Climate change and nutrient influx disrupt karst ecosystem dynamics and tufa deposition in Huanglong, China

Abstract

Climate change and anthropogenic activities have severe and irreversible impacts on aquatic ecosystems globally. Huanglong, a UNESCO World Heritage site with tufa deposits, is significantly impacted by climate change and the influx of exogenous nutrients from tourism and vegetation. In this study, we investigate the influence of climate change (temperature increase) and nutrient input (P and N sources, breadcrumbs, and litter) on aquatic geochemical factors dynamics and associated biota (algae and bacteria) that impact tufa deposition. Our results show that tufa deposition is primarily influenced by abiotic factors, particularly temperature and pH, while biological processes, especially eutrophication by organic matter and phosphate input, negatively affect tufa formation. The nutrient input leads to a regime shift in the biotic communities and significantly impacts tufa deposition. Notably, P was identified as a limiting factor in Huanglong Ravine, showing a strong correlation with Proteobacteria and Chlorophyta. In contrast, nitrogen input has minimal effects on taxonomic composition and tufa deposition. Proteobacteria, Actinobacteria, and Bacteroidetes are conserved bacterial phyla associated with algae proliferation independent of nutrient availability or other environmental factors. Our findings support the efficacy of P reduction strategies in mitigating eutrophication and emphasize restricting nutrient and P inputs to maintain freshwater biodiversity and protect tufa landscapes. These insights are crucial for developing strategies and measures to mitigate the combined effects of climate change and anthropogenic activities on tufaceous karst ecosystems.