Les Algues de l'embassament de Can Borrell (Collserola, Barcelona)

Can Borrell is a small reservoir situated in the Collserola Range, near Barcelona. Its main physical characteristics are described, and benthic and planktonic algae are accounted for. The benthos is more diversified than plankton. Diatoms make up the most important group in the benthos, while Peridinium cinctum is the most abundant species in the plankton. There are no great changes in the populations over the year, but there is an increase in halophile forms during the summer

Using the rescaled range analysis for the study of hydrological records: The river Ter as an example

Water discharges into the Ter river have a strong influence on the water chemistry and on the dynamics of benthic cornmunities. For this reason, the temporal pattems followed by monthly runoff from 1 954 to 1 988 have been studied. From a statistical point of view, discharges show a very regular seasonal cycle, but in practice, climatic events introduce a source of variability on runoffs. To determine whether the series of 420 monthly discharges fluctuates with sorne regularity or at random, a rescaled range analilsis was made. The persistence (H) of the series of discharges was measured by the equation R / S = (T / 2) . In fact, H is a measure of the existence of clear trends or periodicities in the records of persistent stocastic processes. An additional measure of the persistence was obtained by means of the relationship D = 2 - H, where D is the local fractal dimensiono For comparative reasons, a random series of the same length, mean and standard deviation was generated and analysed in the same way as the Ter discharges were. The results were H = 0.68 and D = 1 .38 and H = 0.44 and D = 1 .52, for the Ter data and for the random series respectively. These results show that the simulated series is a case of ordinary Brownian motion while the Ter discharges series has an intermediate value of persistence. Because of the value of H in the Ter series, there are periods whose values were estimated by the autocorrelation function and the periodogram of the series. The results show the existence of short fluctuations of 3, 6 and 12 months deterrnining the seasonality of the annual cycle, and large fluctuations with periods of 5.5, 8.6, 1 0.1 and 11.7 months which can be considered an expression of cycles of circa 7 and 1 1 years.Water discharges into the Ter river have a strong influence on the water chemistry and on the dynamics of benthic cornmunities. For this reason, the temporal pattems followed by monthly runoff from 1 954 to 1 988 have been studied. From a statistical point of view, discharges show a very regular seasonal cycle, but in practice, climatic events introduce a source of variability on runoffs. To determine whether the series of 420 monthly discharges fluctuates with sorne regularity or at random, a rescaled range analilsis was made. The persistence (H) of the series of discharges was measured by the equation R / S = (T / 2) . In fact, H is a measure of the existence of clear trends or periodicities in the records of persistent stocastic processes. An additional measure of the persistence was obtained by means of the relationship D = 2 - H, where D is the local fractal dimensiono For comparative reasons, a random series of the same length, mean and standard deviation was generated and analysed in the same way as the Ter discharges were. The results were H = 0.68 and D = 1 .38 and H = 0.44 and D = 1 .52, for the Ter data and for the random series respectively. These results show that the simulated series is a case of ordinary Brownian motion while the Ter discharges series has an intermediate value of persistence. Because of the value of H in the Ter series, there are periods whose values were estimated by the autocorrelation function and the periodogram of the series. The results show the existence of short fluctuations of 3, 6 and 12 months deterrnining the seasonality of the annual cycle, and large fluctuations with periods of 5.5, 8.6, 1 0.1 and 11.7 months which can be considered an expression of cycles of circa 7 and 1 1 years

Integrating chemical and biological status assessment: assembling lines of evidence for the evaluation of river ecosystem risk

This paper describes various approaches to evaluating ecological risk in rivers affected by multiple chemical stressors, with emphasis on biofilm and invertebrate community responses. Metrics should be considered as different lines of evidence that, when weighted, form an advanced weight of evidence approach to establishing the environmental risk on a basin scale. Combination of field surveys to obtain observational data of communities, in situ experiments, toxicological sediment tests and a good chemical description of the medium (water and sediment) helps give an integrative view of the chemical and biological state of a river ecosystem. The greater and more distinct the variables used, the greater is our ability to identify the effects of major stressors impairing communities. Weight of evidence is an integrative methodology for tackling the challenge of determining causal relations and applying this knowledge in the decision-making processes of river management

Comparative study of algal communities in acidic and alkaline waters from Tinto, Odiel and Piedras River basins (SW Spain)

