ESTUDIOS DE ZOOLOGÍA


1992

Última actualización: 03/07/2017  13:11:11  


1992 /Narcis Prat y María Rieradevall

Benthos of Spanish lakes and reservoirs

Resumen

A summary of the results from the study of benthos of lakes and reservoirs in Spain is provided, with a list of the species found to date. Spanish natural lakes are smaller than European lakes; the largest is Lake Sanabria, of glacial origin, which is 3 Km long and half a kilometer wide. Many are very small and situated in the mountains; more than 200 hundred have been recorded in Spain, but only in Lake Sanabria and Lake Banyoles have the benthos been studied. Lake Sanabria is a cold oligotrophic, monomictic lake with oxygen always present in the deepest zones. Its fauna is similar to that of other central European lakes, with Micropsectra contracta (a chironomid) as the dominan1 species. Lake Banyoles is a karstic, monomictic and multibasin lake; despite the low primary productivity, due to the abundante of sulphate in the water, the allochthonous inflow of organic matter and the inflow of water from bottom springs, the profunda1 environinent is very stressing for benthic fauna. Very low oxygen concentrations and high sulphide content in the water and sediments dueto meromixis mean that only the larva of the dipteran Chaoborus flavicans was present in one of the 5 basins of the lake. In other basins, when oxygen is available (no meromixis), the fauna is similar to that of the mineralized lakes of the Aegean region and some lakes in central Italia. On the other hand, preliminary data from the Pyrenean lakes and from Sierra Nevada ponds reveal no differences with northern cold lakes.

The largest lakes in Spain are the reservoirs. There are nearly 1000 and data are available on 100 of them, including the largest. In addition to oxygen and sulphide content in the bottom waters, water level fluctuation and high sedimentation rates are disturbance factors that prevented the organization of the community. Allochthonous inputs of organic matter are also an important factor both in the reservoirs and also in the small, oligotrophic lakes like Banyoles and Sanabria. As a result the meiofaunal loop is very important in many of the Spanish water bodies . For this reason the natural lakes and reservoirs of Spain are dominated by Oligochaeta, small crustaceans and the microcarnivore chironomids (such as Procladius, Cladopelma and Microchironomus) that feed on these meoifaunal elements. The phytophagous chironomids, like Chironomus, are only abundan1 in the shallow areas of mesotrophic and eutrophic reservoirs. This situation makes it difficult to apply the typological system of SAETHER which predicts with some confidence only the benthic communities of Spanish natural lakes above 1500 m in the Pyrenees or the ponds above 2000 m in Sierra Nevada mountains. Higher temperatures (which originate a longer stratification period), the presence of sulphate in the waters of the eastern part of Spain and high inputs of sediments and allochthonous organic matter seem to be the factors that originated the differences between the benthic profundal faunas of Spanish lakes and reservoirs and those of the temperate lakes of north and central Europe.

 

Consultar el trabajo completo:

  • Limnetica 8  Edita: Asociación Ibérica de Limnología (AIL)

ESTUDIOS DE BOTÁNICA


1996

1998 

 

 

 

Última actualización: 17/07/2017  18:11:11  


1996 / Juan José Aldasoro, Carlos Aedo, Jesús Muñoz, Caridad de Hoyos, José Carlos Vega, Ana I. Negro, Gonzalo Moreno 

A Survey on Cantabrian mires

Resumen

Se estudian 39 turberas cantábricas desde el punto de vista de las características químicas del agua y de las especies de carófitas, musgos y plantas vasculares que crecen en ellas. Un análisis de coordenadas principales de los parámetros químicos y climáticos permitió dividir las turberas en cuatro grupos: 1) turberas de tipo “fen”, pobres y continentales, 2) turberas tipo “fen”, entre pobres e intermedias continentales, 3) turberas tipo “fen”, intermedias atlánticas y 4) turberas tipo “fen”, ricas en cationes. Los mismos grupos fueron establecidos a partir del análisis de coordenadas principales de la matriz de presencia/ausencia de especies. Los dos ejes principales de ambas ordenaciones fueron la mineralización y la oceaneidad.

Del estudio de las preferencias de algunas de las plantas más representativas se concluyó que las especies de los grupos 1 y 4 son muy características, únicamente presentes en estos medios. Por el contrario, las de las turberas intermedias (grupos 2 y 3) pueden aparecer ocasionalmente en turberas pobres o ricas. En consecuencia las últimas parecen inadecuadas para su uso como indicadoras, pues están adaptadas a condiciones fluctuantes. También se discuten otras informaciones acerca de las preferencias ecológicas de las diversas especies.

El texto completo de este trabajo en Clic ¡


1998 / Caridad de Hoyos, Juan José Aldasoro, Manolo Toro, Francisco Comín

Specific composition and ecology of chrysophyte flagellates in Lake Sanabria (NW Spain)

Resumen

Lake Sanabria is a glacial lake located at 1000 m a.s.l. in NW Spain. Its water is characterised by a low content of mineral salts, rather low pH, and oligotrophic status, which are all currently viewed as being favorable for Chrysophyte growth and proliferation. The study of the phytoplankton at different depths of the water column for three years showed that Chrysophytes were one of the groups of algae less well-represented in the phytoplankton (1% and 8%, respectively, for numbers of cells and biovolume).

Ochromonas, Pseudopedinella, Mallomonas and Dinobryon were the more representative chrysophyte genera. D. cylindricum, D. divergens and D. crenulatum were some of the Dinobryon species observed. M. akrokomos, M. crassisquama and M. costata were among the most frequent Mallomonas species. Observations on the Chrysophyte cysts from samples of the lake sediment suggest that variability of representation is higher than in planktonic samples.

The maximum values of Chrysophyte biovolume were found in the nutrient-exhausted epilimnion of summer and autumn which could be related to the mixotrophic capabilities of several species.

El texto completo de este trabajo en Clic ¡