Leaf litter processing in low order streams

Forests produce a large amount of detritus, that inevitably end up in streams, subsidizing aquatic systems with organic matter and nutrients. Here we review some of the research carried out at the University of Coimbra with the objective of getting a better understanding of the breakdown process of these materials and its incorporation to secondary production. Litter-fall in deciduous forests in Central Portugal can reach up to 750 g AFDM of leaves m-2 yr-1, with 73% of the litter produced between October and December. In several retention experiments, we measured a 90% leaf retention in low order (1st- 4th) streams within 15 - 70 m, and a standing stock of up to 450 g AFDM m-2. The amount of nutrients in the water and the plant physical and chemical defenses can be an indicator of the rate at which plant material is incorporated into secondary production or exported as dissolved and fine particles of organic matter. Respiration rates of decomposing leaves incubated with fungicides were severely reduced, supporting the idea that fungi are very important agents in litter breakdown. The fungi group known as aquatic hyphomycetes are capable of producing enzymes able to cause leaf maceration, and by 2 to 3 weeks, up to 15 % of the decomposing leaf biomass corresponds to fungi. Shredder invertebrates are also biological agents involved in litter breakdown. Given their densities and feeding rates, we measured consumption rates of 12 - 54 g of leaves m-2 yr-1 in a stream in Central Portugal, corresponding to 2 to 9 times the litter standing stock. Feeding rates were high in nutrient rich leaves and low in chemical and physically protected leaves with low nutrient content. According to several experiments, fungal colonization facilitates the access of invertebrates to the energy trapped in deciduous leaves in streams. Some invertebrates have strategies to cope with low quality food (leaves with low microbial biomass or high chemical defenses). Those include high mobility, small size, compartmentalized digestion in the gut, presence of endosymbionts, and the capability to decrease respiration rates. The relative importance of fungi and invertebrates in the incorporation of plant litter material into secondary production varies across rivers and biomes. Shredder invertebrates seem to play a key role in litter breakdown in headwaters, but their importance appears to decrease downstream. In the same way, some systems where leaves are hard or protected, shredder invertebrates may be less abundant and the energy may be mainly recovered from litter by fungi. Eucalyptus plantations are systems with low diversity of invertebrates and aquatic hyphomycetes. Streams running through eucalyptus plantations seem therefore ideal to experimentally investigate relationships between structural parameters (biodiversity) and function. Finally, our research has been extended to other climatic areas including the Mediterranean and tropical streams. We reported a wide variety of situation in those systems. A general rule applying to all of them is that if leaf litter is abundant and high quality, the incorporation of energy into detrital food webs can be processed very quickly. However, if leaves are well protected and nutrients in the water are low, processing rates are equally very low, independently of the ambient temperatures.Los bosques producen una gran cantidad de detritus orgánicos, que inevitablemente llegan a los ríos, subsidiando los sistemas acuáticos con materiales y nutrientes. Aquí se revisan algunos de los trabajos que se han hecho en la Universidad de Coimbra con el objetivo de entender mejor el proceso de descomposición de este material y su incorporación en producción secundaria. La entrada de hojarasca en bosques caducifolios del Centro de Portugal puede alcanzar hasta 750 g PSLC (peso seco libre de cenizas) m-2 año-1, con 73 % de este valor ocurriendo entre Octubre y Diciembre. En varios experimentos de retención medimos que cerca de 90 % hojas que entran en ríos de baja orden (1ª- 4ª) eran retenidas entre los 15 y 75 m, y que la biomasa de hojarasca acumulada era de hasta 450 g PSLC m-2. La cantidad de nutrientes en el agua y las defensas físicas y químicas de las plantas pueden ser un indicador de la tasa a que el material orgánico es incorporado en producción secundaria o exportado como material disuelto o finamente particulado. Las tasas de respiración de hojas incubadas con fungicidas disminuyeron severamente apoyando la idea de que los hongos son agentes muy importantes en la descomposición de hojarasca el los ríos. El grupo de hongos conocido como hifomicetos acuáticos producen enzimas que causan la maceración de hojas, y en 2 o 3 semanas, hasta 15 % de la biomasa de una hoja en descomposición puede corresponder a hongos. Los invertebrados desmenuzadores son también agentes biológicos en la descomposición. Dadas las densidades de desmenuzadores y sus tasas de ingestión de alimento, hemos calculado tasas de consumo de hojas en ríos de12 - 54 g m-2 año-1, lo que corresponde a 2 a 9 veces la cantidad de hojarasca presente. Las tasas de consumo son generalmente altas en substratos ricos en nutrientes y bajas en hojas pobres en nutrientes o protegidas del punto de vista químico y físico. De acuerdo varios experimentos, la colonización por hongos facilita el acceso de los invertebrados a la energía de las hojas. Algunos invertebrados han desarrollado estrategias para poder vencer la baja calidad de las hojas, incluyendo un alta movilidad, tamaño pequeño, compartimentalización de la digestión en el intestino, presencia de endosimbiontes y la capacidad para disminuir las tasas respiratorias. La importancia relativa de los hongos e invertebrados en la incorporación de la hojarasca en producción secundaria es variable entre ríos y biomas. Los invertebrados desmenuzadores parecen jugar un papel importante en la descomposición de hojarasca en los ríos de bajo orden, pero su importancia parece disminuir rió abajo. Del mismo modo, en algunos sistemas en que las hojas son duras o protegidas, los invertebrados pueden ser menos abundantes y la energía canalizada en producción secundaria principalmente por los hongos. Las plantaciones de eucaliptos son sistemas con una baja diversidad de invertebrados e hifomicetos acuáticos. Los ríos que corren por plantaciones de eucaliptos parecen ser por este motivo sistemas ideales para investigar las relaciones entre parámetros estructurales (biodiversidad) y función. Finalmente, nuestra investigación ha sido extendida para otras zonas climáticas, incluyendo el Mediterráneo y las zonas tropicales. Hemos reportado una gran variedad de situaciones en esos sistemas. Una regla general a todos ellos es que si la hojarasca es abundante y de alta calidad, la incorporación de la energía de las hojas en las cadenas alimentares se procesa de forma muy rápida. Sin embargo, si las hojas están bien protegidas y los nutrientes el agua son bajos, estas tasas son igualmente muy bajas, independientemente de las temperaturas ambientales

