Metabolism in a macrophyte-rich stream exposed to flooding

The aim of this study was to investigate the effect of floods on the metabolic autotrophic rates of a Pampean stream. We hypothesized that there would be high productivity because of the macrophyte-rich community and the high nutrient levels but that this productivity would be reduced by flooding. Net community production (NCP) and community respiration (CR) were measured using clear and opaque acrylic chambers in the same reach of the stream. Community metabolism was analyzed in relation to biomass and the colonized streambed surface. Prior to the flood, epiphyton was the most productive compartment of the stream, whereas after the flood, the bottom algae compartment was the most productive one. Therefore, the relative contribution of each compartment to the entire ecosystem was influenced by the varying flow conditions. The primary gross production values of the Las Flores stream communities before the flood were higher than most of those reported in other streams worldwide and sustain the complex trophic web associated to the stream. Consequently, production decrease due to the lower relative contribution of macrophytes and epiphyton would lead to a more simplified trophic network.Fil: Vilches, Carolina. Universidad Nacional de Luján; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Giorgi, Adonis David Nazareno. Universidad Nacional de Luján; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Estimating the Self-depuration Capacity of a Reach of the Luján River

A 3-km reach of the Luján River was studied by establishing 6 sampling stations, which were from 300 to 500 m apart. The first station was the control reading for river nutrients and particulate material. The second station measured the continuous effluent from a wastewater treatment plant flow of the city of Luján and was, therefore, considered a continuous addition point of nutrients. The other 4 stations were used to evaluate whether the river captured phosphorus as phosphate, nitrogen as ammonium, nitrite or nitrates, and the suspended particulate material, both organic and inorganic. These data were used to calculate material uptake (U), uptake velocity (Vf), and net distance Snet under two different hydrological situations, during low and high flow, during the same season of the same year. Results indicate that phosphate ions as well as organic matter are retained for less than 2 km in both high and low flow situations. In the case of ammonium, the results appear similar to those of phosphate ions but it may be transformed into nitrates and transported in the latter form for greater distances. It is concluded that this river, in the reach under study, has a variable retention speed according to its flow but the retention capacity is no less than 900 m and as much as 2000 m. Therefore, a 2 km distance must be considered as the minimum distance before another effluent of nutrients or organic matter is added.Fil: Piccinini, Mauricio. Provincia de Buenos Aires. Municipalidad de Lujan; ArgentinaFil: Sánchez Caro, Anibal. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Ecología y Desarrollo Sustentable; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Gultermiriam, M.L.. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Giorgi, Adonis David Nazareno. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Ecología y Desarrollo Sustentable; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

As productive and slow as a stream can be-the metabolism of a Pampean stream

Stream metabolism at both ecosystem and functional-compartment scales was measured in a low-order Pampean stream (La Choza) over a 3-wk period to characterize metabolic rates and discern the contribution of each functional compartment (submerged macrophytes, benthos, floating macroalgae, water column, and hyporheic zone) to ecosystem metabolism. La Choza stream is an autotrophic ecosystem during low flows and has gross primary production rates of up to 22 g O2 m-2d-1, which are among the highest reported in the literature and set an upper bound on how productive streams can be in the absence of light and nutrient limitations. Floating macroalgae provided most of the primary production (30-90%), whereas the hyporheic zone provided most of the ecosystem respiration (40-80%). The differential effects of high flows on the different functional compartments depressed the production:respiration ratio, suggesting a strong relationship between flow and metabolism. Thus, low flows enhanced primary production and led to diel dissolved O2 concentration oscillations between 0 and 25 g O2/m3. In contrast, high flow depressed primary production by an order of magnitude and increased ecosystem respiration. High production rates during the low-flow period and extreme physicochemical conditions (anoxia for 7-8 h on a daily basis) may be typical in this type of ecosystem during extended low-flow periods.Fil: Acuña, V.. Swiss Federal Institute of Aquatic Sciences and Technology; Suiza. Universidad de Girona; EspañaFil: Vilches, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable; ArgentinaFil: Giorgi, Adonis David Nazareno. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable; Argentin

