RESUMO

Tropical stream ecosystems are under increasing human pressure, making the development of effective restoration approaches and expanding knowledge in this field urgent. This study evaluated the impact of riparian vegetation restoration and environmental context on stream ecosystem functioning by measuring key ecosystem functions - gross primary production (GPP), ecosystem respiration (ER), and nutrient uptake of ammonium and soluble reactive phosphorus - across ten tropical streams in southeastern Brazil. The streams represented a gradient from clearcut areas (impacted reaches) to relatively pristine conditions (reference reaches), including intermediate stages of vegetation recovery (restored reaches). In the short-term (~15-20 years after restoration), restoration led to reduced GPP akin to reference reaches. Yet, ER did not show the anticipated increase, suggesting a longer timeframe is necessary for restored streams to emulate the functional characteristics of reference reaches. Additionally, the restored reaches did not achieve the nutrient uptake efficiencies observed in both impacted and reference reaches, pointing to a partial recovery of ecosystem function. This study suggests that while riparian vegetation restoration contributes positively to certain aspects of stream function, environmental variables less related to this type of restoration, such as discharge and hydromorphology, significantly influence stream ecosystem functioning, highlighting the importance of considering environmental context in restoration efforts. A more holistic approach, possibly encompassing broader hydromorphological and habitat enhancements, is needed to fully restore ecological processes in these vital ecosystems. These insights are critical for informing future tropical stream restoration projects, advocating the use of ecosystem function metrics as comprehensive indicators of ecological recovery and restoration success.

Assuntos

RESUMO

Background: Land use is a major factor determining stream water physicochemistry. However, most streams move from one land use type to another as they drain their watersheds. Here, we studied three land use scenarios in a tropical cloud forest zone in Mexico. We addressed three main goals, to: (1) assess how land use scenarios generate different patterns in stream physicochemical characteristics; (2) explore how seasonality (i.e., dry, dry-to-wet transition, and wet seasons) might result in changes to those patterns over the year; and (3) explore whether physicochemical patterns in different scenarios resulted in effects on biotic components (e.g., algal biomass). Methods: We studied Tropical Mountain Cloud Forest streams in La Antigua watershed, Mexico. Streams drained different three scenarios, streams with (1) an upstream section draining forest followed by a pasture section (F-P), (2) an upstream section in pasture followed by a forest section (P-F), and (3) an upstream forest section followed by coffee plantation (F-C). Physicochemistry was determined at the upstream and downstream sections, and at the boundary between land uses. Measurements were seasonal, including temperature, dissolved oxygen, conductivity, and pH. Water was analyzed for suspended solids, alkalinity, silica, chloride, sulfate, magnesium, sodium, and potassium. Nutrients included ammonium, nitrate, and phosphorus. We measured benthic and suspended organic matter and chlorophyll. Results: Streams presented strong seasonality, with the highest discharge and suspended solids during the wet season. Scenarios and streams within each scenario had distinct physicochemical signatures. All three streams within each scenario clustered together in ordination space and remained close to each other during all seasons. There were significant scenario-season interactions on conductivity (F = 9.5, P < 0.001), discharge (F = 56.7, P < 0.001), pH (F = 4.5, P = 0.011), Cl- (F = 12.2, P < 0.001), SO42- (F = 8.8, P < 0.001) and NH4+ (F = 5.4, P = 0.005). Patterns within individual scenarios were associated with stream identity instead of land use. Both P-F and F-C scenarios had significantly different physicochemical patterns from those in F-P in all seasons (Procrustes analysis, m12 = 0.05-0.25; R = 0.86-0.97; P < 0.05). Chlorophyll was significantly different among scenarios and seasons (F = 5.36, P = 0.015, F = 3.81, P = 0.42, respectively). Concentrations were related to physicochemical variables more strongly during the transition season. Conclusion: Overall, land use scenarios resulted in distinctive water physicochemical signatures highlighting the complex effects that anthropogenic activities have on tropical cloud forest streams. Studies assessing the effect of land use on tropical streams will benefit from assessing scenarios, rather than focusing on individual land use types. We also found evidence of the importance that forest fragments play in maintaining or restoring stream water physicochemistry.

Assuntos

RESUMO

Background: Cocoa is an important tropical tree crop that is mainly cultivated in agroforestry systems (AFS). This system, known as cabruca in northeastern Brazil, holds promise to reconcile biodiversity conservation and economic development. However, since cocoa AFS alters forest structure composition, it can affect litter dynamics in riparian zones and streams. Thus, our objective was to determine litter inputs and standing stocks in riparian zones and streams under three types of forest: managed cocoa AFS, abandoned cocoa AFS, and secondary forest. Methods: We determined terrestrial litter fall (TI), vertical (VI) and lateral (LI) litter inputs to streams, and litter standing stocks on streambeds (BS) in the Atlantic Forest of northeastern Brazil. Litter was collected every 30 days from August 2018 to July 2019 using custom-made traps. The litter was dried, separated into four fractions (leaves, branches, reproductive organs, and miscellaneous material) and weighed. Results: Terrestrial litter fall was similar in all forests, ranging from 89 g m-2 month-1 in secondary forest (SF) to 96 g m-2 month-1 in abandoned cocoa AFS (AC). Vertical input were higher in AC (82 g m-2 month-1) and MC (69 g m-2 month-1) than in SF (40 g m-2 month-1), whereas lateral input were higher in MC (43 g m-2 month-1) than in AC (15 g m-2 month-1) and SF (24 g m-2 month-1). Standing stocks followed the order SF > AC > MC, corresponding to 425, 299 and 152 g m-2. Leaves contributed most to all litter fractions in all forests. Reproductive plant parts accounted for a larger proportion in managed AFS. Branches and miscellaneous litter were also similar in all forests, except for higher benthic standing stocks of miscellaneous litter in the SF. Despite differences in the amounts of litter inputs and standing stocks among the forests, seasonal patterns in the abandoned AFS (AC) were more similar to those of the secondary forest (SF) than the managed AFS, suggesting potential of abandoned AFS to restore litter dynamics resembling those of secondary forests.

