Abstract
Small shallow lakes (SSL) support exceptionally high and original biodiversity, providing numerous ecosystem services. Their small size makes them especially sensitive to anthropic activities, which cause a shift to dysfunctional turbid states and induce loss of services and biodiversity. In this study we investigated the relationships between environmental factors and macrophyte communities. Macrophytes play a crucial role in maintaining functional clear states. Better understanding the factors determining the composition and richness of aquatic plant communities in least-impacted conditions may be useful to protect these shallow lakes. We inventoried macrophyte communities and collected chemical, climatic, and morphological data from 89 least-impacted SSL widely distributed in France. SSL were sampled across four climatic ecoregions, various geologies, and elevations. Hierarchical cluster analysis showed a clear separation of four macrophyte assemblages strongly associated with mineralization. Determinant factors identified by distance-based redundancy analysis (db-RDA) analysis were, in order of importance, geology, distance from source (DIS, a proxy for connectivity with river hydrosystems), surface area, climate, and hydroperiod (water permanency). Surprisingly, at a country-wide scale, climate and hydroperiod filter macrophyte composition weakly. Geology and DIS are the major determinants of community composition, whereas surface area determines floristic richness. DIS was identified as a determinant in freshwater lentic ecosystems for the first time.
Highlights
Ward clustering analysis resulted in four defined plant community groups (Figure 2, Table 1) based on the major variables identified by Dunn’s test
The first group of stations corresponded to acid soft-water lakes (median = 1.83 ± 3.25 mg/L, median alkalinity = 0.18 ± 0.21 meq/L)
Our findings suggest that mineralization and, to a lesser extent, total phosphorus concentrations were determinant variables of Small shallow lakes (SSL) macrophyte community composition, but not of their richness, which is mostly correlated with surface area
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Human activities such as fish stocking, impoundment, or mineral extraction have induced the creation of numerous small shallow lakes (hereafter SSL) [1,2]. The term SSL includes both man-made and natural waterbodies. These freshwater ecosystems are the most abundant on Earth [3]. The mean depth of SSL in temperate regions is less than
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