Impacts of global changes and extreme hydroclimatic events on macroinvertebrate community structures in the French Rhône River

Abstract

We assessed the temporal changes in and the relationships between the structures of the macroinvertebrate communities and the environmental conditions of the French Rhône River (the river from Lake Geneva to the Mediterranean Sea) over the last 20 years (1985-2004). Multisite environmental and biological datasets were analysed using multiple CO-inertia analysis (MCOA) and Procrustean analysis. Changes in environmental conditions were mainly marked by an improvement in water quality between 1985 and 1991 and by an increase in water temperature from 1985 onwards due to climate change. Improvement in water quality seemed to delay changes in community structures under global warming. We then observed trends in community structures coupled with high temperatures and a decrease in oxygen content. Interestingly, we observed both gradual changes and rapid switches in community states. These shifts seemed coupled to extreme hydroclimatic events (i.e. pulse disturbances). Floods and the 2003 heatwave enhanced the development of eurytolerant and invasive taxa which were probably able to take advantage of gradual warming environmental conditions. Despite various site-specific "press" constraints (e.g. hydropower schemes, nuclear power plants), similar changes in community structures were observed along the French Rhône River. Such consistency in temporal processes at large geographical scales underlined the strength of hydroclimatic constraints on community dynamics compared to specific local disturbances. Finally, community structures did not show any sign of recovery, and their relative sensitivities to extreme hydroclimatic events seemed to increase with time. Thus, our results suggest that global changes may reduce the resilience of current community states.

Population dynamics and life cycle of Pisidium amnicum (Müller) (Bivalvia : Sphaeriidae) and Valvata piscinalis (Müller) (Gastropoda : Prosobranchia) in the Saône river, a nine-year study

“…A decrease in the resilience of macroinvertebrate communities affected by extreme hydroclimatic events was also observed in the Rhône river (Daufresne et al 2007). On a wider scale, increases of mean temperature and the frequency of heatwaves during the century predicted by different models (Beniston & Diaz 2004, EEA 2004, Schär et al 2004, Meehl & Tebaldi 2004 could result in the gradual disappearance of P. amnicum from the potamon and of V. piscinalis from the freshwater systems most directly exposed to climatic warming (Webb 1996), such as the Saône River.…”

Impacts of Europe's changing climate – 2008 indicator based assessment

“…Fish and invertebrate communities have been found to respond to increases in water temperature in the upper Rhône River in France (Daufresne et al, 2004(Daufresne et al, , 2007.…”

Temporal Changes in Biological Communities Affecting Models for Evaluating of Ecological Status

“…The study [11] observed influence of changes in environmental conditions on the change of macroinvertebrates in the river Rhone in France. It observed temporal change at the nine sites that were sampled from 1985 to 2004.…”

“…Their results are very controversial. Some studies have shown community structure to be relatively stable, especially if environmental conditions do not vary over time [6], [7], [8], whereas others have reported considerable temporal changes in community structure [9], [10], [11], [12].…”