Assessment of Anthropogenic Impact versus Climate Change on the Succession of the Diatom Community in Lugu Lake (Yunnan-Guizhou Plateau, China) Using the Sedimentary Record of Geochemical Elements

Abstract

The lake ecosystems on the Yunnan-Guizhou Plateau in China have degraded in recent decades under the effects of anthropogenic activities and climate change. The human impact on the oligotrophic Lugu Lake aquatic ecosystem was evaluated using the sediment records of metals, nitrogen isotopes (δ15N) and magnetic susceptibility over the past 200 years. Three periods were identified based on the trace metal and δ15N records. During the first stage (1816–1976 AD), the concentrations of metals, δ15N and magnetic susceptibility were low with small variations. The anthropogenic contributions to the inputs were also small, except for Ni, reflecting minor human activities in the watershed, and no significant change was observed in the sediment record of the diatom assemblage. During the second stage (1976–2001 AD), the concentrations of Zn and δ15N increased, as well as the anthropogenic contribution of Zn. However, no significant change was detected in the anthropogenic sources of the other metals. These results reflect the low-level use of chemical fertilizers. The major shift in the sediment diatom assemblage during this stage was mainly attributed to regional climate change. During the third stage (2001–2010 AD), the concentrations of the sedimentary metals (Ni, Cr, Mn, Cu, Hg and Al) increased rapidly, with the exception of As and Zn, and a similar increasing trend was observed in the changes by anthropogenic sources of Ni, Cr, Mn and Cu. RDA (Redundancy Analysis) and variance partitioning analysis showed that the human impact and climate proxies independently explained 31.59% and 4.26% of the change of diatom community, respectively, and the interaction between climate change and human impact accounted for 18.61% of the change of diatom community. Tourism-dominated human activities, which were reflected in the metals profiles, facilitated the dominance of eutrophic species and reduced that of oligotrophic species. The development of tourism was likely the main driving force for the succession of diatom assemblages in the third stage. In summary, the anthropogenic input of trace metals in Lugu Lake is still at a low level. However, the significant growth trend in metals over the past decade is significantly related to the change in the lake ecosystem. Therefore, the effects of human activities, especially tourism, on the watershed should be controlled for the protection of the oligotrophic Lugu Lake.

Climate and Nutrient-Driven Regime Shifts of Cyanobacterial Communities in Low-Latitude Plateau Lakes

“…Sedimentation chronology was constructed via the radiometric activity of 137 Cs and excess 210 Pb. The sedimentation rates for the sample sites were determined using 210 Pb and 137 Cs analyses (see Figure S2), which were compared with previous studies. ,, Sediment accumulation rates (SARs) were 0.045 g cm –2 a –1 for Lake Erhai, 0.050 g cm –2 a –1 for Lake Lugu, and 0.071 g cm –2 a –1 for Lake Fuxian. The SARs of each lake were used to reconstruct temporal trends in the trophic states and cyanobacterial communities represented by the sediment cores.…”

Aquatic community structure as sentinel of recent environmental changes unraveled from lake sedimentary records from the Atacama Desert, Chile

“…Detrended correspondence analysis (DCA) [54] with detrending by segments was applied to the diatom percentage data to explore the temporal patterns of species changes [55]. A DCA axis gradient length of 1.65 standard deviations (SD) was obtained, indicating that RDA (redundancy analyses) was appropriate to explore the relationships between the diatom community and the environmental variables [56].…”

Using Algal Indices to Assess the Ecological Condition of the Aras River, Northwestern Iran

“…Diatoms react directly to many physical, chemical, and biological changes in water ecosystems, such as temperature and concentration of nutrients [55]. They also respond to chemical changes in the water, seasons, and physical variables [56][57][58][59]. Diatom species have very strong relationships with nutrients such as salinity, alkaline conductivity, and total phosphate, which can be measured at different stations.…”

“…They are strongly influenced by the main controlling factors such as hydrological features, biogeochemical processes, temperature, and surface runoff caused by precipitation in these systems [63][64][65][66][67][68][69]. This shows that diatom community dynamics are a function of natural factors such as temporal variability [70][71][72] as well as anthropogenic factors such as pollutant emissions [58,[73][74][75]. Diatoms are seen in brown and gold colors due to xanthophyll pigment [76], and photosynthetic pigments are bioactive compounds.…”