Environmental changes in Lake Taihu during the past century as recorded in sediment cores

2007 ◽  
pp. 117-123 ◽  
Author(s):  
Bin Xue ◽  
Shuchun Yao ◽  
Weilan Xia
Keyword(s):  
Environmental Changes ◽  
Lake Taihu ◽  
Sediment Cores ◽  
Past Century ◽  
The Past

Environmental changes in Lake Taihu during the past century as recorded in sediment cores

Hydrobiologia ◽  
2007 ◽  
Vol 581 (1) ◽  
pp. 117-123 ◽  
Author(s):  
Bin Xue ◽  
Shuchun Yao ◽  
Weilan Xia
Keyword(s):  
Environmental Changes ◽  
Lake Taihu ◽  
Sediment Cores ◽  
Past Century ◽  
The Past

scholarly journals Recent environmental changes in the Yunnan–Guizhou Plateau inferred from organic geochemical records from the sediments of Fuxian Lake

Elem Sci Anth ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Haibo He ◽  
Zaihua Liu ◽  
Dongli Li ◽  
Hongbo Zheng ◽  
Jianxin Zhao ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Anthropogenic Impacts ◽  
Anthropogenic Activities ◽  
Sediment Cores ◽  
High Amplitude ◽  
Average Chain Length ◽  
Past Century ◽  
The Past ◽  
The 1950S ◽  
Guizhou Plateau

During the past century, many lacustrine environments have changed substantially at the ecosystem level as a result of anthropogenic activities. In this study, the distributions of n-alkane homologues, carbon isotopes (δ13Corg), organic carbon, and the C/N atomic ratio in two sediment cores from Fuxian Lake (Yunnan, southwest China) are used to elucidate the anthropogenic impacts on this deep, oligotrophic, freshwater lake. The carbon preference index (CPI) of long-chain components, average chain length (ACL), proportion of aquatic macrophytes (Paq), and terrigenous/aquatic ratios (TAR) show different temporal patterns that reflect variations in biological production. Notably, the n-alkane homologues are shown to be more sensitive to environmental changes than δ13Corg and the C/N ratio. Prior to the 1950s, minor variations in the sedimentary geochemical record were likely caused by climate changes, and they represent a natural stage of lake evolution. The onset of cultural eutrophication in Fuxian Lake occurred in the 1950s, when the n-alkane proxies collectively exhibited high-amplitude fluctuations but overall decreasing trends that coincided with population growth and related increases in land-use pressure. In the 21st century, Fuxian Lake has become even more eutrophic in response to human activities, as indicated by sharp increases in C/N ratio, Paq, δ13Corg, ACL, CPI, and TAR. Our findings provide robust molecular sedimentary evidence confirming that the environmental evolution of lakes in the Yunnan–Guizhou Plateau over the past century was closely associated with enhanced anthropogenic activities.

scholarly journals Sedimentation rates in the Lake Qattinah using 210Pb and 137Cs as geochronometer

2014 ◽  
Vol 41 (1) ◽  
pp. 81-86 ◽  
Author(s):  
Eskander Alhajji ◽  
Iyas Ismail ◽  
Mohammad Al-Masri ◽  
Nouman Salman ◽  
Mohammad Al-Haleem ◽  
...  
Keyword(s):  
Sediment Cores ◽  
Past Century ◽  
Sedimentation Rates ◽  
Accumulation Rates ◽  
210Pb And 137Cs ◽  
The Past ◽  
Activity Concentrations ◽  
210Pb Activity ◽  
Constant Rate ◽  
210Pb Method

Abstract The constant rate of supply (CRS) of excess 210Pb model was successfully applied to assess 210Pb data of two sediment cores from the lake Qattinah, Syria. Gamma spectrometry was used to determine 137Cs and 210Pb activity concentrations. The bottom of the cores was 210Pb-dated to years 1907 and 1893. The accumulation rates were determined using 210Pb method and found to vary similarly in both cores from 0.10 ± 0.01 to 3.78 ± 0.57 kg m−2 y−1 during the past century. 137Cs was used as an in-dependent chronometer. The two distinct peaks observed on the 137Cs record of both cores, corresponding to 1965 and 1986, have allowed a successful validation of the CRS model.

