Abstract: Sewage effluents are one of the main anthropogenic stressors in Mediterranean rivers. The establishment of a cause-effect relationship is hindered in natural systems by the existence of confounding factors (i.e. biotic interactions). Here we analyzed the effects that anthropogenic stressors have on a mono-specific fish community (Iberian redfin barbel population, Barbus haasi) inhabiting the northern edge of its distribution range. Principal component analysis (PCA) was used to build synthetic environmental stressor gradients and the PCA scores for each gradient were used for general linear analysis. In Spring 2009, a total of 40 sampling sites were surveyed in Vallvidrera creek, 1,331 specimens were measured and weighed and 22 environmental variables were determined. Water quality was the main stressor gradient and caused a decrease in fish density, size (fish weight and length) and body condition factor. The QBR score was not related to the pollution gradient and the Index of Biotic Integrity (IBI), using fish as bioindicators in Catalonia, did not show significant differences between sampling sites. Our findings suggested that more measurements at the organism level are needed in IBIs, particularly in those regions with low species richness (e.g. Vallvidrera creek). Furthermore, our study revealed deleterious effects in those specimens exposed to sewage effluents, which corroborates the need for ongoing improvements in the treatment of sewage in the Mediterranean area.
Abstract: In this study, we report new data on the biodiversity and the geographic and bathymetric distribution of bryozoans collected during the ANT XXI/2 cruise (November 2003 to January 2004) in the Eastern Weddell Sea and Bouvet Island, and during the Spanish Antarctic expedition ECOQUIM (January 2006) in the South Shetland Islands. Our data on distribution were analysed together with previous studies carried out in the same regions. A total of 54 species of Antarctic bryozoans (206 samples), including a new species of the genus Reteporella were found. Two species were reported for the first time from Bouvet Island, one from the Weddell Sea and one from Spiess Seamount. Fifty-five per cent of all species identified were endemic to Antarctica. In the Weddell Sea, the regions of Austasen and Kapp Norvegia exhibit the highest relative species richness, followed by the Vestkapp region. Multivariate and cluster analyses revealed small-scale spatial variability in the community structure along depth and between localities.
Abstract: Sewage sludge production increases in Europe proportionally to the number of municipalities that put wastewater treatment plants into service. Recycling to soil is among the main sludge outlets, since amending with sludge meets requirements of efficient recycling of resources while providing organic matter for poor or degraded soils. As raw sludge contains substances potentially harmful for environmental and human health, it must be stabilized before application to the soil. We tested three kinds of anaerobically digested sludge, differing by the post-treatments they had undergone (dewatering, composting or thermal drying), for their effects on soil microbial activity, microarthropod density and biological soil quality quantified as QBS indicator. Our experimental treatments were set on plots located in a burnt Mediterranean forest and consisted of spreading sludge on the soil surface to achieve a dose of 6 Mg o.m. ha−1. Although amendment with any of the three kinds of sludge increased soil organic matter and nitrogen, thermally dried sludge caused a transitory increase of the soil microbial metabolic coefficient that we considered indicative of soil disturbance. One year after soil amendment, all sludge effects on the soil microbial activity had disappeared. When working with microarthropods’ density and biodiversity, no sludge improved soil biological quality, fresh digested sludge being the most detrimental, since it caused the decline of the most sensitive taxa (oribatid mites) and increased the density of soil forms resistant to disturbance and pollution (astigmatic mites and symphypleon collembolans). Sludge effects on soil microarthropods were still evident three years after soil amendment, which suggests that soil invertebrate diversity is less resilient to soil disturbance than global microbial metabolism.