Assuntos

RESUMO

Bacillus thuringiensis var. israelensis (Bti) Berliner, 1911 is widely used in the biological control of black fly and mosquito populations. The objective of this study was to evaluate the effects of Bti on the black fly communities in streams in the Atlantic Forest domain. The study was carried out in eight streams of Serra do Mar, in the municipality of Ubatuba, São Paulo. Some parts of the streams in this locality have received applications of Bti fortnightly for more than 25 years by the sanitary agency of the region. In each stream, two sections were sampled, with and without application of Bti (June 2015 and 2016). Black flies were collected and identified to the species level in the laboratory with 1382 larvae being identified, distributed in six species. Of this total, 73% of the individuals were found in sections where Bti was not applied. There was a difference in the abundance of simulids between the sections with and without Bti application, being more abundant in the latter. We measured the head capsule of individuals of the most abundant species, Simulium pertinax Kollar 1832, using a stereoscopic microscope with millimeter lens. These measurements demonstrated that there was a difference between the sections regarding the age structure of Simuliidae populations. In the sections without Bti application, there was a higher proportion of larvae in the last instar, while in the Bti-treated sections, smaller instars were predominant, possibly due to constant recolonization processes.

Assuntos

RESUMO

Patterns of species replacement and richness differences along environmental gradients or ecoregions shed light on different ecological and evolutionary mechanisms acting on community structure. Communities of aquatic ecosystems of different watersheds are supposed to host distinct species and lineages. Quantifying and understanding the degree to which these differences are affected by environmental and biogeographical factors remains an open question for these environments, particularly in the Neotropical region. We investigated patterns of taxonomic and phylogenetic composition of headwater streams of the Paraná and Paraguai River basins to understand how local and biogeographical factors affect the assembly of fish communities. We also quantified taxonomic and phylogenetic beta diversity by decomposing them into nestedness and turnover components. We found that local environmental factors are the main factors influencing the composition of stream fish communities. Whereas pH affected both taxonomic and phylogenetic turnover, water velocity was responsible for phylogenetic turnover and pH was the main driver of phylogenetic nestedness. Our results indicate an effect of local environmental factors in determining the structure of headwater stream fish communities through a combination of a species sorting mechanism (water velocity and pH) and phylogenetic habitat filtering (pH).(AU)

Padrões de substituição de espécies ou diferenças de riqueza ao longo de gradientes ambientais ou ecoregiões lançam luz sobre diferentes processos e mecanismos ecológicos atuando na estruturação das comunidades. Supõe-se que comunidades aquáticas pertencentes a diferentes bacias pertençam a linhagens evolutivas distintas. Quantificar e entender o grau em que tais diferenças são resultado de fatores ambientais locais e/ou processos biogeográficos ainda é uma questão pouco explorada. Neste estudo nós investigamos os padrões de composição taxonômica e filogenética em riachos de cabeceira das bacias dos Rios Paraná e Paraguai, para entender como fatores locais e biogeográficos afetam a estruturação das comunidades de peixes. Nós quantificamos a diversidade beta taxonômica e filogenética decompondo estas em aninhamento e substituição. Encontramos que os fatores ambientais locais são os principais determinantes da composição das comunidades de peixes destes riachos. Enquanto o pH afetou tanto a substituição de linhagens e de espécies, a velocidade da água foi responsável por uma substituição de linhagens, enquanto o pH foi o principal responsável pelo aninhamento de linhagens. Nossos resultados indicam a importância dos fatores locais através da combinação entre mecanismos de preferência de nicho (velocidade da água e pH) e filtragem ambiental de linhagens (pH).(AU)

Assuntos

RESUMO

Patterns of species replacement and richness differences along environmental gradients or ecoregions shed light on different ecological and evolutionary mechanisms acting on community structure. Communities of aquatic ecosystems of different watersheds are supposed to host distinct species and lineages. Quantifying and understanding the degree to which these differences are affected by environmental and biogeographical factors remains an open question for these environments, particularly in the Neotropical region. We investigated patterns of taxonomic and phylogenetic composition of headwater streams of the Paraná and Paraguai River basins to understand how local and biogeographical factors affect the assembly of fish communities. We also quantified taxonomic and phylogenetic beta diversity by decomposing them into nestedness and turnover components. We found that local environmental factors are the main factors influencing the composition of stream fish communities. Whereas pH affected both taxonomic and phylogenetic turnover, water velocity was responsible for phylogenetic turnover and pH was the main driver of phylogenetic nestedness. Our results indicate an effect of local environmental factors in determining the structure of headwater stream fish communities through a combination of a species sorting mechanism (water velocity and pH) and phylogenetic habitat filtering (pH).(AU)

Padrões de substituição de espécies ou diferenças de riqueza ao longo de gradientes ambientais ou ecoregiões lançam luz sobre diferentes processos e mecanismos ecológicos atuando na estruturação das comunidades. Supõe-se que comunidades aquáticas pertencentes a diferentes bacias pertençam a linhagens evolutivas distintas. Quantificar e entender o grau em que tais diferenças são resultado de fatores ambientais locais e/ou processos biogeográficos ainda é uma questão pouco explorada. Neste estudo nós investigamos os padrões de composição taxonômica e filogenética em riachos de cabeceira das bacias dos Rios Paraná e Paraguai, para entender como fatores locais e biogeográficos afetam a estruturação das comunidades de peixes. Nós quantificamos a diversidade beta taxonômica e filogenética decompondo estas em aninhamento e substituição. Encontramos que os fatores ambientais locais são os principais determinantes da composição das comunidades de peixes destes riachos. Enquanto o pH afetou tanto a substituição de linhagens e de espécies, a velocidade da água foi responsável por uma substituição de linhagens, enquanto o pH foi o principal responsável pelo aninhamento de linhagens. Nossos resultados indicam a importância dos fatores locais através da combinação entre mecanismos de preferência de nicho (velocidade da água e pH) e filtragem ambiental de linhagens (pH).(AU)

