Bay areas are not only transport gateways but also key spaces where trade, finance and regional markets are connected. Recent geopolitical conflicts and global supply-chain reconfiguration have renewed attention to how coastal regions can maintain market integration and supply-chain resilience under external shocks. Against China's policy agenda of building a unified domestic market and reducing economy-wide logistics costs, a staggered difference-in-differences framework is used to identify effects of port resource integration on supply-chain resilience. The Yangtze River Delta (YRD) provides a suitable empirical setting because it combines a world-class port cluster, the Yangtze River inland hinterland, and one of China's most intensive manufacturing bases. Using a panel of YRD prefecture-level cities from 2008 to 2024, we exploit staggered port integration reforms, including Zhejiang port integration, the creation of Jiangsu Port Group, and Anhui port and waterway resource integration. The key economic mechanism is that port resource integration reduce logistics frictions by coordinating port functions, improving hinterland access and strengthening land-sea connectivity, thereby enhancing bay-area supply-chain resilience. To measure this mechanism more directly, the study incorporates Automatic Identification System (AIS) vessel trajectory data. Rather than treating shipping as a black box, AIS data are used to construct micro-level indicators between coastal gateways and inland river ports. These measures are then linked to city-level outcomes to test whether improvements in real transport efficiency transmit port integration reforms to broader economic resilience. This study contributes to the literature on transport infrastructure, market integration and supply-chain resilience by showing how an institutional reform in port resource allocation can reshape economic connectivity within a major bay area. It also provides policy evidence for coordinated bay planning, port-city-industry integration and the construction of a unified domestic market.