were detected on oak litter at late decomposition stages under fast current velocity conditions, suggesting that both current velocity and the incubation time might influence diversity effects on litter decomposition in streams. This finding contributes to explain the lack of litter-mixing effects reported previously by many studies.

Changes in forest composition and litter inputs to streams due to invasion by exotic tree species can affect the functioning of freshwater ecosystems. Acacia dealbata is an important invasive tree species in Mediterranean areas, and often replaces the native riparian vegetation. In this study, we assessed the chemical characteristics of three litter types produced by the invasive Ac. dealbata (leaflets, flowers and pods) and leaf litter produced by two native tree species with contrasting litter characteristics (Quercus robur and Alnus glutinosa). We then assessed litter decomposition and associated microbial activity (i.e., overall microbial metabolism as respiration, fungal growth as biomass accumulation, and reproduction by aquatic hyphomycetes as conidial production), and the aquatic hyphomycetes community structure, in laboratory microcosms. In general, Ac. dealbata pods supported lower microbial activity and decomposed slower than all other litter types, due to their low nutrient concentrations and high carbon:nutrients molar ratio. Alnus glutinosa leaf litter supported high microbial activity and decomposed fast, due to its relatively high nutrient concentrations, low carbon:nutrients molar ratios and low lignin concentration. Acacia dealbata leaflets and flowers and Q. robur leaf litter generally had similar microbial activity and decomposition rates, intermediate between those of Ac. dealbata pods and Al. glutinosa leaf litter, likely due to trade-offs between nutrient concentrations and concentrations of structural and secondary compound among litter types. Aquatic hyphomycetes community structure also differed among litter types. For instance, Ac. dealbata pods had the lowest species richness per sampling date, but due to high dissimilarity among replicates, total species richness over the incubation period was comparable to that of other litter types. The invasion of native riparian forests by Ac. dealbata can affect the quality of litter inputs into streams, potentially affecting the community structure and activity of microbial decomposers, thus altering the functioning of stream ecosystems.

Excess nitrogen (N) and phosphorus (P) inputs to streams occur globally, and affect not only stream autotrophs, but also heterotrophic microbes and detrital carbon processing. Detrital carbon, such as leaf litter, supports stream food webs and their connectivity via downstream detritus fluxes. Nutrient enrichment increases litter decomposition rates across multiple scales and trophic levels by stimulating activity of microbial decomposers and enhancing interactions among microbial decomposers, detritivores, and physical abrasion. Nutrient effects on microbial and detritivore-mediated decomposition are typically greater for recalcitrant vs. labile litter, especially when coupled to low initial nutrient concentrations. Recent studies and syntheses show that (1) dissolved N and P affect litter by stimulating fungal activity and nutrient immobilization, thus, increasing detrital nutrient content, (2) nutrient effects are greatest with N and P together (vs. individually) and when detritivores are present, and (3) ecosystem-level effects of nutrient enrichment can be predicted from small-scale measurements. Despite extensive studies of leaf litter decomposition, its application as a tool to manage nutrient enrichment issues trails comparable tools for autotrophic (i.e., algal) pathways. Thus, better understanding of the consequences of nutrient enrichment on leaf litter and other detrital carbon is important to predict how nutrients will affect stream ecosystem functioning.

The need for tree-derived industrial products is causing an increase in the land surface covered by fast-growing monoculture plantations throughout the world. Species planted are selected mostly prioritizing their rapid growth, with less consideration to minimizing the negative environmental effects they create. Among the various ecosystems that can be negatively affected by plantations, streams are among the most impacted, as they strongly depend on dead organic matter from the surrounding vegetation. Changes in land use in favour of monocultures can have large consequences on stream biodiversity and functioning since they can lead to alterations in the diversity, quantity, quality and timing of litter inputs. Here, we review the literature dealing with the effects of plantations on litter decomposition in streams, with special focus on eucalyptus and conifer plantations, which have been more thoroughly studied than other planted tree species. The effects of plantations on litter decomposition in streams have a degree of regional specificity, and depend on the composition of detritivores, litter characteristics (of native and exotic species) and local environmental conditions. There is, nonetheless, a need for further research describing the effects of specific planted exotic species and for more studies out of Europe and North America.

