Tectonic Lake Research Articles

The Pond Snails of the Genus Radix (Gastropoda, Lymnaeidae) in Issyk-Kul Lake (Central Asia), with a Review of Radix in Ancient Tectonic Lakes of the World

Lake Issyk-Kul, situated in the Republic of Kyrgyzstan, is one of the largest lakes in Central Asia. Though this brackish-water basin holds only a species-poor fauna of molluscs, the number of species inhabiting Issyk-Kul and their true taxonomic position remain unsatisfactorily studied. Most nominal species of Mollusca reported from Issyk-Kul are known from empty shells only and have never been studied molecularly. This study reports the results of a revision of the genus Radix (Gastropoda:Hygrophila:Lymnaeidae) based on the integrated approach. We revealed that only two species of this genus inhabit Issyk-Kul Lake: Radix auricularia (Linnaeus, 1758) and R. obliquata (von Martens, 1864). The former species is widespread in the Palearctic and has an enormous range, whereas the latter is considered here to be endemic to Issyk-Kul Lake. All records of R. obliquata from waterbodies other than Issyk-Kul Lake are, most probably, based on misidentification. To date, no molecular evidence of the presence of R. obliquata outside Issyk-Kyl is available. The third species of Radix discussed in this paper, R. subdisjuncta (Nevill, 1878) sensu Kruglov and Starobogatov, 1993, is identical to R. obliquata and represents, most probably, an ecological morph (“race”) of the latter. The paper provides a review of Radix species recorded in other ancient tectonic lakes of the world (Baikal, Victoria, Ohrid, etc.). Though the lymnaeid snails are generally scarce in such lakes, the genus Radix represents an exception, with several species being endemics of various tectonic lakes (Issyk-Kul, Lugu, Skadar, Trichonis, and Biwa).

Simulation and Prediction of Thermokarst Lake Surface Temperature Changes on the Qinghai–Tibet Plateau

Thermokarst lakes are shallow bodies of freshwater that develop in permafrost regions, and they are an essential focus of international permafrost research. However, research regarding the mechanisms driving temperature fluctuations in thermokarst lakes and the factors that influence these changes is limited. We aimed to analyze seasonal variations in the surface water temperature, clarify historical trends in the phenological characteristics of lake ice, and predict future temperature changes in surface water of the thermokarst lakes using the air2water model. The results indicated that in comparison with air temperature, the thermokarst lake’s surface water temperature showed a certain lag and significantly higher values in the warm season. The warming rate of the thermokarst lake’s average surface water temperature based on historical data from 1957 to 2022 was 0.21 °C per decade, with a notably higher rate in August (0.42 °C per decade) than in other months. Furthermore, the ice-covered period steadily decreased by 2.12 d per decade. Based on the Coupled Model Intercomparison Project 6 projections, by 2100, the surface water temperatures of thermokarst lakes during the warm season are projected to increase by 0.38, 0.46, and 2.82 °C (under scenarios SSP126, SSP245, and SSP585), respectively. Compared with typical tectonic lakes on the Qinghai–Tibet Plateau, thermokarst lakes have higher average surface water temperatures during ice-free periods, and they exhibit a higher warming rate (0.21 °C per decade). These results elucidate the response mechanisms of thermokarst lakes’ surface water temperature and the phenological characteristics of lake ice in response to climate change.

Development genetic and stability classification of seasonal glacial lakes in a tectonically active area—A case study in Niangmuco, east margin of the Eastern Himalayan Syntaxis

The Niangmuco region on the east margin of the Eastern Himalayan Syntaxis features a large number of glacial lakes. The development process and stability classification of glacial lakes is of great significance to the study of seasonal glaciers in the eastern Himalayan margin, with implications for economic development and disaster prevention. Based on Landsat remote sensing image data from 2000 to 2021, this study analyzed the development and change characteristics of glacial lakes in the Niangmuco region during the past 21 years, and classified the stability of lakes with areas >0.02 km2 using the fuzzy consistent matrix method. In this area, 126 glacial lakes were identified within an elevation range of 3044–4156 m with a total area of 10.94 km2. These lakes primarily included glacial erosion lakes, valley lakes, tectonic lakes, and landslide dam lakes. Specifically, glacial erosion lakes accounted for 88.9% of the total number of lakes and 60.3% of the total lake area, followed by valley lakes with 6.3% and 23.7%, respectively. From 2000 to 2010, the total area of glacial lakes decreased from 10.53 km2 to 10.09 km2, which may be attributable to climate fluctuations. Subsequently, the area of lakes increased significantly to 10.94 km2 in 2021, an increase of 0.41 km2. Compared with 2000, among the lakes with a growth rate of 0.019 km2/a in 21 years, glacial erosion lakes exhibited the largest change. Among the classified glacial lakes in the study area, 95.7% were stable and relatively stable, mostly comprising glacial erosion lakes at high altitudes between 3468 and 4156 m. Only 4 unstable and extremely unstable glacial lakes were identified, and they were located near a fault zone. The findings show that the development and the change of glacial lakes in the area are primarily controlled by temperature and precipitation, and the topography and fault activity have important influences on the stability of glacial lakes.

