Historical variations of sedimentary organic matter sources and their relationships with human socio-economic activities in multiple habitats of a shallow lake

Abstract

Understanding the source and historical variation of sedimentary organic matter (OM) and their relationships with human socio-economic activities is of great significance to water resource management. In this work, sediment cores from five different habitats were collected in Baiyangdian Lake, China. A Bayesian model (stable isotope analysis in R, SIAR) was utilized to apportion the historical changes of the proportional contributions of potential sources in sediments based on carbon and nitrogen stable isotopes (δ13C and δ15N) and C/N ratios. The impacts of human socio-economic activity factors (GDP, population) on the historical variations of sedimentary OM source have been evaluated by the generalized additive models (GAMs). The results showed that autochthonous OM (phytoplankton) was the dominant sediment OM source in river course (13%–48%), lotus pond (16%–48%) and open water (16%–47%), and the contributions began to increase after 1944, 1950 and 1962, respectively. Phytoplankton (37%–53%) was also the main source of OM in sediments of fish pond, but its contribution had remained high throughout. Allochthonous OM (soil OM: 29%–42%) was the main source of sedimentary OM in reed marshes, and it showed a slow increasing trend after 1995. The GAMs results showed that population was the dominant contributor to the variations of OM sources in sediments of lotus pond, open water and fish pond and GDP was the dominant contributor to that in sediments of reed marshes, with the interpretation rates of 70%–99%. Both GDP and population were dominant influence factors on sedimentary OM sources of river course, which account for 52%–98%. It is proved that human socio-economic activities have significant impact on the historical variations of sedimentary OM sources.