Reconstructing high resolution environmental change from carbonate-rich lakes in Turkey and Mexico using varve microfacies analysis

Analysis of lacustrine sediment records provide insight into terrestrial environmental change throughout the Holocene; however, poor chronological control often limits a record’s ability to identify the precise dynamics and drivers of these changes. Exploring these important aspects of environmental change can develop our understanding of the mechanisms driving long-term climatology and its influence on regional hydrological systems. To fully investigate these past environmental systems, high resolution, climatically-sensitive proxies are required. Here, microfacies analysis of varved sediment records from Nar Gölü, Turkey and Yaal Chac, Mexico provide long annually-resolved records of environmental, limnological and climatic change, from two regions lacking in continuous, high resolution archives. From Nar Gölü, varves were analysed from discrete sequences deposited during the early-mid and late Holocene (9,064 – 7,630 cal yrs BP and 2,540 – -51 cal yrs BP respectively), and from Yaal Chac, the early-mid Holocene (8,812 – 7,245 cal yrs BP and 5,346 – 4,295 cal yrs BP). These long, continuous depositional archives have permitted the reconstruction of both low- and high-frequency limnological change, where the sequences’ incremental chronologies have further enabled the pace and timing of change to be identified and robustly dated. In both lakes, organic-calcareous varve deposition is driven by the regions’ wet-dry seasonality. At Nar Gölü, sedimentological calibration using meteorological data identified the March-May evaporation/precipitation ratio as the primary control on the deposition of endogenic carbonates. Comparing specific carbonate sublayers’ mineralogy and thickness with their δ18Ocarbonate value further indicates that regional water balance over the last 2,600 years primarily drives carbonate deposition. Considering the sites’ similar seasonality and sedimentary microfacies, changes to the endogenic carbonate deposition and mineralogy are used to indicate high resolution changes to lake hydrology and the timing/intensity of dry-season E/P conditions in both lakes. Spectral analysis of these varved records, which provide incremental timeseries, is used to identify the multi-decadal drivers to depositional variability. The Atlantic Multi-decadal Oscillation (AMO) is likely detected within both lake records at various stages through the Holocene, where changes to sea surface temperatures are known to influence moisture supply and rainfall during each region’s respective wet-seasons. From Nar Gölü, changes to cyclicity are also proposed to reflect shifts in the relative influence of Atlantic-and tropical-derived climates, as the multi-decadal variability of Indian monsoon intensity is also known to drive dry-season aridity. Sedimentological-inferred changes to past conditions, specifically changes to the regional evaporation/precipitation (E/P) ratio, are finally used to provide the environmental context to societal change. Each region’s wet-dry seasonality increases societal vulnerability to drought, where periods of elevated evaporation/precipitation conditions may have influenced food and/or water security, and hence socio-economic stability. Temporal correlation between microfacies and societal changes provide circumstantial evidence that climatic change may have contributed to major societal shifts through the Holocene in both Turkey and Mexico

20,000 years of societal vulnerability and adaptation to climate change in southwest Asia.

The Fertile Crescent, its hilly flanks and surrounding drylands has been a critical region for studying how climate has influenced societal change, and this review focuses on the region over the last 20,000 years. The complex social, economic, and environmental landscapes in the region today are not new phenomena and understanding their interactions requires a nuanced, multidisciplinary understanding of the past. This review builds on a history of collaboration between the social and natural palaeoscience disciplines. We provide a multidisciplinary, multiscalar perspective on the relevance of past climate, environmental, and archaeological research in assessing present day vulnerabilities and risks for the populations of southwest Asia. We discuss the complexity of palaeoclimatic data interpretation, particularly in relation to hydrology, and provide an overview of key time periods of palaeoclimatic interest. We discuss the critical role that vegetation plays in the human-climate-environment nexus and discuss the implications of the available palaeoclimate and archaeological data, and their interpretation, for palaeonarratives of the region, both climatically and socially. We also provide an overview of how modelling can improve our understanding of past climate impacts and associated change in risk to societies. We conclude by looking to future work, and identify themes of "scale" and "seasonality" as still requiring further focus. We suggest that by appreciating a given locale's place in the regional hydroscape, be it an archaeological site or palaeoenvironmental archive, more robust links to climate can be made where appropriate and interpretations drawn will demand the resolution of factors acting across multiple scales. This article is categorized under:Human Water > Water as Imagined and RepresentedScience of Water > Water and Environmental ChangeWater and Life > Nature of Freshwater Ecosystems

Reconstructing high resolution environmental change from carbonate-rich lakes in Turkey and Mexico using varve microfacies analysis

