摘要：River deltas are important for human habitation, commerce, food, and natural resources. Most terrestrial freshwater, dissolved substances, and suspended sediment supplied to the ocean pass through delta distributary channels. Transitions are complex as this river discharge moves through the serial environments of delta systems: tidal river, estuary, shoreline, continental shelf. The bulk of Mekong sediment accumulates as a muddy clinoform deposit on the shallow continental shelf (10 cm yr –1 ) in the relatively steep foreset region. Intense landward and southwestward currents transport the other two-thirds of Mekong discharge during energetic shelf conditions (December–April). These sediments create a relatively shallow clinoform structure, cause the delta to grow asymmetrically toward the southwest, and form the Ca Mau Peninsula. In the future, these same natural processes will operate under different conditions. Construction of many dams within the drainage basin (>200 constructed or approved) and the impacts of climate change (i.e., alterations in monsoonal conditions) will significantly decrease Mekong River discharge. In addition, the delta land surface will be flooded due to acceleration of eustatic sea level rise and local land subsidence. Together, loss of river discharge and rise of local sea level will cause many secondary impacts, including erosion of distributary channels, ocean shorelines, and the shelf seabed; saltwater intrusion farther into the channels, along with transfer of associated estuarine processes; and decreased supply of freshwater and solutes, including nutrients, to the coastal ocean. The collaborative research among international and Vietnamese scientists described in this special issue of Oceanography provides an integrated understanding of the Mekong Delta system, and could help formulate strategies to enhance the resiliency of the system and its ability to cope with future impacts.
