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sábado, 15 de julio de 2017

AGRHYDROM: Poster in SEFS10 conference


We are back with a new update on AGRYDROM project!

From the 2nd  to the 7th of July the 10th SEFS conference took place in Olomouc (Czech Republic). In this conference we presented a poster (click here to download it) with the main objectives of the project, the participant groups and the expected results. We have to say that we received a great feedback and some new ideas on data analysis!




Moreover, we took this opportunity to meet with all the AGRHYDROM participants that attended the conference and share ideas and impressions. One of the main concern was related to the dry hydrological year that we are facing (some groups found their streams dry before they could sample the contraction phase) and that is making us rearrange the timetable scheduled at the beginning of the project.


















So, for those who haven’t sampled in contraction phase, good luck!! Let’s hope that there are still some more streams with flowing waters!


Edurne and Rubén

domingo, 18 de junio de 2017

DOMIPEX project: collaborative research meet large-scale stream ecology

El pasado mes se publicó en Limnetica – 36 (1): 67-85 (2017) el primer artículo derivado del proyecto colaborativo entre Jóvenes AIL, DOMIPEX, titulado “Local and regional drivers of headwater streams metabolism: insights from the first AIL collaborative project”. Sus autores, un equipo multidisciplinar formado por 35 limnólogas y limnológos de mas de 7 paises, han preparado un resumen para el blog J-AIL.




Los ecosistemas fluviales tienen un papel esencial a la hora de vertebrar el paisaje, a parte de la continuidad longitudinal aguas abajo, están altamente conectados con los sistemas terrestres adyacentes donde hay un intercambio constante de energía y materiales.  Por ello, cuando definimos un ecosistema fluvial hay que considerar tanto la biota presente como las interacciones biológicas, físicas y químicas que tienen lugar. Este conjunto de interacciones es el que determina el funcionamiento del sistema, es decir, los flujos de materia y energía. Un método integrador de estudiar el funcionamiento de los ríos es a través del metabolismo fluvial.  Este consiste básicamente en la medida del intercambio de oxígeno entre la biota y su medio y cuenta con dos descriptores básicos: por un lado, la producción primaria bruta (PPB), que es la generación de oxígeno por la comunidad autotrófica del río y por otro, la respiración del ecosistema (RE), que es el consumo de oxígeno por parte de todos los organismos fluviales.

En este trabajo nos preguntamos: ¿Qué factores controlan el metabolismo de un río? ¿Varían entre regiones o estaciones? Para responder esas preguntas, es necesario estudiar el río como parte de la cuenca hidrográfica, y así, plantear en qué medida el paisaje y el clima afectan a su funcionamiento. Tener información sobre ríos muy diversos geográficamente es fundamental a la hora de entender los factores que controlan el metabolismo a escala global.

El primer experimento colaborativo convocado por la AIL nos ofreció la oportunidad de colaborar con grupos de jóvenes de diferentes áreas geográficas. En total, se muestrearon diez ríos de cabecera en los meses de verano y otoño en varias bioregiones climáticas desde el sur de Alemania al sur de España. En dichos ríos, se determinó la magnitud y variabilidad de la PPB y la RE mediante el método de canal abierto. Asimismo, se examinaron los factores climáticos, hidrológicos y físico-químicos que potencialmente pueden afectar las tasas metabólicas fluviales.
Los ríos estudiados presentaron valores muy contrastados – un valor de PPB entre 0.06 y 4.33 g O2 m–2 día–1 y un valor de RE de 0.72 y 14.20 g O2 m–2 día–1 –. No obstante, a excepción del río más meridional, todos ellos presentaron tasas más altas de respiración que de producción. Dicho resultado sugiere que los ríos de cabecera muestreados se abastecen mayoritariamente de las aportaciones de materia orgánica, como por ejemplo la hojarasca del bosque de ribera, la cual es indispensable para el funcionamiento del río. Además, no se encontraron diferencias en el metabolismo fluvial entre los dos períodos muestreados (verano y otoño).

La comparación entre los ríos estudiados indicó que no sólo las características locales del tramo estaban relacionadas con el metabolismo (por ej. la granulometría del lecho del río o la temperatura del agua), sino que los factores regionales eran esenciales para entender el funcionamiento fluvial. De estas características, destacó el papel de la climatología, que afectaba tanto a la producción como a la respiración del ecosistema. Además, los impactos humanos en la cuenca, derivados de usos agrícolas o urbanos, también tuvieron un efecto desacatado en la respiración fluvial.
Con todo ello, este estudio pone de manifiesto la importancia de incluir el paisaje y los factores climáticos a la hora de determinar y entender el funcionamiento de nuestros ríos, y muestra la experiencia positiva de una red coordinada de jóvenes investigadores para lograr retos científicos en una amplia escala geográfica.