Assuntos

RESUMO

Ecologists studying emerging wildlife diseases need to confront the realism of imperfect pathogen detection across heterogeneous habitats to aid in conservation decisions. For example, spatial risk assessments of amphibian disease caused by Batrachochytrium dendrobatidis (Bd) has largely ignored imperfect pathogen detection across sampling sites. Because changes in pathogenicity and host susceptibility could trigger recurrent population declines, it is imperative to understand how pathogen prevalence and occupancy vary across environmental gradients. Here, we assessed how Bd occurrence, prevalence, and infection intensity in a diverse Neotropical landscape vary across streams in relation to abiotic and biotic predictors using a hierarchical Bayesian model that accounts for imperfect Bd detection caused by qPCR error. Our model indicated that the number of streams harboring Bd-infected frogs is higher than observed, with Bd likely being present at ~ 43% more streams than it was detected. We found that terrestrial-breeders captured along streams had higher Bd prevalence, but lower infection intensity, than aquatic-breeding species. We found a positive relationship between Bd occupancy probability and stream density, and a negative relationship between Bd occupancy probability and amphibian local richness. Forest cover was a weak predictor of Bd occurrence and infection intensity. Finally, we provide estimates for the minimum number of amphibian captures needed to determine the presence of Bd at a given site where Bd occurs, thus, providing guidence for cost-effective disease risk monitoring programs.

Assuntos

RESUMO

Abstract: The aim of this study was to analyze aquatic oligochaete distribution in relation to water column physicochemical variables, structural environmental variation, and predominant substrates in the preserved Amazonian streams of the Saracá-Taquera National Forest (FLONA Saracá-Taquera), northwest Pará, Brazil. Oligochaetes are widely used as bioindicators for monitoring aquatic environments as they are very sensitive to pollution and environmental changes. Physicochemical and structural variables were measured from 100 stream segments in order to understand the distribution of oligochaetes in Amazonian streams. Biotic samples were collected using Surber samplers in three of the most predominant substrate types in each segment. PERMANOVA testing showed that there was a significant difference in the oligochaete community among some substrates, potentially caused by a difference in the abundance of the most common taxa. Canonical Correspondence Analysis showed that physical variables drive the distribution of oligochaetes in preserved Amazonian streams, as they determine the formation of different substrates along the stream, from the source to the mouth; favoring the presence of oligochaetes with more specific ecological needs in low-order streams, and the presence of oligochaetes capable of colonizing various types of substrates and deeper zones in high-order streams. These results suggest that water depth and channel width are the main drivers of aquatic oligochaete distribution along Amazonian streams, determining the formation of unstable and low-quality substrates and, consequently, the low colonization by oligochaetes in high-order streams; and more diverse and stable substrate formation in low-order streams, favoring the colonization by diverse taxa of aquatic oligochaetes in low-order Amazonian streams.

Resumo: O objetivo deste trabalho foi analisar a distribuição da comunidade de oligoquetos em relação às variáveis físico-químicas da coluna da água, variação estrutural do ambiente, e substratos predominantes em riachos amazônicos conservados na FLONA Saracá-Taquera, noroeste do Pará, Brasil. Oligochaetes são amplamente utilizados como bioindicadores para monitoramento de ambientes aquáticos, pois são muito sensíveis à poluição e às mudanças ambientais. Variáveis físico-químicas e estruturais de 100 trechos de riachos foram mensuradas para entender a distribuição de oligoquetos em riachos amazônicos. Amostras bióticas foram coletadas com amostrador Surber em três dos tipos de substratos mais predominantes em cada trecho. A PERMANOVA mostrou que há uma diferença significativa da comunidade de oligoquetos entre alguns substratos, possivelmente baseada nas diferenças no número do táxon mais comum. A Análise de Correspondência Canônica mostrou que as variáveis físicas controlam a distribuição da comunidade de oligoquetos em riachos amazônicos preservados, porque estas variáveis determinam a formação dos diferentes substratos ao longo do riacho, desde a nascente até a foz, favorecendo a presença de oligoquetos com necessidades ecológicas mais específicas em riachos de baixa ordem, e oligoquetos capazes de colonizar diferentes tipos de substrato e zonas mais profundas em riachos de ordem maior. Os resultados deste trabalho sugerem que a profundidade da água e a largura do canal são as variáveis que controlam a distribuição da comunidade de oligoquetos em riachos amazônicos, determinando a formação de substratos instáveis e de baixa qualidade, e consequentemente baixa colonização de oligoquetos, em riachos de ordem maior; e formação de substratos mais diversificados, mais estáveis e de qualidade em riachos de baixa ordem, favorecendo a colonização de diversos taxa de oligoquetos aquáticos em riachos amazônicos de baixa ordem.

RESUMO

Detrital-based trophic cascades are often considered weak or absent in tropical stream ecosystems because of the prevalence of omnivorous macroconsumers and the dearth of leaf-shredding insects. In this study, we isolate top-down effects of three macroconsumer species on detrital processing in headwater streams draining Trinidad's northern mountains. We separated effects of different macroconsumers by experimentally manipulating their temporal access to isolated benthic habitat over the diel cycle. We found no evidence that omnivorous macroconsumers, including a freshwater crab (Eudaniela garmani) and guppy (Poecilia reticulata), increased leaf decomposition via consumption. By contrast, above a waterfall excluding guppies, the insectivorous killifish, Anablepsoides hartii, reduced the biomass of the leaf-shredding insect Phylloicus hansoni 4-fold, which consequently reduced leaf decomposition rates 1.6-fold. This detrital cascade did not occur below the barrier waterfall, where omnivorous guppies join the assemblage and reduce killifish densities; here killifish had no significant effects on Phylloicus or decomposition rates. These patterns of detrital processing were also observed in upstream-downstream comparisons in a landscape study across paired reaches of six streams. Above waterfalls, where killifish were present, but guppies absent, leaf decomposition rates and Phylloicus biomass were 2.5- and ~35-fold lower, respectively, compared to measurements below waterfalls. Moreover, the strength of top-down control by killifish is reflected by the 20- and 5-fold reductions in variability (±SE) surrounding mean Phylloicus biomass and leaf decomposition rates in upstream relative to downstream reaches where no top-down control was detected. Findings show a clear, detrital-based trophic cascade among killifish, a leaf-shredding insect, and leaf decomposition rates. Results also show how omnivorous guppies disrupt this cascade by depressing killifish densities, thereby releasing invertebrate shredders from predation, and significantly increasing decomposition rates. Moreover, this combination of direct and indirect trophic interactions drives patterns in decomposition rates in stream networks at a landscape scale, resulting in significantly lower rates of decomposition above vs. below barrier waterfalls. Our findings reveal that omnivory can result in significant indirect effects on a key ecosystem process, illustrating the importance of these hidden trophic pathways in detrital-based systems and suggesting that resource control in tropical systems may be even more complex than previously envisioned.