Over the past decades, three major challenges to marine life have emerged as a consequence of anthropogenic emissions: ocean warming, acidification and oxygen loss. While most experimental research has targeted the first two stressors, the last remains comparatively neglected. Here, we implemented sequential hierarchical mixed-model meta-analyses (721 control–treatment comparisons) to compare the impacts of oxygen conditions associated with the current and continuously intensifying hypoxic events (1–3.5 O2 mg l−1) with those experimentally yielded by ocean warming (+4 °C) and acidification (−0.4 units) conditions on the basis of IPCC projections (RCP 8.5) for 2100. In contrast to warming and acidification, hypoxic events elicited consistent negative effects relative to control biological performance—survival (–33%), abundance (–65%), development (–51%), metabolism (–33%), growth (–24%) and reproduction (–39%)—across the taxonomic groups (mollusks, crustaceans and fish), ontogenetic stages and climate regions studied. Our findings call for a refocus of global change experimental studies, integrating oxygen concentration drivers as a key factor of ocean change. Given potential combined effects, multistressor designs including gradual and extreme changes are further warranted to fully disclose the future impacts of ocean oxygen loss, warming and acidification. A meta-analysis of experimental effects of stressors on marine organisms shows that hypoxia could harm crustaceans, mollusks and fish to a larger extent than warming and acidification.

The physiology, biochemistry and diversity of aquatic microbial decomposers have been largely investigated in low-order streams. However, some aspects still need further attention to better ascertain how microbial decomposer diversity can ensure ecosystem processes and services, particularly under the challenges posed by global environmental change. Aquatic microbial decomposers play a key role in processing plant litter in streams by degrading the most recalcitrant compounds and facilitating nutrient and energy transfer to higher trophic levels. Among microbial decomposers, fungi, particularly aquatic hyphomycetes, play a fundamental role at the early stages of plant litter decomposition, while the relevance of bacteria increases at the late stage of the decomposition. High-throughput sequencing and metagenomic techniques open new avenues towards a more comprehensive understanding of the microbial decomposer ecology. This chapter provides a general overview of aquatic microbial diversity and activity on decomposing plant litter. Attention will be paid to the relationships between microbial diversity and their ecological functions under the major threats posed by the ongoing global environmental change to provide the response patterns of microbial decomposers to maintain nutrient and energy fluxes in streams., This study was supported by the STREAMECO project [PTDC/CTAAMB/31245/2017] funded by Portuguese funding through FCT I.P. and ERDF through the COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI), and VF was supported by FCT (CEECIND/02484/2018)

The decomposition of plant litter in freshwaters is an integrative process involving multiple organism groups and connecting terrestrial and freshwater ecosystems. The quantification of leaf litter decomposition has been advocated as an effective indicator of ecosystem functional integrity in the bioassessment of freshwaters. Indeed, variation in litter decomposition rates has been used to detect the impacts of a wide range of anthropogenic disturbances on the functioning of detritus-based food webs in freshwater ecosystems, particularly in streams. However, these assessments have almost exclusively been undertaken as part of research projects, and the application of litter decomposition as a tool in routine biomonitoring remains limited. We evaluate the potential for litter decomposition as a tool for ecosystem assessment by environmental agencies and managers, drawing on insights and experiences from three lines of evidence: (i) a broad selection of published research projects, (ii) an existing national-scale monitoring program and (iii) a meta-analysis comparing litter decomposition rates between nutrient-enriched and reference sites. We use this as a basis for discussing inter alia common substrates used in decomposition assays, alternatives for field protocols and sampling designs, and the use of different indices and reference conditions when arriving at an assessment of functional status.

Tese de mestrado em Informática, Faculdade de Ciências, Universidade de Lisboa, 2021 Submitted by Cristina Manessiez (camanessiez@fc.ul.pt) on 2021-07-23T15:10:36Z No. of bitstreams: 1 TM_Lucia_Abreu.pdf: 8286488 bytes, checksum: 1e9a6b25c85e8c7a1d5a17f0b317b091 (MD5) Made available in DSpace on 2021-07-23T15:10:46Z (GMT). No. of bitstreams: 1 TM_Lucia_Abreu.pdf: 8286488 bytes, checksum: 1e9a6b25c85e8c7a1d5a17f0b317b091 (MD5) Previous issue date: 2021

