2.1 Experimental design and sample collection
A total of 29 sedimental samples were collected in the Beibu Gulf, a semi-enclosed oceanic bay located in the southern coast of China (Supplementary Figure 1). Samples were collected from a near rectangle area that was 149.25 km long and 128.73 km wide, covering approximately 19212.57 km2. The sampling area were then divided into 9 blocks, with each block covering 3-4 samples. By merging neighborhood blocks, a series of multi-block sampling areas were generated, enabling TAR analysis in the experiment.