Ricerc@Sapienza

In human-impacted rivers, nutrient pollution
has the potential to disrupt biodiversity organisation
and ecosystem functioning, prompting calls for
effective monitoring and management. Pollutants,
together with natural variations, can modify the
isotopic signature of aquatic organisms. Accordingly,
we explored the potential of isotopic variations as an
indicator of drainage basin influences on river food
webs. We assessed stable N and C isotopes within six
food webs along a river affected by multiple pollution
sources. CORINE land cover maps and Digital
Elevation Models (DEMs) were also applied to
understand the impact on surface waters of anthropogenic
pressures affecting the catchment. N isotopic
signatures of taxa fell in association with ammonium
inputs from agriculture, indicating that nitrogen pollution
was related to synthetic fertilizers. Isotopic
variations were consistent across trophic levels, highlighting
site-specific communities and identifying taxa
exposed to pollutants. This allowed us to locate point
sources of disturbance, suggesting that food web
structure plays a key role in pollutant compartmentalisation
along the river. Thematic maps and DEMs
helped understand how the anthropogenic impact on
river biota is mediated by hydro-geomorphology.
Thus, the integration of site-scale analyses of
stable isotopes and land use represents a promising
research pathway for explorative nutrient pollution
monitoring in human-impacted rivers.