Assuntos

RESUMO

Abstract Caddisflies are abundant, diverse, and important insects in freshwater ecosystems. However our knowledge on their life history is incomplete, in particular for the Neotropics. The objectives of this study were to describe the life history and phenology of Phylloicus pulchrus in the Luquillo Experimental Forest, Puerto Rico. Eggs and larvae were reared to determine the species lifespan and time in each instar. Larval instars were determined based on a head width vs. pronotal suture length correlation (N= 120). Larvae and benthic leaf litter were sampled monthly at a headwater stream for a year; all specimens were classified into instars based on their case size. Adult P. pulchrus were sampled monthly for a year with a light trap and at various times with a Malaise trap. Monthly environmental variables were related to species and sex abundance. There was a gradient of egg development where eggs (within compound masses) closest to the water were more developed. There were five larval instars and reared larvae showed longer development times and more variable body measurements in later instars. The best correlation for larval instar determination was case length-head width (Pearson= 0.90, P= 2.2e-16, N= 120). Phylloicus pulchrus has a multivoltine life cycle, with asynchronous larval development. Adult abundance was low. First to third instar larvae were influenced significantly by rainfall and rainfall seasonality had a negative significant effect on second instar larval abundance (ANOVA= 7.45, P= 0.02).Compound egg masses were probably oviposited by different females that gathered for oviposition. Phylloicus pulchrus follows the predominant developmental characteristic of Trichoptera of having five larval stages. Development times were longer than expected (longest times for a Phylloicus species) and may be an effect of laboratory rearing. The influence of rainfall (and seasonality) on different larval instars highlights the importance of this variable on early larval development. The cause of low adult abundance remains unclear, but may be related to low emergence rates and trap efficiency. Rev. Biol. Trop. 66(2): 814-825. Epub 2018 June 01.

Resumen Los tricópteros son insectos abundantes, diversos e importantes en los ecosistemas de agua dulce. Sin embargo el conocimiento sobre su historia de vida es incompleto, en particular para el Neotrópico. Los objetivos de este estudio fueron describir la historia de vida y fenología de Phylloicus pulchrus en el Bosque Experimental de Luquillo, Puerto Rico. Huevos y larvas fueron criadas para determinar la extención y tiempo de vida de cada estadio de la especie. Los estadios larvales fueron determinados basados en la correlación del ancho de cabeza vs. largo de la sutura pronotal (N= 120). Se muestrearon larvas y hojarasca béntica mensualmente por un año, todos los especímenes se clasificaron en estadios por el tamaño del estuche. Los adultos de P. pulchrus fueron recolectados mensualmente por un año utilizando una trampa de luz y varias recolectas con una trampa Malaise. Datos mensuales de variables ambientales fueron usados para explicar la abundancia total y por sexo de la especie. Se detectó un gradiente de desarrollo de los huevos donde los huevos (dentro de masa compuesta) más cercanos al agua estaban más desarrollados. Fueron cinco los estadios larvales y las larvas criadas mostraron tiempos de desarrollo más largos y mayor dispersión en las medidas corporales de los estadios tardíos. La mejor correlación para la determinación de estadios fue largo del estuche-ancho de cabeza (Pearson= 0.90, P= 2.2e-16, N= 120). Phylloicus pulchrus tiene un ciclo de vida multivoltino con desarrollo larval asíncrono. La abundancia de adultos fue baja. Los primeros tres estadios larvales fueron influenciados significativamente por la lluvia y la estacionalidad de la lluvia tuvo un efecto significativo en la abundancia del segundo estadio larval (ANOVA= 7.45, P= 0.02). Las masas de huevo complejas fueron probablemente ovipositadas por diferentes hembras que se reunieron para oviponer. Phylloicus pulchrus mantiene la característica de desarrollo predominante en Trichoptera de tener cinco estadios larvales. Los tiempos de desarrollo fueron mayores a lo esperado (los más largos para una especie de Phylloicus) y puede ser un efecto de la crianza en el laboratorio. El ciclo de vida multivoltino asíncrono observado es el esperado en un entorno tropical debido a las temperaturas más cálidas del agua, la disponibilidad constante de recursos y la baja estacionalidad. La causa de la poca abundancia de adultos permanece incierta, aunque puede estar relacionada con bajas tasas de emergencia y la eficiencia de la trampa de luz. La influencia de la lluvia (y su estacionalidad) en diferentes estadios larvales evidencian la importancia de esta variable en el desarrollo larval temprano.

Assuntos

RESUMO

Abstract Macroinvertebrate shredders have been widely recognized as an important functional feeding group that contributes to leaf decomposition in temperate streams, but little is known about their role in upland Neotropical streams. In this study, we investigated the effect of macroinvertebrate exclusion on leaf breakdown rates in two upland streams in Colombia. The study was carried out between January and April of 2009, including the dry season and the beginning of the wet season. We measured leaf mass loss using coarse- (15 mm; accessible to macroinvertebrates) and fine- (200 µm; macroinvertebrates excluded) mesh litter bags that were anchored with wood stakes to the bottom of each stream and recovered after 7, 14, 21, 28, and 56 days. We selected leaves from two dominant plant species and used three leaf treatments: two single species (Palicourea cuatrecasasii and Critoniopsis ursicola) and mixed-species (P. cuatrecasasii and C. ursicola). We compared leaf breakdown rates between the Peña Bonita and Marianela stream, mesh-sizes, and leaf treatments. Macroinvertebrates that colonized the litter bags were measured for density and biomass and categorized in functional feeding groups. In general, there were no significant differences in breakdown rates between the streams and the mesh-sizes. In contrast, leaf breakdown rates had significant differences between all leaf species, where C. ursicola had higher breakdown rates than mixed-species, and P. cuatrecasasii. Macroinvertebrate exclusion did not affect leaf breakdown rates and their assemblages were composed by high densities of collectors (mainly Chironomidae) and few shredders with a large body size. The similar macroinvertebrate colonization between leaf species, the relatively slow breakdown rates, and the shredder scarcity, suggest that leaves were a refractory substrate. Further studies should include leaf species with different nutritional qualities and larger spatial-temporal scales to test the hypothesis of shredder presence and its role on leaf decomposition in upland Colombian streams. Rev. Biol. Trop. 66(1): 457-467. Epub 2018 March 01.

