A decade-long perspective on marine health changes in Dalian, China

The ocean, serving as the cradle of life on Earth and the regulator of global climate, constitutes an invaluable resource repository for human survival and development. The preservation of ocean health is pivotal for the sustainable progression of human society. This study chose Dalian in China to assess the marine health using the Ocean Health Index (OHI) at the city-level by selecting appropriate parameters and reference points to align with data sources. The results indicated that the overall OHI score declined by 5.81 in Dalian from 2012 to 2022. For decades, the scores for Clean Waters and Coastal livelihoods and economies had consistently maintained perfection. The scores for Food Provision, Natural Products, and Carbon Storage increased, while those for Tourism and Recreation, Coastal Protection, Sense of Place, Artisanal Fishing Opportunities, and Biodiversity experienced decline. Food Provision saw the most substantial growth, increasing by 16.44, while Tourism and Recreation experienced the steepest decline, dropping by 30.57. It was indicated that the quality of seawater had consistently remained at a high level, and the economy developed well. However, there was a slight decline in marine health, with a notable downturn in tourism. Coastal ecosystems still face ongoing risks of degradation. For the next steps, the focus should be on coastal zone protection and revitalizing the tourism industry. Greater support and effective management should be provided to traditional fisheries. We recommend that parameters and reference points be standardized, and emphasize the importance of prioritizing the use of official data for calculations and assessments when applying the OHI at the city-level to ensure comparability.