Metabolismo de productores de un arroyo pampeano

Low current velocities, high nutrient levels, the lack of riparian forest vegetation, and the development of dense and rich macrophyte communities characterize many Pampean streams. The objective of this study was to describe the most important sources of production and respiration in different communities of a pampean stream, and to compare the energetic support of the trophic web in streams of other places. Production and respiration estimations were carried out using clear and opaque acrylic chambers in the same reach of the stream, in two opportunities in summer and one opportunity in winter. The results indicated that the macrophyte community is the most important one in capturing and transforming light energy, although the epiphyton and phytobenthos communities support many herbivorous and are the bottom of the trophic web at this stream. Therefore, the gross production is higher than many others are streams but no the food offer to grazers.Facultad de Ciencias Naturales y Muse

Los indicadores biológicos como herramientas de gestión de la calidad del agua

Tradicionalmente se usaron los análisis físico-químicos y químicos para el monitoreo de las alteraciones antrópicas de los ambientes acuáticos naturales. Luego surgieron otras alternativas, como el estudio de los cambios que producen los impactos antrópicos en las comunidades biológicas. La diferencia entre las comunidades afectadas por diferentes grados de contaminación y las que se encuentran en un lugar “prístino” o de “referencia”, puede ser utilizada para establecer una escala de “calidad biológica del agua”. Así surgió como herramienta el “Indicador Biológico de Calidad del Agua” o “Bioindicador”. A esto se agregaron luego conceptos más integradores: el “estado ecológico o integridad ecológica” que además del estado del agua, incorpora el de su entorno, así como su capacidad de mantenerse en el tiempo. Aquí se presentan estos conceptos, y se discute su rol en la comunicación y educación, ya que esta información puede ser fácilmente accesible para toda la comunidad, desde escolares hasta pobladores locales, gestores, políticos y público en general.Traditionally, physical-chemical and chemical analyses were used to monitor anthropic alterations of natural aquatic environments. Then other alternatives emerged, such as the study of the changes that the anthropic impacts produce in the biological communities. The difference between communities affected by different degrees of pollution and those in a “pristine” or “reference” place can be used to establish a “biological water quality” scale. Thus the “Biological Indicator of Water Quality” or “Bioindicator” emerged as a tool. Later, a more integrative concept was developed: the “ecological state” or “ecological integrity” that also incorporates the status of its environment, as well as its ability to maintain itself over time. We present these concepts here and discuss their role in communication and education as this information can easily be accessible to the entire community, from schoolchildren to local people, managers, politicians, and the general public.Fil: Dominguez, Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biodiversidad Neotropical. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Biodiversidad Neotropical. Instituto de Biodiversidad Neotropical; ArgentinaFil: Giorgi, Adonis David Nazareno. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable; Argentin

Temporal variation of the periphyton biomass of Egeria densa Planch: In a pampean stream

