Long-term effects of global and local changes on benthic macroinvertebrate communities in multi-stressed large rivers: the example of the Rhône River during the last 30 years

Abstract

Key-words:freshwater macroinvertebrates, Rhône River, climate change, long-term survey, biological traits, alien speciesThe study of biological traits have enhanced the understanding of the changes in the macroinvertebrate communities of the Rhône River during the last thirty years, as well as the potential effects of hydroclimatic factors and thermal discharges on the structure and the functioning of these communities at the regional scale. If every section of the Rhône had specific features, we observed over time a trend towards a higher uniformisation of invertebrate communities, especially in the Lower section. The strong impacts of the alien species and the water warming subsequent to the 2003 heat wave have been detected in the Lower Rhône and the Middle Rhône: the communities of the Middle Rhône gradually exhibit profiles closer to those of the communities of the Lower Rhône. The Upper Rhône was less colonized by alien species but was impaired by the global warming: its communities exhibited biological profiles closer to those of communities of further-downstream zones. In this site, the thermal discharges have led to a lower diversity of the communities and a higher occurrence of eurythermic species. Hence the benthic macrofauna of the Rhône River seems to have reacted quickly and strongly to environmental changes and to the arrival of invasive species. However numerous trait adaptations being common to Mediterranean and alien species, it seems complex to evaluate the respective weight of each of these potential sources of impairment. Predicting trends in invertebrate community composition is a complex objective because of the competition between native and/or invasive species in addition to man-induced environmental variation (flow, temperature). However, if biological invasion does not occur continuously but only based on specific events (especially hydroclimatology), we can legitimately believe that this drift will continue with the arrival of new Ponto-Caspian species via the Danube-Main Canal, their usual way to western and southern Europe. The common feature of these different species is that they are essentially predators or filterers, thermophilic and euryecic, and efficient functional competitors. Finally, this study once again emphasizes the importance of long-term monitoring in the study of biological communities in the context of global warming.

Long‐Term Monitoring of Macroinvertebrate Communities Over 2,300 km of the Murray River Reveals Ecological Signs of Salinity Mitigation Against a Backdrop of Climate Variability

“…This would suggest a shift in the geographic range of these taxa, although abundances generally decreased again when the drought ended. These findings are in agreement with the majority of long-term studies of macroinvertebrates (Chessman, 2009;Daufresne et al, 2007;Durance & Ormerod, 2007;Floury et al, 2013;Fruget et al, 2001Fruget et al, , 2015.…”

“…One of the longest running programs is the River Murray Water Quality Monitoring Program (WQMP), which started in 1980, spans 2,300 km of the Murray River, and includes both water quality and macroinvertebrate monitoring (Lawrence & Paterson, 2005). While there are other long-term (Daufresne et al, 2007;Floury et al, 2013;Fruget et al, 2015;Jackson & Füreder, 2006) and large-river-scale (Angradi et al, 2009) macroinvertebrate monitoring programs that have been reported in the literature, this is to the best of our knowledge the longest running, large-river-scale monitoring program reported thus far.…”

“…There is also some evidence that community structures do not recover following these hydroclimatic events and that their sensitivity to such events might decrease over time (Daufresne et al, ). Where interventions have been made to improve water quality, long‐term studies generally indicate that the effects were secondary to those of gradual warming (Daufresne et al, ; Fruget et al, , ). The general consistency of these findings suggests that similar patterns will be observed in the macroinvertebrate communities of the Murray River.…”

Changes in the benthic fauna composition in the Upper Vistula over the last 50 years – the consequences of the water pollution reduction and alien species invasion

“…The composition of benthic fauna as well as other communities in the Upper Vistula should be monitored, as in other big rivers (Fruget et al 2015), in order to determine further directions and the rate of changes taking place.…”

Surveillance sanitaire estivale des populations piscicoles du Rhône au voisinage du Centre Nucléaire de Production d'Électricité (CNPE) du Tricastin. Synthèse 2008–2013

“…Enfin, avec l'effet de plus en plus prégnant du changement climatique global sur les peuplements aquatiques des hydrosystèmes continentaux (Daufresne et al, 2003 ;Daufresne & Boët, 2007 ;Durance & Ormerod, 2009 ;Fruget et al 2015), une réflexion sur la prise en compte et le suivi des effets potentiels du réchauffement engendré sur le développement des maladies des poissons et sur le comportement des espèces résidentes et migratrices semble nécessaire. D'autant plus que non seulement nous disposons d'indicateurs pathobiologiques pertinents, fiables, peu onéreux et facilement utilisables sur le terrain (Indice de condition, Codes pathologie, Indice pathologique), mais aussi que d'autres descripteurs (hématologiques et histologiques) sont également susceptibles d'être intégrés dans ces outils de diagnostic et de surveillance de l'état de santé des populations piscicoles et de la qualité des milieux qui les hébergent.…”