INHABIT project

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Home Themes & Results Nutrients (I2)

Relationship between nutrients, community and environmental conditions (I2)

Description
This action group deals with the interaction between nutrients, local hydro-morphology, habitat conditions and biological community. Three major paths of nutrient pollutants to European freshwaters can be considered: point sources, diffuse pollution from agricultural sites and atmospheric deposition of nitrogen compounds derived from air pollutants. Point and diffuse sources are generally located inside the catchment of each water body. On the contrary, the sources of atmospheric deposition of nitrogen compounds can be located outside the catchments, in industrial and agricultural areas as far as hundreds of kilometres from the receiving catchment. On the basis of data gained in the group of actions P, we will evaluate the relative importance of point and non-point sources of nitrogen and phosphorous for each of the study catchment and examine the relationships between catchment features (land use, topography, landscape configuration), reach features and nutrient loadings.
The action of this group will focus on both rivers and lakes, in order to detect the relationship between nutrients on the ecological quality of water bodies and to identify management options to reduce their effects on aquatic ecosystems to be included in RBMPs.

Methods employed
Rivers - We will evaluate the nutrient retention efficiency by measuring the nutrient uptake length in short-term nutrient additions experiments in the study river reaches. Short distances indicate greater retention efficiency than long distances. Based on this parameter we will also calculate the nutrient uptake rate and the mass transfer coefficient. While uptake length is affected by variations in stream flow, these two other parameters are not, and they therefore allow inter-site comparisons. We will also estimate the size of the transient storage zone and the surface-subsurface hydrologic linkages within each study reach by conducting additions of conservative tracers and measuring the vertical hydraulic gradient. We will measure nutrient retention in two regions (Sardinia and Piedmont) and, within each region, in one of the river types selected for action I1. We will focus the activities on small to mid-sized rivers as they have a crucial role in the transformation of nutrients at the catchment level, thus excluding the high altitude, steep streams for which, actually, there is not a good experience in nutrient  retention measurements.
To test the effects of morphological and habitat features and hydrological linkages on stream nutrient retention, we will examine the relationship between data obtained from CARAVAGGIO applications (see I1) and results from nutrient retention measurements within each study site and among study sites. Because the CARAVAGGIO method is known to provide useful information to be linked to biological elements and to properly quantify some aspects of natural variability, this method will be one of the methods to be surely applied for the evaluation of hydromorphological and habitat features in the field at the river stretch level (minimum length of 500m). Moreover CARAVAGGIO is a WFD compliant method and takes into account many of the different categories CEN standards ask to consider.
The fact that the CARAVAGGIO method will be applied does not prevent other methods to be applied as well, in relation to the results of the preparatory phase and regions’ requirements. In particular, other methods than the CARAVAGGIO will be applied when the aim is to look at a wider spatial scale than the river stretch. Nutrient retention will be also related to aquatic invertebrates distribution and abundance, with focus on habitats structure and feeding categories. In addition, nutrient-related factors (e.g. uptake length, nutrient concentrations, hydro-morphological drivers) will be connected to ecological status classification.  
A total of at least 1000 water samples will be collected and analysed in Piedmont and Sardinia. Also data already available from CNR (for the up-scaling) will be examined.
Lakes - Both monitoring data and modelling of lake catchments will be considered. Existing high quality data series will be collected in a central database and analysed to identify common trends on a regional basis, and to identify factors affecting the ecological response of lakes to nitrogen deposition. No large scale monitoring is foreseen, but new monitoring data will be occasionally collected if necessary to improve the knowledge of key processes. Soil catchment models, calibrated on some selected watersheds, will also be used to infer on the evolution of aquatic ecosystems under different deposition scenarios and under the constraints of climatic change. A model for the evaluation of the effects of nitrogen pollution on lakes and rivers will be developed. On the basis of this model management practices will be introduced in RBPMs and included in I2d6 and I2d8 deliverable. As in Italy a large latitudinal gradient in nitrogen deposition is evident, with minimum values in the Southernmost regions and maximum values in the Po Plain, the biological data collected within the project (group of actions I1) will also be analysed to detect spatial pattern which can be related to the potential effects of nitrogen pollution, suggesting relations to be included in ecological models and considered when compiling RBMPs. Long time series of nitrogen concentration in atmospheric deposition are available, above all on alpine and sub-alpine lakes. Sovra-basin Management Plans, including the territory where the sources of nitrogen emission are identified, will be elaborated for achieving good ecological quality of the water bodies. These elaborations will be included in I2d6 and I2d8 deliverables.

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