Se analiza la variación de descriptores de la biomasa del perifiton (peso seco, peso orgánico, y clorofila-a) sobre Egeria densa durante 21 meses de muestreo en el arroyo Las Flores, un arroyo pampeano afluente del Río Luján. El porcentaje de materia orgánica en las muestras de perifiton varía entre 10 y 80. El porcentaje de clorofila en relación al peso seco varía entre 0.10 y 3 y entre 0.6 y 32 en relación al peso seco orgánico. La variación espacial dentro del stand de E. densa fue mayor que la variación temporal. Los cambios en la biomasa perifítica también se relacionan con los factores que afectan al desarrollo de autótrofos y heterótrofos tales como las lluvias, velocidad del agua, la temperatura y la biomasa de macrófitas. El perifiton esta dominado por autótrofos en casi todos los casos, excepto luego de fuertes lluvias cuando se incrementa la proporción de heterótrofos o de material detrítico.  La componente autotrófica del perifiton se reduce en meses de alta temperatura por el sombreado producido por las macrófitos flotantes sobre E. densa. El predominio de autótrofos en el curso del año permitiría sustentar el gran número de herbívoros hallados en el arroyo en otros estudios.The variation of the periphyton biomass descriptors (dry weight, organic weight, and chlorophyl!-a) on Egeria densa is analyzed during 21 months of sampling at the Las Flores stream, a pampean stream that flows into the Lujan River. The percentage of organic matter in the periphyton samples varies between 10 and 80 %. The percentage of chlorophyl!-a in relation to dry weight ranges from 0.10 to 3, and between 0.6 and 32 in relation to the dry organic weight. The spatial variation inside the E. densa stand was higher than the temporal variation. The changes in the periphytic biomass are also associated with the factors that affect the development of autotrophs and heterotrophs, such as precipitations, water velocity, temperature, and macrophyte biomass. The periphyton is dominated by autotrophs in almost al! of the cases, except after heavy rains when the proportion of hetero-trophs or detritic material increases. The autotrophic component of the periphyton is reduced in high temperature months by the shading produced by the floating macrophytes on E. densa. The predominance of autotrophs throughout the year would allow the support of the high number of herbivorous found in the stream in other studies.Fil: Giorgi, Adonis David Nazareno. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Feijoó, Claudia Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentin

Evaluación de una matriz para decolorar efluentes textiles utilizando Pleurotus ostreatus

Los efluentes industriales textiles constituyen un graveproblema de contaminación ambiental. Dada la grancomplejidad y diversidad de los compuestos utilizadosen los procesos y la magnitud en que son eliminados enlos efluentes, producen un gran impacto sobre los ecosistemasacuáticos receptores. Con el objetivo de evaluarla capacidad de una matriz biológica conformada pormicelio para decolorar efluentes textiles, se realizaronuna serie de experimentos estáticos, en los que se utilizómicelio de Pleurotus ostreatus, desarrollado en avenacomo sustrato e incubado en oscuridad durante 25 díasa 25°C. Se comprobó que el micelio continuó creciendoadecuadamente al exponerlo al efluente, aun cuandoéste no hubiera sido esterilizado. Además, se demostróque el tiempo necesario para la decoloración varía entre24 y 72 horas dependiendo de la intensidad del colordel efluente. Se encontró que la mejor relación sustratocolonizado por P. ostreatus (matriz)/efluente fue de 5%masa/volumen y se comprobó que dicha matriz de miceliopuede reutilizarse, aunque se reduce su capacidaddecolorativa. Los resultados indicaron que este sistemapodría ser utilizado para la decoloración de efluentesde industrias textiles, disminuyendo así su impacto sobrelos ecosistemas naturales.The textile industrial wastewaters cause a serious problem of environmental pollution. Given the complexity and diversity of the compounds used in the process and the high quantity to which they are released by the effluents, they produce an important impact on aquatic ecosystems. In order to evaluate the ability of a mycelium biological matrix to bleach textile effluents, a series of static experiments were conducted, in which mycelia of Pleurotus ostreatus grown in oatmeal and incubated in darkness for 25 days at 25°C were used. Results show that the mycelium continued to grow properly when exposed to the effluent even though it had not been sterilized, and that the time required for discoloration ranged from 24 to 72 hours, depending of the intensity of effluent coloration. It was estimated that the best matrix/effluent relationship was 5% mass/volume and that this mycelium matrix can be reused, although its discoloration capability would be lower. Results indicate that this system could be used for bleaching the effluents of textile industries, thus reducing their impact on natural ecosystems.Fil: Kravetz, Sebastián. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: González, Beatrìz. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Giorgi, Adonis David Nazareno. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján. Departamento de Tecnología; Argentin

Efectos de la exclusión de ganado sobre la calidad ambiental de un arroyo pampeano