Resumen Los macroinvertebrados fragmentadores han sido ampliamente reconocidos como un importante grupo funcional alimenticio que contribuye a la descomposición de la hojarasca en quebradas del hemisferio norte, pero poco se sabe sobre su papel en quebradas de montaña neotropicales. En el presente estudio investigamos el efecto de la exclusión de los macroinvertebrados sobre las tasas de fragmentación de la hojarasca en dos quebradas de montaña en Colombia. Nuestra hipótesis es que la fragmentación de la hojarasca es mediada principalmente por macroinvertebrados fragmentadores en quebradas de montaña en Colombia. Este estudio fue llevado a cabo entre enero y abril 2009, incluyendo la época seca y el comienzo de la época de lluvias. Se midieron las pérdidas de masa de hojarasca usando bolsas de malla gruesa (15 mm; accesible a macroinvertebrados) y fina (200 µm; macroinvertebrados excluidos); estas fueron atadas con estacas de madera al fondo de cada quebrada y recuperadas transcurridos 7, 14, 21, 28 y 56 días. Se seleccionó hojarasca de dos especies dominantes en los sitios de estudio y se usaron tres tratamientos para las bolsas de hojarasca: Critoniopsis ursicola, Palicourea cuatrecasasii y una mezcla de estas dos especies. Se compararon las tasas de fragmentación de la hojarasca entre las dos quebradas, los dos tipos de malla y las especies de hojarasca. Los macroinvertebrados que colonizaron las bolsas de hojarasca fueron medidos en términos de densidad, biomasa y categorizados en grupos funcionales alimenticios. En general, nuestros resultados no mostraron diferencias significativas en las tasas de fragmentación de la hojarasca entre las quebradas y entre los tipos de malla. En contraste, las tasas de fragmentación presentaron diferencias significativas entre las especies de hojarasca; específicamente, C. ursicola tuvo tasas más altas de fragmentación que las especies mezcladas y que P. cuatrecasasii. Con respecto a los macroinvertebrados, el presente estudio encontró que su exclusión no tuvo un efecto sobre las tasas de fragmentación y los ensamblajes estuvieron compuestos por una alta densidad de recolectores (principalmente de la familia Chironomidae) y pocos fragmentadores con gran tamaño corporal. La colonización similar de macroinvertebrados entre las especies de hojarasca, las relativamente lentas tasas de fragmentación, sugieren que las hojas fueron un sustrato refractario. Futuros estudios deberían incluir especies de hojarasca con diferentes calidades nutricionales y una mayor escala espacio-temporal para estudiar la hipótesis de la presencia de fragmentadores en quebradas de montaña en Colombia.

RESUMO

We evaluated the growth of periphyton and colonization of sterilized cobbles by invertebrates in three coastal streams of the Atlantic Forest (Southeast Brazil) that differ in the conservation level of riparian zones. Because of differences in light availability and water temperature, we hypothesized the growth of periphytic algae would be higher in the most altered stream. Consequently, invertebrate assemblages would differ among streams. Cobbles with similar sizes were ashed and incubated for 7, 15, 30, 45 and 60 days in the studied streams. Despite periphyton growth was faster in the most altered stream, contents of chlorophyll-a did not differ among streams. A total of 954 individuals (98% insects) belonging to 36 taxa was found. Invertebrate density was higher and increased throughout the experiment in the preserved stream, while invertebrate biomass was higher on the initial sampling intervals (7 and 15 days). A stream effect on invertebrate assemblages was observed after the 15th day and 17 taxa were found only in the preserved stream. Leptophlebiidae (Ephemeroptera), Hydroptilidae, Helichopsychidae, Leptoceridae (Trichoptera) and Orthocladiinae (Diptera) showed specificities with the assemblages found in the preserved stream and no taxa proved to be an indicator of the assemblages found in the altered streams. These results showed that changes in the riparian zones of Atlantic Forest streams did not affect the content of chlorophyll-a on rocky substrates, but the growth of periphyton influenced the density and structural composition of invertebrate assemblages. Our findings partially support the proposed hypothesis and conform to the notion of the importance of periphyton community for the colonization of exposed substrates by invertebrates and for evaluating the consequences of anthropogenic changes in ecosystem functioning and aquatic communities.

O crescimento do perifíton e a colonização de seixos esterilizados por invertebrados foram avaliados em três riachos costeiros de Mata Atlântica (Sudeste do Brasil) que diferem no estado de conservação das zonas ripárias. Devido a diferenças na disponibilidade de luz e temperatura da água, foi hipotetizado que o crescimento das algas perifíticas seria maior no riacho mais alterado. Consequentemente, as assembleias de invertebrados iriam diferir entre os riachos. Seixos com tamanhos similares foram incinerados e incubados por 7, 15, 30, 45 e 60 dias nos riachos estudados. Apesar do crescimento do perifíton ter sido mais rápido no riacho mais alterado, os teores de clorofila-a não diferiram entre os riachos. Um total de 954 indivíduos (98% insetos) pertencentes a 36 táxons foi encontrado. A densidade de invertebrados foi maior e aumentou ao longo do experimento no riacho preservado, enquanto a biomassa de invertebrados foi maior nos intervalos iniciais de amostragem (7 e 15 dias). Um efeito dos riachos nas assembleias de invertebrados foi observado após o 15o dia e 17 táxons foram encontrados somente no riacho preservado. Leptophlebiidae (Ephemeroptera), Hydroptilidae, Helichopsychidae, Leptoceridae (Trichoptera) e Orthocladiinae (Diptera) apresentaram especificidades com as assembleias encontradas no riacho preservado e nenhum táxon foi indicador das assembleias encontradas nos riachos alterados. Estes resultados demonstraram que alterações nas zonas ripárias de riachos de Mata Atlântica não afetaram os teores de clorofila-a em substratos rochosos, mas o crescimento do perifíton influenciou a densidade e a composição estrutural das assembleias de invertebrados...

