Alterations and changes that affect the conservation of the biodiversity of Estanho de Vilac (Aran Valley) (original) (raw)
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LIFE+LIMNOPIRINEUS: Conservation of aquatic habitats and species in high mountains of the Pyrenees
2020
Mire ecosystems found in Alpine mountains are of great ecological value, since their distribution is very limited by rough physiography and by Mediterranean climatic influence. Understanding how environmental factors together with varying water regime drive the vegetation patterns is a key step for the management and conservation of vulnerable mire systems. Here, we analyse the relationship between these abiotic drivers and the distribution of different plant community types in the Trescuro mire system. We set up 30 sampling points across the vegetation mosaic where pH, electrical conductivity, water table depth and ion concentration were recorded during the 2014 and 2015 summers. The results evidenced that variation in the water table level is the main driver for small-scale vegetation distribution, followed by the ion concentration. Soligenous communities, which are highly dependent on water runoff, were the most affected by drought events, and thus the most sensitive to eventual invasion by trees.
Long-term changes of macrophyte vegetation in lakes of the Dovinė river catchment area
2007
Changes of submerged vegetation over the last 50 years in lakes Dusia, Simnas, Žuvintas and Amalvas, related with re-arrangement of the Dovinė river basin and alteration of the hydrological regime are discussed. The study is based on reference information and data of recent field investigations. Most significant changes of submerged vegetation were revealed in the shallow Lake Žuvintas. Twenty species of submerged plants became extinct (8 Charophyta, 10 Potamogeton, 2 Bryophyta) in the period from 1961 to 2004. The group of extinct plants includes sparse in the lake and rare in Lithuania species (Tolypella prolifera, Nitella syncarpa, N. mucronata, Fontinalis hypnoides). Formerly abundant and dominant species, such as Chara globularis, C. strigosa, C. hispida, Nitellopsis obtusa, significantly decreased. The increase of the number of charophytes and their abundance in 1997 has indicated that reduction of inflow of nutrients from the basin can significantly improve the state of submerged vegetation in the lake. Significant changes took place only in the deepest (8–10 m) zone of the deep Lake Dusia (mean depth 15.7 m). Vegetation of this zone after damming did not recover and communities formed by filamentous algae and mosses became extinct. The zone of vegetation distribution reduced from 9 to 6 m depth limit. It is possible that in the last 50 years charophytes became extinct in Lake Simnas, whereas in Lake Amalvas pondweeds and possibly charophytes disappeared.
Effects of building up a dam in a shallow mountain lake(Baciver, Central Pyrenees, Spain)
Changes in the water, the sediment, and the structure and dynamics of the submerged macrophyte populations were studied after the building up of a dam in a high mountain Pyrenean lake in late summer 1990. The most outstanding variations in the physical and chemical features were: (a) a 5.5 m rise of the shore level, (b) a decrease in light transmittance into the water column, (c) an oxygen depletion in deep waters, coupled to a pH decrease and a rise in conductivity and cation concentration, (d) an increase in the total dissolved nitrogen (mainly ammonium) and phosphorus concentration in the water column, and (e) an increase in the reduced N-compounds (nitrite and ammonium) in the sediment pore-water of the Isoetes lacustris community, coupled to a decrease in nitrate. Changes in the chemical features seem to be related to the decomposition of organic matter provided by the flooded terrestrial subalpine meadows and shrubs, and the lake's submersed vegetation. Both the area occupied by the submersed vegetation and the number of macrophyte species suffered an important reduction with the daming of Lake Baciver. All the small, non dominant species (Eleocharis acicularis, Subularia aquatica and Isoetes setacea) dissappeared along the summer 1991. Sparganium angustifolium experienced a degradation (low density of shoots, short leaves) in 1991 which lead to its complete die off in spring 1992. The strong attenuation of the light regime could account for these losses. Isoetes lacustris individuals originally living below 0.6 m depth were completely dead in summer 1991, probably due to an oxygen depletion in winter time. The only surviving Isoetes plants (those originally living abo ye 0.6 m depth which were between 5.8 and 6.1 m depth after the dam) increased its leaf length as a response to the decrease in available irradiance. Although the number of produced leaves was slightly lower in 1991 than it was before the daming, the production of biomass increased, since leaves were longer. However, the lost of leaves was very high, resulting in a global decay of the population. In late spring 1992 surviving Isoetes lacustris had the remaining leaves very damaged, probably because of the winter anoxy, and no leaves were produced in summer 1992. This brought a complete dissapearence of the community in the lake.
Threats to the conservation of biotic integrity in Iberian fluvial ecosystems
Fluvial ecosystems are highly modified by human activity and the species inhabiting them are more imperiled than their aerial or oceanic counterparts. In addition, freshwater biodiversity per surface unit is higher than terrestrial and marine biodiversity. But from a conservation point of view rivers and streams have received less attention than any other natural system. Impacts in water and habitat quality, flow regime and biotic interactions can be considered the main factors responsible for the lack of biotic integrity in Mediterranean rivers. Dams and impoundments alter drastically the physical habitat structure and the ecological functioning of running waters. But at the same time also modify the flow regime. Biotic interactions are deeply altered by introduced invasive species, which are common and proliferate in reservoirs and other artificial lentic habitats. In this paper we have adapted this classification of the main human impacts on fluvial ecosystems to the Iberian situation summarising them in three groups: water pollution, damming, and introduction of invasive species. We discuss their effects on biotic integrity of running waters through some examples from some of our previous works. Pollution is treated in two alternative ways. Quantifying its importance in the drainage network of a large Mediterranean area in southern Spain, as well as analysing its effect on the structure of macroinvertebrate communities and otter (Lutra lutra) distribution. Invasive species are widespread in Iberian inland waters. We hereby present the spatial relationship between native fish communities and invasive centrarchids that populate the peninsula. Finally, the damming impacts are considered through the analysis of its role in the spread and establishment of the invasive species. All of them are just a few examples about how alterated is the natural composition and dynamics of Iberian rivers and streams, i.e. its biotic integrity. The challenge for the future lies in the efficient protection of the biodiversity of Iberian freshwaters in the face of increasing pressures on the aquatic resources. But the first step in preserving our rivers is the real recognition of the extent of the problem, particularly among scientists.
