Longitudinal variation of macroinvertebrate communities in a Mediterranean river subjected to multiple anthropogenic stressors

Abstract

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.

Assessing the influence of source distance and hydroecoregion on the invertebrate assemblage similarity in central Italy streams

“…The greatest separation between HER for the three wiSD groups underlined the importance of using both levels of site classifications in evaluating physico-chemical differences between sites. Indices and metrics are generally used as a proxy of water quality and of structure of macroinvertebrate assemblages (AQEM consortium, 2002;Lewin et al, 2013;Manfrin et al, 2013). The LUI output confirms that HER15 sites showed the highest anthropic impact, the opposite for HER13, confirming the PCA scatter plot.…”

Macrophyte and macroinvertebrate patterns in unimpacted mountain rivers of two European ecoregions

“…In the case of rivers, such conditions are very rare today, due to the scale of river degradation in the biosphere (Moss, 2008;Demars et al, 2012). Human impact causes a variety of problems leading to the deterioration of river habitats, one of the most serious include eutrophication, acidification, and changes in hydrology and river morphology (Malmqvist & Rundle, 2002;Johnson & Hering, 2009;Manfrin et al, 2013). Moreover, several groups of aquatic organisms suffer markedly from impoundments and losses of river integrity (Marzin et al, 2012).…”

Effect of spatial scale on macroinvertebrate assemblages along a Mediterranean river

“…Lenat & Barbour, 1994;Hering et al, 2004;Larsen et al, 2012;Manfrin et al, 2013), and are frequently monitored to detect changes in hydrological and sediment regimes as well as in water quality of river in ecosystems (Boulton et al, 1992;Pace et al, 2013).…”