Assuntos

RESUMO

ABSTRACT: We evaluated the growth of periphyton and colonization of sterilized cobbles by invertebrates in three coastal streams of the Atlantic Forest (Southeast Brazil) that differ in the conservation level of riparian zones. Because of differences in light availability and water temperature, we hypothesized the growth of periphytic algae would be higher in the most altered stream. Consequently, invertebrate assemblages would differ among streams. Cobbles with similar sizes were ashed and incubated for 7, 15, 30, 45 and 60 days in the studied streams. Despite periphyton growth was faster in the most altered stream, contents of chlorophyll-a did not differ among streams. A total of 954 individuals (98% insects) belonging to 36 taxa was found. Invertebrate density was higher and increased throughout the experiment in the preserved stream, while invertebrate biomass was higher on the initial sampling intervals (7 and 15 days). A stream effect on invertebrate assemblages was observed after the 15th day and 17 taxa were found only in the preserved stream. Leptophlebiidae (Ephemeroptera), Hydroptilidae, Helichopsychidae, Leptoceridae (Trichoptera) and Orthocladiinae (Diptera) showed specificities with the assemblages found in the preserved stream and no taxa proved to be an indicator of the assemblages found in the altered streams. These results showed that changes in the riparian zones of Atlantic Forest streams did not affect the content of chlorophyll-a on rocky substrates, but the growth of periphyton influenced the density and structural composition of invertebrate assemblages. Our findings partially support the proposed hypothesis and conform to the notion of the importance of periphyton community for the colonization of exposed substrates by invertebrates and for evaluating the consequences of anthropogenic changes in ecosystem functioning and aquatic communities.

RESUMO: O crescimento do perifíton e a colonização de seixos esterilizados por invertebrados foram avaliados em três riachos costeiros de Mata Atlântica (Sudeste do Brasil) que diferem no estado de conservação das zonas ripárias. Devido a diferenças na disponibilidade de luz e temperatura da água, foi hipotetizado que o crescimento das algas perifíticas seria maior no riacho mais alterado. Consequentemente, as assembleias de invertebrados iriam diferir entre os riachos. Seixos com tamanhos similares foram incinerados e incubados por 7, 15, 30, 45 e 60 dias nos riachos estudados. Apesar do crescimento do perifíton ter sido mais rápido no riacho mais alterado, os teores de clorofila-a não diferiram entre os riachos. Um total de 954 indivíduos (98% insetos) pertencentes a 36 táxons foi encontrado. A densidade de invertebrados foi maior e aumentou ao longo do experimento no riacho preservado, enquanto a biomassa de invertebrados foi maior nos intervalos iniciais de amostragem (7 e 15 dias). Um efeito dos riachos nas assembleias de invertebrados foi observado após o 15o dia e 17 táxons foram encontrados somente no riacho preservado. Leptophlebiidae (Ephemeroptera), Hydroptilidae, Helichopsychidae, Leptoceridae (Trichoptera) e Orthocladiinae (Diptera) apresentaram especificidades com as assembleias encontradas no riacho preservado e nenhum táxon foi indicador das assembleias encontradas nos riachos alterados. Estes resultados demonstraram que alterações nas zonas ripárias de riachos de Mata Atlântica não afetaram os teores de clorofila-a em substratos rochosos, mas o crescimento do perifíton influenciou a densidade e a composição estrutural das assembleias de invertebrados. Estas observações suportam parcialmente a hipótese proposta e estão em conformidade com a noção da importância da comunidade perifítica para a colonização de substratos expostos por invertebrados e para a avaliação das consequências das alterações antrópicas no funcionamento dos ecossistemas e nas comunidades aquáticas.

RESUMO

We evaluated the growth of periphyton and colonization of sterilized cobbles by invertebrates in three coastal streams of the Atlantic Forest (Southeast Brazil) that differ in the conservation level of riparian zones. Because of differences in light availability and water temperature, we hypothesized the growth of periphytic algae would be higher in the most altered stream. Consequently, invertebrate assemblages would differ among streams. Cobbles with similar sizes were ashed and incubated for 7, 15, 30, 45 and 60 days in the studied streams. Despite periphyton growth was faster in the most altered stream, contents of chlorophyll-a did not differ among streams. A total of 954 individuals (98% insects) belonging to 36 taxa was found. Invertebrate density was higher and increased throughout the experiment in the preserved stream, while invertebrate biomass was higher on the initial sampling intervals (7 and 15 days). A stream effect on invertebrate assemblages was observed after the 15th day and 17 taxa were found only in the preserved stream. Leptophlebiidae (Ephemeroptera), Hydroptilidae, Helichopsychidae, Leptoceridae (Trichoptera) and Orthocladiinae (Diptera) showed specificities with the assemblages found in the preserved stream and no taxa proved to be an indicator of the assemblages found in the altered streams. These results showed that changes in the riparian zones of Atlantic Forest streams did not affect the content of chlorophyll-a on rocky substrates, but the growth of periphyton influenced the density and structural composition of invertebrate assemblages. Our findings partially support the proposed hypothesis and conform to the notion of the importance of periphyton community for the colonization of exposed substrates by invertebrates and for evaluating the consequences of anthropogenic changes in ecosystem functioning and aquatic communities.(AU)