The distribution patterns of benthic algal assemblages in the Tinto, Odiel and Piedras rivers were analyzed during the winter of 2005 in 18 sampling stations. The main objective was to assess and compare the algal communities and parameters affecting them both in the zones affected by acid mine drainage (AMD) and in naturally alkaline waters. A total of 108 benthic diatom taxa and 31 non-diatom taxa were identified. Results showed large differences between algal communities in the two environments: Pinnularia acoricola, P. subcapitata and Eunotia exigua were the most frequent diatom taxa in regions affected by acid mine drainage, along with algae like Klebsormidium and Euglena mutabilis were the most relevant non-diatom taxa. In alkaline waters the dominant diatom taxa were Planothidium frequentissimum, Gomphonema angustum, Fragilaria capucina, and some species of Navicula (N. viridula, N. veneta or N. radiosa), accompanied by Oscillatoria and Anabaena as well as by streptophytes of the group of zygnemataceae and desmidiaceaeSe han analizado los patrones de distribución de las comunidades algales bentónicas en los ríos Tinto, Odiel y Piedras, sumando un total de 18 estaciones de muestreo visitadas durante el invierno de 2005. El objetivo principal ha sido evaluar y comparar las comunidades algales y los parámetros que las afectan tanto en zonas influenciadas por el drenaje ácido como en las zonas libres del mismo. Se han identificado un total de 108 taxones de diatomeas bentónicas y 31 taxones de otras algas. Se observaron grandes diferencias en las poblaciones de productores primarios en ambos tipos de ambientes: Pinnularia acoricola, P. subcapitata y Eunotia exigua fueron las diatomeas más frecuentes en los ambientes afectados por el drenaje ácido, acompañadas por algas como Klebsormidium y Euglena mutabilis. En las aguas alcalinas las diatomeas dominantes fueron Planothidium frequentissimum, Gomphonema angustum, Fragilaria capucina y algunas especies de Navicula (N. viridula, N. veneta o N. radiosa), acompañadas por Oscillatoria y Anabaena y estreptófitos del grupo de las zygnematáceas y de las desmidiácea

Composición y ciclo de pigmentos clorofílicos en las poblaciones del fitobentos del rio Ter durante un período de nueve meses.

Composition and seasonal variations of the chlorophyllic pigments in phytobcnthos assemblages of the Ter river along a nine-month period. Dynamics of pigments were studied in eighteen sites in the Ter river basin during a túne-month period. Clorophyll a has been revealed as the most abundant form of ehlorophyllic pigmenls throurih an HPLC analysis. Highest chl a concentrations were observed downstream the reservoirs (around 300 mg/mí and in sorne calcareous tributaries. Minimal values were recorded in the headwaters (20-50 mg/m2 ) and in somne siliceous mountain tributaires. Spring and summer were the periods when the chl a concentration reached the highest values in the basin, with lower ones in winter. The phaeopigment concentration was imponant during summer and winter, but was near to zero during spring, suggesting chl a was completely active at this time. The D43()/D66.5 ratio was around 2 always. Correlation analysis and PCA carried out between physico-chemical variables and ch! a values suggested a clear arrangement with salinity and nutriem concentralion. In fact, an stepwise regression analysis carried out with the five first principal components of PCA, pointed out that the pigment concentration is a result of the linear combination of river salinity (space) and water flow (time). The sites of the middle stretch in the axis of the river, seem to be the most favoured by this combination, mainly during spring and summer.Composition and seasonal variations of the chlorophyllic pigments in phytobcnthos assemblages of the Ter river along a nine-month period. Dynamics of pigments were studied in eighteen sites in the Ter river basin during a túne-month period. Clorophyll a has been revealed as the most abundant form of ehlorophyllic pigmenls throurih an HPLC analysis. Highest chl a concentrations were observed downstream the reservoirs (around 300 mg/mí and in sorne calcareous tributaries. Minimal values were recorded in the headwaters (20-50 mg/m2 ) and in somne siliceous mountain tributaires. Spring and summer were the periods when the chl a concentration reached the highest values in the basin, with lower ones in winter. The phaeopigment concentration was imponant during summer and winter, but was near to zero during spring, suggesting chl a was completely active at this time. The D43()/D66.5 ratio was around 2 always. Correlation analysis and PCA carried out between physico-chemical variables and ch! a values suggested a clear arrangement with salinity and nutriem concentralion. In fact, an stepwise regression analysis carried out with the five first principal components of PCA, pointed out that the pigment concentration is a result of the linear combination of river salinity (space) and water flow (time). The sites of the middle stretch in the axis of the river, seem to be the most favoured by this combination, mainly during spring and summer