On aquatic macrophytes in the ultracontinental climate conditions of the Upper Indigirka River

The first results of the study of aquatic macrophytes of the Upper Indigirka River area are presented. The species composition includes ~84 species (~74 vascular plants and more than 10 cryptogamous macrophytes). 47 water bodies of different age, size and origin (tectonic, glacial, river, thermokarst and artificial) were studied. For each type of water bodies, the main ecological characteristics, features of the species composition and vegetation cover are given. The most common type of water bodies of the territory is thermokarst, and the greatest floristic diversity (54 species of macrophytes) is found here. There are 40 species in tectonic lakes, 37 - in rivers lakes, 35 - in glacial lakes, the lowest diversity was for small artificial waterbodies. For the Oimyakon District, new records of protected species are reported: macroalga Tolypella canadensis, vascular plants Isoetes echinospora, Nuphar pumila, Nymphaea tetragona (common and its rare pink-flowered form) and Subularia aquatica. Possible consequences for aquatic ecosystems while maintaining current trends in climate change (increase in average annual temperature, shift to earlier periods of spring warmth, changes in the amount and distribution of precipitation, depth of seasonal thawing of soils) leading to degradation of permafrost and their impact on the biodiversity of aquatic macrophytes in the region are discussed. The most vulnerable aquatic ecosystems of the Oimyakon Highlands are the mature thermokarst lakes.

Fire, volcanism and climate change: the main factors controlling mercury (Hg) accumulation rates in Tropical Lake Lantoa, Sulawesi, Indonesia (∼16,500–540 cal yr BP)

The effects of climate change on long-term mercury (Hg) cycling are still not well understood, as climate changes are usually gradual and can only be assessed using high-resolution archives. Our study site (a small, lowland tectonic lake in Sulawesi, Indonesia) provides a unique opportunity to further understanding of Hg cycling in the Southeast Asian (SEA) tropics during the transition from the Pleistocene to the Holocene, a period of significant climate variability. We present a high-resolution record of Late Glacial and Holocene Hg deposition within the sediments of tropical Lake Lantoa, Sulawesi. Using a multi-proxy framework (including pollen, charcoal, carbon:nitrogen ratio and high-resolution geochemistry records) we investigate the response of Hg accumulation rates (HgAR) in sediments to shifts in climate between ∼16,488 and 538 cal BP. This period encompasses the Bølling-Allerød (BA) warming, Younger Dryas (YD) cooling and Holocene warming events, providing new insights into the effects of global climatic transitions on HgAR in SEA sediments. The Pleistocene Termination had the highest HgAR and substantial variability (µ = 11.32, 5.38–33.91 μg m−2 yr−1), when drier conditions and high charcoal accumulation rates suggest that fire activity was the main source of Hg to the lake. The Holocene Transition was marked by a decrease in HgAR (µ = 8, 3.50–18.84 μg m−2 yr−1) as humid conditions precluded forest burning, followed by high HgAR (µ = 11.35, 3.30–158.32 μg m−2 yr−1) in the Early Holocene. Mercury accumulation rate in the Late Holocene (µ = 3.80, 1,67–43.65 μg m−2 yr−1) was the lowest in the Lake Lantoa record, marked by the lowest fire events and a stable catchment. An increase in carbon:nitrogen ratios during the Late Holocene, coupled with a decrease in HgAR, suggests that the establishment of lowland forest resulted in suppressed Hg erosion/leaching. Our results demonstrate that forest fires, vegetation change and volcanism are important drivers of Hg inputs to Lake Lantoa, a relationship which is strongly mediated by climate and lake-catchment dynamics.

