Boletín de la RSEHN. Sección Biológica

Se ha realizado un estudio de las cabeceras de los ríos Bergantes, Mijares y Palancia, situados al Este de la Península Ibérica. Para ello se han muestreado los primeros 2,5 km desde el nacimiento, es decir, desde la fuente más elevada aguas arriba. Fueron establecidas diez estaciones de muestreo en cada uno de los ríos, situadas a una distancia desde el nacimiento de 0, 20, 50, 100, 200, 400, 650, 1000, 1500 y 2500 m. Cada una de las estaciones se visitó periódicamente y de forma regular, realizándose dos campañas: primavera-verano y otoño-invierno. Todas las estaciones de un mismo río se muestrearon el mismo día para poder obtener así un seguimiento más continuo de los datos. Los principales objetivos que se han llevado a cabo en el presente trabajo son: conocer las comunidades de macroinvertebrados acuáticos que habitan en estas cabeceras; aplicar el índice biótico IBMWP (ÒIberian Biomonitoring Working PartyÓ) para determinar el grado de contaminación de las aguas; conocer las principales características fisicoquímicas del agua, estudiando la correlación existente entre el índice biótico aplicado y los parámetros fisicoquímicos analizados; interpretar, mediante análisis estadístico, la distribución geográfica de los taxones en relación con los factores fisicoquímicos y ambientales, así como la ordenación de las estaciones de muestreo en función de las especies y de los factores ambientales y fisicoquímicos más relevantes; aplicar el índice QBR (ÒQualitat del Bosc de RiberaÓ) para evaluar la calidad de estos ecosistemas de ribera y aplicar el índice ECOSTRIMED (ÒECOlogical STatus RIver MEDiterraneanÓ) para determinar el estado ecológico de los ríos.

A study of headwater ecosystems of rivers Bergantes, Mijares and Palancia located at the East of the Iberian Peninsula has been done. To do this the first 2.5 km from their furthest upstream source have been sampled. Ten sampling sites placed from the furthest upstream source at 0, 20, 50, 100, 200, 400, 650, 1000, 1500 and 2500 m were located at each river. Each sampling site was visited periodically twice: at spring-summer and autum-winter seasons. All sampling sites of the same river were sampled the same day to obtain a more continuous monitoring of the data. The main aims that have been achieved in this research are: to know the aquatic macroinvertebrate communities that live in these headwater ecosystems; using the biotic index IBMWP (ÒIberian Biomonitoring Working PartyÓ) in order to assess the water quality; to find out the main physico-chemical water characteristics; to study the existent correlation between the biotic index used and the physico-chemical parameters analised. Interpreting, with statistical analysis, the geographic distribution of the taxa in relation with the physico-chemical and environmental parameters, as well as the ordenation of the sampling points in relation with the species and the most relevant environmental and physico-chemical parameters; to use the QBR index (ÒQualitat del Bosc de RiberaÓ) to evaluate the quality of these riparian ecosystems and to use the ECOSTRIMED index (ÒECOlogical Status River MEDiterraneanÓ) to assess the ecological status of the rivers. At Bergantes headwater ecosystem 37 taxa were identified. The most frequent were: Chironomidae, Oligochaeta, Agabus sp., Caenis luctuosa, Eiseniella tetraedra and Coleoptera. The most abundant were: Chironomidae and Simuliidae families, the Baetis rhodani species, the Agabus genus and the Oligochaeta class. The biological indexes used, have proved that this headwater ecosystem is strongly altered, showing a low diversity concerning the macroinvertebrate communities, as well as an important alteration of its riparian forest. In general terms, these results are obtained as a consequence of the farms placed in the nearby, that throw high quantities of organic matter to the water. To summarize, ten sampling points were studied, three showed very bad water quality, one of them bad, and the other six an average quality. That is why it is impossible to set up reference sampling points in this headwater ecosystem. At Mijares headwater ecosystem 92 taxa were identified. The most frequent were: Habrophlebia fusca, Nemoura cambrica, Plectrocnemia sp., Limnephilidae, Chironomidae, Centroptilum luteolum, Paraleptophlebia submarginata, Amphinemura triangularis, Protonemura meyeri, Limnephilus rhombicus, Mesophylax impunctatus, Baetis sp., Stratiomyidae, Oligochaeta, Heptagenia sp., Capnia sp., Baetis rhodani, Leuctra sp., Ceratopogonidae, Isoperla grammatica, Agabus sp., Deronectes sp., Helodes sp. and Elmidae. The most abundant were: Gammaridae and Chironomidae families, the Elmis genus and the Paraleptophlebia submarginata species and the Amphinemura triangularis species. This headwater ecosystem displays a good water quality, the same as a good preservation of its riparian forest. In some places though, mainly at 400 m from its source, the riparian forest has been slightly altered by anthropical activity. To summarize, ten sampling points were studied, two showed a good ecological quality and the other eight very good, that is why three reference sampling points have been established from its source, at 0, 100 and 200 m. At Palancia headwater ecosystem 81 taxa were identified. The most frequent were: Baetis rhodani, Centroptilum luteolum, Paraleptophlebia submarginata, Hydropsyche siltalai, Sericostoma personatum, Baetis sp., Deronectes sp., Chironomidae, Oligochaeta, Eiseniella tetraedra, Hydropsyche sp., Polycentropus sp., Dytiscidae, Empididae, Ancylus fluviatilis, Hydroptila sp., Rhyacophilidae, Simuliidae, Protonemura meyeri, Agabus sp., Stratiomyidae, Plectrocnemia sp., Haliplus sp., Dicranota sp., Hydrophilidae and Rhagionidae. The most abundant were: the Baetis genus, the Paraleptophlebia submarginata species, the Chironomidae family, the Baetis rhodani species and the Simuliidae family. As the used biological indexes show, this headwater ecosystem presents an excellent healthy status, both the riparian forest and the water quality, which proves the very good ecological status in this plot. These results have made possible to establish two reference sampling points, those placed at 1000 and 1500 m from the river source.