Sedimentary records of mangrove evolution during the past one hundred years based on stable carbon isotope and pollen evidences in Maowei, SW China

Abstract

Mangroves accumulate sedimentary sequences, where cores can provide historical records of mangrove evolution with past climate change and human activity. The study traced the history of mangrove evolution during the past one hundred years in a mangrove swamp of Maowei Sea, SW China. The sedimentation rates (0.38-0.95 cm yr−1) were calculated on the basis of ln (210Pbxs/Al) and mass depth in the core sediments. Chemical tracers, such as δ13Corg and C:N values, were utilized to trace the contribution of mangrove-derived organic matter using a ternary mixing model. Because of potential diagenetic alteration and / or overlap in the isotopic signatures of different components, simultaneous use of mangrove pollen diagrams can help to supplement some of these limitations. Combined with mangrove pollen, mangrove evolution was reconstructed and could be divided into three stages: flourishment (1886-1905 AD), slight degradation (1905-1949 AD) and rapid degradation period (1949-2007 AD), which was consistent with previous reports. The reclamation of mangrove swamps to shrimp ponds was the major reason for rapid degradation of mangrove ecosystems in recent years, rather than climate change in the region.