Network parameters quantify loss of assemblage structure in human-impacted lake ecosystems.

Lake biodiversity is an incomplete indicator of exogenous forcing insofar as it ignores underlying deformations of community structure. Here, we seek a proxy for deformation in a network of diatom assemblages comprising 452 species in 273 lakes across China. We test predictions from network theory that nodes of similar type will tend to self-organize in an unstressed system to a positively skewed frequency distribution of nodal degree. The empirical data reveal shifts in the frequency distributions of species associations across regions, from positive skew in lakes in west China with a history of low human impacts, to predominantly negative skew amongst lakes in highly disturbed regions in east China. Skew values relate strongly to nutrient loading from agricultural activity and urbanization, as measured by total phosphorus in lake water. Reconstructions through time show that positive skew reduces with temporal intensification of human impacts in the lake and surrounding catchments, and rises as lakes recover from disturbance. Our study illustrates how network parameters can track the loss of aquatic assemblage structure in lakes associated with human pressures.

The deficiency of miR-214-3p exacerbates cardiac fibrosis via miR-214-3p/NLRC5 axis.

Cardiac fibrosis is a common pathological feature of many cardiovascular diseases. The regulatory mechanisms of miRNAs in cardiac fibrosis are still unknown. Previous studies on miR-214-3p in cardiac fibroblasts reached contradictory conclusions. Thus the role of miR-214-3p in cardiac fibrosis deserves further exploration. Using a combination of in vitro and in vivo studies, we identified miR-214-3p as an important regulator of cardiac fibrosis, and the proliferation and activation of cardiac fibroblasts. We demonstrated that the expression of miR-214-3p is down-regulated in TGF-ß1-treated myofibroblasts and transverse aortic constriction (TAC)-induced murine model. Additionally, miR-214-3pflox/flox/FSP1-cre mice and miR-214-3pwt/wt/FSP1-cre mice were subjected to TAC operation or sham operation, and the conditional knockout of miR-214-3p in cardiac fibroblasts aggravates TAC-induced cardiac fibrosis. In vitro, our results indicate that miR-214-3p is an important repressor for fibroblasts proliferation and fibroblast-to-myofibroblast transition by functionally targeting NOD-like receptor family CARD domain containing 5 (NLRC5). In conclusion, our findings show that the deficiency of miR-214-3p exacerbates cardiac fibrosis and reveal a novel miR-214-3p/NLRC5 axis in the regulation of cardiac fibrosis.

Catchment-mediated atmospheric nitrogen deposition drives ecological change in two alpine lakes in SE Tibet.

The south-east margin of Tibet is highly sensitive to global environmental change pressures, in particular, high contemporary reactive nitrogen (Nr) deposition rates (ca. 40 kg ha(-1)  yr(-1) ), but the extent and timescale of recent ecological change is not well prescribed. Multiproxy analyses (diatoms, pigments and geochemistry) of (210) Pb-dated sediment cores from two alpine lakes in Sichuan were used to assess whether they have undergone ecological change comparable to those in Europe and North America over the last two centuries. The study lakes have contrasting catchment-to-lake ratios and vegetation cover: Shade Co has a relatively larger catchment and denser alpine shrub than Moon Lake. Both lakes exhibited unambiguous increasing production since the late 19th to early 20th. Principle component analysis was used to summarize the trends of diatom and pigment data after the little ice age (LIA). There was strong linear change in biological proxies at both lakes, which were not consistent with regional temperature, suggesting that climate is not the primary driver of ecological change. The multiproxy analysis indicated an indirect ecological response to Nr deposition at Shade Co mediated through catchment processes since ca. 1930, while ecological change at Moon Lake started earlier (ca. 1880) and was more directly related to Nr deposition (depleted δ(15) N). The only pronounced climate effect was evidenced by changes during the LIA when photoautotrophic groups shifted dramatically at Shade Co (a 4-fold increase in lutein concentration) and planktonic diatom abundance declined at both sites because of longer ice cover. The substantial increases in aquatic production over the last ca. 100 years required a substantial nutrient subsidy and the geochemical data point to a major role for Nr deposition although dust cannot be excluded. The study also highlights the importance of lake and catchment morphology for determining the response of alpine lakes to recent global environmental forcing.

The "2.8 ka BP Cold Event" Indirectly Influenced the Agricultural Exploitation During the Late Zhou Dynasty in the Coastal Areas of the Jianghuai Region.