Distinct Modes of Aged Soil Carbon Export in a Large Tropical Lake Basin Identified Using Bulk and Compound‐Specific Radiocarbon Analyses of Fluvial and Lacustrine Sediment

AbstractThe 14C content of sedimentary organic matter (OM) and specific organic molecules provide valuable information on the source and age of OM stored in sediments, but these data are limited for tropical fluvial and lake sediments. We analyzed 14C in bulk OM, palmitic acid (C16), and long‐chain n‐alkanoic acids (C24, C26, and C28), within fluvial and lake sediments in the catchment of Lake Izabal, a large tectonic lake basin in Guatemala. We combined these measurements with bulk and compound‐specific δ13C measurements, as well as sediment organic carbon to nitrogen (OC:N) ratios, to understand the source and age of sedimentary OM in different regions of the lake catchment. Most fatty acid and bulk OM samples were characterized by pre‐modern carbon, indicating important input of aged carbon with residence times of hundreds to thousands of years into sediments. We identified two mechanisms leading to aged carbon export to sediments. In the high‐relief and deforested Polochic catchment, older OM and fatty acids are associated with low % total organic carbon (TOC) and low OC:N, indicating aged OM associated with eroded mineral soil. In the smaller, low‐relief, and largely forested Oscuro catchment, old OM and fatty acids are associated with high %TOC and high OC:N ratios, indicating export of undegraded aged plant biomass from swamp peat. The age of bulk OM and fatty acids in Lake Izabal sediments is similar to the ages observed in fluvial sediments, implying that fluvial input of aged soil carbon makes an important contribution to lake sediment carbon reservoirs in this large tropical lake.

The paleolacustrine significance of sedimentary nitrogen isotopes: A comparative study of late Holocene records in two lakes on the eastern Qinghai-Tibet Plateau

The bulk nitrogen isotope composition of lacustrine sediments can be a useful proxy of past climatic and environmental changes. We previously reconstructed paleoenvironmental histories recorded in sediments of Lake Ximencuo and Lake Ngoring, both located on the eastern Qinghai-Tibetan Plateau (QTP), using a suite of biogeochemical paleoclimate proxies that included the sedimentary δ15Ntot values. We have revisited the different patterns of δ15Ntot variations in the two lakes and now conclude that their isotopic trends over the last millennium have been controlled by multiple factors. Regional temperature evidently is one potential factor affecting the sedimentary δ15Ntot values, indicating that the lake ecosystems respond to regional temperature changes on a sub-millennial timescale but in indirect and lake-specific ways. The processes involved in the sedimentary δ15Ntot changes appear to be more strongly influenced by the shapes of lake basins and associated hydrologic characteristics that control the origins of nitrogen-containing compounds in the lakes. To help understand the dynamics of nitrogen cycling and nitrogen isotope records in the QTP lakes, we identified two patterns - a terrestrial nitrogen-controlled pattern (TNCP) that is observed in deeper, steep-walled glacial-basin lakes and an aquatic nitrogen-controlled pattern (ANCP) that is observed in shallower, tectonic-basin lakes. We also considered the influences of the "amount effect" and the "temperature effect" on sedimentary δ15Ntot values and their possible operative mechanisms in these montane lakes. We postulate that both patterns are applicable to the QTP lakes, including both glacial and tectonic lakes, and probably to lakes in other regions that have also not experienced significant human disturbance.

Exploring the Relationship between Hydroclimate and Lake Area in Source Area of the Yellow River: Implications for the Paleoclimate Studies

