Climate Change and Water Exploitation as Co-Impact Sources on River Benthic Macroinvertebrates

Abstract

Climate change can affect freshwater communities superimposing on other major stressors, such as water exploitation, with effects still poorly understood. The exacerbation of naturally-occurring periods of low flows has been reported as a major hydrological effect of water diversions, with severe impacts on river benthic macroinvertebrate communities. This study aimed at assessing long-term modifications of low-flow events in a large lowland Italian river possibly associated to climate change and the effects of these events, intensified by water withdrawals, on benthic macroinvertebrates. A 77-year dataset on daily discharge was thus analyzed through Mann-Kendall test and Sen’s method to investigate modifications of the main hydrological parameters. Moreover, macroinvertebrates were collected during the low-flow periods that occurred from 2010 to 2015 at three sites downstream of water withdrawals, representing three different conditions of hydrological impairment. After assessing possible differences in taxonomical and functional composition between sites and impairment conditions, redundancy analysis and ordinary least squares regression were performed to link benthos metrics to environmental (hydrological and physico-chemical) characteristics. An increase in the duration of the low-flow periods and reduced summer flows were detected on the long term, and the magnitude of low flows was significantly altered by water withdrawals. These hydrological features shaped both structural and functional characteristics of benthic assemblages, highlighting the need for a more environmentally-sustainable water resource management in the current context of climate change.

The increasing spread of the European barbel in the Italian large lowland rivers is threatening the native species

“…Both species can be affected by the hydrological alteration of the regulated Ticino and Oglio rivers, mainly by the minimum flows which in recent years have been exacerbated by the climate change (Salmaso et al, 2021). Their habitat requirements vary with development; for B. barbus, areas in the littoral zone with minimal flow are important for larvae, riffle areas for juveniles, and midchannel habitats for adults (Britton and Pegg, 2011).…”

“…In the first 20 km, the lower Oglio hosts six run of the river hydropower plants that creates a sequence of lentic and lotic stretches; the remaining part of the river suffers mainly from water abstraction for agricultural uses. In both rivers, the environmental flow is a seasonally modulated minimum flow that varies depending on the reach, with approximately 5% of the annual mean discharge being the lowest allowed flow (Laini et al, 2018;Salmaso et al, 2021).…”

Characteristics of Key Biological Assemblage Dynamics and Biotic Integrity Assessment in the Upper Yellow River, China

“…Sensitive benthic taxa such as Ephemeroptera, Plecoptera, Trichoptera, and Odonatataxa have also demonstrated robust indicator capabilities in distinguishing disturbance gradients [13]. On the other hand, climate-induced changes in hydrological conditions may significantly impact the community structure and functional characteristics of macroinvertebrates [34]. Therefore, in assessing the B-IB, it is necessary not only to consider native species but also to focus on the presence of environmentally sensitive groups.…”

Monitoring and Management of Inland Waters: Insights from the Most Inhabited Italian Region

“…At the same time, advanced biomonitoring and modelling tools are required to improve quantitative prediction of the effects of hydropower [107,109], supporting a comprehensive management strategy of the water resources, aimed to sustain the production of renewable and clean energy while improving at the same time the environmental quality of exploited rivers. Moreover, water management strategies should account for the effects of current climate changes, such as the increased duration of low-flow periods [110], the increased river temperature [111] and the occurrence of catastrophic events, such as landslides increasing sediment input in regulated streams [112,113].…”