Evaluating the effectiveness of sediment retention by comparing the spatiotemporal burial of sediment carbon, nitrogen and phosphorus in a plateau lake and its affiliated reservoirs

Abstract

Evaluating the effectiveness of sediment retention by comparing the spatiotemporal burial of sediment C, N, and P in a plateau lake and its affiliated reservoirs is critical in dealing with global eutrophication in freshwater ecosystems. The objective of the study was to estimate the spatial–temporal of C, N and P accumulation rates (CAR, NAR and PAR) in sediment cores of a plateau Lake Dianchi (DC) and its four affiliated reservoirs (Dashiba-DSB, Xibaisha-XBS, Baoxianghe-BXH, and Shuanlong-SHL). The results indicated that the average sediment accumulation rates (SARs) ranged from 0.040 to 1.187 g cm−2 a−1 in DC and 0.201 to 3.965 g cm−2 a−1 in its affiliated reservoirs. Spatially, all of the values of CAR, NAR and PAR exhibited similar distribution characteristics, along with two high-value regions concentrated in the southern and northern parts of the lake DC. Temporally, these three values of Lake DC and its affiliated reservoirs showed upward trends from bottom to top over the past ∼ 150 years, especially occurring in the 1950s. The change in the C/N ratio indicated that intensive anthropogenic factors promoted the CAR, NAR and PAR in sediments. Based on a developed proportional model, the ratios of sediment retention by each reservoir on TOC, TN and TP were calculated to be 2.15 %, 4.38 % and 9.01 % for DSB, 0.14 %, 0.18 % and 0.14 % for XBS, 1.61 %, 5.77 % and 1.23 % for BXH, and 0.97 %, 2.07 % and 0.46 % for SHL, respectively. Reservoirs located in the upper and middle reaches of the lake catchment play a critical role in sediment retention and prevent a potential risk from water deterioration of the downstream Lake DC. Linkages between reservoir-sources and lake-sinks not only provide valuable information for managing the environmental changes within the catchment, but also contribute to new insight into the regulation of water eutrophication in global lake ecosystem.