O crescimento do perifíton e a colonização de seixos esterilizados por invertebrados foram avaliados em três riachos costeiros de Mata Atlântica (Sudeste do Brasil) que diferem no estado de conservação das zonas ripárias. Devido a diferenças na disponibilidade de luz e temperatura da água, foi hipotetizado que o crescimento das algas perifíticas seria maior no riacho mais alterado. Consequentemente, as assembleias de invertebrados iriam diferir entre os riachos. Seixos com tamanhos similares foram incinerados e incubados por 7, 15, 30, 45 e 60 dias nos riachos estudados. Apesar do crescimento do perifíton ter sido mais rápido no riacho mais alterado, os teores de clorofila-a não diferiram entre os riachos. Um total de 954 indivíduos (98% insetos) pertencentes a 36 táxons foi encontrado. A densidade de invertebrados foi maior e aumentou ao longo do experimento no riacho preservado, enquanto a biomassa de invertebrados foi maior nos intervalos iniciais de amostragem (7 e 15 dias). Um efeito dos riachos nas assembleias de invertebrados foi observado após o 15o dia e 17 táxons foram encontrados somente no riacho preservado. Leptophlebiidae (Ephemeroptera), Hydroptilidae, Helichopsychidae, Leptoceridae (Trichoptera) e Orthocladiinae (Diptera) apresentaram especificidades com as assembleias encontradas no riacho preservado e nenhum táxon foi indicador das assembleias encontradas nos riachos alterados. Estes resultados demonstraram que alterações nas zonas ripárias de riachos de Mata Atlântica não afetaram os teores de clorofila-a em substratos rochosos, mas o crescimento do perifíton influenciou a densidade e a composição estrutural das assembleias de invertebrados...(AU)

Assuntos

RESUMO

Patterns of species' abundance and occurrence over time and space allow division of species into (i) common species, which are abundant, but have a low diversity, and (ii) rare species, which are far more diverse and less abundant. Understanding the relationships among these two species groups and how they are affected by environmental conditions is a major challenge for ecologists, especially considering the distinction between local environmental factors and regional factors and variations in abundance over the course of the year. In this study, we focused on the long-term relationship between the abundance of rare and common ephemeropterans and abiotic factors on local and regional scales. Our hypotheses are that common species will be affected primarily by regional environmental variables (i), whereas rare species will be influenced more by temporal variation (ii). Together, both local and regional abiotic variables, plus temporal variation, best explained the abundance of the common species, whereas temporal variation was the best predictor of rare species. Considering the theoretical aspects and the empirical evidence, we discuss the results based on the plasticity of the common species and the life cycle of the rare ones. We believe that our findings reinforce the need for the deconstruction of communities for a deeper understanding of their relationships with abiotic variables and, in particular, the specific aspects of these relationships in the context of the different guilds of the community.

Assuntos

RESUMO

The ichthyofauna of the Río Acahuapa was analyzed sampling 17 sites that included the basin main channel and its tributaries. Fish were collected using dip-nets, seine-nets and electrofishing. Fish standard length and species abundance were recorded. Species origin and salinity tolerance criteria were used to classify fish species. Water physicochemical variables, habitat structure and sampling sites elevation were recorded. A total of 33 fish species were registered, 12.1% are primary, 45.5% are secondary and 42.4% are of marine derivation. Fish species richness declined with increase of elevation (R2=0.55, p=0.0006). Two assemblages of fishes were identified: the first one associated to sites of low elevations (19-184 masl), composed mainly of secondary and marine-estuarine fish species related with high temperature, water velocity, river width, dissolved oxygen and low sand and silt substrate cover; the second one associated to sites of middle and higher elevations (185-519 masl), composed by primary and secondary freshwater fishes related with high pH, logs and rocks substrate cover. In summary, elevation and environmental variables contributed to the composition and distribution of fish in the Río Acahuapa.(AU)

La ictiofauna del Río Acahuapa fue analizada en 17 sitios que incluyen el canal principal de la cuenca y sus tributarios. Los peces fueron recolectados utilizando chinchorros, redes de mano y electropesca. Se registró la longitud estándar y la abundancia por especie. El criterio de origen y tolerancia a la salinidad de las especies fue utilizado para clasificar a los peces. Las variables fisicoquímicas del agua, estructura del hábitat y elevación se registraron en cada sitio. Un total de 33 especies fueron registradas, cuyo 12.1% son primarias, 45.5% secundarias y 42.4% son de derivación marina. La riqueza de especies de peces disminuyó con el aumento de la elevación (R2=0.55, p=0.0006). Dos ensamblajes de peces fueron identificados: el primero está asociado con sitios de bajas elevaciones (19-184 msnm), compuesto principalmente de especies de peces secundarias y marino-estuarinas relacionadas con altas temperaturas, velocidad del agua, ancho de río, oxígeno disuelto y baja cobertura de sustrato de arena y limo; el segundo está asociado con sitios de mediana y alta elevación (185-519 msnm), compuesto por peces dulceacuícolas primarios y secundarios relacionados con altos valores de pH y cobertura de sustrato de troncos y rocas. Se determina que la elevación y las variables ambientales contribuyen a la composición y distribución de peces en el Río Acahuapa.(AU)

Assuntos

RESUMO

The ichthyofauna of the Río Acahuapa was analyzed sampling 17 sites that included the basin main channel and its tributaries. Fish were collected using dip-nets, seine-nets and electrofishing. Fish standard length and species abundance were recorded. Species origin and salinity tolerance criteria were used to classify fish species. Water physicochemical variables, habitat structure and sampling sites elevation were recorded. A total of 33 fish species were registered, 12.1% are primary, 45.5% are secondary and 42.4% are of marine derivation. Fish species richness declined with increase of elevation (R2=0.55, p=0.0006). Two assemblages of fishes were identified: the first one associated to sites of low elevations (19-184 masl), composed mainly of secondary and marine-estuarine fish species related with high temperature, water velocity, river width, dissolved oxygen and low sand and silt substrate cover; the second one associated to sites of middle and higher elevations (185-519 masl), composed by primary and secondary freshwater fishes related with high pH, logs and rocks substrate cover. In summary, elevation and environmental variables contributed to the composition and distribution of fish in the Río Acahuapa.(AU)

