River impoundments and waste water discharge are a serious threat to the integrity and biodiversity of river ecosystems, especially in central Italy. Benthic macroinvertebrates were sampled in autumn and summer along the Aniene River to assess the cumulative biological effect of the numerous dams and sewage treatment plants that affect its middle and lower course. We hypothesized that (i) increasing habitat impairment would promote the formation of nestedness in species assemblage, where species poor locations support only a sub‐set of organisms from richer sites; (ii) specific life‐history traits would confer sensitivity to habitat degradation. Patterns of macroinvertebrate richness and diversity along the river tracked the distribution of dams and sewage treatment plants. Partial Mantel test showed that dissimilarity in assemblages increased with the number of dams and treatment plants between reaches after controlling for longitudinal distance. Assemblages were significantly nested, and nestedness appeared related to both water quality gradients (phosphorous, turbidity) that reflected anthropogenic inputs, and to natural gradient in altitude. Reaches with nested assemblages (supporting a sub‐set of the species pool) were characterized by greater representations of taxa with shorter life cycles, while, in contrast, species rich sites supported taxa with longer life cycles and lower dispersal ability. These results suggest that the cumulative effect of dams and sewage treatment plants promoted the formation of nested subsets in species distribution. Moreover, it appeared that certain functional traits that conferred sensitivity also dictated the progressive non‐random loss of taxa in face of multiple anthropogenic stressors. These findings have conservation implications in the regions, but need to be considered preliminary since anthropogenic and natural factors co‐varied systematically along the study river precluding the identification of single factor effects.
Investigations on asymmetries showed that deviations from perfect bilateral symmetry are interpreted as environmental changes inducing developmental instability. Since morphological abnormalities increase with pollution, deformations may be considered indicators of the organism exposition to pollution. Therefore, the onset of asymmetry in otherwise normally symmetrical traits has been used as a measure of some stresses as well. In this context, we studied how marine pollution affects the valve morphological alterations in the mussel Mytilus galloprovincialis. We used 180 specimens (30 per site) from the aquaculture area of Goro (River Po delta, northern Adriatic Sea), translocated, and released within 50 × 50 × 50 cm cages in five sites: two disturbed and one undisturbed near Naples (eastern Tyrrhenian Sea), and one disturbed and one undisturbed near Siracusa (western Ionian Sea). Disturbed sites were stressed by heavy industrialization and heavy tankers traffic of crude and refined oil, and were defined basing on sediment contamination. In particular, by the cone-beam computed tomography we obtained 3D virtual valve surfaces to be analyzed by the geometric morphometric techniques. Specifically, we focused the levels of the shell shape fluctuating asymmetry in relation to the degrees of marine pollution in different sites of the Tyrrhenian Sea. The Mahalanobis distances (interpreted as proxy of the individual shape asymmetry deviation from the mean asymmetry) significantly regressed with the sediment contamination gradient. Indeed, although the left-right differences were normally distributed in each studied site, the individual asymmetry scores (IAS) significantly varied amongst the investigated sites. IAS showed higher values in disturbed areas than those of undisturbed ones in both Tyrrhenian and Ionian Sea. Our results are consistent with past studies on molluscans and other taxa, demonstrating some detrimental effects of chemicals on organisms, although the investigated morphological marker did not discriminate the real disturbance source. Our findings indicate that the mussels act as a prognostic tool for sea pollution levels driving detrimental effects on benthic community.
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