Abstract
The current climate warming and eutrophication are known to interactively threaten freshwater biodiversity; however, the interactive effects on lacustrine bacterioplankton diversity remain to be determined. Here, we analyzed the spring bacterioplankton community composition (BCC) in 24 outdoor, flow-through mesocosms (mimicking shallow lake environments) under 3 temperature scenarios and 2 nutrient regimes. Our results revealed that neither long-term warming (8.5 years) nor nutrient enrichment had significant effects on bacterioplankton alpha diversity, whereas long-term enhanced warming (elevated 50% above the IPCC A2 climate scenario) and nutrient enrichment in combination increased bacterioplankton beta diversity. We also found that BCC shifted significantly under enhanced warming and nutrient-enriched conditions towards decreased relative abundances of Actinobacteria, Bacteroidetes and Betaproteobacteria, whereas the percentages of Cyanobacteria, total rare phyla and unclassified phyla significantly increased. Null-model tests indicated that deterministic processes played a more important role than stochastic processes in determining BCC. However, the relative importance of stochasticity, primarily ecological drift, was enhanced and contributed to the increased beta diversity of BCC under enhanced warming and nutrient-enriched conditions. Overall, our study suggests that the synergetic effects of warming and nutrient enrichment may result in high variability in the composition of bacterioplankton communities in lacustrine water bodies.
Highlights
Our results revealed that neither long-term warming (8.5 years) nor nutrient enrichment had significant effects on bacterioplankton alpha diversity, whereas long-term enhanced warming and nutrient enrichment in combination increased bacterioplankton beta diversity
We found that bacterioplankton community composition (BCC) shifted significantly under enhanced warming and nutrient-enriched conditions towards decreased relative abundances of Actinobacteria, Bacteroidetes and Betaproteobacteria, whereas the percentages of Cyanobacteria, total rare phyla and unclassified phyla significantly increased
Shift in BCC at warming and nutrient enrichment We found that BCC was significantly impacted by warming scenarios (PERMANOVA, incidence-based Jaccard’s dissimilarity: F = 1.724, P = 0.002, Figure 1a; Bray-Curtis’s dissimilarity: F = 2.081, P = 0.001, Figure 1b; Table 1) and nutrient levels was significantly positively correlated with gross primary production, whereas the BCC in all nutrient-unenriched mesocosms and most nutrient-enriched but unheated mesocosms was significantly positively correlated with plant coverage
Summary
Most of water temperature and nutrient conditions, shallow these studies suggest that warming, when interacting water habitats may exhibit multiple stable states with eutrophication, enhances the growth of lacus- under similar or identical nutrient conditions trine bacterioplankton (Christoffersen et al, 2006; (Scheffer et al, 1993).
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