Podéis encontrar el artículo completo aquí¡¡Esperamos que lo disfrutéis!!

domingo, 4 de junio de 2017

Leaf litter decomposition is a good tool to assess the effects of acidification on stream health


New research on functional stream ecology by Young AIL researchers

  • Leaves are a key source of energy for small forest streams
  • Small bugs (invertebrates) and microbes (bacteria and fungi) feed on these leaves, being key to transfer leaf energy to bigger animals such as fishes or birds
  • The rate at which bugs and microbes decompose leaf litter (litter decomposition) is tested as a measure of river health in response to human-caused stream acidification
  • Litter decomposition was strongly reduced in acidified streams
  • The magnitude of the reduction depends on river geology and the presence of bugs
  • Litter decomposition can be a useful tool to assess stream health

Text in Spanish and Portuguese

The burning of fossil fuels (in the industry or cars), the use of fertilizers and cattle production release large amounts of sulfur dioxide, nitrogen oxides and ammonia into the atmosphere. There, these compounds originate acid substances that can return to the earth’s surface as acid rain or dry acidic deposition (atmospheric acid deposition). Atmospheric acid deposition affects large areas worldwide, and is a transboundary problem as acid-forming substances released into the atmosphere can be transported over long distances and affect areas far away from where they originated. Atmospheric acid deposition poses more problems in acid-sensitive regions, which are regions with low buffering capacity, as those located at high elevation, where rainfall is high and soil thickness is low, and with weathering-resistant bedrock (for example, siliceous rocks can’t counteract acidity). In these regions, acid deposition leads to decreases in the concentrations of base cations (e.g., calcium, magnesium, which are essential elements for life), increases in the concentration of sulfur and nitrogen, and liberation of aluminum in the soil. This all translates into acidic water bodies, which may cause severe damage to freshwater organisms and to the benefits we get from them (such as clean water or angling).
The assessment of stream health is generally based on the presence of sensitive aquatic organisms. However, these indicators don’t necessarily inform about the capacity of streams to function and provide benefits. Therefore, it is crucial to understand how stream functions respond to acidification to create useful indicators of stream health.
Leaf litter decomposition is a fundamental ecosystem function in small forest streams. The rate at which litter decomposes depends on litter characteristics. Soft litter with high nutrient concentration decomposes faster than more recalcitrant litter, since microbial colonization is faster and microbial activities are higher. Leaf litter decomposition is also faster in the presence of bugs. Stream acidification generally slows down litter decomposition rates, as a result from inhibited microbial activity and disappearance of acid-sensitive shredders (bugs that feed on leaves). Leaf litter decomposition is thus particularly interesting as an assessment tool of acidification effects on stream functions since it is a key stream process, which has been widely studied and whose response to acidification can be predicted a priori.
Recently, a study carried out by Verónica Ferreira from the University of Coimbra (Portugal) and François Guérold from the University of Lorraine (France), and published in Ecological Indicators, assessed the potential for leaf litter decomposition to be used as an assessment tool to detect acidification effects on stream functions by means of a field experiment. The authors individually enclosed three leaf types differing in their suitability for bugs and microbes (alder Alnus glutinosa, sycamore Acer pseudoplatanus, and beech Fagus sylvatica) in fine mesh (where bugs cannot enter) and coarse mesh bags (both bugs and microbes can enter). The litter bags were incubated along an acidification gradient in two areas differing in geology in the Vosges Mountains, north-eastern France (Figure 1). This allowed the authors to assess if the response of litter decomposition to acidification depends on leaf type, mesh size, geology and acidification level. Also, to assess if the effects of acidification are consistent across studies, authors performed a meta-analysis, which combined the results of 17 empirical studies comparing reference and acidified streams.

Figure 1. Circumneutral stream flowing through granite bedrock in autumn (A) and an acidic stream flowing through sandstone bedrock in spring (B). Photos: François Guérold.
The authors of this study showed that acidification reduced litter decomposition in their field study by an average of 64% (Figure 2A). This reduction was quite similar to the overall result observed in the meta-analysis (63%, Figure 2B). The decline in decomposition rate was proportional to the acidification degree.
This study found that the effect of acidification was similarly strong for the three types of leaves, which suggests that decomposers are inhibited to a similar degree in leaves with distinct characteristics. On the other hand, authors found that decomposition resulting from bugs was more severely reduced by acidification than microbial-driven decomposition, although effects were strong for both mesh sizes. This probably occurred because most leaf-decomposing bugs are acid-sensitive. Finally, authors also showed that acidification caused a greater reduction in litter decomposition on streams flowing through sandstone rocks compared to those draining granite bedrocks, although the reduction of leaf decomposition by acidification was strong for both geological areas.
The effects of acidification on litter decomposition were overall strong and robust to leaf type, mesh size and geology. This supports the proposal of using litter decomposition as an indicator of stream health.

Figure 2. Inhibition (%, ±95confidence limit) of leaf litter decomposition in acidified streams, overall and as a function of leaf type, mesh size and geology in the field study (A) and in the published studies (B); significant inhibition is indicated by black symbols. Within each category, levels with the same letter do not significantly differ.
Ferreira V. & Guérold F. 2017. Leaf litter decomposition as a bioassessment tool of acidification effects in streams: evidence from a field study and meta-analysis. Ecological Indicators 79: 382–390, doi: 10.1016/j.ecolind.2017.04.044