PALEOLIMNOLOGY OF THE MAYA LOWLANDS

2002 ◽  
Vol 13 (1) ◽  
pp. 141-157 ◽  
Author(s):  
Mark Brenner ◽  
Michael F. Rosenmeier ◽  
David A. Hodell ◽  
Jason H. Curtis
Keyword(s):  
Late Holocene ◽  
Environmental Changes ◽  
Anthropogenic Activities ◽  
Yucatan Peninsula ◽  
Sediment Cores ◽  
Maya Lowlands ◽  
Holocene Climate ◽  
The Past ◽  
Yucatán Peninsula ◽  
Paleoclimate Records

Since the late 1950s, scientists have used sediment cores from lakes on the Yucatan Peninsula to explore the complex interactions among climate, environment, and ancient Maya culture. Early paleolimnological studies generally assumed that late Holocene climate was invariable. Consequently, paleolimnologically inferred environmental changes that occurred during the past 3,000 years or so—for example, forest decline and soil erosion—were attributed wholly to anthropogenic activities such as land clearance for agriculture and construction. Recent high-resolution, proxy-based paleoclimate records from continental and insular sites around the Caribbean Sea contradict the assumption of late Holocene climate stability. Instead, these core data suggest that regional drying began about 3,000 years ago and that the past three millennia were characterized by variable moisture availability. Paleoclimate inferences from Lakes Chichancanab and Punta Laguna, northern Yucatan Peninsula, indicate that drought events over the past 2,600 years were cyclical. These dry events, thought to have been driven by solar forcing, appear to have occurred approximately every two centuries (about 208 years). The driest period of the late Holocene occurred between A.D. 800 and 1000, coincident with the Classic Maya Collapse. We review the history of paleolimnological studies in the Maya Lowlands, discuss the difficulty of differentiating climatic signals from anthropogenic signals in late Holocene lake sediment profiles, and assess current understanding of past climate changes in the region based on regional lacustrine sediment studies.

Contribution of Deforestation to Severe Flooding in Southeast Parts of the Caspian Sea: A Case Study with NDVI Analysis

2020 ◽  
Vol 07 (01n02) ◽  
pp. 2050008 ◽  
Author(s):  
Farahnaz Fazel-Rastgar
Keyword(s):  
Rural Areas ◽  
Caspian Sea ◽  
Vegetation Index ◽  
Environmental Changes ◽  
Discharge Rate ◽  
Past Century ◽  
The Caspian Sea ◽  
The Past ◽  
Color Composite ◽  
Severe Flooding

Iran has been faced with increase in flooding cases during the past 60 years. The human activities have been considered as a devastating factor in the environmental change causing the occurrence of severe flooding cases during past decades. On August 11, 2001, a relatively severe rainfall in the south east of Caspian Sea led to the occurrence of a severe deadly flooding in Golestan province and some parts in northern Khorasan province have been unprecedented in Iran over the past century. The destructive extent of flooding in the urban and rural areas reached about 5,000 km2. Here, the synoptic surface and upper levels of the weather charts have been analyzed along with the monitoring of half hourly METEOSAT7 images to show the convective clouds development over the area of the study. The total precipitation in this area during the flooding period was reported between 2.5 and 153 mm with the maximum estimation over the center of the storm around less than 250[Formula: see text]mm. Using satellite imagery in 1979 and 2000, vegetation changes and environmental changes have been investigated and shown extensive decline in vegetation. The image processing and Normalized Difference Vegetation Index (NDVI) calculation of the color composite 433 of LANDSAT5 and the color composite 211 of TERRA (MODIS sensor) images between 1998 and 2001 have been revealed significant deforestation around 248,131,534.3[Formula: see text][Formula: see text] over the study, particularly over the rivers’ neighborhood. Also, by assumption of the same precipitation for 1998 and 2001, the discharge rate in flood case of 2001 has been intensified 1.3 times (at 13 percent) larger than that of 1998. This shows the direct impact of the deforestation and land use changes over the study area during 1998–2001.

scholarly journals Continuing Environmental Change - An Example from Nova Scotia

2004 ◽  
Vol 118 (1) ◽  
pp. 39 ◽  
Author(s):  
Edmund S. Telfer
Keyword(s):  
Nova Scotia ◽  
Environmental Changes ◽  
Human Impacts ◽  
Castor Canadensis ◽  
Dermacentor Variabilis ◽  
Fagus Grandifolia ◽  
Past Century ◽  
Lynx Lynx ◽  
The Past ◽  
Severe Reduction