La ictiofauna del Río Acahuapa fue analizada en 17 sitios que incluyen el canal principal de la cuenca y sus tributarios. Los peces fueron recolectados utilizando chinchorros, redes de mano y electropesca. Se registró la longitud estándar y la abundancia por especie. El criterio de origen y tolerancia a la salinidad de las especies fue utilizado para clasificar a los peces. Las variables fisicoquímicas del agua, estructura del hábitat y elevación se registraron en cada sitio. Un total de 33 especies fueron registradas, cuyo 12.1% son primarias, 45.5% secundarias y 42.4% son de derivación marina. La riqueza de especies de peces disminuyó con el aumento de la elevación (R2=0.55, p=0.0006). Dos ensamblajes de peces fueron identificados: el primero está asociado con sitios de bajas elevaciones (19-184 msnm), compuesto principalmente de especies de peces secundarias y marino-estuarinas relacionadas con altas temperaturas, velocidad del agua, ancho de río, oxígeno disuelto y baja cobertura de sustrato de arena y limo; el segundo está asociado con sitios de mediana y alta elevación (185-519 msnm), compuesto por peces dulceacuícolas primarios y secundarios relacionados con altos valores de pH y cobertura de sustrato de troncos y rocas. Se determina que la elevación y las variables ambientales contribuyen a la composición y distribución de peces en el Río Acahuapa.(AU)

Assuntos

RESUMO

RESUMO O uso e a ocupação do solo alteram sensivelmente os processos físico-químicos e biológicos dos sistemas naturais. Dessa forma, os mananciais de superfície são integradores dos fenômenos ocorrentes sobre a área da bacia hidrográfica. Assim, os objetivos do trabalho foram explorar a variabilidade temporal e espacial da qualidade da água e avaliar as possíveis relações entre os padrões de uso e ocupação do solo da bacia hidrográfica do Ribeirão Vermelho. Foram coletadas amostras de água em dois períodos (verão e inverno) e em 15 seções ao longo do curso d'água. Verificou-se forte influência temporal e espacial na qualidade das águas, e foram apresentadas no período de inverno as maiores concentrações de nutrientes (Cl-, P, NO3 -), condutividade elétrica e matéria orgânica. Esses valores interferem nos valores do Índice de Qualidade da Água, que varia entre 84 e 9 no período do verão e 66 e 6 no inverno. Quanto à trofia dos mananciais, foram encontrados valores médios de Índice de Estado Trófico de 30 no período chuvoso e de 93 no inverno. No tocante aos padrões de uso do solo, observaram-se fortes relações na qualidade da água nos dois períodos avaliados; a principal fonte de contaminação são as áreas urbanas. O Ribeirão Vermelho e seus afluentes apresentam forte influência das formas de uso e ocupação do solo confirmada pela entrada de matéria orgânica e de nutrientes nos sistemas hídricos por meio do lançamento de esgoto doméstico sem tratamento e pela agropecuária na rede de drenagem da bacia.

ABSTRACT Land use significantly alters the physicochemical and biological processes of natural systems. Thus, surface water sources are integrators of phenomena occurring on the catchment area. In this way, the study aimed to explore the spatial and temporal variability of water quality, and to assess the possible relationships between patterns of land use of the Ribeirão Vermelho basin. Water samples were collected in two periods (summer and winter) and in 15 sections along the watercourse. There has been strong temporal and spatial influence on water quality, and winter period showed the highest nutrient concentrations (Cl-, P, NO3 -), electrical conductivity and organic matter. These values influence the values of the Water Quality Index, ranging from 84 to 9 in the summer period and 66 to 6 in the winter. With respect to trophic conditions of water sources, average values of Trophic State Index of 30 were verified during the rainy season and 93 in winter. Regarding land use patterns, strong relationships in water quality in both periods were observed, the main source of contamination are urban areas. Ribeirão Vermelho and its effluent have shown strong influence of the forms of land use and occupation evidenced by the input organic matter and nutrients in water systems through domestic sewage release untreated and by agriculture in the drainage system of the basin.

RESUMO

Despite the strong representativeness of streams in the Amazon basin, their role in the accumulation of coarse particulate organic carbon (CPOC), fine particulate organic carbon (FPOC), and dissolved organic carbon (DOC) in transport, an important energy source in these environments, is poorly known. It is known that the arboreal vegetation in the Amazon basin is influenced by soil fertility and rainfall gradients, but would these gradients promote local differences in organic matter in headwater streams? To answer this question, 14 low-order streams were selected within these gradients along the Amazon basin, with extensions that varied between 4 and 8 km. The efficiency of the transformation of particulate into dissolved carbon fractions was assessed for each stream. The mean monthly benthic organic matter storage ranged between 1.58 and 9.40 t ha(-1) month(-1). In all locations, CPOC was the most abundant fraction in biomass, followed by FPOC and DOC. Rainfall and soil fertility influenced the distribution of the C fraction (p = 0.01), showing differentiated particulate organic carbon (POC) storage and DOC transportation along the basin. Furthermore, the results revealed that carbon quantification at the basin level could be underestimated, ultimately influencing the global carbon calculations for the region. This is especially due to the fact that the majority of studies consider only fine particulate organic matter and dissolved organic matter, which represent less than 50 % of the stored and transported carbon in streambeds.

Assuntos

RESUMO

Many tropical countries contain a high density of protected ecosystems, and these may often be bordered by intensive agricultural systems. We investigated the chemical and ecological status of a stream connecting an area with conventional rice production and a downstream protected nature reserve; Mata Redonda. Three sites were sampled: 1) an upstream control, 2) in the rice production area and 3) a downstream site in Mata Redonda. We sampled benthic macroinvertebrates and pesticides in water and sediments along with supporting physical and chemical data. Pesticide concentrations in water exceeded current safety thresholds at sites 2 and 3, especially during the rainy season, and sediment associated pesticide concentrations exceeded current safety thresholds in three of six samples. Importantly, the highest predicted pesticide toxicity in sediments was observed at site 3 in the Mata Redonda confirming that the nature reserve received critical levels of pesticide pollution from upstream sections. The currently used macroinvertebrate index in Costa Rica (BMWP-CR) and an adjusted version of the SPecies At Risk index (SPEAR) were not significantly correlated to any measure of anthropogenic stress, but the Average Score Per Taxon (ASPT) index was significantly correlated with the predicted pesticide toxicity (sumTUD.magna), oxygen concentrations and substrate composition. Our results suggest that pesticide pollution was likely involved in the impairment of the ecological status of the sampling sites, including site 3 in Mata Redonda. Based on our results, we give guidance to biomonitoring in Costa Rica and call for increased focus on pesticide transport from agricultural regions to protected areas.

Assuntos