Trends in the chemistry of atmospheric deposition and surface waters in the Lake Maggiore catchment

The Lake Maggiore catchment is the area of Italy most affected by acid deposition. Trend analysis was performed on long-term (15-30 years) series of chemical analyses of atmospheric deposition, four small rivers draining forested catchments and four high mountain lakes. An improvement in the quality of atmospheric deposition was detected, due to decreasing sulphate concentration and increasing pH. Similar trends were also found in high mountain lakes and in small rivers. Atmospheric deposition, however, is still providing a large and steady flux of nitrogen compounds (nitrate and ammonium) which is causing increasing nitrogen saturation in forest ecosystems and increasing nitrate levels in rivers. Besides atmospheric deposition, an important factor controlling water acidification and recovery is the weathering of rocks and soils which may be influenced by climate warming. A further factor is the episodic deposition of Saharan calcareous dust which contributes significantly to base cation deposition.</p> <p style='line-height: 20px;'><b>Keywords: </b>trend, atmospheric deposition, nitrogen, stream water chemistry

Trends in the chemistry of atmospheric deposition and surface waters in the Lake Maggiore catchment

International audienceThe Lake Maggiore catchment is the area of Italy most affected by acid deposition. Trend analysis was performed on long-term (15-30 years) series of chemical analyses of atmospheric deposition, four small rivers draining forested catchments and four high mountain lakes. An improvement in the quality of atmospheric deposition was detected, due to decreasing sulphate concentration and increasing pH. Similar trends were also found in high mountain lakes and in small rivers. Atmospheric deposition, however, is still providing a large and steady flux of nitrogen compounds (nitrate and ammonium) which is causing increasing nitrogen saturation in forest ecosystems and increasing nitrate levels in rivers. Besides atmospheric deposition, an important factor controlling water acidification and recovery is the weathering of rocks and soils which may be influenced by climate warming. A further factor is the episodic deposition of Saharan calcareous dust which contributes significantly to base cation deposition. Keywords: trend, atmospheric deposition, nitrogen, stream water chemistry

Modelling the effects of atmospheric sulphur and nitrogen deposition on selected lakes and streams of the Central Alps (Italy)

International audienceThe dynamic model MAGIC was calibrated and applied to selected sites in north-western Italy (3 rivers, 10 alpine lakes) to predict the future response of surface water to different scenarios of atmospheric deposition of S and N compounds. Results at the study sites suggest that several factors other than atmospheric deposition may influence the long-term changes in surface water chemistry. At present the lumped approach of dynamic models such as MAGIC cannot represent all the processes occurring at the catchment scale. Climate warming in particular and its effects on surface water chemistry proved to be important in the study area. Furthermore the river catchments considered here showed clear signs of N saturation. This condition and the increasing concentrations of NO3 in river water were simulated using N dynamics recently included in MAGIC. The modelling performed in this study represents the first application of MAGIC to Italian sites. The results show that inclusion of other factors specific to the Mediterranean area, such as dust deposition and climate change, may improve the fit to observed data and the reliability of the model forecast. Despite these limitations, the model captured well the main trends in chemical data in both rivers and lakes. The outputs clearly demonstrate the benefits of achieving the emission reductions in both S and N compounds as agreed under the Gothenburg Protocol rather than making no further emission reductions. It was also clear that, besides the substantial reduction of SO4 deposition from the peak levels of the 1980s, N deposition must also be reduced in the near future to protect freshwaters from further acidification. Keywords: MAGIC, northern Italy, acidification, recovery, nitrogen saturatio

Studies on the phytoplankton of the deep subalpine Lake Iseo

This paper reports the results of investigations carried out on the chemical characteristics and phytoplankton community of Lake Iseo. Samplings were performed on a monthly basis from 1998 to 2000. At least three main algal groups dominated the community throughout the study period. The large Bacillariophyceae were dominant mainly during late winter and early spring (Aulacoseira spp., Melosira varians, Asterionella formosa), with few species able to maintain occasional positive growth also during mid summer and/or autumn (Fragilaria crotonensis and Diatoma elongatum). The thermal stability of the water column and silica depletion were the main factors responsible for the decline of the large spring diatoms. The subsequent growth of Mougeotia sp. (Conjugatophyceae) was favoured by its lower sinking rate and resistance to increasing grazing pressure by the dominant copepods (Copidodiaptomus steueri) and cladocerans (Daphnia hyalina × galeata). Among the cyanobacteria, the greater development of Planktothrix rubescens in the autumn months, with conditions of vertical homogenisation and decreasing Zeu/Zmix ratios, was favoured by its ability to survive at low light irradiances. The temporal replacement of these three groups constitutes the main sequence of the annual phytoplankton succession in Lake Iseo. A large development of other algal groups was recorded only in one or two of the three study years (e.g. Dinophyceae and Chlorococcales). The changes observed in the annual phytoplankton development are discussed in the light of differences in the spring fertilisation of the waters, caused by differences in the depth of the layer involved in the late winter and spring vertical mixing

