A Conceptual Framework for Understanding the Biogeochemistry of Dry Riverbeds Through the Lens of Soil Science

Intermittent rivers and ephemeral streams (IRES) encompass fluvial ecosystems that eventually stop flowing and run dry at some point in space and time. During the dry phase, channels of IRES consist mainly of dry riverbeds (DRBs), prevalent yet widely unexplored ecotones between dry and wet phases that can strongly influence the biogeochemistry of fluvial networks. DRBs are often overlooked because they do not strictly belong to either domain of soil or freshwater science. Due to this dual character of DRBs, we suggest that concepts and knowledge from soil science can be used to expand the understanding of IRES biogeochemistry. Based on this idea, we propose that DRBs can be conceptually understood as early stage soils exhibiting many similarities with soils through two main forces: i) time since last sediment transport event, and ii) the development status of stabilizing structures (e.g. soil crusts and/or vascular plants). Our analysis suggests that while DRBs and soils may differ in master physical attributes (e.g. soil horizons vs fluvial sedimentary facies), they become rapidly comparable in terms of microbial communities and biogeochemical processes. We further propose that drivers of DRBs biogeochemistry are similar to those of soils and, hence, concepts and methods used in soil science are transferable to DRBs research. Finally, our paper presents future research directions to advance the knowledge of DRBs and to understand their role in the biogeochemistry of intermittent fluvial networks

Spatial factors control the structure of fish metacommunity in a Mediterranean intermittent river

International audienceWhile in recent years intermittent rivers and ephemeral streams (IRES) are receiving increasing attention from ecologists, fish metacommunity dynamics have drawn less attention than other taxa. In this study, we explored fish metacommunity dynamics at a Mediterranean intermittent river (Evrotas River, Southern Greece) to unravel which factors (i.e. environmental and/or spatial) best explain fish metacommunity structure. To this end, we investigated fish compositional structure in perennial and intermittent sites distributed longitudinally along the river during the low flow period of a wet year (2009), following two extremely dry years (2007-2008). To disentangle the effects of spatial control versus local environmental variables in shaping fish metacommunities, asymmetric eigenvector map (AEM) analysis designed to model directional spatial processes, and variation partitioning were applied. Our results point out that fish metacommunity structure was largely explained by spatial (53%) rather than local environmental (3%) factors, whereas only a small fraction (16%) was explained by the spatial structure of the environmental variables. Irrespectively of their hydrological regime, neighboring sites harbored similar fish communities, with a strong longitudinal gradient in local community structure, suggesting a homogenizing effect of dispersal. Local environmental factors were not associated with shifts in community structure. These results differ markedly from those drawn from most perennial aquatic ecosystems, where environmental factors are prevailing. Overall, this study emphasizes the need to account for regional processes in IRES and adopt a metacommunity perspective for guiding conservation and restoration efforts, by promoting the connectivity within the river network and the protection of perennial refugia. (C) 2020 European Regional Centre for Ecohydrology of the Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved

Personal care products reconnaissance in EVROTAS river (Greece): Water-sediment partition and bioaccumulation in fish

Twenty-six common ingredients of personal care products (PCPs) in water, sediment and fish from the Evrotas River (Greece) were investigated. Water sample analysis revealed the occurrence of twenty PCPs at concentrations ranging from 2.8 to 2031.0 ng l−1, the maximum corresponding to the endocrine disrupting UV filter benzophenone 3 (BP3). In sediment samples, six compounds were found to be adsorbed, the highest concentration being that of 4-methylbenzylidene camphor (4MBC, 1400.4 ng g−1 dw). Evrotas cyprinid fish (Squalius keadicus) showed a high accumulation potential for these chemicals, 100% detection frequency with maximum concentration that of benzophenone 2 (BP2, 41.9 ng g−1 dw). These data allowed estimating the distribution coefficients sediment-water (DCs-w) and the bioaccumulation factors (BAFs) of the pollutants investigated. Calculated rates revealed that benzophenone 1 (BP1), 4-hydroxybenzophenone (4HB) and ethyl-4-(dimethyl-amino)benzoate (EtPABA) have a strong tendency to adsorb onto the sediments, showing high DCs-w, i.e. 8.2E + 4 l g−1, 6.7E + 4 l g−1 and 5.7E + 3 l g−1, respectively. BFAs were only estimated for 5-methyl benzotriazole (MeBT), the compound having paired data from fish and water. The obtained values (range 2.0E + 2 l g−1–3.8E + 3 l g−1), indicated MeBT's strong bioaccumulation. Risk assessment of the investigated compounds for several aquatic organisms indicated a high ecological risk (HQ > 1) for BP3 and medium ecological risk (HQ ~ 0.5) for ODPABA. © 2018 The AuthorsThis study has been supported by the EU project GLOBAQUA ( FP7-ENV-2013 , GA 603629 ) and by the Generalitat de Catalunya (Water and Soil Quality Unit 2017- SGR-1404 ).Peer reviewe

Multiple stressor effects on biodiversity and ecosystem functioning in a Mediterranean temporary river