The use of biological methods based on macroinvertebrates to an Iberian stream (Central Portugal) receiving a paper mill effluent

The impact of a paper mill effluent on the macroinvertebrate communities of an Iberian stream located in Central Portugal was assessed. We used a modification of the BMWP' and BBI indices, diversity measurements (number of taxa and 1-Simpson index) and multivariate methods (cluster, MDS and CA analyses). All techniques indicated a strong impact in the vicinity of the effluent output with a slow recovery ca 4 - 7 km downstream. Multivariate analyses clearly segregated reference (upstream) sites from strongly and moderately impacted sites. Analysis of similarity (ANOSIM) showed also significant differences among groups of sites defined by MDS analysis (P < 0.001). There was a significant correlation (P < 0.001) between BBI and BMWP' indices and the first CA axis (pollution gradient) which suggests that both indices were suitable for water quality assessment in this stream and pollution type. However, we recommend the use of the BMWP' index due to the lesser needs in terms of taxonomic expertises.Se ha evaluado el impacto producido por el vertido de una fábrica de papel sobre las comunidades de macroinvertebrados de un arroyo Ibérico localizado en el Centro de Portugal. Se utilizó una modificación de los índices BMWP' y BBI, medidas de diversidad (número de taxones e índice 1-Simpson) y métodos multivariantes (cluster, MDS y análisis CA). Todas las técnicas indicaron un fuerte impacto en las inmediaciones del vertido con una lenta recuperación a lo largo de 4 - 7 km. río abajo. Los análisis multivariantes segregaron claramente las estaciones de referencia (cabecera) de aquellas fuertemente o moderadamente impactadas. El análisis de similitud (ANOSIM) mostró también diferencias significativas entre los grupos de estaciones definidos por el análisis MDS (P < 0.001). Hubo una correlación significativa (P < 0.001) entre los índices BBI y BMWP', y el primer eje CA (gradiente de contaminación), lo que sugiere que ambos índices fueron adecuados para evaluar la calidad del agua en este arroyo y para este tipo de contaminantes. No obstante, se recomienda el uso del índice BMWP' por sus menores exigencias en lo que respecta a los expertos en taxonomía

A meta-analysis of drought effects on litter decomposition in streams

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)

Do different sites in the same river have similar Trichoptera assemblages?