Water Resources Management, 2010
Lake Pamvotis, NW Greece is a shallow Mediterranean eutrophic lake that has changed drastically over the past 50 years. Strong effects, resulted mainly from anthropogenic causes, in the hydrological regime are shown for this area using long term hydrological data and a GIS system for extracting land cover/use changes. A set of aerial imagery acquired in 1945 through 2002 were used to monitor and assess the spatial and temporal changes in land cover/use, focused mainly on the lake’s surface area and its surrounding ecosystem (Natura 2000 area). The significance of the changes in land cover/use distribution within Pamvotis wetland is further discussed depicting the role of the anthropogenic influence on the fragile ecosystem that resulted in the shrinkage of lake’s habitats extent. The purpose of this analysis was to examine the long-term changes on macrophyte community composition, species occurrence and relative abundance with water quality and water level changes over the past century, using historical data, aerial photos and GIS techniques. The results showed that for the last 25 years annual water level fluctuation ranged from 70 to 159 cm. Water level starts decreasing in mid June and increasing again gradually from November until March–April. Intra annual water level fluctuation seems to be affected by land use for agricultural purpose through intensive irrigation and the summer drought as well. A dramatic decline of the submerged vegetation is apparent mainly attributed to anthropogenic pressures. Regarding the land cover/use changes, the most notable and significant alterations are concerning the urban development around the lake, the disappearance of wet meadows and the extension of reed beds. Finally it seems that water budget data as well as the response of the key eutrophication parameters are affected from both hydrological alterations and point/non-point pollution sources.
Limnetica, 2006
Hydrological disturbances, light availability and nutrients are the most relevant factors determining the structure of the biological communities in Mediterranean rivers. While some hydrological disturbances are able to induce catastrophic effects, which may cause a complete reset in physical and biological conditions, continued enrichment or changes in light availability are factors leading to the progressive shift in the communities of autotrophs and heterotrophs in the systems. Primary production in Mediterranean streams shows relevant seasonal changes which mainly follows the variations in light availability. In most forested streams, the algal community is shade-adapted. Nutrient enrichment (especially phosphorus) leads to marked increases in primary production, but this increase is not lineal and there is a saturation of algal biomass even in the most enriched systems. The heterotrophs (bacteria, fungi) are related to the pattern of DOC availability (which most depends on the seasonal discharge and leaf fall dynamics) and to the available substrata in the stream. It has been repeatedly observed that shorttime increases of extracellular enzyme activities are related to the accumulation of autochthonous (algal) and/or allochthonous (leaves) organic matter on the streambed during spring and summer, this being more remarkable in dry than in wetter years. Flow reduction favours detritus concentration in pools, and the subsequent increase in the density and biomass of the macroinvertebrate community. In Mediterranean streams collectors are accounting for the highest density and biomass, this being more remarkable in the least permanent systems, in accordance with the effect of floods on the organic matter availability. Nutrients, through the effect on the primary producers, also affect the trophic food web in the streams by favouring the predominance of grazers.
BOLETÍN GEOLÓGICO Y MINERO
Cerveriz), en el Parque Natural de Somiedo (Asturias), han sufrido una notable presión antrópica en tiempos recientes (minería metálica, pastoreo de ganado vacuno, actividades de represamiento y trabajos de canalización). Este trabajo presenta los resultados y principales conclusiones de un reciente estudio realizado en estos lagos, sobre los cuales no existía información previa. En base a perfiles de temperatura, conductividad, pH y ORP, así como de concentración de oxígeno disuelto, clorofila-a, carbono orgánico, nutrientes y metales disueltos, se discute el impacto de la presión antrópica sobre estos lagos. En el periodo de estudio (Julio a Septiembre, 2014-2016), estos lagos presentaron una marcada estratificación térmica y química con notables gradientes verticales como resultado de diversos procesos físicos y biogeoquímicos. Todos los lagos mostraron un buen estado ambiental sin aparente contaminación por metales. Sin embargo, este conjunto de lagos no es homogéneo en cuanto a la disponibilidad de nutrientes, productividad primaria, o déficit de oxígeno hipolimnético, existiendo un espectro de condiciones tróficas que van desde oligotróficas (El Valle) a eutróficas (Calabazosa). Esta tendencia parece estar provocada principalmente por la variabilidad del contenido en fósforo (p.ej., 10 µg/L P en El Valle frente a 35 µg/L P en Calabazosa), aunque los procesos erosivos en la cuenca también podrían estar contribuyendo a incrementar el consumo de oxígeno mediante el aporte de materia orgánica alóctona. Las zonas con mayor presencia de ganado (ej., El Valle) parecen presentar contenidos más altos en nitratos, aunque no puede establecerse una relación directa entre ganado y eutrofización. Palabras clave: eutrofización, explotación minera, gestión hidrológica, lagos de alta montaña, Parque Natural de Somiedo. Características hidrogeoquímicas de los lagos de Saliencia (Parque Natural de Somiedo, NO España): estado trófico y relación con diferentes presiones antrópicas