The large tectonic lake is one of the most important water bodies in the source area of the Yellow River (SAYR), northeastern Qinghai-Tibet Plateau (QTP). It plays a key role in decelerating climatic change and regulating regional climate patterns. In this study, we used Landsat images (MSS, TM, ETM+ and OLI) of Lake Gyaring and Lake Ngoring (the Two Sisters Lakes), which are the two largest tectonic lakes in the SAYR, to determine annual lake area fluctuations from 1986 to 2020. The results show that lake area increases were generally consistent with a warming trend in the SAYR. The temperature signals were separated from the lake area changes by using a detrending analysis and found that the processed data are closely correlated with variations of precipitation and streamflow in the SAYR, and the previously reported paleoclimate records, which include the δ18O record from stalagmite, A/C (Artemisia/Chenopodiaceae) ratio from lake sediment and scPDSI (self-calibrating Palmer Drought Severity Index) from the tree ring on the northeastern margin of the QTP. The phase of relatively large lake areas typically coincides with a negative excursion in δ18O, a high A/C ratio, and elevated scPDSI values, while the opposite is true for smaller lake areas. It is suggested that the total area of the Two Sisters Lakes is closely associated with hydroclimatic conditions in the SAYR. Furthermore, an association of high TSI anomalies with the water area expansion of the Two Sisters Lakes is also observed, implying that solar activity is the key driving factor for the hydrologic variability in the SAYR on decadal timescales. The findings of our study highlight the validity of previous paleoclimate archives in the northeastern QTP and demonstrate the potential of using remote sensing techniques to investigate paleoclimate.

Trace elements accumulation over a century in sediment cores from a tectonic lake on the Qinghai-Tibet plateau: Source identification and risk assessment

A record of trace elements in lake sediment can help in assessing the impact of anthropogenic activities on aquatic environments. In the present work, the trace elements profiles (Cu, Cr, Pb, Zn, As, and Cd) were determined in four sediment cores (QH01, QH02, QH07, and Z04) collected in 2012 and 2014 from Lake Qinghai to reconstruct the history of anthropogenic activity in the watershed and to evaluate the pollution status and eco-environmental risks of a typical Third Pole lake environment over the past century. The concentrations of Cu, Cr, Pb, Zn, As, and Cd in these studies ranged between 19.4 and 34.2μgg-1, 35.6-53.6μgg-1, 3.10-26.8μgg-1, 56.4-93.5μgg-1, 6.20-15.3μgg-1, and 0.086-0.572μgg-1, respectively. Statistical analyses indicated that the Pb, Zn, and Cd contents combination of coal, gasoline burning, and agricultural activities in the Lake Qinghai catchment and larger-scale atmospheric inputs during the past 60 years. The enrichment factors for Pb, Zn, and Cd in the sediments of Lake Qinghai are considered to be related to the region of the Qinghai-Tibet Plateau and national socioeconomic development. Enrich factor of Cd values was higher than 3.5 and maximum values of the geo-accumulation index of Pb and Cd were observed in the top layer of the sediment (0-2cm), indicating moderate contamination. The RI values suggest that the risks to the ecological environment of Lake Qinghai are increasing since the 1950s. The results of this study illustrate that Lake Qinghai is still experiencing high trace elements pollution pressure due to the rapid environmental changes caused by anthropogenic activities on the remote and isolated Qinghai-Tibet Plateau.

Microplastic pollution in the surface water of Lake Singkarak, Indonesia

Microplastic pollution is already at an “alarming” level in Indonesia’s marine and freshwater ecosystems. However, to the best of our knowledge, no study has reported the microplastic occurrence in the lake ecosystem in Indonesia. Lake Singkarak, a big tectonic lake, has been considered one of the priority lakes to be restored. The lake receives a high influx of plastic waste from rivers and catchment runoff. Controlling the outflow through the hydropower dam and the sluice in the main lake outlet may prevent the microplastic’s outflux. The study’s objective was to determine the microplastic first occurrence and abundance in the lake’s surface water. Water samples were collected from three sites in the lake inlet area, one in the intake area of the hydropower dam and one in the outlet area, by performing four parallel trawls in each site using a modified plankton net. The most abundant microplastics in the lake’s surface water were 9 particles/m3 in the lake inlet area, which received a high plastic waste input from the river. The lowest abundance was 2 particles/m3 in the main lake outlet area. Foams and fragments, white and clear in color, size of 300 μm, were the dominant types of microplastics observed. Our preliminary study suggests that the lake could act as a sink of microplastics. Therefore, ceasing the input sources of plastic waste from the river should be prioritized to prevent further microplastic pollution of Lake Singkarak.