Scarcity and multiple stressors in the Mediterranean water resources: The SCARCE and GLOBAQUA research projects

The Mediterranean basin is one of the regions of the world most vulnerable to global change and one of the “hot spots” for predicted problems in water availability. Current climate change models forecast that the Mediterranean region will register increased summer drought and stronger rainfall events. Since freshwater ecosystems deliver important services to society, water scarcity affects both ecosystems and humans. Within this context, two different research projects have assembled a multidisciplinary team of leading scientists in the fields of hydrology, chemistry, ecology, ecotoxicology, economy, sociology, engineering, and modeling to study the interaction of multiple stressors with respect to pressure on water resources. SCARCE (2009-2014), with the full title of “Assessing and predicting effects on water quantity and quality in Iberian Rivers caused by global change,” focuses on the Mediterranean river basins of the Iberian Peninsula. GLOBAQUA (2014-2019), with the full title “Managing the effects of multiple stressors on aquatic ecosystems under water scarcity,” expands the area of concern to several Mediterranean basins in Europe. Both research projects link basic research aspects with management practices and policy implications in a single framework. SCARCE is funded by the Spanish Ministry of Economy and Competitiveness through the Consolider-Ingenio 2010 program (CSD2009-00065), whereas GLOBAQUA has the financial support of the European Communities 7th Framework Programme, under Grant Agreement No. 603629-ENV-2013-6.2.1-Globaqua.This work has been supported by the Spanish Ministry of Economy and Competitiveness through the project SCARCE of Consolider-Ingenio 2010 program (CSD2009-00065). It has also received funding from the European Communities 7th Framework Programme under Grant Agreement No. 603629-ENV-2013-6.2.1-Globaqua. This work has been partly supported by the Generalitat de Catalunya (Consolidated Research Group: Water and Soil Quality Unit 2009-SGR-965). Special thanks are due to all partners of the SCARCE and GLOBAQUA consortium and the peer review panels for ensuring quality results and fruitful collaboration within the projects.Peer reviewe

Effects of riparian vegetation removal on nutrient retention in a Mediterranean stream

We examined the effects of riparian vegetation removal on algal dynamics and stream nutrient retention efficiency by comparing NH4-N and PO4-P uptake lengths from a logged and an unlogged reach in Riera Major, a forested Mediterranean stream in northeastern Spain. From June to September 1995, we executed 6 short-term additions of N (as NH4Cl) and P (as Na2HPO4) in a 200-m section to measure nutrient uptake lengths. The study site included 2 clearly differentiated reaches in terms of canopy cover by riparian trees: the first 100 m were completely logged (i.e., the logged reach) and the remaining 100 m were left intact (i.e., the shaded reach). Trees were removed from the banks of the logged reach in the winter previous to our sampling. In the shaded reach, riparian vegetation was dominated by alders (Alnus glutinosa). The study was conducted during summer and fall months when differences in light availability between the 2 reaches were greatest because of forest canopy conditions. Algal biomass and % of stream surface covered by algae were higher in the logged than in the shaded reach, indicating that logging had a stimulatory effect on algae in the stream. Overall, nutrient retention efficiency was higher (i.e., shorter uptake lengths) in the logged than in the shaded reach, especially for PO4-P. Despite a greater increase in PO4-P retention efficiency relative to that of NH4-N following logging, retention efficiency for NH4-N was higher than for PO4-P in both study reaches. The PO4-P mass-transfer coefficient was correlated with primary production in both study reaches, indicating that algal activity plays an important role in controlling PO4-P dynamics in this stream. In contrast, the NH4-N mass-transfer coefficient showed a positive relation-ship only with % of algal coverage in the logged reach, and was not correlated with any algal-related parameter in the shaded reach. The lack of correlation with algal production suggests that mechanisms other than algal activity (i.e., microbial heterotrophic processes or abiotic mechanisms) may also influence NH4-N retention in this stream. Overall, this study shows that logging disturbances in small shaded streams may alter in-stream ecological features that lead to changes in stream nutrient retention efficiency. Moreover, it emphasizes that alteration of the tight linkage between the stream channel and the adjacent riparian zone may directly and indirectly impact biogeochemical processes with implications for stream ecosystem functioning