A long-term assessment of the benthic habitat quality of intertidal flats in Liaohe Estuary was conducted by three integrating ecological indices, AZTI’s Marine Biotic Index (AMBI), Multivariate-AMBI (M-AMBI), and Shannon–Wiener diversity index (H′) based on macrobenthos data from 2013 to 2020. The results showed that the macrobenthic communities were characterized by indifferent and sensitive species of AMBI ecological groups. The annual ranges of H′, AMBI, and M-AMBI were 0.77–1.56, 1.44–3.73 and 0.36–0.54, respectively. Noticeable differences were found among assessment obtained by these biotic indices. Approximately 100%, 24%, and 78% sampling sites had “moderate”, “poor”, and “bad” statuses as assessed by H′, AMBI, and M-AMBI, respectively. Compared with H′ and AMBI, M-AMBI may be more applicable to evaluate the benthic habitat quality of intertidal flats in Liaohe Estuary. Results suggest that the benthic habitat quality in the middle parts of intertidal flats still had an unacceptable status and has not improved radically to date after large-scale “mariculture ponds restored to intertidal flats”.

A large-scale ecological restoration project has been implemented since 2015 in the Liaohe Estuary of China to restore mariculture ponds to tidal flats and to ultimately improve the ecological environment. However, the influence of the project on landscape patterns remains unclear. This study analyzes spatiotemporal changes in the landscape pattern of the tidal flat in the estuary from 2013 to 2023, utilizing high-resolution remote sensing images (GF-1/GF-2) and landscape indices. Results indicate that the mariculture pond areas decreased from 74.84 km ² in 2013 to 33.68 km ² in 2023 after the implementation of various projects. This reduction was temporally associated with the conversion to tidal flats, which constitute 85% of the newly formed tidal flat area and Suaeda salsa marshes. The landscape stability index exhibited considerable variations between 2013 and 2017. Moreover, the landscape pattern of the tidal flat transitioned from fragmentation to connectivity, and the stability of the estuarine tidal flat ecosystem gradually improved in the period following the reclamation restoration project. This study demonstrates the effectiveness of mariculture ponds restored to tidal flats as strategies for future restoration initiatives, offering insights for assessing the effects of ecological restoration and contributing to the protection of estuarine ecosystems.