During the summer of 2001, trichoptera larvae were sampled with a kick-net in 15 sites belonging to 3 rivers of the Mondego River basin, in central-north Portugal. Simultaneously, 42 environmental variables were evaluated for each site. Twenty five species and genera of caddisflies were identified. The objective was to assess if trichoptera assemblages within a river tended to be more similar among each other than between rivers, giving the physical continuity of the habitat. Localities showed low segregation between all samples (MDS, CLUSTER and ANOSIM). The Alva River samples had the higher number of taxa and animals while the Ceira River samples had the lowest values. In terms of environmental characteristics, PCA showed high similarities between samples of the same river. However there was not total segregation of rivers. BIOENV analysis identified the set of parameters that best explain trichopteran associations per river. For the rivers, these variables were all related to habitat (e.g. pool quality, depth, substrate quality). The differences between the Alva and Ceira rivers seem to be related to the deterioration of the water quality in the Ceira river (increasing levels of sulphate, chloride and % of industrial, urban and degraded areas), which increased down the river.Durante el verano de 2001 se capturaron larvas de tricópteros en 15 puntos de muestreo pertenecientes a 3 ríos de la cuenca hidrográfica del Mondego, en el centro-norte de Portugal. Los muestreos fueron realizados con una red de mano (tipo "kicknet") y, simultáneamente, se evaluaron 42 variables ambientales para cada localidad. En total fueron identificadas 25 especies de tricópteros. El objetivo del estudio era evaluar si, dada la continuidad físico-química del habitat, las asociaciones de tricópteros de las localidades situadas en un mismo río son más semejantes entre sí que las pertenecientes a localidades de ríos diferentes. Los locales se presentaran poco segregados de acuerdo con los análisis MDS, CLUSTER y ANOSIM. Las muestras del río Alva tuvieron un número más elevado de taxa y animales mientras que las muestras del río Ceira tuvieron los valores más bajos. Desde el punto de vista ambiental el PCA reveló que las muestras de un mismo río eran más semejantes entre si. Sin embargo, no hubo segregación completa de ríos. El análisis BIOENV identificó el grupo de parámetros que mejor explican las asociaciones de tricópteros por río. Para los ríos, esas variables estaban todas relacionadas con el hábitat (e.g., calidad de las zonas lénticas, calidad de substrato y profundidad). Las diferencias entre los ríos Alva y Ceira parecen ser debidas al empeoramiento de la calidad de las aguas del río Ceira (mayores niveles de sulfato, cloro y porcentaje de degradación industrial y urbana) que aumentan río abajo

The performance of biological indicators in assessing the ecological state of streams with varying catchment urbanisation levels in Coimbra, Portugal

