Assessing spatial patterns and ecological risks to coastal ecotourism: A case study from the Bohai Sea

The Bohai Sea, a semi-enclosed marginal sea in northeastern China, plays a critical role in regional coastal ecotourism and marine biodiversity. However, intensifying industrialization and urban expansion have raised significant environmental concerns, particularly regarding trace metal contamination in coastal sediments that threaten both ecosystem services and the long-term viability of ecotourism. This study evaluates the spatial distribution, ecological risk levels, and potential sources of key trace metals—Cu, Cd, As, Pb, Zn, Cr, and Hg—across five prominent coastal tourism and ecological zones: Shuangtaizi Estuary, Jinzhou Bay, Luanhekou Estuary, Bohai Bay, and Laizhou Bay. A total of 108 surface sediment samples were collected in August 2015 and analyzed using a suite of geochemical risk assessment models, including the Contamination Factor (CF), Geo-accumulation Index (Igeo), Pollution Load Index (PLI), and Potential Ecological Risk Index (PERI). Results revealed elevated ecological risk from Hg and Cd, particularly in Jinzhou Bay, where concentrations exceeded background levels and posed substantial threats to sediment quality and marine life. Igeo values indicated variable contamination, ranging from unpolluted to highly polluted conditions, with Jinzhou Bay identified as a critical hotspot. Multivariate statistical analyses (PCA and HCA) attributed Hg, Cd, and As primarily to anthropogenic sources, while Cu, Zn, Pb, and Cr were linked to natural geological inputs. Although over 90 % of samples for most metals were below the Threshold Effect Concentration (TEC), 33.3 % of As and 15.7 % of Hg samples fell between TEC and the Probable Effect Concentration (PEC), posing moderate ecological risks. These findings underscore the urgent need for targeted pollution mitigation and environmental governance, especially in industrially impacted areas, to safeguard coastal ecotourism and preserve the ecological resilience of the Bohai Sea.