ABSTRACT
Typology systems are frequently used in applied and fundamental ecology and are relevant for environmental monitoring and conservation. They aggregate ecosystems into discrete types based on biotic and abiotic variables, assuming that ecosystems of the same type are more alike than ecosystems of different types with regard to a specific property of interest. We evaluated whether this assumption is met by the Broad River Types (BRT), a recently proposed European river typology system, that classifies river segments based on abiotic variables, when it is used to group biological communities. We compiled data on the community composition of diatoms, fishes, and aquatic macrophytes throughout Europe and evaluated whether the composition is more similar in site groups with the same river type than in site groups of different river types using analysis of similarities, classification strength, typical species analysis, and the area under zeta diversity decline curves. We compared the performance of the BRT with those of four region-based typology systems, namely, Illies Freshwater Ecoregions, the Biogeographic Regions, the Freshwater Ecoregions of the World, and the Environmental Zones, as well as spatial autocorrelation (SA) classifications. All typology systems received low scores from most evaluation methods, relative to predefined thresholds and the SA classifications. The BRT often scored lowest of all typology systems. Within each typology system, community composition overlapped considerably between site groups defined by the types of the systems. The overlap tended to be the lowest for fishes and between Illies Freshwater Ecoregions. In conclusion, we found that existing broad-scale river typology systems fail to delineate site groups with distinct and compositionally homogeneous communities of diatoms, fishes, and macrophytes. A way to improve the fit between typology systems and biological communities might be to combine segment-based and region-based typology systems to simultaneously account for local environmental variation and historical distribution patterns, thus potentially improving the utility of broad-scale typology systems for freshwater biota.
Subject(s)
Diatoms , Ecosystem , Animals , Rivers , Fishes , Environmental Monitoring/methodsABSTRACT
Diatom analysis was undertaken on a 200-year sediment record in an alpine lake (Popradské pleso, Tatra Mountains, Central Europe). Due to its remote character and well-documented human influence since the mid-nineteenth century, it allows a study of the relationship between anthropogenic pressures and diatom assemblages. Altogether, 122 diatom taxa of 40 genera were identified, and two major taxonomic shifts were revealed in the stratigraphic record. The timing of the first significant shift in ~ 1850 precludes the possibility of being caused by direct human activities, since according to historic documents there was neither continuous human presence nor grazing in the valley before that time. In addition, the direct effect of organic pollution early in the 1960s connected with the operation of a tourist hotel was not clearly reflected in the diatom signal. The diatom-inferred total phosphorus (DI-TP) reconstruction indicated the highest TP content well before the most direct wastewater pollution from a newly built hotel. There was a considerable effect of climate to diatom assemblage structure as well as diatom life forms. Our results suggest that direct organic pollution influenced the diatom communities less than expected, and the main driver of change was climate warming. We hypothesize that it is because of the short residence time of the lake, since it has both strong inlet and outlet, and it has been showed that the inlet had significant effect on benthic communities in the past. At the same time, fish manipulation could have been the reason for some fluctuation in DI-TP unrelated to climate and organic pollution.
