Holocene diatom assemblages from Dunderbukhta sediments, West Svalbard

2019 ◽  
pp. 242-245
Author(s):  
Ksenya V. Poleshchuk ◽  
Zinaida V. Pushina ◽  
Sergey R. Verkulich
Keyword(s):  
Environmental Changes ◽  
Ecological Groups ◽  
Diatom Assemblages ◽  
Diatom Analysis ◽  
Diatom Flora ◽  
Sediment Samples ◽  
Ecological Zones ◽  
Middle Holocene ◽  
Temperature Trends

The diatom analysis results of sediment samples from Dunderbukta area (Wedel Jarlsberg Land, West Svalbard) are presented in this paper. The diatom flora consists of four ecological groups, which ratio indicates three ecological zones. These zones show environmental changes of the area in early–middle Holocene that is demonstrating periods of regression and temperature trends.

scholarly journals Using Paleoecological Proxies to Determine Holocene Environmental Change: A Case Study at Onaero Beach, North Taranaki

2021 ◽  
Author(s):  
◽  
Rachel Skudder
Keyword(s):  
Late Holocene ◽  
Environmental Changes ◽  
Marine Species ◽  
Loss On Ignition ◽  
Diatom Assemblages ◽  
Diatom Analysis ◽  
Global Context ◽  
Prevailing Wind Direction ◽  
Climatic Event

<p>A multi-proxy paleoecological and sedimentological record for the last ~8.3kyr is extracted from a 2.1m coastal seacliff at Onaero Beach, North Taranaki. This record is used to infer both local environmental changes including shoreline, coastal conditions, as well as regional changes in atmospheric circulation and climate wetness. Analysis of diatom and pollen populations, particle size, and loss on ignition provide the raw data from which inferences regarding salinity and vegetation are made. Changes are tied to a chronology determined through radiocarbon ages and tephrochronology.  Key objectives of this study are: (1) To characterize changes in salinity and relative shoreline position at Onaero Beach (2) To characterise changes in vegetation and relate these changes to overall state of the climate through the Holocene (3) Compare the results of this study with others from New Zealand and the wider south pacific to investigate how the Onaero Beach section fits in both a regional and global context.  Diatom analysis of the Onaero section revealed the dominance of brackish to marine species which suddenly at 7.3ka after which time diatom assemblages were dominated by fresh and salt intolerant species. The marine to freshwater transition represents a transition from a brackish to freshwater coastal lagoon.  Pollen analysis of the Onaero Beach section indicates the region was dominated by podocarp forest. The increasing dominance of Dacrydium and decline in other podocarps suggests an increase in overall climate wetness.  The disappearance of pollen in conjunction with the deposition of tephra at ~4.15ka is not conclusive proof of, but certainly fits with, the idea of a significant climatic event occurring at ~4.2ka resulting in a reversal of the current prevailing wind direction and supports the case for a formal Middle/Late Holocene boundary at this time.</p>

scholarly journals Using Paleoecological Proxies to Determine Holocene Environmental Change: A Case Study at Onaero Beach, North Taranaki

2021 ◽  
Author(s):  
◽  
Rachel Skudder
Keyword(s):  
Late Holocene ◽  
Environmental Changes ◽  
Marine Species ◽  
Loss On Ignition ◽  
Diatom Assemblages ◽  
Diatom Analysis ◽  
Global Context ◽  
Prevailing Wind Direction ◽  
Climatic Event

<p>A multi-proxy paleoecological and sedimentological record for the last ~8.3kyr is extracted from a 2.1m coastal seacliff at Onaero Beach, North Taranaki. This record is used to infer both local environmental changes including shoreline, coastal conditions, as well as regional changes in atmospheric circulation and climate wetness. Analysis of diatom and pollen populations, particle size, and loss on ignition provide the raw data from which inferences regarding salinity and vegetation are made. Changes are tied to a chronology determined through radiocarbon ages and tephrochronology.  Key objectives of this study are: (1) To characterize changes in salinity and relative shoreline position at Onaero Beach (2) To characterise changes in vegetation and relate these changes to overall state of the climate through the Holocene (3) Compare the results of this study with others from New Zealand and the wider south pacific to investigate how the Onaero Beach section fits in both a regional and global context.  Diatom analysis of the Onaero section revealed the dominance of brackish to marine species which suddenly at 7.3ka after which time diatom assemblages were dominated by fresh and salt intolerant species. The marine to freshwater transition represents a transition from a brackish to freshwater coastal lagoon.  Pollen analysis of the Onaero Beach section indicates the region was dominated by podocarp forest. The increasing dominance of Dacrydium and decline in other podocarps suggests an increase in overall climate wetness.  The disappearance of pollen in conjunction with the deposition of tephra at ~4.15ka is not conclusive proof of, but certainly fits with, the idea of a significant climatic event occurring at ~4.2ka resulting in a reversal of the current prevailing wind direction and supports the case for a formal Middle/Late Holocene boundary at this time.</p>

