Ecological lock-in and functional mismatch in abandoned coastal ponds: mechanisms and management implications

The recovery of coastal aquaculture ponds and salt pans into functional wetlands represents a widespread challenge in global coastal restoration, yet passive recovery strategies often fail to address legacy effects associated with habitat degradation and functional deficits. Taking the Yellow River Delta National Park as a case study, a comprehensive field survey was conducted on water and soil conditions, vegetation communities, and benthic assemblages. Results indicated that salinity and organic load in both water and soil were key environmental gradients associated with cross-habitat differences in biological communities, with redundancy analysis explaining 44.2% of the variance. Abandoned salt pans exhibited an ecological lock-in characterized by extremely depauperate biotic communities, where excessive soil salinity exceeding 3% and strong environmental filtering prevented vegetation colonization. In contrast, although abandoned aquaculture ponds maintained higher benthic biomass, elevated chemical oxygen demand (COD) and legacy soil phosphorus indicate a risk of endogenous pollution. Moreover, excessive water depth (>1 m) substantially limited the effective foraging potential for shorebirds, resulting in a pronounced mismatch between resource abundance and accessibility. To address these constraints, this study proposes a conceptual "1+3+L" adaptive management framework, encompassing ecological production, functional zonal restoration, and ecological corridor connectivity. This framework integrates observed ecological constraints and functional patterns to form evidence-based management hypotheses aimed at addressing key legacy barriers in constructed wetlands and enhancing their functional potential as foraging habitats for waterbirds.