Analysis of lacustrine sediment records provide insight into terrestrial environmental change throughout the Holocene; however, poor chronological control often limits a record’s ability to identify the precise dynamics and drivers of these changes. Exploring these important aspects of environmental change can develop our understanding of the mechanisms driving long-term climatology and its influence on regional hydrological systems. To fully investigate these past environmental systems, high resolution, climatically-sensitive proxies are required. Here, microfacies analysis of varved sediment records from Nar Gölü, Turkey and Yaal Chac, Mexico provide long annually-resolved records of environmental, limnological and climatic change, from two regions lacking in continuous, high resolution archives. From Nar Gölü, varves were analysed from discrete sequences deposited during the early-mid and late Holocene (9,064 – 7,630 cal yrs BP and 2,540 – -51 cal yrs BP respectively), and from Yaal Chac, the early-mid Holocene (8,812 – 7,245 cal yrs BP and 5,346 – 4,295 cal yrs BP). These long, continuous depositional archives have permitted the reconstruction of both low- and high-frequency limnological change, where the sequences’ incremental chronologies have further enabled the pace and timing of change to be identified and robustly dated. In both lakes, organic-calcareous varve deposition is driven by the regions’ wet-dry seasonality. At Nar Gölü, sedimentological calibration using meteorological data identified the March-May evaporation/precipitation ratio as the primary control on the deposition of endogenic carbonates. Comparing specific carbonate sublayers’ mineralogy and thickness with their δ18Ocarbonate value further indicates that regional water balance over the last 2,600 years primarily drives carbonate deposition. Considering the sites’ similar seasonality and sedimentary microfacies, changes to the endogenic carbonate deposition and mineralogy are used to indicate high resolution changes to lake hydrology and the timing/intensity of dry-season E/P conditions in both lakes. Spectral analysis of these varved records, which provide incremental timeseries, is used to identify the multi-decadal drivers to depositional variability. The Atlantic Multi-decadal Oscillation (AMO) is likely detected within both lake records at various stages through the Holocene, where changes to sea surface temperatures are known to influence moisture supply and rainfall during each region’s respective wet-seasons. From Nar Gölü, changes to cyclicity are also proposed to reflect shifts in the relative influence of Atlantic-and tropical-derived climates, as the multi-decadal variability of Indian monsoon intensity is also known to drive dry-season aridity. Sedimentological-inferred changes to past conditions, specifically changes to the regional evaporation/precipitation (E/P) ratio, are finally used to provide the environmental context to societal change. Each region’s wet-dry seasonality increases societal vulnerability to drought, where periods of elevated evaporation/precipitation conditions may have influenced food and/or water security, and hence socio-economic stability. Temporal correlation between microfacies and societal changes provide circumstantial evidence that climatic change may have contributed to major societal shifts through the Holocene in both Turkey and Mexico

Data from: Diversity and linkage disequilibrium in farmed Tasmanian Atlantic salmon

Farmed Atlantic salmon (Salmo salar) is a globally important production species, including in Australia where breeding and selection has been in progress since the 1960s. The recent development of SNP genotyping platforms means genome-wide association and genomic prediction can now be implemented to speed genetic gain. As a precursor, this study collected genotypes at 218 132 SNPs in 777 fish from a Tasmanian breeding population to assess levels of genetic diversity, the strength of linkage disequilibrium (LD) and imputation accuracy. Genetic diversity in Tasmanian Atlantic salmon was lower than observed within European populations when compared using four diversity metrics. The distribution of allele frequencies also showed a clear difference, with the Tasmanian animals carrying an excess of low minor allele frequency variants. The strength of observed LD was high at short distances (<25 kb) and remained above background for marker pairs separated by large chromosomal distances (hundreds of kb), in sharp contrast to the European Atlantic salmon tested. Genotypes were used to evaluate the accuracy of imputation from low density (0.5 to 5 K) up to increased density SNP sets (78 K). This revealed high imputation accuracies (0.89–0.97), suggesting that the use of low density SNP sets will be a successful approach for genomic prediction in this population. The long-range LD, comparatively low genetic diversity and high imputation accuracy in Tasmanian salmon is consistent with known aspects of their population history, which involved a small founding population and an absence of subsequent introgression. The findings of this study represent an important first step towards the design of methods to apply genomics in this economically important population

SNP genotypes

Genotypes from 106,492 SNP collected in 777 Atlantic Salmon. Contains a bed, bim and fam file formatted for analysis using Plinkv1.9

20,000 years of societal vulnerability and adaptation to climate change in southwest Asia.

The Fertile Crescent, its hilly flanks and surrounding drylands has been a critical region for studying how climate has influenced societal change, and this review focuses on the region over the last 20,000 years. The complex social, economic, and environmental landscapes in the region today are not new phenomena and understanding their interactions requires a nuanced, multidisciplinary understanding of the past. This review builds on a history of collaboration between the social and natural palaeoscience disciplines. We provide a multidisciplinary, multiscalar perspective on the relevance of past climate, environmental, and archaeological research in assessing present day vulnerabilities and risks for the populations of southwest Asia. We discuss the complexity of palaeoclimatic data interpretation, particularly in relation to hydrology, and provide an overview of key time periods of palaeoclimatic interest. We discuss the critical role that vegetation plays in the human-climate-environment nexus and discuss the implications of the available palaeoclimate and archaeological data, and their interpretation, for palaeonarratives of the region, both climatically and socially. We also provide an overview of how modelling can improve our understanding of past climate impacts and associated change in risk to societies. We conclude by looking to future work, and identify themes of "scale" and "seasonality" as still requiring further focus. We suggest that by appreciating a given locale's place in the regional hydroscape, be it an archaeological site or palaeoenvironmental archive, more robust links to climate can be made where appropriate and interpretations drawn will demand the resolution of factors acting across multiple scales. This article is categorized under:Human Water &gt; Water as Imagined and RepresentedScience of Water &gt; Water and Environmental ChangeWater and Life &gt; Nature of Freshwater Ecosystems