The invasion of native riparian forests by exotic tree species can lead to profound changes in the ecological integrity of freshwater ecosystems. We assessed litter decomposition of native (Alnus glutinosa and Quercus robur) and invasive (Acacia melanoxylon and Acacia dealbata) tree species, and associated microbial activity and community structure, after being immersed for conditioning in 3 reference and 3 "invaded" streams in Serra da Lousã (central Portugal) and used in microcosms simulating stream conditions. Litter decomposition differed among species, in the order: Al. glutinosaQ. robur(Ac. melanoxylon ~ Ac. dealbata). Alnus glutinosa litter decomposed faster probably because it was soft and had high nitrogen concentration for decomposers. Quercus robur litter decomposed slower most likely because it was tough and had high polyphenol and low nitrogen concentrations. Acacia melanoxylon litter was the toughest and had a thick cuticle that likely acted as a physical barrier for microbial colonization. In Ac. dealbata, the small-sized leaflets and high lignin concentration may have limited microbial litter decomposition. Litter decomposition was faster in "invaded" streams, probably because they were N-limited and increases in nitrogen concentration in water, promoted by Acacia species invasion, stimulated microbial activity on litter. The aquatic hyphomycete community structure differed among litter species and between stream types, further suggesting that microbes were sensitive to litter characteristics and water nutrient concentrations. Overall, the invasion of native riparian forests by Acacia species may affect microbial decomposer activity, thus altering important stream ecosystem processes, such as litter decomposition and nutrient cycles.

Forest change is a major environmental problem worldwide. Forest streams, with their large aquatic–terrestrial interface and strong dependence on terrestrially derived organic matter, are highly sensitive to forest changes. Fast-wood plantations can be particularly threatening if they markedly differ from native forests. Eucalyptus plantations, in particular, cover large areas worldwide (> 20 million ha, mostly from 35°S to 35°N), but their effects on stream functioning have been addressed mostly in the Iberian Peninsula, which limits generalization to other regions. We assessed the effect of eucalyptus plantations on total (microbial decomposers and macroinvertebrates; in coarse mesh bags) and microbial-driven (in fine mesh bags) leaf litter decomposition by comparing streams flowing through native forests and eucalyptus plantations in seven regions in the Iberian Peninsula, Central Africa and South America. We found an overall significant inhibition of total litter decomposition by 23%. The effect did not significantly differ across regions, although a significant inhibition was found for Spain (− 41%), South Brazil (− 31%) and Uruguay (− 36%) (Portugal had a marginally nonsignificant inhibition by 50%) but not for other regions, suggesting that the effects of plantations in temperate climates are mediated through effects on macroinvertebrate communities. Contrarily, the overall effect for microbial-driven litter decomposition was non-significant, but it significantly differed across regions with a significant stimulation in Central Brazil (110%) and Uruguay (32%), and nonsignificant effects for other regions (Kenya had a marginally nonsignificant inhibition by 48%), suggesting that functional redundancy among microbial communities is not general and effects can occur if plantations induce changes in nutrient availability, solar irradiation or litter characteristics.

Human appropriation of water resources may induce water stress in freshwater ecosystems when ecosystem needs are not met. Intensive abstraction and regulation cause river ecosystems to shift towards non-natural flow regimes, which might have implications for their water quality, biological structure and functioning. We performed a meta-analysis of published studies to assess the potential effects of water stress on nutrients, microcontaminants, biological communities (bacteria, algae, invertebrates and fish), and ecosystem functions (organic matter breakdown, gross primary production and respiration). Despite the different nature of the flow regime changes, our meta-analysis showed significant effects of human-driven water stress, such as significant increases in algal biomass and metabolism and reduced invertebrate richness, abundance and density and organic matter decomposition. Water stress also significantly decreased phosphate concentration and increased the concentration of pharmaceutical compounds. The magnitude of significant effects was dependent on climate, rainfall regime, period of the year, river size and type of water stress. Among the different causes of water stress, flow regulation by dams produced the strongest effects, followed by water abstraction and channelization. © 2018, The Author(s)., This project was funded by the European Commission under the grant No. 603629 – project GLOBAQUA. VF acknowledges financial support from the Portuguese Foundation for Science and Technology (FCT) through UID/MAR/04292/2013 and IF/00129/2014. The authors acknowledge the support from the Economy and Knowledge Department of the Catalan Government through the Consolidated Research Group (ICRA-ENV 2017 SGR 1124).

