INHABIT project

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Home Themes & Results Nutrients (I2) Retention metrics and benthic community relationship

Rivers – Relationship between nutrient and invertebrates abundance, distribution, trophic roles and ecological status classification

In this phase of I2 activity the relationships between the dynamics related to the nutrients retention and the conditions of the macrobenthic communities have been considered. In this sense, this work represents a synthesis between two of the issues addressed during the INHABIT project. The analysis was carried out with reference to macrobenthic taxa distribution and abundance, the trophic roles characterizing the community and the associated classification of ecological status. In particular, about community structure and trophic roles, associations  have been analysed considering the association to the principal axes of variation identified by a set of multivariate analyses. Two distinct sets of multivariate analyses were carried out with the aim, in the first case, to contextualize river sites considered for the nutrient addition experiment in a wider regional framework (‘addition sites’) and, in the second case, to more specifically characterize such traits with an analysis carried out at microhabitat level. Direct linear correlations between selected biological metrics, descriptive of trophic roles and ecological quality, and retention metrics were also considered. The results of the multivariate analyzes have emphasized the importance, for the characterization of the addition sites, of some of trophic roles in relation to the concentration of nutrients (in particular PO4).
Particularly interesting results were also observed for the relations between the retention metric 'coefficient of mass transfer' of ammonium and selected biological metrics,  describing the composition in trophic roles (ratio of Scrapers and Passive Filterers) and the ecological quality (STAR_ICMi). In both cases a positive linear correlation is observed, suggesting on one hand the importance of the association between the scrapers taxa and dynamics of nutrient retention, presumably in relation to the development of periphyton, and on the other hand the relationship between the increase of retention efficiency at increasing environmental quality.
From these results it is possible to infer that, in riverine environments, the protection of a high ecological status can simultaneously ensure the activation of the processes reducing nutrients accumulation.
Full description of the results is available in Deliverable I2d4.

  

Linear regression between biological metric STAR ICMi-riffle (left) and ratio Grazers/Passive Filterers (right) and log-transformed 'coefficient of mass transfer' for ammonium Vf_NH4.