The growth of human populations has resulted in the expansion of metropolitan areas and changes in land use, both of which affect watersheds and streams. The ecological integrity of streams is likely to be negatively affected by urbanisation, compromising freshwater ecosystem services. The aim of this study was to assess how efficient structural and functional indicators are in evaluating the ecological conditions of water in urban stream ecosystems. Two urban streams crossing the city and one stream crossing a suburban area of Coimbra, Portugal were selected. Total impervious area (TIA) was used as an indicator of urbanisation. Physical and chemical parameters of water were measured and analysed within the Water Framework Directive (WFD/2000/60/EC). Benthic macroinvertebrates were used as structural indicators, and the IBMWP biotic index (modified) and the Portuguese IPtIS index were calculated. The decomposition rates of oak (Quercus robur) and alder (Alnus glutinosa) leaves were used as indicators of functional quality. Biotic indices and litter decomposition rates indicated poor ecological conditions in the urban streams compared to the suburban stream, consistent with the degree of urbanisation. The decrease in ecological quality in urban streams most likely reflected decreases in dissolved oxygen and increases in water temperature and conductivity. We emphasise (a) the need to combine physical and chemical data with biological data and (b) the high performance of a novel functional indicator based on litter breakdown rate as an accurate, efficient and integrative measure of ecological integrity in urban streams.El crecimiento de la población humana en las últimas décadas ha provocado el aumento de las áreas urbanas y cambios en los usos del suelo que afectan a las cuencas hidrográficas y a sus ríos. Es probable que la integridad ecológica de los ríos urbanos se vea afectada negativamente, comprometiendo los servicios ecosistémicos proporcionados por las aguas dulces. El objetivo de este estudio fue comparar el rendimiento entre diferentes metodologías en la evaluación química y ecológica del agua en ríos urbanos. Se han seleccionado dos ríos urbanos que cruzan la ciudad de Coimbra, Portugal, y un río que cruza un área suburbana. Como indicador de urbanización se us'o el área total impermeable (TIA). Se han utilizado parámetros físico-químicos que se han analizado siguiendo la Directiva Marco del Agua (2000/60/EC). Como indicadores estructurales se han utilizado los macroinvertebrados bentónicos, calculándose el índice biológico IBMWP (modificado) y el índice IPtIS portugués. Como indicadores funcionales de la calidad ecológica se han usado las tasas de descomposición de hojarasca de roble (Quercus robur L.) y aliso (Alnus glutinosa (L.) Gaertner). Los parámetros físicos y químicos de todos los ríos indicaron "buena calidad" según los parámetros de calidad nacionales y la Directiva Marco del Agua. Sin embargo, los indicadores biológicos y las tasas de descomposición de hojarasca indicaron malas condiciones ecol'ogicas en los ríos urbanos comparados con el río en el área suburbana coincidiendo también con el grado de urbanización. Esto sugiere que los indicadores biológicos (estructurales y funcionales) proporcionan información más temprana, precisa e integrada del sistema que las medidas de la química del agua que no reflejan el valor ecológico de las aguas, su calidad o los impactos ecológicos potenciales. En el estudio se hace especial énfasis en (a) la necesidad de combinar datos físico-químicos con medidas biológicas y (b) la elevada eficiencia de la descomposición como indicador preciso de la integridad ecológica y calidad ambiental en un número creciente de ríos urbanos

Water quality in the Mondego river basin : pollution and habitat heterogeneity

The "IMAR- Departamento de Zoologia, Universidade de Coimbra" and "Direcção Regional de Ambiente e Ordenamento do Território" started a partnership with the objective of establishing bases for the assessment of water quality in the Mondego river basin. Here we present the preliminary results of the study. We sampled 75 sites covering the Mondego river basin. At each site we took 18 physical and chemical measurements and sampled macroinvertebrates with a hand net. Site quality was assessed by the application of a biotic index (BMWP'), water chemistry and habitat heterogeneity. Fifty two percent of the sites had good biological water quality (based on BMWP' index). The strongly polluted sites were concentrated in the Lower Mondego region. Thirty three percent of sites had bad chemical water quality and 45% of the sites had low habitat complexity. Only 40% of the sites with low biological quality also had low chemical water quality. We concluded that (1) in general, the waters on the Mondego river basin do not suffer from strong water pollution and (2) low BMWP' values can be explained by low water quality or low habitat heterogeneity (natural or man-made).El "IMAR- Departamento de Zoologia, Universidade de Coimbra" y la "Direcção Regional de Ambiente e Ordenamento do Território" iniciaron una colaboración con el objetivo de establecer las bases para la evaluación de la calidad del agua en la cuenca hidrográfica del Río Mondego. En esta publicación presentamos los datos preliminares de ese estudio. Se muestrearon 75 localidades, repartidas por toda la cuenca del Mondego. En cada localidad se midieron 18 parámetros químicos y físicos y se muestreó la comunidad de macroinvertebrados acuáticos con una red de mano. La calidad ambiental fue calculada mediante la aplicación del índice biótico BMWP', por las características químicas del agua y por la heterogeneidad del hábitat. Un 51% de las localidades muestreadas tenían una buena calidad ambiental, de acuerdo con el índice BMWP'. Los sitios fuertemente contaminados estaban concentrados en la zona del Bajo Mondego. Un 33% de los locales tenían una calidad química mala, mientras que el 45% tenían una baja heterogeneidad del hábitat. Solamente un 40% de las localidades con baja calidad biológica también tenían baja calidad química. Concluimos que (1) en general, las aguas de la cuenca del río Mondego no sufre de contaminaciones fuertes, y (2) que los bajos valores de BMWP' pueden ser explicados por la baja calidad del agua o bien por una baja heterogeneidad del hábitat (por causas humanas o naturales)

