One-year monitoring of grass-type architectural waterscapes with long-term operation: Water quality and microorganism

Grass-type architectural waterscapes (GAWs) utilize submerged plants to enhance self-purification ability and maintain a clear-water state. However, knowledge about their long-term water quality and microbial community dynamics remains limited. This study monitored the water quality, microbial community composition, and networks in two GAWs. GAW1 consisted solely Hydrilla verticillata with a water depth of 0.70 m, while GAW2 primarily contained Vallisneria natans, Microsorum pteropus, and Aquarius grisebachii with a water depth of 0.30 m. Results show that both water depth and submerged plant species play crucial roles in GAW establishment. The water depth of 0.7 m enabled Hydrilla verticillata to thrive underwater despite temperature variations, which demonstrated excellent nutrient uptake capacity. Thus, GAW1 exhibited superior self-purification ability, consistently meeting Class III standard for surface water in China. In contrast, GAW2 had a shallow water depth and contained ornamental plants, only meeting Class V standard. Furthermore, microbial communities were shaped by water quality, with distinct enriched genera serving as potential “microbial indicators”. Enrichment of the hgcI clade and Sporichthyaceae_unclassified indicated superior water quality in GAW1, while prevalence of Comamonadaceae_unclassified, Flavobacterium, Rhodoluna, and Pseudarcicella suggested poor water quality in GAW2. Additionally, highly complex and connected microbial networks suggested elevated pollutant levels in GAWs. This study emphasized the significance of submerged plant species and water depth in GAWs construction and highlighted microbial communities and networks as potential indicators of water quality.