Information from personal experience, from community elders and published literature served as a basis for evaluating environmental changes in the District of North Queens and adjacent areas of Southwestern Nova Scotia over the past century. Major events included disappearance of the Caribou (Rangifer tarandus), the arrival of White-tailed Deer (Odocoileus virginianus), the severe reduction of Canada Yew (Taxus canadensis), disappearance of Lynx (Lynx canadensis), a major dieoff of Striped Skunks (Mephitis mephitis), decline of American Beech (Fagus grandifolia), the loss of mature birch (Betula spp.), the severe reduction of Moose (Alces alces), the arrival of the American Dog Tick (Dermacentor variabilis) and Coyotes (Canis latrans), and the restoration of Beaver (Castor canadensis). The proximate cause of many of those changes were plant and animal disease, while the ultimate causes were naturally occurring animal range expansion and human impacts. The warming of the climate over the past 150 years probably played a role. The nature and timing of the events could not have been predicted.

scholarly journals Faunal isotope records reveal trophic and nutrient dynamics in twentieth century Yellowstone grasslands

2012 ◽  
Vol 8 (5) ◽  
pp. 838-841 ◽  
Author(s):  
Kena Fox-Dobbs ◽  
Abigail A. Nelson ◽  
Paul L. Koch ◽  
Jennifer A. Leonard
Keyword(s):  
Nutrient Dynamics ◽  
Environmental Changes ◽  
Bone Collagen ◽  
Past Century ◽  
Significant Shift ◽  
Gray Wolves ◽  
The Past ◽  
Grassland Ecosystems ◽  
Population Sizes ◽  
Insight Into

Population sizes and movement patterns of ungulate grazers and their predators have fluctuated dramatically over the past few centuries, largely owing to overharvesting, land-use change and historic management. We used δ 13 C and δ 15 N values measured from bone collagen of historic and recent gray wolves and their potential primary prey from Yellowstone National Park to gain insight into the trophic dynamics and nutrient conditions of historic and modern grasslands. The diet of reintroduced wolves closely parallels that of the historic population. We suggest that a significant shift in faunal δ 15 N values over the past century reflects impacts of anthropogenic environmental changes on grassland ecosystems, including grazer-mediated shifts in grassland nitrogen cycle processes.

Shot gun sequencing of sedimentary ancient DNA from an Arctic lake reveals ecosystem changes through climate regime transitions over the last 50,000 years 

2021 ◽  
Author(s):  
Kathleen R. Stoof-Leichsenring ◽  
Sichao Huang ◽  
Luidmila A. Pestryakova ◽  
Boris K. Biskaborn ◽  
Ulrike Herzschuh
Keyword(s):  
Ancient Dna ◽  
Environmental Changes ◽  
Sediment Cores ◽  
Arctic Lakes ◽  
The Arctic ◽  
Ecosystem Change ◽  
The Past ◽  
Dna Libraries ◽  
Compositional Patterns ◽  
Climate Transitions

<p>Sedimentary ancient DNA is a valuable proxy to study ecosystem change during the past. In particular, Arctic lakes provide fantastic archives of well-preserved DNA in lake sediment cores and provide reconstructions of ecosystem change during climate transitions in the past, which help to predict prospective environmental changes under current rapid warming known to be strongest in the Arctic. Our analyses are conducted on a 10 m sediment core from Lake Ilirney, located in Eastern Chukotka, which covers the last 50 ka of major climate transitions from the lake’s development within a warmer period previous to the last glacial towards nowadays. We prepared seventeen single-stranded DNA libraries from different time slices and used shot gun sequencing, an innovative method neglecting target enrichment, to achieve a portray of the past biotic composition. The bioinformatic data analyses included data trimming and merging with Fastp and k-mer based taxonomic classification against the nucleotide database using Kraken2. Preliminary results revealed about 372 bacterial families (about 90.1% of total reads), 651 eukaryotic families (8.7%) and a few Archaea (1.1%). Dominant eukaryotic groups are plants (Saliceae, Poaceae, and Rosaceae), protists (Monodopsidaceae, Oomycota and flagellates), fish (Salmonidae, Cyprinidae), birds (Phasianidae) and mammals (Muridae). Our data confirms compositional changes of plants throughout the last 28 ka known from pollen and metabarcoding analyses of a parallel core. Further, our data revealed most prominent turnover of the eukaryotic key taxa at about 30 and 12 ka which corresponds to the major climatic transitions from glacial-interglacial periods. The detailed investigation of compositional patterns and authenticity of ancient DNA data will improve our understanding of ecosystem change in the Arctic over millennial time scales.</p>

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