Modeling of ecological conditions in the Euxine Basin in the Sarmatian and Maeotian by methods of diatom analysis

2019 ◽  
pp. 257-261
Author(s):  
Eleonora P. Radionova
Keyword(s):  
Black Sea ◽  
Late Miocene ◽  
The Black Sea ◽  
Subtidal Zone ◽  
Diatom Analysis ◽  
Diatom Flora ◽  
North West ◽  
Ecological Conditions ◽  
The North

The associations and ecological conditions of the existence of modern diatoms of the North-West (Pridneprovsky), Prikerchensky and Eastern regions of the subtidal zone of the Black Sea are considered. Based on the unity of the composition of the Present and Sarmatian-Meotian diatom flora, an attempt has been made to model some of the ecological c situation of the Late Miocene Euxinian basin.

An Assessment of Environmental Changes in Three Lakes from King's County (Nova Scotia, Canada) Using Diatom-Based Paleolimnological Techniques

2008 ◽  
Vol 43 (2-3) ◽  
pp. 85-98 ◽  
Author(s):  
Joshua R. Thienpont ◽  
Brian K. Ginn ◽  
Brian F. Cumming ◽  
John P. Smol
Keyword(s):  
Nova Scotia ◽  
Environmental Changes ◽  
Sediment Cores ◽  
Lake Management ◽  
River System ◽  
210Pb Dating ◽  
Hydroelectric Power ◽  
Diatom Assemblages ◽  
Shoreline Development ◽  
Before And After

Abstract Paleolimnological approaches using sedimentary diatom assemblages were used to assess water quality changes over the last approximately 200 years in three lakes from King's County, Nova Scotia. In particular, the role of recent shoreline development in accelerating eutrophication in these systems was assessed. Sediment cores collected from each lake were analyzed for their diatom assemblages at approximately 5-year intervals, as determined by 210Pb dating. Analyses showed that each system has changed, but tracked different ecosystem changes. Tupper and George lakes recorded shifts, which are likely primarily related to climatic warming, with diatom assemblages changing from a preindustrial dominance by Aulacoseira spp. to present-day dominance by Cyclotella stelligera. In addition to the recent climatic-related changes, further diatom changes in the Tupper Lake core between approximately 1820 and 1970 were coincident with watershed disturbances (farming, forestry, and construction of hydroelectric power infrastructure). Black River Lake has recorded an increase in diatom-inferred total phosphorus since about 1950, likely due to impoundment of the Black River system for hydroelectric generation and subsequent changes in land runoff. Before-and-after (i.e., top-bottom) sediment analyses of six other lakes from King's County provided further evidence that the region is being influenced by climatic change (decreases in Aulacoseira spp., increases in planktonic diatom taxa), as well as showing other environmental stressors (e.g., acidification). However, we recorded no marked increase in diatom-inferred nutrient levels coincident with shoreline cottage development in any of the nine study lakes. Paleolimnological studies such as these allow lake managers to place the current limnological conditions into a long-term context, and thereby provide important background data for effective lake management.

