Eco-geomorphological dynamics in contrasting Mediterranean rivers with different degrees of flow regulation

Aquesta tesi analitza l’efecte de les preses sobre el règim de cabals, el transport de sediments, la mobilitat de la llera, i la comunitat de macroinvertebrats en rius Mediterranis de la Península Ibèrica a diferents escales espacio-temporals. A gran escala espacio-temporal, els resultats mostren que la regulació modifica el règim de cabals reduint la magnitud i la freqüència de les crescudes. Aquest fet, juntament amb la disminució de l’aportació de sediments des d’aigües amunt, produeix una pèrdua de barres sedimentaries que són ocupades per la vegetació causant una ràpida estabilització la llera, limitant el dinamisme del riu i pot contribuir a la degradació de l’ecosistema fluvial. A petita escala (els rius Ésera i Siurana) es comprova que els embassaments retenen fins el 90% de la càrrega de sediment en suspensió, però l’aportació hídrica només es redueix en el cas de l’Ésera. En els trams d’aigües amunt, les partícules de la llera són mobilitzades de forma freqüent i s’observen canvis morfològics després de cada crescuda, mentre que els trams d'aigües avall es mantenen estables. En el cas del Siurana aquests canvis causen diferències notables en la composició taxonòmica dels macroinvertebrats, encara que la riquesa d’espècies es manté intacte. La densitat i la biomassa augmenten aigües avall però la biodiversitat disminueix. La tesi descriu i quantifica canvis en l’estructura bio-física i el funcionament de l’ecosistema fluvial en rius Mediterranis regulats i proporciona informació inèdita fins ara en el camp de la Eco-Geomorfologia.Esta tesis analiza el efecto de las presas sobre el régimen de caudales, el transporte de sedimentos, la morfología y la movilidad del cauce, y la comunidad de macroinvertebrados en ríos Mediterráneos de la Península Ibérica a diferentes escalas espacio-temporales. A gran escala espacio-temporal, los resultados muestran una reducción generalizada de la magnitud y la frecuencia de las crecidas que, juntamente con la reducción del suministro de sedimentos, produce una pérdida de barras que son ocupadas por la vegetación, hecho que estabiliza el cauce fluvial, limitando el dinamismo del lecho del río y puede contribuir a la degradación del ecosistema fluvial. En pequeña escala (los ríos Ésera y Siurana) se comprueba que los embalses retienen hasta el 90% de la carga de sedimentos en suspensión, aunque la aportación hídrica solo se reduce en Ésera. En los tramos de aguas arriba, las partículas del lecho son movilizadas frecuentemente y se observan cambios morfológicos después de cada crecida, mientras que los tramos de aguas abajo se mantienen estables. En el Siurana, estos cambios provocan diferencias significativas en la composición taxonómica de los macroinvertebrados en el Siurana, aunque la riqueza de especies se mantiene prácticamente intacta. Por otro lado, la densidad y la biomasa aumentan aguas abajo pero la biodiversidad disminuye. La tesis describe y cuantifica cambios en la estructura bio-física y el funcionamiento del ecosistema fluvial en ríos Mediterráneos regulados y proporciona información inédita en el campo de la Eco-Geomorfología.The effects of dams on river flow regimes, sediment transport, channel morphology, bed mobility and macroinvertebrate communities were studied in Mediterranean rivers of the Iberian Peninsula at multiple temporal and spatial scales. At the large spatio-temporal scales, results show that regulation changes their flow regimes, with a generalized reduction in flood magnitude and frequency. This, in addition to the decrease in downstream sediment supply, results in the loss of active bars as they are encroached by vegetation (channel stabilization). Geomorphic stabilization limits riverchannel dynamics and may contribute to the environmental degradation of the fluvial ecosystem. At the small scale (the Ésera and the Siurana rivers), the reservoirs trap up to 90% of the suspended load, although total runoff is only reduced in the Ésera. In the upstream reaches, riverbed material is frequently entrained and morphological changes were observed following floods, while the downstream reaches were stables. In the Siurana, damming causes significant differences in taxonomic composition of the benthic invertebrate communities, but the species richness remained almost the same. Density and biomass increase notably below the dam although diversity decreases. The thesis describes and quantifies changes on the bio-physical structure and functioning of the fluvial ecosystem in dammed Mediterranean rivers and provides comprehensive insights in the field of the Eco-Geomorphology

Esterases activities and lipid peroxidation levels in muscle tissue of the shanny Lipophrys pholis along several sites from the Portuguese Coast