Evaluating Inflow Result from SWAT Model at Singkarak Lake Under Limited Data

Sustained lake functioning requires proper management in the catchment area and the water body. To address this, information on lake water balance is crucial because it is the basis for many scientific investigations of processes that occur in lake ecosystems. In many lakes, inflow from catchment areas is dominated by river flow. The problem is that inflow measurement data on rivers into the lake are difficult to obtain. Several models are used for inflow estimation, but validation will undoubtedly be complex because there is no observational data. The approach taken is to analyze the model results’ inflow accuracy through water balance analysis based on observational data on water level, climatology, and outflow. This approach will be implemented on Singkarak Lake, 109.08 km2, which is a tectonic lake located in West Sumatra. The method used to calculate inflow uses the SWAT hydrological model based on land use data in 2014 and Chirps rainfall in the 2010-2019 period. Water balance analysis is used to evaluate the inflow of the model results based on observational data on water level and outflow. The results show that the monthly inflow is too high, with an average excess of 6.21cms, which causes the average water level to be 0.52 meters higher.

Permafrost degradation is accelerating beneath the bottom of Yanhu Lake in the Hoh Xil, Qinghai-Tibet Plateau

Lakes on the Qinghai-Tibet Plateau (QTP) have notably expanded over the past 20 years. Due to lake water level rise and lake area expansion, the permafrost surrounding these lakes is increasingly becoming submerged by lake water. However, the change process of submerged permafrost remains unclear, which is not conducive to further analyzing the environmental effects of permafrost change. Yanhu Lake, a tectonic lake on the QTP, has experienced significant expansion and water level rise. Field measurement results indicate that the water level of Yanhu Lake increased by 2.87 m per year on average from 2016 to 2019. Cold permafrost, developed in the lake basin, was partially submerged by lake water at the end of 2017. Based on the water level change and permafrost thermal regime, a numerical heat conduction permafrost model was employed to predict future changes in permafrost beneath the lake bottom. The simulated results indicate that the submerged permafrost would continuously degrade because of the significant thermal impact of lake water. By 2100, the maximum talik thicknesses could reach approximately 7, 12, 16, and 19 m under lake-bottom temperatures of +2.0, +4.0, +6.0, and +8.0 °C, respectively. Approximately 291 years would be required to completely melt 47 m of submerged permafrost under the lake-bottom temperature of +4 °C. Note that the permafrost table begins to melt earlier than does the permafrost base, and the decline in the permafrost table occurs relatively fast at first, but then the process is attenuated, after which the permafrost table again rapidly declines. Compared to climate warming, the degradation of the submerged permafrost beneath the lake bottom occurred more rapidly and notably.

Water Quality of a Tectonic Lake: Hazar Lake

In this study, water quality parameters of Hazar Lake have been investigated and evaluated according to water quality regulations. Some water quality parameters, such as dissolved oxygen, water temperature pH, electrical conductivity salinity, transparency, (Sechii disc depth), Chlorophyll a, total alkalinity, BOD, chloride, calcium, magnesium, total phosphorus, sulfate, ammonium nitrogen, nitrite nitrogene, nitrate nitrogene, total nitrogen were examined between September 2019-August 2020. The results were evaluated according to the quality criteria of the In-Continental Water Resources Classes of The Water Pollution and Control Regulation. According to the regulation, the water quality of Hazar Lake is classified as the 1st class in terms of dissolved oxygen, water temperature, ammonium nitrogen, total phosphorus, nitrate-nitrogen, nitrate nitrogen, biological oxygen demand; as the 3rd class in terms of chloride ion; as 4th class in terms of pH. The average chlorophyll a value of 1.09 µg/L in Lake Hazar indicates that the lake shows oligotrophic lake category feature. Secchi disc depth was 3.8 m), which shows that Hazar Lake is at the oligotrophic level in terms of light transmittance. It is noticed that for total phosphorus less than 10 µg/L, the lake is oligotrophic, for 10-20 µg/L is called mesotrophic, and for more than 20 µg/L is so-called eutrophic. This value was measured 0.02 µg/L in the lake; therefore, it can be concluded that the lake is oligotrophic. In addition, the change in alkalinity values of the lake between 402-450 mg CaCO3/L indicates that the lake has very hard water characteristics. Precautions should be taken to protect ecological balances and prevent water pollution in Hazar Lake.

