Macroinvertebrate Community Responses and Recovery Mechanisms to Extreme Drought in Small Water Bodies of Eastern China

Extreme summer droughts increasingly threaten freshwater biodiversity in monsoonal regions, yet community responses within heterogeneous small water bodies (SWBs) remain poorly understood. This study evaluated how drying events influence macroinvertebrate taxonomic and functional composition across different SWB types and explored the mechanisms driving post-drought recovery. We sampled isolated ponds (IPs), stream-fed ponds (SFPs), pond-linked streams (PLSs), and non-pond-linked streams (NPLSs) in Eastern China during an extreme summer drought (2022) and a subsequent recovery year (2023). Ponds exhibited high resistance, maintaining stable taxonomic and functional richness. PLSs suffered substantial summer biodiversity declines but showed rapid post-drought recovery, possibly facilitated by spatial dispersal from nearby pond refuges. In contrast, NPLSs experienced severe, lasting biodiversity loss. Drought conditions drove overall community homogenization, with spatial dispersal playing a more important role in structuring assemblages than environmental filtering. Furthermore, functional trait analysis indicated that post-drought recovery was more closely associated with resilience-linked traits rather than resistance traits. These findings demonstrate that lateral connectivity within SWB networks buffers drought impacts by providing refugial support and enabling rapid recolonization. Preserving diverse, interconnected SWBs is a critical management strategy for maintaining metacommunity resilience under growing climatic volatility.