9 pages, 2 figures, 4 tables.-- PMID: 18295805 [PubMed].-- Printed version published May 2008.This study is part of a project aiming to validate the use of the intertidal shanny Lipophorys pholis as a sentinel species in pollution monitoring in NW European marine ecosystems. To this end, a characterisation of acethylcholin (AChE), butyrylcholin (BChE) and propionylcholin (PrChE) esterases in L. pholis muscle was performed and the results indicated that AChE was predominant. Furthermore, the use of eserine sulphate and BW284c51 (0.64–800 μM), and iso-OMPA (0.08–16 mM), confirmed the measurement of true cholinesterases (ChEs) as well as the presence of pseudocholinesterases. The field application of these markers to L. pholis, sampled in seven locations along the Portuguese coast, revealed that fish were likely to be affected by neurotoxic compounds. This was indicated by the significant depletion of AChE (p < 0.05) in animals collected at urban and industrialised sites, compared with those from reference locations. The inclusion of a marker of effect, measured as lipid peroxidation levels in muscle tissue, also revealed the existence of site differences. Overall, the study further validates the utility of L. pholis in pollution monitoring studies.The present study was funded by a CSIC-GRICES agreement and Interreg III B “Atlantic Area” project EROCIPS.Peer reviewe

Responses of resources and consumers to experimental flow pulses in a temporary Mediterranean stream

Determining the resistance and resilience of resources and benthic invertebrates connected to instream refuges and species re-colonization in post-flood periods may help to elucidate mechanisms behind community recovery. This experiment simulated flow pulses in a small temporary stream in an extremely wet year, using upstream control and downstream flooded reaches at three sites in order to assess community resistance and resilience (benthos and drift), and analyse resources (periphyton and benthic organic matter) and invertebrates at pre- and post-flood time periods. The hyporheos was sampled in order to explore species exchanges with benthos. Fewer resources and benthic invertebrates at the beginning of the experiment were found than in previous studies when base flow conditions prevailed. Resource stocks and benthic invertebrates showed high resistance to the flow pulse. Interestingly, there was low resilience of benthic organic matter to natural seasonal flooding. Chlorophyll a did not recover after experimental floods; instead, it was reduced after floods, despite the more benign flow conditions and non-limiting irradiance levels, pointing to top-down control by consumers. Additionally, the experimental flood significantly disturbed only the invertebrate composition in the groundwater-fed stream, which was inhabited by the fewest adapted-to-flood-disturbances macroinvertebrates. Despite the low resilience observed, richness and densities of benthos increased during the study, evidencing progressive colonization. Around 50–60% of macroinvertebrates were present in both benthos and hyporheos. Richness increased after flooding, suggesting that the hyporheic zone could be the main source of colonizers. Three species traits characterized the hyporheos: small size, cocoons and feeders of microorganisms within the fine sediment matrix. The main results indicate that longer-than-normal flood periods in early spring may constrain invertebrate succession before the next summer drought in temporary streams. This study underscores the importance of hyporheic fauna as a significance source of colonizers, highlighting the importance of connectivity to the groundwater.</p

Cholinesterases activities and lipid peroxidation levels in muscle from shelf and slope dwelling fish from the NW Mediterranean: its potential use in pollution monitoring

12 pages, 2 figures, 7 tables.-- PMID: 18558422 [PubMed].-- Printed version published Sep 1, 2008.We selected muscle tissue from nine commercial fish species, seven teleosts and two elasmobranchs, frequently caught in the NW Mediterranean trawling grounds in two different habitats (the continental shelf at 53 m and the slope at 660 m) for cholinesterases (ChEs) characterisation and activities determination, as well as the measure of lipid peroxidation (LP) levels. Acethyl- (AChE), butyryl- (BChE) and propionyl- (PrChE) cholinesterase were chosen as exposure markers of neurotoxic chemicals/molecules and LP as an effect marker of oxidative damage. The use of diagnose inhibitors: eserine sulphate, iso-OMPA and BW284c51 confirmed the measurement of true ChEs as well as the presence of pseudocholinesterases. The present study has evidenced the existence of interspecies differences, especially between teleosts and elasmobranchs but not in relation to depth. Moreover, the good correlation observed between all ChEs in most of the studied fish, supports the use of AChE as neurotoxic marker in field pollution monitoring. The non-metric multidimensional scaling analysis identified the commercial species hake Merluccius merluccius, among teleosts, and the shark, Galeus melastomus, as more adequate sentinel species in commercial fishing grounds. AChE activity showed a relationship with the fish trophic level, while all ChEs revealed a relationship with the feeding habits (benthic, suprabenthic, pelagic) and the stomach fullness. BChE activity and LP levels were the only markers to show a relationship with their swimming capacity.This work was financed by the project BIOMARE (CTM2006-13508-CO2-02/MAR). Julian Ríos acknowledged a visiting fellowship to the ICM-CSIC from “Fondo Mixto de Cooperación Técnica y Científica México-España CSIC/CONACYT J200.142” awarded to L.M. García de la Parra.Peer reviewe