Terrestrial organic matter input changes recorded by biomarkers alter phosphorus burial in the upper Yangtze River Basin

Abstract

Exploring the impacts of anthropogenic processes on the organic matter (OM) input and phosphorus (P) burial characteristics is essential for describing the carbon (C) cycle and its environmental effects on aquatic ecosystems from multiple perspectives. In this study, the centennial sedimentary P, C, and nitrogen (N) characteristics and terrestrial OM input changes in the upper Yangtze River were reconstructed by ²¹⁰Pb-dated and positive matrix factorization (PMF) methods, and the key factors were identified. The P accumulation and stock averaged at 2.23 ± 1.08 g P m⁻² yr⁻¹ and 0.01–0.07 Mg P ha⁻¹ from 1855 to 2019. Changes in corresponding loads of total organic C (TOC) and N (TN) separately ranged between 0.58 and 1.81 Mg C ha⁻¹ and 0.07–0.29 Mg N ha⁻¹ over the past century. The total sequestration was 4.20 × 10⁵ t of C, 5.51 × 10⁴ t of N, and 1.22 × 10⁴ t of P, respectively, accounting for 33%, 54%, and 14% of Dianchi Lake. The strength and contribution of terrestrial OM driven by anthropogenic activities were constantly increased, and the proportion increased sharply from 34 to 52%. About 67–86% of biogenic OM was the main source of P sedimentation. In the context of recent warming, the combined effects of C and N loading, redox environment, climate change, and anthropogenic activities enhanced the P accumulation and retention by 1.29 g P m⁻² yr⁻¹ per 1 ℃ increase in temperature. These findings suggest that the sediment in this area generally acts as a sink pool of nutrients, which is critical for predicting P fate and nutrient cycle.