Species distribution modeling reveals the ecological niche of extinct megafauna from South America

2021 ◽  
pp. 1-8
Author(s):  
Thaísa Araújo ◽  
Helena Machado ◽  
Dimila Mothé ◽  
Leonardo dos Santos Avilla
Keyword(s):  
South America ◽  
Species Distribution ◽  
Environmental Changes ◽  
Species Distribution Modeling ◽  
Human Action ◽  
Northeastern Brazil ◽  
Climate Conditions ◽  
Middle Holocene ◽  
Distribution Modeling ◽  
The Impact

Abstract Climatic and environmental changes, as well as human action, have been cited as potential causes for the extinction of megafauna in South America at the end of the Pleistocene. Among megamammals lineages with Holarctic origin, only horses and proboscideans went extinct in South America during this period. This study aims to understand how the spatial extent of habitats suitable for Equus neogeus and Notiomastodon platensis changed between the last glacial maximum (LGM) and the middle Holocene in order to determine the impact that climatic and environmental changes had on these taxa. We used species distribution modeling to estimate their potential extent on the continent and found that both species occupied arid and semiarid open lands during the LGM, mainly in the Pampean region of Argentina, southern and northeastern Brazil, and parts of the Andes. However, when climate conditions changed from dry and cold during the LGM to humid and warm during the middle Holocene, the areas suitable for these taxa were reduced dramatically. These results support the hypothesis that climatic changes were a driving cause of extinction of these megamammals in South America, although we cannot rule out the impact of human actions or other potential causes for their extinction.

scholarly journals The structure and diversity of freshwater diatom assemblages from Franz Josef Land Archipelago: a northern outpost for freshwater diatoms

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e1705 ◽  
Author(s):  
Sergi Pla-Rabés ◽  
Paul B. Hamilton ◽  
Enric Ballesteros ◽  
Maria Gavrilo ◽  
Alan M. Friedlander ◽  
...  
Keyword(s):  
Seasonal Changes ◽  
Ph Gradient ◽  
Diatom Assemblages ◽  
Diatom Flora ◽  
Human Footprint ◽  
Franz Josef Land ◽  
Freshwater Diatoms ◽  
Arctic Conditions ◽  
Cell Densities ◽  
Freshwater Diatom

We examined diatom assemblages from 18 stream and pond samples in the Franz Josef Land Archipelago (FJL), the most northern land of Eurasia. More than 216 taxa were observed, revealing a rich circumpolar diatom flora, including many undescribed taxa. Widely distributed taxa were the most abundant by cell densities, while circumpolar taxa were the most species rich. Stream and pond habitats hosted different assemblages, and varied along a pH gradient.Diatoma tenuiswas the most abundant and ubiquitous taxon. However, several circumpolar taxa such asChamaepinnularia gandrupii, Cymbella botellus, Psammothidiumsp. andHumidophila laevissimawere also found in relatively high abundances. Aerophilic taxa were an important component of FJL diatom assemblages (Humidophilaspp.,Caloneisspp. andPinnulariaspp.), reflecting the large and extreme seasonal changes in Arctic conditions. We predict a decrease in the abundance of circumpolar taxa, an increase in local (α-) freshwater diatom diversity, but a decrease in regional diversity (circumpolar homogenization) as a result of current warming trends and to a lesser extent the increasing human footprint in the region.

Using Diatoms as Ecological and Paleoecological Indicators in Riverine Environments

2007 ◽  
Vol 13 ◽  
pp. 121-130
Author(s):  
Jeffery R. Stone
Keyword(s):  
Spatial Distribution ◽  
Environmental Changes ◽  
Climatic Factors ◽  
Diatom Assemblages ◽  
Meandering River ◽  
Rates Of Change ◽  
Terminal Lakes ◽  
Riverine Systems ◽  
The Impact ◽  
Selection Of

Fossil diatom assemblages are useful for reconstructing past environmental changes in riverine systems. However, few studies have attempted to utilize paleolimnological techniques in these settings. Analysis of sediments from riverine environments can provide key information predating the impact of human development, which cannot be acquired by other means. Paleolimnological techniques can be used to determine the natural variability in these systems and to estimate the magnitude and rates of change that the environment may have undergone as a result of anthropogenic or climatic factors, and to provide realistic goals for management of negatively-impacted systems.Reconstructing past riverine settings requires an understanding of the factors that control the spatial distribution of diatoms in riverine settings; this paper discusses the impact of resources, stressors, and disturbance events, which are the primary controls on the distribution of benthic diatoms in modern riverine environments. A selection of case studies that utilize paleolimnological techniques to infer past stream hydrology are also discussed; these examples encompass the use of fossil diatom assemblages from sediments recovered from lowland floodplain and meandering river systems, estuarine environments, fluvial lakes, arctic deltaic environments, and terminal lakes.

Sign in / Sign up

Export Citation Format

Share Document