Emerging concepts in temporary-river ecology

• Published in: Freshwater biology 2010-04, Vol.55 (4), p.717-738
• Main Authors: LARNED, SCOTT T, DATRY, THIBAULT, ARSCOTT, DAVID B, TOCKNER, KLEMENT
• Format: Article
• Language: English
• Subjects: Aquatic plants; Aquatic-terrestrial habitat mosaics; Biodiversity; connectivity; Endangered & extinct species; Environmental Sciences; flow intermittence; Freshwater; meta-systems; Rivers; temporary rivers
• ISSN: 0046-5070; 1365-2427
• DOI: 10.1111/j.1365-2427.2009.02322.x

1. Temporary rivers and streams are among the most common and most hydrologically dynamic freshwater ecosystems. The number of temporary rivers and the severity of flow intermittence may be increasing in regions affected by climatic drying trends or water abstraction. Despite their abundance, temporary rivers have been historically neglected by ecologists. A recent increase in temporary-river research needs to be supported by new models that generate hypotheses and stimulate further research. In this article, we present three conceptual models that address spatial and temporal patterns in temporary-river biodiversity and biogeochemistry. 2. Temporary rivers are characterised by the repeated onset and cessation of flow, and by complex hydrological dynamics in the longitudinal dimension. Longitudinal dynamics, such as advancing and retreating wetted fronts, hydrological connections and disconnections, and gradients in flow permanence, influence biotic communities and nutrient and organic matter processing. 3. The first conceptual model concerns connectivity between habitat patches. Variable connectivity suggests that the metacommunity and metapopulation concepts are applicable in temporary rivers. We predict that aggregations of local communities in the isolated water bodies of temporary rivers function as metacommunities. These metacommunities may become longitudinally nested due to interspecific differences in dispersal and mortality. The metapopulation concept applies to some temporary river species, but not all. In stable metapopulations, rates of local extinction are balanced by recolonisation. However, extinction and recolonisation in many temporary-river species are decoupled by frequent disturbances, and populations of these species are usually expanding or contracting. 4. The second conceptual model predicts that large-scale biodiversity varies as a function of aquatic and terrestrial patch dynamics and water-level fluctuations. Habitat mosaics in temporary rivers change in composition and configuration in response to inundation and drying, and these changes elicit a range of biotic responses. In the model, aquatic biodiversity initially increases directly with water level due to increasing abundance of aquatic patches. When most of the channel is inundated and most aquatic patches are connected, further increases in aquatic habitat and connectivity cause aquatic biodiversity to decline due to community homogenisation and reduced habitat diversity.