Extreme flood events favour floodplain mollusc diversity

Abstract

Floods are fundamental for the maintenance of floodplain biodiversity. As a result, wellfunctioning floodplains are characterized by a high spatio-temporal heterogeneity. Most floodplainorganisms need this shifting landscape mosaic to fulfil their environmental requirements and display a range of adaptations to survive floods. However, in temperate areas, where winter floods are common, extraordinary floods occurring in summer, a period of high physiological activity, may seriously impact the floodplain fauna. This is especially true for guilds characterized by low mobility, such as molluscs. Here we examined the immediate and longer-term response of Elbe grassland molluscs to the extreme 2002 Elbe summer flood in terms of abundance, diversity, and community composition by comparing pre-and post-flood data collected with identical methods. The flood favoured the colonization of aquatic species and led to a shift of the community towards a more hydrophilic composition. Both diversity and abundance increased significantly in the first year following the flood but decreased later gradually to the pre-flood levels. The high spatiotemporal habitat heterogeneity played an important part in the maintenance of mollusc diversity by increasing refuge opportunities and favouring the maintenance of various mollusc communities with different environmental requirements within the floodplain.

Massive die-offs of freshwater bivalves as resource pulses

“…Little attention has been paid to researching flood impacts on biota; systematic studies are still rare due to the obvious difficulties associated with predicting these events and the collection of data, complicating the analysis of short-and long-term effects (Hering et al, 2004;Ilg et al, 2009). Studies quantifying the material transported by physical processes such as floods from aquatic to adjacent terrestrial habitats are even rarer.…”

Shifts in mollusc traits following floodplain reconnection: Testing the response of functional diversity components

“…Resilience Timing reproduction with the flow regime of the river, allows species to re-establish populations rapidly benefiting from the humidity after flooding (Hershkovitz & Gasith, 2013;Ilg et al, 2009;Lytle & Poff, 2004) (Continues)…”

“…Locally, the high environmental heterogeneity typical of (semi-)natural floodplains allows very different species to co-occur within a small area (Ilg et al, 2009), resulting in high alpha FD. Coincidentally, habitat filtering leads to a high functional redundancy among mollusc communities (i.e.…”

Human effects on ecological connectivity in aquatic ecosystems: Integrating scientific approaches to support management and mitigation

“…In contrast, more frequent and extreme flooding events may connect habitats and communities that have been isolated from each other for extended periods of time (Bunn et al 2006). This increase in connectivity may benefit some organisms (Ilg et al 2009), but only if the floods are not so frequent and extreme as to be damaging to the newly connected habitats (Sousa et al 2012). Indeed, because flood flows shape and restructure riverine environments, ecological communities may effectively become less stable and more variable as a consequence of more frequent 460 and extreme flood events (Ilg et al 2009).…”

“…This increase in connectivity may benefit some organisms (Ilg et al 2009), but only if the floods are not so frequent and extreme as to be damaging to the newly connected habitats (Sousa et al 2012). Indeed, because flood flows shape and restructure riverine environments, ecological communities may effectively become less stable and more variable as a consequence of more frequent 460 and extreme flood events (Ilg et al 2009). The interplay between species traits and adaptability to large and abrupt changes in connectivity is likely to shape the way that aquatic ecosystems and species respond to future climate change (Hadwen & Arthington 2011).…”