112 research outputs found
Algal biomass and macroinvertebrate dynamics in intermittent braided rivers: new perspectives from instream pools
Perennial streams and rivers are now largely subjected to fragmentation and lentification processes due to flow reduction, which creates a number of lateral habitats with different degrees of hydrological connectivity. These habitats have environmental conditions and biotic interactions that can be far divergent than those of main channel habitats. However, they remain largely unexplored, especially in temperate regions. We here focused on studying algal dynamics and their interactions with aquatic invertebrates across mesohabitats (i.e., main channel, secondary channel, pools) in streambeds under both normal and low flow conditions. We selected four watercourses in the Po Plain (northern Italy), where we detected the main dynamics and drivers of algal and invertebrate communities by applying mixed effect modelling. A clear algal growth trend was detected in summer, and was similar for all mesohabitats, but with temporal decoupling and doubled values in pools. Mesohabitat and time were central factors in driving benthic algae dynamics that, in turn, negatively affected aquatic invertebrates. Hydrology and algae seemed to have a mutually reinforcing effect on macroinvertebrates by reducing almost all the investigated metrics. By considering future projections on further regime shifts in lotic systems, loss of biodiversity driven by algal blooms could become a major concern, and also for potential cascade impacts on other biotic compartments of river networks
Physical habitat modeling for river macroinvertebrate communities
Habitat models rarely consider macroinvertebrate communities as ecological targets in rivers. Available approaches mainly focus on single macroinvertebrate species, not addressing the ecological needs and functionality of the whole community. This research aimed at providing an approach to model the habitat of the macroinvertebrate communities. The study was carried out in three rivers, located in Italy and characterized by a braiding morphology, gravel riverbeds, and low flows during the summer period. The approach is based on the recently developed Flow-T index, together with a Random Forest (RF) regression, which is employed to apply the Flow-T index at the mesohabitat scale. Using different datasets gathered from field data collection and 2D hydrodynamic simulations, the model was calibrated in the Trebbia River (2019 field campaign) and validated in the Trebbia, Taro, and Enza rivers (2020 field campaign). The RF model selected 12 mesohabitat descriptors as important for the macroinvertebrate community. These descriptors belong to different frequency classes of water depth, flow velocity, substrate grain size, and connectivity to the main river channel. The cross-validation R2 coefficient (R2cv) of the training dataset was 0.71, whereas the R2 coefficient (R2test) for the validation dataset was 0.63. The agreement between the simulated results and the experimental data shows sufficient accuracy and reliability. The outcomes of the study reveal that the model can identify the ecological response of the macroinvertebrate community to possible flow regime alterations and river morphological modifications. Lastly, the proposed approach allowed to extend the MesoHABSIM methodology, widely used for the fish habitat assessment, to a different ecological target community. Further applications of the approach can be related to ecological flows design in both perennial and non-perennial rivers, including river reaches in which fish fauna is absent
Civil society participation in international governance : the UN and the WTO compared
Civil society participation has become a buzzword in the debate about the legitimacy and accountability of international governance. Many organizations, prominently among them the World Trade Organization (WTO), have come under considerable pressure to open up their policy-making process towards non-state actors. Although the WTO has become more transparent in recent years, direct stakeholder access to its policy making is still denied. This situation is often contrasted with that at the United Nations (UN), where there is (allegedly) much more formally regulated and more substantial participation of civil society. In this paper, we compare the patterns of participation in these two organizations and seek to identify some common dynamics. We present a general framework for analysis based on a model of the policy cycle that allows us to distinguish ‘push’ and ‘pull’ factors that determine cooperation in different phases of policy making. In our empirical study, we find that in the WTO, there are few incentives for the organization itself to pull civil society actors into its policy-making process. Agendasetting is the task of governments; research and analysis is delivered by the Secretariat; compliance control is undertaken jointly by the organization and its members. To push the door to trade policy making open, civil society can only rely on public shaming, that is, threatening to undermine the organization’s legitimacy as it violates widely accepted standards of good governance. In the UN system, there is in fact more cooperation, but it remains largely limited to the policy phases of agenda-setting, research and analysis and compliance control. Quite like the WTO, the UN protects an intergovernmental core of policy making in which cooperation with civil society remains at the discretion of state parties. Evidence for this are informal and ad hoc ways of collaboration and a lack of participatory rights for non-state actors in the Security Council and the General Assembly. We conclude that studying civil society participation in international public organizations through the lens of the policy cycle can give us a fine-grained picture of cooperative arrangements and enables us to identify potentials for cooperation as well as exclusion. Yet, we also observed two other factors at work that were not really grasped by the model of the policy cycle. First, the institutional culture of organizations can be more or less amenable to civil society. Second, organizations are susceptible to campaigns for ‘good governance’ that invoke standards of due process and may open the door to nonstate actors
Nitrogen balance and fate in a heavily impacted watershed (Oglio River, Northern Italy): in quest of the missing sources and sinks
Abstract. We present data from a comprehensive investigation carried out from 2007 to 2010, focussing on nitrogen pollution in the Oglio River basin (3800 km2, Po Plain, Northern Italy). Nitrogen mass balances, computed for the whole basin with 2000 and 2008 data, suggest a large N surplus in this area, over 40 000 t N yr−1, and increasing between 2000 and 2008. Calculations indicate a very large impact of animal husbandry and agricultural activities in this watershed, with livestock manure and synthetic fertilizers contributing 85% of total N inputs (about 100 000 t N yr−1) and largely exceeding crop uptake and other N losses (about 60 000 t N yr−1). Nitrogen from domestic and industrial origin is estimated as about 5800 and 7200 t N yr−1, respectively, although these loads are overestimated, as denitrification in treatment plants is not considered; nonetheless, they represent a minor term of the N budget. Annual export of nitrogen from the basin, calculated from flow data and water chemistry at the mouth of the Oglio River, is estimated at 13 000 t N yr−1, and represents a relatively small fraction of N inputs and surplus (∼12% and 34%, respectively). After considering N sinks in crop uptake, soil denitrification and volatilization, a large excess remains unaccounted (∼26 000 t N yr−1) in unknown temporary or permanent N sinks. Nitrogen removal via denitrification was evaluated in the Oglio riverbed with stable isotope techniques (δ15N and δ18O in nitrate). The downstream final segment of the river displays an enriched nitrate stable isotope composition but calculations suggest a N removal corresponding to at most 20% of the unaccounted for N amount. Denitrification was also evaluated in riverine wetlands with the isotope pairing technique. Areal rates are elevated but overall N removal is low (about 1% of the missing N amount), due to small wetland surfaces and limited lateral connectivity. The secondary drainage channel network has a much higher potential for nitrogen removal via denitrification, due to its great linear development, estimated in over 12 500 km, and its capillary distribution in the watershed. In particular, we estimated a maximum N loss up to 8500 t N yr−1, which represents up to 33% of the unaccounted for N amount in the basin. Overall, denitrification in surface aquatic habitats within this basin can be responsible for the permanent removal of about 12 000 t N yr−1; but the fate of some 14 000 t remains unknown. Available data on nitrate concentration in wells suggest that in the central part of the watershed groundwater accumulates nitrogen. Simultaneously, we provide evidences that part of the stored nitrate can be substantially recycled via springs and can pollute surface waters via river-groundwater interactions. This probably explains the ten fold increase of nitrate concentration in a reach of the Oglio River where no point pollutions sources are present
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