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

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 character-istics, 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 similar to 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.

Automated summary

The effectiveness of sediment retention in dealing with global eutrophication in freshwater ecosystems can be evaluated by comparing the burial of sediment C, N, and P in a plateau lake and its affiliated reservoirs. This study estimated the spatial-temporal accumulation rates of C, N, and P in sediments of Lake Dianchi and its four affiliated reservoirs. The results showed that sediment accumulation rates varied spatially and temporally, with high-value regions in the southern and northern parts of Lake Dianchi. Anthropogenic factors were found to contribute to the accumulation of C, N, and P in sediments. The reservoirs located upstream and in the middle of the lake catchment played a critical role in sediment retention and preventing water deterioration in Lake Dianchi downstream.