A synoptic study of phytoplankton in the deep lakes south of the Alps (lakes Garda, Iseo, Como, Lugano and Maggiore)

This paper presents a synoptic account of the most important results emerging from studies on the phytoplankton communities in the deep southern subalpine lakes Garda, Iseo, Como, Lugano and Maggiore (DSL) in the second half of the 1990s. At present, the trophogenic layers of these lakes are trophically different, ranging from the oligo-mesotrophy of lakes Maggiore and Garda to the meso-eutrophy of lakes Iseo and Lugano. The research confirmed the existence of a common pool of species developing in the DSL, as already suggested by early studies conducted on a seasonal basis from the end of the 1970s to the first half of the 1980s. However, multivariate analyses (Correspondence Analysis, CA, and a subsequent application of Non Metric Multidimensional Scaling) demonstrated that the species in this common pool were developing differently or exclusively along a geographic and a trophic gradient. The major differences in the geographic distribution were found between the easternmost lakes (Garda and Iseo) and those farthest to the West (Lugano and, partly, Maggiore), with intermediate characteristics in Lake Como. These differences were due mainly to changes in the dominance relationships and only secondarily to compositional changes. The detection of the ultimate causes of these differences should take into account other factors not considered in the paper (i.e. the specific analysis of the food webs, local climatic conditions, hydrology and seasonal input of nutrients). Despite the observed differences, common patterns in the sequence of seasonal assemblages in the DSL could be recognised and defined. The second gradient in the species distribution identified by CA was strongly correlated with the principal trophic descriptors (algal biomass and total phosphorus); this meant that the phytoplankton taxa could be ranked along a trophic spectrum, from oligotrophy to eutrophy. A brief examination of the main differences which have historically arisen with the progress of eutrophication in the DSL showed that the species identified in this study as being indicative of more eutrophic conditions were increasing in importance in some of the lakes

Gender and sustainable livelihoods: linking gendered experiences of environment, community and self

In this essay I explore the economic, social, environmental and cultural changes taking place in Bolsena, Italy, where agricultural livelihoods have rapidly diminished in the last two decades. I examine how gender dynamics have shifted with the changing values and livelihoods of Bolsena through three women’s narratives detailing their gendered experiences of environment, community and self. I reflect on these changes with Sabrina, who is engaged in a feminist community-based organization; Anna, who is running an alternative wine bar; and Isabella, a jeweler, who is engaged in ecofeminist practices. My analysis is based on concepts developed by feminist political ecology: specifically, the theory of rooted networks from Dianne Rocheleau, Donna Haraway’s concept of naturecultures (and the work of J. K. Gibson-Graham on new economic imaginaries emerging from the politics of place. I aim to think with, reflect upon and provoke from the ‘‘otherwise’’, taking into account the lived relations entwining nature and gender. My article looks at the interconnections of gender, environment and livelihoods, attentive to the daily needs, embodied interactions and labours of these three women as part of a reappropriation, reconstruction and reinvention of Bolsena’s lifeworld. By listening to the stories of their everyday lives and struggles, I show the dynamic potential of the politics of place and the efforts to build diverse economies and more ethical economic and ecological relationships based on gender-aware subjectivities and values

Limnological research in the deep southern subalpine lakes: synthesis, directions and perspectives.

Based on a selection of 230 papers published during the last 15 years in international journals, the present work aims at evaluating the state of the art of limnological research in the deep southern subalpine lakes (DSL: Garda, Iseo, Como, Lugano and Maggiore). Historically, most of the limnological research was fostered by the need to find solutions to the problems connected with eutrophication and pollution. Many data are available on the thermal structure, algal nutrient concentrations and phytoplankton of the DSL, while other topics still remain more or less constrained to single lakes. Apart from this geographical bias, a number of aspects emerged from this synoptic view. Limnological research is still linked to the concept of scientific monitoring, while experimental studies and modelling are confined to specific niches; the integration of different disciplines is held back by the division of studies on different compartments; integration of studies and synoptic analyses at a macro regional scale have been carried out only for specific research areas. The DSL are increasingly threatened by new pressures (climatic change, excessive proliferation of toxic cyanobacteria, introduction of new species and new micropollutants) and by the interactions among these new and old stressors. In this rapidly changing situation, the paper emphasises the need to define criteria to be used to distinguish research able to produce relevant results and predictive models, which are essential elements for an efficient management of water resources