Litter Quality Is a Stronger Driver than Temperature of Early Microbial Decomposition in Oligotrophic Streams: a Microcosm Study

[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

Saccharomyces cerevisiae as a model to confirm the ability of FTIR to evaluate the presence of protein aggregates

It is known that the presence of protein aggregates in biological samples is associated with natural aging processes and age-related diseases. The objective of this technical study was to evaluate the potential of Fourier Transform Infrared Spectroscopy to identify the presence of protein aggregates in Saccharomyces cerevisiae containing high levels of protein aggregates. We acquired ATR-FTIR spectra at mid-infrared range (between 4000 and 600 cm−1) and used multivariate analysis to analyze the data. Significant differences between spectra of wild type and mutant strains in the spectral range assigned to proteins were observed. In particular, an increase in β-sheet structures in mutant strains (spectral signals at 1683 and 1628 cm−1) was observed, indicating the putative presence of protein aggregates. These results prove the capacity of FTIR to evaluate changes in protein conformation, mainly protein aggregation, in a fast, simple and non-expensive way, producing insights on the possible application of this technique to the detection of protein aggregates in human biological samples.publishe

A stable temperature may favour continuous reproduction by Theodoxus fluviatilis and explain its high densities in some karstic springs

Theodoxus fluviatilis is a common gastropod in many karstic springs in central Portugal. We investigated the possible reasons for the near-total restriction of this species to these springs. We first determined the spatial distribution of the species within a spring (Anços) and related the densities at sampling-patch scales to selected physical and chemical variables. We then determined the densities at several locations downstream from the spring and related these densities to selected physical and chemical variables. Finally, we assessed the population dynamics of the gastropod in the spring. In the spring, T. fluviatilis was more abundant in shallow areas with a rapid current and cobble-boulder substrates. In June-July 2006, the mean densities of T. fluviatilis in the spring varied from ~ 10 to ~ 9000 individuals m-2 but decreased to zero 3800 m downstream. The physical and chemical changes along the stretch studied were minor; no significant correlations (Spearman rank correlation; p > 0.05) were observed between the gastropod abundances and the measured environmental variables or the PCA axes. In the spring, juveniles and egg masses were observed year-round, suggesting continuous reproduction. The temperature at the spring was fairly constant, ranging from 15.3 to 16.6 ºC during the year (daily variation 0.05) entre la abundancia de T. fluviatilis y las variables ambientales o los ejes de Análisis de Componentes Principales. En el manantial, juveniles y masas de huevos fueron observadas durante todo el año y no se obsevaron cohortes, sugeriendo reproducción contínua. La temperatura en el manantial varió entre 15.3 y 16.6 ºC durante todo el año (variación diaria < 0.1 ºC). Novecientos metros río abajo las variaciones térmicas diarias llegaron a los 5 ºC. Proponemos pues que la elevada densidad de T. fluviatilis en el manantial kárstico de Anços se mantiene gracias a las temperaturas elevadas y constantes que favorecen su continua reproducción

Applications of fractional calculus in electrical and computer engineering

Fractional Calculus (FC) goes back to the beginning of the theory of differential calculus. Nevertheless, the application of FC just emerged in the last two decades, due to the progress in the area of chaos that revealed subtle relationships with the FC concepts. In the field of dynamical systems theory some work has been carried out but the proposed models and algorithms are still in a preliminary stage of establishment. Having these ideas in mind, the paper discusses a FC perspective in the study of the dynamics and control of several systems. This article illustrates several applications of fractional calculus in science and engineering. It has been recognized the advantageous use of this mathematical tool in the modeling and control of many dynamical systems. In this perspective, this paper investigates the use of FC in the fields of controller tuning, electrical systems, digital circuit synthesis, evolutionary computing, redundant robots, legged robots, robotic manipulators, nonlinear friction and financial modeling.N/