The hydrological and biological complexity of temporary rivers as well as their importance in providing goods and services is increasingly recognized, as much as it is the vulnerability of the biotic communities in view of climate change and increased anthropogenic pressures. However, the effects of flow intermittency (resulting from both seasonal variations and rising hydrological pressure) and pollution on biodiversity and ecosystem functioning have been overlooked in these ecosystems. We explore the way multiple stressors affect biodiversity and ecosystem functioning, as well as the biodiversity-ecosystem functioning (B-EF) relationship in a Mediterranean temporary river. We measured diversity of benthic communities (i.e. diatoms and macroinvertebrates) and related ecosystem processes (i.e. resource use efficiency-RUE and organic matter breakdown-OMB) across a pollution and flow intermittency gradient. Our results showed decreases in macroinvertebrate diversity and the opposite trend in diatom assemblages, whereas ecosystem functioning was negatively affected by both pollution and flow intermittency. The explored B-EF relationships showed contrasting results: RUE decreased with higher diatom diversity, whereas OMB increased with increased macroinvertebrate diversity. The different responses suggest contrasting operating mechanisms, selection effects possibly driving the B-EF relationship in diatoms and complementarity effects driving the B-EF relationship in macroinvertebrates. The understanding of multiple stressor effects on diversity and ecosystem functioning, as well as the B-EF relationship in temporary rivers could provide insights on the risks affecting ecosystem functioning under global change. © 2018The authors would like to thank P. Kouraklis for field work, A. Vourka, C. Theodoropoulos, A. Andriopoulou and M. Koutsodimou for laboratory assistance in macroinvertebrate identification and E. Anastasopoulou for chemical analysis. This study was conducted within the frame of the European Communities 7th Framework Programme under Grant Agreement no 603629-ENV-2013-6.2.1-GLOBAQUA . Appendix APeer reviewe

Unravelling the effects of multiple stressors on diatom and macroinvertebrate communities in European river basins using structural and functional approaches

International audienceRivers suffer from more severe decreases in species diversity compared to other aquatic and terrestrial ecosys- tems due to a variety of pressures related to human activities. Species provide different roles in the functioning of the ecosystem, and their loss may reduce the capacity of the ecosystems to respond to multiple stressors. The effects on diversity will differ based on the type, combination and severity of stressors, as well as on the char- acteristics of the community composition and tolerance. Multiple trait-based approaches (MTBAs) can help to unravel the effects of multiple stressors on communities, providing a mechanistic interpretation, and, thus, complementing traditional biodiversity assessments using community structure. We studied the relationships between diversity indexes and trait composition of macroinvertebrate and diatom communities, as well as envi- ronmental variables that described the hydrological and geomorphological alterations and toxic pollution (pes- ticides and pharmaceuticals) of three different European river basins: the Adige, the Sava, and the Evrotas. These river basins can be considered representative cases of different situations in European freshwater systems. Hy- drological variables were the main drivers determining the community structure and function in the rivers, for both diatoms and macroinvertebrates. For diatom communities, pharmaceutical active compound (PhAC) toxic units were also identified as a very important driver of diversity changes, explaining up to 57% of the variance in taxonomic richness. For macroinvertebrates, river geomorphology was an important driver of structural changes, particularly affecting Plecoptera richness. In addition, PhAC and pesticide toxic units were also identified as stressors for macroinvertebrate communities. MTBA provided a detailed picture of the effects of the stressors on the communities and confirmed the importance of hydrological variables in shaping the functional attributes of the communities

Unravelling the effects of multiple stressors on diatom and macroinvertebrate communities in European river basins using structural and functional approaches

Rivers suffer from more severe decreases in species diversity compared to other aquatic and terrestrial ecosystems due to a variety of pressures related to human activities. Species provide different roles in the functioning of the ecosystem, and their loss may reduce the capacity of the ecosystems to respond to multiple stressors. The effects on diversity will differ based on the type, combination and severity of stressors, as well as on the characteristics of the community composition and tolerance. Multiple trait-based approaches (MTBAs) can help to unravel the effects of multiple stressors on communities, providing a mechanistic interpretation, and, thus, complementing traditional biodiversity assessments using community structure. We studied the relationships between diversity indexes and trait composition of macroinvertebrate and diatom communities, as well as environmental variables that described the hydrological and geomorphological alterations and toxic pollution (pesticides and pharmaceuticals) of three different European river basins: the Adige, the Sava, and the Evrotas. These river basins can be considered representative cases of different situations in European freshwater systems. Hydrological variables were the main drivers determining the community structure and function in the rivers, for both diatoms and macroinvertebrates. For diatom communities, pharmaceutical active compound (PhAC) toxic units were also identified as a very important driver of diversity changes, explaining up to 57% of the variance in taxonomic richness. For macroinvertebrates, river geomorphology was an important driver of structural changes, particularly affecting Plecoptera richness. In addition, PhAC and pesticide toxic units were also identified as stressors for macroinvertebrate communities. MTBA provided a detailed picture of the effects of the stressors on the communities and confirmed the importance of hydrological variables in shaping the functional attributes of the communities

Integrated river basin management under water stress conditions case study: the Evrotas river basin

Μη διαθέσιμη περίληψηNot available summarizationΠαρουσιάστηκε στο: 1st EWaS-MED International Conference, “Improving Efficiency of Water Systems in a Changing natural and financial Environment