Organic-matter decomposition has long been proposed as a tool to assess stream functional integrity, but this indicator largely depends on organic-matter selection. We assessed eight decomposition-based indicators along two well-known environmental gradients, a nutrient-enrichment gradient (0.2–1.4 mg DIN/L) in central Portugal and an acidification gradient (pH: 4.69–7.33) in north-eastern France to identify the most effective organic-matter indicator for assessing stream functional integrity. Functional indicators included natural leaf litter (alder and oak) in 10-mm and 0.5-mm mesh bags, commercial tea (Lipton green and rooibos teas in 0.25-mm mesh bags), wood sticks (wood tongue depressors) and cotton strips. Biotic indices based on benthic macroinvertebrates (IPtIN for Portugal and IBGN for France) were calculated to compare the effectiveness of structural and functional indicators in detecting stream impairment and to assess the relationship between both types of indicators. The effectiveness of organic-matter decomposition rates as a functional indicator depended on the stressor considered and the substrate used. Decomposition rates generally identified nutrient enrichment and acidification in the most acidic streams. Decomposition rates of alder and oak leaves in coarse-mesh bags, green and rooibos teas and wood sticks were positively related with pH. Only decomposition rates of rooibos tea and wood sticks were related with DIN concentration; decomposition rates along the nutrient-enrichment gradient were confounded by differences in shredder abundance and temperature among streams. Stream structural integrity was good to excellent across streams; the IPtIN index was unrelated to DIN concentration, while the IBGN index was positively related with pH. The relationships between decomposition rates and biotic indices were loose in most cases, and only decomposition rates of alder leaves in coarse-mesh bags and green tea were positively related with the IBGN. Commercial substrates may be a good alternative to leaf litter to assess stream functional integrity, especially in the case of nutrient enrichment.

Aquatic ecosystems worldwide have been substantially altered by human activities, which often induce changes in multiple factors that can interact to produce complex effects. Here, we evaluated the combined effects of dissolved nutrients (nitrogen [N] and phosphorus [P]; three levels: concentration found in oligotrophic streams in the Cerrado biome, 10× and 100× enriched) and oxygen (O2; three levels: hypoxic [4% O2], depleted [55% O2], and saturated [96% O2]) on plant litter decomposition and associated fungal decomposers in laboratory microcosms simulating stream conditions under distinct scenarios of water quality deterioration. Senescent leaves of Maprounea guianensis were incubated for 10 days in an oligotrophic Cerrado stream to allow microbial colonization and subsequently incubated in microcosms for 21 days. Leaves lost 1.1–3.0% of their initial mass after 21 days, and this was not affected either by nutrients or oxygen levels. When considering simultaneous changes in nutrients and oxygen concentrations, simulating increased human pressure, fungal biomass accumulation, and sporulation rates were generally inhibited. Aquatic hyphomycete community structure was also affected by changes in nutrients and oxygen availability, with stronger effects found in hypoxic treatments than in depleted or saturated oxygen treatments. This study showed that the effects of simultaneous changes in the availability of dissolved nutrients and oxygen in aquatic environments can influence the activity and composition of fungal communities, although these effects were not translated into changes in litter decomposition rates.

Atmospheric acid deposition affects many streams worldwide, leading to decreases in pH and in base cations concentrations and increases in aluminum (Al) concentration. These changes in water chemistry induce profound changes in the diversity, structure and activity of biological communities and in ecosystem processes. However, monitoring programs rely only on chemical and structural indicators to assess stream integrity. Nevertheless, the ability of ecosystems to provide services rely on their functional integrity and thus ecosystem processes should be considered in monitoring programs. We assessed the potential for leaf litter decomposition, a fundamental ecosystem process in forest streams, to be used as a bioassessment tool of acidification effects on stream ecosystem functioning. In a field study in the Vosges Mountains (North-eastern France), using three leaf litter species ( Alnus glutinosa , Acer pesudoplatanus and Fagus sylvatica ) enclosed in fine and coarse mesh bags and incubated in streams flowing over granite or sandstone bedrock along an acidification gradient, we assessed if the response of litter decomposition to acidification depended on litter species, mesh size, parent lithology and acidification level. In a meta-analysis of 17 primary studies on the effect of acidification on leaf litter decomposition, reporting 67 acidified – reference stream comparisons, we assessed the consistency in the response of litter decomposition to acidification cross studies and the robustness of litter decomposition to be used as a bioassessment tool. Both the field study and meta-analysis revealed an overall strong inhibition (>60%) of leaf litter decomposition in acidified streams likely resulting from previously well described altered decomposer community structure and activity. No effect of leaf species was found in the field study, while in the meta-analysis inhibition of leaf litter decomposition in acidified streams was stronger for Fagus than for Acer , Quercus and Liriodendron . However, differences among leaf species in the meta-analysis might have been confounded by other differences among studies. The response of leaf litter decomposition to acidification was stronger in coarse than in fine mesh bags, indicating strong impairment of detritivore community structure and activity. The magnitude of inhibition also depended on parent lithology, but this is likely related to differences in the degree of acidification. Indeed, the magnitude of the inhibition of leaf litter decomposition increases with increases in H + in Al concentration. Litter decomposition has the potential to be used as a bioassessment tool of acidification effects in streams since it shows consistent response to acidification across regions and is robust to experimental choices.