Variations in lake water storage over Inner Mongolia during recent three decades based on multi-mission satellites

• Long-term lake level time series were reconstructed and lake water storage was calculated. • Lake water storage in Inner Mongolia was decreasing or maintaining over the past 30 years. • Human activities are most significant driving factors of water storage changes for most Lakes. Lake shrinkage is a frequent water resource problem in arid and semi-arid regions that can affect the hydrological cycle and damage the local aquatic environment. Since the 1990 s, many lakes in Inner Mongolia have shrunk significantly. However, the causes of the shrinkage and long-term storage trends of lakes in Inner Mongolia are still poorly understood. Using observations from multi-mission satellites, we analyzed water storage changes in six major lakes in Inner Mongolia over the past 30 years and explored the underlying causes. The results reveal divergent changes between the two lake categories. For each of the tectonic lakes (including Lake Hulun, Lake Dalinuoer, Lake Daihai, and Lake Hongjiannao), the water storage has continuously decreased with annual rates of 0.067 km 3 /yr, 0.012 km 3 /yr, 0.021 km 3 /yr, and 0.01 km 3 /yr, respectively. In contrast, for oxbow lakes (including Lake Hasuhai and Lake Wuliangsuhai), the storage trends were insignificant (0.001 km 3 /yr for both). Human activities were the most significant driving factors, especially coal mining, agricultural irrigation, and grazing, which explained more than 70% of the storage changes in Lake Hulun, Lake Dalinuoer, and Lake Hasuhai. Among the natural factors, evapotranspiration and runoff were secondary influences on these lake storage changes. This study provides a systematic analysis and attribution of water storage changes for major lakes in Inner Mongolia and provides scientific guidance for local water resource management and planning. Our method provides a useful example of using multi-mission satellite data for estimating water storage changes.

WATER CHEMISTRY OF A TECTONIC LAKE OF ASSAM WITH REFERENCE TO PRIMARY NUTRIENTS

The present investigation was carried out to study the variations of the physicochemical properties and primary nutrient parameters of Chandubi Lake, a tectonic lake. Water quality parameters such as water temperature, dissolved oxygen, free carbon dioxide, pH, total hardness, total alkalinity, total carbon, bicarbonate ion and primary nutrients nitrate, orthophosphate and potassium were estimated. The study revealed low levels of total hardness and total alkalinity which is unique in the present investigation for the state of Assam. The presence of free carbon dioxide was recorded throughout the study period indicating the absence of carbonate alkalinity in all zones of Chandubi Lake. The investigation also revealed that the nutrient input in Chandubi Lake is of autochthonous origin. ANOVA (p = 0.05) revealed that there were significant difference in water quality parameters dissolved oxygen (DO), total carbon dioxide (CO2), total hardness (TH) and primary nutrient orthophosphate among the studied zones. The Pearson correlation (p = 0.05) showed that, water temperature has a negative correlation with DO (r = - 0.72), pH (r = - 0.64), dissolved oxygen (DO) has a negative correlation with free carbon dioxide (FCO2) (r = -0.91) and potassium (K) (r = - 0.86), while having a positive correlation with nitrate (NO3) (r = 0.71) and free carbon dioxide (FCO2) having a negative correlation with pH ( r = - 0.90). The overall water quality condition was found to be excellent, which was evident from WQI (< 25%).

Species divergence and repeated ancient hybridization in a Sulawesian lake system.

An increasing volume of empirical studies demonstrated that hybridization between distant lineages may have promoted speciation in various taxa. However, the timing, extent and direction of introgressive hybridization remain unknown in many cases. Here, we report a possible case in which repeated hybridization promoted divergence of Oryzias ricefishes (Adrianichthyidae) on Sulawesi, an island of Wallacea. Four Oryzias species are endemic to the Malili Lake system in central Sulawesi, which is composed of five tectonic lakes; of these, one lake is inhabited by two species. Morphological and population genomic analyses of genome-wide single-nucleotide polymorphisms revealed that these two sympatric species are phylogenetically sister to but substantially reproductively isolated from each other. Analyses of admixture and comparison of demographic models revealed that the two sympatric species experienced several substantial introgressions from outgroup populations that probably occurred soon after they had secondary contact with each other in the lake. However, the ratio of migrants from the outgroups was estimated to be different between the two species, which is consistent with the hypothesis that these introgressions aided their divergence or prevented them from forming a hybrid swarm. Repeated lake fragmentations and fusions may have promoted diversification of this freshwater fish species complex that is endemic to this ancient lake system.