For two years, records of channel morphology and quality of the bank on a section of a stream were made because the cattle farming have been excluded at a section of 500 meters of long near the bank and 10 meters at each bank. There were registered also changes in the aquatic vegetation and some physico-chemical parameters. Fish sampling was conducted annually to observe species presence and their relative abundance. It was detected a rapid improvement in the quality of banks and an increase of the richness of fishes in each sample. Contrary to expectations macrophyte richness was reduced and morphological heterogeneity of the channel is not increased. However, the stream ceased to be interrupted and started having more water in the entire stretch. This was as a result of reshaping the banks. Although this register should be validated with future surveys, the results suggest that the recovery of the banks is very fast and the runway and the fish colonization are staggered. Despite this, there was a clear recovery at the studied reach, with the exclusion of cattle in the area as the unique management practice.Facultad de Ciencias Naturales y Muse

Effects of macrophyte heterogeneity and food availability on structural parameters of the macroinvertebrate community in a Pampean stream

Environmental heterogeneity in natural ecosystems influences several parameters at the population and community levels. In freshwater ecosystems, habitat heterogeneity can be provided by macrophyte species with different structural shapes. Previous studies suggest that aquatic plants with more complex architectures will support higher number, biomass, and taxon richness of macroinvertebrates than plants with simpler shape. We investigated the influence of macrophyte structural heterogeneity (quantified by fractal dimension) and food availability (represented by epiphytic biomass) on several parameters (number of individuals, biomass, body size distribution, taxon richness, and diversity) of the macroinvertebrate community in a Pampean stream. Four submerged macrophyte species (Egeria densa, Elodea ernstae, Ceratophyllum demersum, and Stuckenia striata) and associated macroinvertebrates were sampled in late spring, summer, and autumn. Plants were photographed and fractal dimension was estimated from the images by the box-counting method. Fractal dimension was independent of plant surface area per unit of macrophyte biomass and differed significantly among species. Mean fractal dimension varied between 1.29 and 1.62, and increased following the sequence E. densa → S. striata → E. ernstae → C. demersum. Macrophyte species with higher fractal dimension supported a greater abundance of macroinvertebrates, especially those of small body size (500-1,000 lm); but fractal dimension was unrelated to macroinvertebrate biomass, richness, and diversity. However, overall animal biomass was significantly associated to the epiphytic abundance. Consequently, macrophyte heterogeneity influences macroinvertebrate density and body size distribution, while animal biomass depends on epiphytic food resources provided by plants.Fil: Ferreiro, Nicolas Andres. Universidad Nacional de Luján. Departamento de Ciencias Básicas. Laboratorio de Ecología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable; ArgentinaFil: Feijoó, Claudia Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable; ArgentinaFil: Giorgi, Adonis David Nazareno. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable; ArgentinaFil: Leggieri, Leonardo Ramón. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable; Argentin

La calidad del agua del río Luján (Buenos Aires) y el potencial aporte del biofilm para su evaluación

Luján River rises in the north-eastern part of Buenos Aires Province and flows through a lowland region where it joins the River Plate Estuary. The river’s upper basin comprises a rural area which is mainly used for extensive agriculture and livestock with industrial areas of minor influence. As moving downstream, densely populated urban regions develop and industrial activity increases. Samples were collected seasonally from August 2004 to August 2005 in 12 sampling sites located along the river basin, from its headwater tributaries (Los Leones y El Durazno streams) to the crossing of the national route 9, located in the river’s lower basin. In two out of the four sampling occassions, biofilm samples were taken with the aim of assesing to what extent the biofilm community fitted the degradation level indicated by the measured physical-chemical variables of the river water (particularly BOD; N; P and DO concentrations). The samples were taken with a 3 cm2 brush and piston from submerged surfaces of natural (“tosca”) or artificial substrates (piers; walls). Bacillariophyta generally dominates the biofilm, but there seems to be a relationship between the industrial and urban sewage discharges, the water quality and the relative abundance of the different biofilm groups. In the river reaches where a heavy load of effluents is discharged, an increment of Cyanophyceae is observed. In the reaches of intermediate degradation, associations of cyanophytes and euglenoids appear. Over the course of the river, the algae abundance diminishes along with the water quality degradation, but there are also reaches of recovery due to the river’s own processing capacity where no urban nor industrial wastewaters are discharged.Instituto de Limnología "Raúl A. Ringuelet