Oceanic freshwater communities tend to be species poor but rich in endemism due to their physical isolation. The ecology of endemic freshwater species is, however, poorly known. This study assessed allometric relationships, feeding preferences, growth and survival of larvae of the endemic stream insect Limnephilus atlanticus (Trichoptera, Limnephilidae) exposed to four leaf species differing in their physical and chemical characteristics (Ilex perado, Morella faya, Alnus glutinosa and Clethra arborea), in laboratory trials. All regression models used to estimate L. atlanticus dry mass from body and case dimensions and wet mass were significant, but wet mass and body length were the best predictors. Limnephilus atlanticus consumed all the four leaf species offered, but when given a choice, shredders significantly preferred A. glutinosa over the other three leaf species. Relative larval growth rate was significantly higher when L. atlanticus fed on A. glutinosa and I. perado leaves in comparison with the other leaf species. Survival of 95% was found when individuals fed on A. glutinosa leaves while it decreased to 75% when they fed on the other leaf species. Our results suggest that L. atlanticus can be an active shredder and that it exhibits the same basic patterns of food exploitation as its continental counterparts. The lack of an effect of shredders on litter decomposition in Azorean streams revealed by previous studies may thus be due to low densities or to a preference for food resources other than the low quality native litter species.

Nutrient enrichment of soils and water will intensify in the future and has the potential to alter fundamental ecosystem processes, such as litter decomposition. We tested the direct (via water nutrient enrichment) and indirect (via changes in leaf chemistry) effects of nutrient enrichment on microbial activity and decomposability of Quercus robur L. (oak) leaves in laboratory microcosms simulating streams. Senescent leaves of oak trees grown without and with fertilization were incubated under ambient and elevated water nutrient [nitrogen (N) and phosphorus (P)] concentrations for 60 days. Soil fertilization led to an increase in leaf (3.4×) and leaf litter (2.3×) N concentration. Increased water-dissolved nutrients concentrations stimulated microbial activity (N uptake, microbial respiration, fungal biomass buildup and conidia production by aquatic hyphomycetes) that translated into accelerated litter decomposition (2.1× for unfertilized and 1.6× for fertilized trees). Leaves from fertilized trees had higher microbial activity and decomposition rates than leaves from unfertilized trees only at low dissolved nutrient availability. When both litter and water nutrients concentration increased, microbial activity and leaf decomposition were stimulated, but the effects were additive and direct effects from increased dissolved nutrient availability were stronger than those mediated by increases in litter N concentration (indirect effects). Our results suggest that increases in water nutrient availability (within the range used in this study) may exert a stronger control on microbial activity and litter decomposition than litter nutrient enrichment.

Peritoneal dissemination is a particular form of metastasis typically observed in ovarian cancer and the major cause for poor patient’s outcome. Identification of the molecular players involved in ovarian cancer dissemination can offer an approach to develop treatment strategies to improve clinical prognosis. Here, we identified mesothelin (MSLN) as a crucial protein in the multistep process of peritoneal dissemination of ovarian cancer. We demonstrated that MSLN is overexpressed in primary and matched peritoneal metastasis of high-grade serous carcinomas (HGSC). Using several genetically engineered ovarian cancer cell lines, resulting in loss or gain of function, we found that MSLN increased cell survival in suspension and invasion of tumor cells through the mesothelial cell layer in vitro. Intraperitoneal xenografts established with MSLNhigh ovarian cancer cell lines showed enhanced tumor burden and spread within the peritoneal cavity. These findings provide strong evidences that MSLN is a key player in ovarian cancer progression by triggering peritoneal dissemination and provide support for further clinical investigation of MSLN as a therapeutic target in HGSC. This work was partly developed at IPATIMUP, an Associate Laboratory of the Portuguese Ministry of Science, Technology and Higher Education and I3S. This work was supported by FEDER–Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020–Operational Programme for Competitiveness and Internationalisation (POCI), Portugal 2020, and by Portuguese funds through FCT–Fundação para a Ciência e a Tecnologia/ Ministério da Ciência, Tecnologia e Inovação in the framework of the project “Institute for Research and Innovation in Health Sciences” (POCI-01-0145-FEDER-007274). This research was funded by projects PTDC/MEC-ONC/29503/ 2017 (to L.D.), NORTE 2020 grant numbers NORTE-01-0145-FEDER-000029, NORTE-01-0145-FEDER-000003, Wilhelm Sander Stiftung 2018.010.1 (to F.J.), Swiss Cancer League KLS-3841-02-2016 (to F.J.), and FCT PhD fellowship number SFRH/BD/111885/2015 (to R.C.) We would like to thank Dr. Ronny Drapkin (University of Pennsylvania) for sharing the fallopian tube cell lines.