760 / 2024-09-19 10:47:46

The impact of sea level changes on mangrove establishment around Sundaland since the Last Glacial Maximum

Mangroves Pollen, Sea-Level Changes, Climate Change, Sundaland, Last Glacial Maximum

Session 23 - Sea level rise: understanding, observing, and modelling

Mangrove dynamics is generally associated with global climate and sea-level changes since the Last Glacial Maximum (LGM). However, the mechanisms vary across different regions, and the process of mangrove establishment in Southeast Asia, particularly since the Last Glacial Maximum, remains unclear. We present high-resolution terrestrial mangrove palynomorph records from five different core sediments—ADM-C1, YDY05, NS2007-8, NS07-46, and NS07-25—around Sundaland since the Last Glacial Maximum to observe mangrove distribution in the region. The ADM-C1 core, spanning the Holocene period in the Andaman Sea, reveals that the highest concentration of mangrove pollen occurred during the early Holocene, between 11.24 kyr and 9.03 kyr; however, this concentration progressively declined towards the late Holocene, coinciding with the rapid rise in sea levels from the early to mid-Holocene. Mangrove pollen concentration significantly declined after 5.41 kyr, coinciding with the period of high and stable sea levels during the mid to late Holocene. Cores YDY05, NS2007-8, and NS07-46 revealed similar patterns: mangrove pollen concentration was very low during the Last Glacial Maximum (26–17 kyr) and gradually increased during the Last Glacial Marine Transgression, which supported the development of tidal estuaries. However, following the LGMT, mangrove pollen concentration of YDY05 and NS07-46 dropped to near zero, likely due to the increased distance between pollen sources and core locations as a result of high sea levels during the Holocene. In contrast, the NS07-25 core from the southern South China Sea showed high mangrove pollen concentrations during the LGM, as low and stable sea levels reduced the distance required for pollen dispersal. Despite cooler and drier conditions, previous palynological analysis confirmed the presence of mangroves in the southern SCS during the LGM, suggesting that suitable coastal habitats allowed these ecosystems to persist. A review of mangrove distributions across South Asia since the LGM indicates that sea-level change is an important factor controlling mangrove establishment around the Sundaland. Understanding these influences, particularly sea-level changes, is crucial for conserving the coastal ecosystems around the Sundaland.