As a global cooling event, many of the climatic and socio-cultural mechanisms that resulted in changes after the 2. 8 ka BP event remain unclear. In China, this period roughly corresponds with the Zhou Dynasty (1046-212 BC), a critical period when ancient Chinese civilization was experiencing significant cultural and technological changes, including the movement of people to modern-day Jiangsu Province, where they intensively used the natural resources found in this the coastal area. Recent archaeobotanical evidence, and two radiocarbon dates on wheat and foxtail millet, indicate that the Datongpu site, which dates around 2,600 cal a BP, was occupied during this period of transition around the 2.8 ka BP climate event. In total, our investigations recovered 3,399 carbonized seeds from seventy-four flotation samples, of which rice, foxtail millet, broomcorn millet, and wheat seeds where predominant along with 2,296 weed seeds. Additionally, we identified several rice spikelets and wheat rachises. The high number of carbonized rice grains indicates that rice farming was the primary crop in an otherwise mixed rice-dry farming system at Datongpu. In addition, we argue that the "2.8 ka BP cold event" probably influenced population growth and caused food shortages throughout Central China, leading people to migrate southeastward along the Huai River to the coastal areas of Jianghuai Region. We argue that this abrupt shift in the climate indirectly facilitated the exploitation and emergence of large-scale agriculture in this area. Our study provides an example for the indirect impact of climate change in areas with relatively favorable climate conditions.

Disturbance mechanisms of lacustrine organic carbon burial: Case study of Cuopu Lake, Southwest China.

Lakes are important organic carbon (OC) traps in the global carbon cycle. Recent studies have shown that the rate of OC burial in lacustrine sediments is influenced by factors such as climate change, land-use change, and eutrophication. In this study, we use multiproxy methods to reveal the mechanisms of lacustrine sediment OC burial in an alpine lake (Cuopu Lake), in southwest China. Combined with the dating from 210Pbex and n-alkanes distribution analysis using the Positive Matrix Factorization model, the sedimentary history was divided into five stages: religious activity (the 1840s-1880s), earthquake (the 1880s-1910s), garrison (the 1910s-1960s), transition (the 1960s-1990s), and ecotourism (the 1990s-2010s). During the earthquake stage, OC burial was dominated by terrestrial solids (>40%) and co-precipitated algae (>30%), with a rapid deposition rate (>4 mm a-1) and low OC concentration (<4 mg g-1). During the other stages, when the level of disturbance was relatively low, a change in nutrient conditions either promoted or inhibited plant growth, which influenced the type of buried OC. The contribution of OC derived from combustion sources varied from stage to stage. Severe anthropogenic disturbances have led to a significant increase in nutritional levels in the lake water, leading to an increase in the OC burial rate. Climate change, which leads to changes in temperature and rainfall, did not significantly influence OC burial, whereas nitrogen deposition (and associated ecological changes) was a significant determinant. When the general mechanism is dominant, the total nitrogen to inorganic phosphorus ratio is an effective indicator of OC burial due to its selective promotion of different plant types. In conclusion, our results suggest that lacustrine sediment OC burial is closely linked to physical and anthropogenic factors in Cuopu Lake, as well as similar montane lakes.

Long-term variation of phytoplankton biomass and physiology in Taihu lake as observed via MODIS satellite.

Estimation of phytoplankton biomass (noted as phytoplankton carbon, Cphyto) and evaluation of phytoplankton physiology is central to the estimation of primary productivity and the carbon cycle. This issue has been widely considered in oceans but not in inland water. Here, we develop experiential and semi-analytical models, which validated by independent in situ measurement data, respectively, to derive Cphyto and phytoplankton absorption coefficient at 675 nm (aph(675)) from MODIS. The effects of nutrients and temperature on the seasonal variation of phytoplankton physiology were assessed through a novel proxy of Cphyto to aph(675) ratio (Cphyto/aph(675)) over the Lake Taihu, the third largest lake in China. Significant seasonal climatological cycles of Cphyto, aph(675) and Cphyto/aph(675) were observed in Lake Taihu, especially in Meiliang Bay and Zhushan Bay, where algal blooms occur frequently. The highest Cphyto and aph(675) values were observed in summer due to the growth of phytoplankton biomass and chlorophyll-a concentration. Lower values were observed in winter and spring, which are characterized by relatively high total nitrogen levels and low irradiance, owing to the low temperature astricts the algae growth. However, the Cphyto/aph(675) shows an opposite trend compared to Cphyto and aph(675), which have high values in winter and low values in summer. The analysis of Cphyto, aph(675) and Cphyto/aph(675) with total phosphorus (TP) levels and temperature indicates that TP are the main positive driver of the increase in Cphyto and aph(675) and negatively regulate Cphyto/aph(675). Warming promotes an increase in Cphyto and aph(675) and restricts Cphyto/aph(675) in summer. Biomass and nutrient levels are the primary drivers of the decrease of Cphyto/aph(675) in such a typical eutrophic lake. The results present some new findings compared to previous oceanic studies and expand our knowledge in the study of phytoplankton biomass and physiology in eutrophic lakes.