Hydroclimate changes in eastern Africa over the past 200,000 years may have influenced early human dispersal

Reconstructions of climatic and environmental conditions can contribute to current debates about the factors that influenced early human dispersal within and beyond Africa. Here we analyse a 200,000-year multi-proxy paleoclimate record from Chew Bahir, a tectonic lake basin in the southern Ethiopian rift. Our record reveals two modes of climate change, both associated temporally and regionally with a specific type of human behavior. The first is a long-term trend towards greater aridity between 200,000 and 60,000 years ago, modulated by precession-driven wet-dry cycles. Here, more favorable wetter environmental conditions may have facilitated long-range human expansion into new territory, while less favorable dry periods may have led to spatial constriction and isolation of local human populations. The second mode of climate change observed since 60,000 years ago mimics millennial to centennial-scale Dansgaard-Oeschger cycles and Heinrich events. We hypothesize that human populations may have responded to these shorter climate fluctuations with local dispersal between montane and lowland habitats.

Mitochondrial introgression by ancient admixture between two distant lacustrine fishes in Sulawesi Island.

Sulawesi, an island located in a biogeographical transition zone between Indomalaya and Australasia, is famous for its high levels of endemism. Ricefishes (family Adrianichthyidae) are an example of taxa that have uniquely diversified on this island. It was demonstrated that habitat fragmentation due to the Pliocene juxtaposition among tectonic subdivisions of this island was the primary factor that promoted their divergence; however, it is also equally probable that habitat fusions and resultant admixtures between phylogenetically distant species may have frequently occurred. Previous studies revealed that some individuals of Oryzias sarasinorum endemic to a tectonic lake in central Sulawesi have mitochondrial haplotypes that are similar to the haplotypes of O. eversi, which is a phylogenetically related but geologically distant (ca. 190 km apart) adrianichthyid endemic to a small fountain. In this study, we tested if this reflects ancient admixture of O. eversi and O. sarasinorum. Population genomic analyses of genome-wide single-nucleotide polymorphisms revealed that O. eversi and O. sarasinorum are substantially reproductively isolated from each other. Comparison of demographic models revealed that the models assuming ancient admixture from O. eversi to O. sarasinorum was more supported than the models assuming no admixture; this supported the idea that the O. eversi-like mitochondrial haplotype in O. sarasinorum was introgressed from O. eversi. This study is the first to demonstrate ancient admixture of lacustrine or pond organisms in Sulawesi beyond 100 km. The complex geological history of this island enabled such island-wide admixture of lacustrine organisms, which usually experience limited migration.

Geomorphic characterization of faults as earthquake sources in the Cuitzeo Lake basin, central México

The Trans-Mexican Volcanic Belt is an active continental volcanic arc characterized by several arc-parallel Miocene-Holocene tectonic lake basins, such as the Cuitzeo, Zacapu, Chapala, and Zacoalco. Normal faults and related continental seismicity shape these basins. In the central part of this volcanic arc, the Cuitzeo Lake basin presents neotectonic fault activity, accommodating oblique extension through ENE-striking normal fault zones of the Morelia-Acambay Fault System and transfer faulting. Specific faults have been described in the basin, and various geological and structural studies have outlined its kinematics and structural geometry. However, these fault zones have not been fully characterized. Characterizing earthquake sources in the Cuitzeo Lake basin is essential to constrain the regional potential seismic hazard, aiming toward better territory planning. This study presents the first regional fault compilation in the Cuitzeo Lake basin that characterizes 21 fault zones from geomorphic data. We integrated previous volcanic and tectonic studies with new geomorphic and paleoseismic evaluations to assess potential seismic sources in the Cuitzeo Lake basin. Furthermore, we evaluate fault zone segmentation, fault slip distribution, transtensional partitioning, seismic hazard implications, and basin development. We improved the current understanding of the basin's transformation, subsidence, and sedimentation with all this information. Here, fault zones present a mean vertical slip-rate of 0.17 ± 0.27 mm/yr for 1 Ma, capable of generating Mw 6.2 to 7.0 earthquakes and average single-event displacements from 0.2 to 1.2 m. Multi-fault ruptures could be up to 63 km-long, capable of generating Mw 7.0 to 7.2 earthquakes, representing an important regional seismic hazard.

Trophic state assessment based on summer phytoplankton community structure and trophic indices: a small tectonic lake in Turkey

Trophic state assessment based on summer phytoplankton community structure and trophic indices: a small tectonic lake in Turkey