| 1. |
- Ecke, Frauke
(författare)
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Compositional breakpoints of freshwater plant communities across continents
- 2023
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Ingår i: Limnetica. - : Asociacion Iberica de Limnologia. - 0213-8409. ; 42, s. 291-301
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Konferensbidrag (refereegranskat)abstract
- Unravelling patterns and mechanisms of biogeographical transitions is crucial if we are to understand compositional gradients at large spatial extents, but no studies have thus far examined breakpoints in community composition of freshwater plants across continents. Using a dataset of almost 500 observations of lake plant community composition from six continents, we examined, for the first time, if such breakpoints in geographical space exist for freshwater plants and how well a suite of ecological factors (including climatic and local environmental variables) can explain transitions in community composition from the subtropics to the poles. Our combination of multivariate regression tree (MRT) analysis and k-means partitioning suggests that the most abrupt breakpoint exists between temperate to boreal regions on the one hand and freshwater plant communities harbouring mainly subtropical or Mediterranean assemblages on the other. The spatially structured variation in current climatic conditions is the most likely candidate for controlling these latitudinal patterns, although one cannot rule out joint effects of eco-evolutiona-ry constraints in the harsher high-latitude environments and post-glacial migration lags after Pleistocene Ice Ages. Overall, our study supports the foundations of global regionalisation for freshwater plants and anticipates further biogeographical research on freshwater plant communities once datasets have been harmonised for conducting large-scale spatial analyses.
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| 2. |
- Williams, Clayton J., et al.
(författare)
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Add a dash of salt? Effects of road de-icing salt (NaCl) on benthic respiration and nutrient fluxes in freshwater sediments : [¿Agregar una pizca de sal? Efectos de la sal usada en carreteras (NaCl) sobre la respiración béntónica y los flujos de nutrientes en los sedimentos de agua dulce]
- 2023
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Ingår i: Limnetica. - : Asociación Ibérica de Limnología. - 0213-8409. ; 42:2, s. 233-250
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Tidskriftsartikel (refereegranskat)abstract
- Winter road salt applications are increasing chloride concentrations in many freshwater ecosystems. This trend is alarming, given chloride’s potential to impair aquatic ecosystems. Short- and long-term exposure to salt could affect ecosystem metabolism and nutrient cycles. Here, we examine connections between chloride concentrations, water quality conditions, benthic respiration, and sediment-water nutrient flux throughout a large (722 km2) lake and its catchment. Aquatic locations experiencing high concentrations of chloride are indicators of anthropogenic activities and are often associated with additional pollutants. We used sediment core flow-through incubations under ambient and enriched chloride concentrations to determine the effects of road salt on benthic respiration and nutrient fluxes in stream, stormwater pond, and lake sites. Salt (as sodium chloride) additions caused a significant overall increase in benthic respiration. Acute exposure to road salt caused the strongest increase in benthic respiration when water was warm and at sites that had low (< 50 mg Cl-/L) or high (> 400 mg Cl-/L) ambient chloride concentrations or when water was cold and sites had intermediate (100-400 mg Cl-/L) ambient chloride concentrations. Nitrate flux responded less uniformly to salt additions. Depending on waterbody type and season, ambient nitrate flux into the sediment was similar, increased, or decreased post-chloride addition. Dissolved phosphorus flux was not significantly impacted by salt additions. Across lake and stream sites, our results supported the hypothesis that chloride causes increased respiration while nutrient cycles were weakly and inconsistently altered under experimental pulse road salt additions.
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