Anthropogenic sustained increase in near bottom suspended particulate matter concentration of the deep marginal sea

Anthropocene sediment flux from land to sea has quadrupled from 1950 to 2010, mainly due to mineral extraction. The distribution of suspended particulate matter (SPM) in the deep sea influences the marine environment, sedimentation processes, and material cycling. Using long-term survey data and published findings, we identified an upwardtrend in near-bottom SPM across three representative marginal seas, based on profile data collected during the same month or season over time spans ranging from 3 to 10 years. In the South China Sea, four stations indicate a consistent increase in near-bottom SPM, with an average increase of more than twofold, although the rate of increase varied across different regions and depths. Similarly, profiles from the Gulf of Mexico and the Mediterranean Sea also demonstrated an increasing trend in near-bottom SPM. These three marginal seas are known hotspots for bottom trawling, with frequent engineering activities and mining. Human activities, especially bottom trawling, are identified as the primary drivers behind the ongoing increase in near-bottom turbidity in these marginal seas. As human activities continue to intensify, near-bottom SPM in these marginal seas is expected to further increase in the future.