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Lake Ohrid shared by the Republics of Albania and Macedonia is formed by a tectonically active graben within the south Balkans and suggested to be the oldest lake in Europe. Several studies have shown that the lake provides a valuable record of climatic and environmental changes and a distal tephrostratigraphic record of volcanic eruptions from Italy. Fault structures identified in seismic data demonstrate that sediments have also the potential to record tectonic activity in the region. Here, we provide an example of linking seismic and sedimentological information with tectonic activity and historical documents. Historical documents indicate that a major earthquake destroyed the city of Lychnidus (today: city of Ohrid) in the early 6th century AD. Multichannel seismic profiles, parametric sediment echosounder profiles, and a 10.08m long sediment record from the western part of the lake indicate a 2m thick mass wasting deposit, which is tentatively correlated with this earthquake. The mass wasting deposit is chronologically well constrained, as it directly overlays the AD472/AD 512 tephra. Moreover, radiocarbon dates and cross correlation with other sediment sequences with similar geochemical characteristics of the Holocene indicate that the mass wasting event took place prior to the onset of the Medieval Warm Period, and is attributed it to one of the known earthquakes in the region in the early 6th century AD. [ABSTRACT FROM AUTHOR]

Lake Ohrid shared by the Republics of Albania and Macedonia is formed by a tectonically active graben within the South Balkan and suggested to be the oldest lake in Europe. Several studies have shown that the lake provides a valuable record of climatic and environmental changes and a distal tephrostratigraphic record of volcanic eruptions from Italy. Fault structures identified in seismic data demonstrate that sediments have also the potential to record tectonic activity in the region. Here, we provide an example of linking tephrostratigraphic information and environmental changes with tectonic activity and anthropogenic impact. Historical documents indicate that a major earthquake destroyed the city of Ohrid in the early 6th century AD. This earthquake is documented in multichannel seismic profiles, in parametric sediment echosounder profiles, and in a ca. 10m long sediment record from the western part of the lake. The sediment record exhibits a ca. 2m thick mass wasting deposit, which is chronologically well constrained by the underlying 472 AD/512AD tephra and cross correlation with 15 other sediment sequences with similar geochemical characteristics of the Holocene. [ABSTRACT FROM AUTHOR]

Ancient Lake Ohrid is a steep sided, oligotrophic, karst lake of likely Pliocene age and often referred to as a hotspot of endemic biodiversity. This study aims on tracing significant lake level fluctuations at Lake Ohrid using high-resolution acoustic data in combination with lithological, geochemical, and chronological information from two sediment cores recovered from sub-aquatic terrace levels at ca. 32 and 55 m. According to our data, significant lake level fluctuations with prominent lowstands of ca. 60 and 35m below the present water level occurred during MIS 6 and MIS 5, respectively. The effect of these lowstands on biodiversity in most coastal parts of the lake is negligible, due to only small changes in lake surface area, coastline, and habitat. In contrast, biodiversity in shallower areas was more severely affected due to disconnection of today sub-lacustrine springs from the main water body. Multichannel seismic data from deeper parts of the lake clearly imaged several clinoform structures stacked on top of each other. These stacked clinoforms indicate significantly lower lake levels prior to MIS 6 and a stepwise rise of water level with intermittent stillstands since its existence as water filled body, which might have caused enhanced expansion of endemic species within Lake Ohrid. [ABSTRACT FROM AUTHOR]

Abstract: A 1075 cm long core (Lz1120) was recovered in the south-eastern part of the Lake Ohrid (Republics of Macedonia and Albania) and sampled for identification of tephra layers. Magnetic susceptibility investigations show rather high magnetic values throughout the core, with peaks unrelated to the occurrence of tephra layers but instead to the relative abundance of detrital magnetic minerals in the sediment. Naked-eye inspection of the core allowed us to identify of two tephra layers, at 896–897 cm and 1070–1075 cm. Laboratory inspection of the grain-size fraction >125 μm allowed for the identification of a third cryptotephra at 310–315 cm. Major element analyses on glass shards of the tephra layers at 896–897 cm and 1070–1075 cm show a trachytic composition, and indicate a correlation with the regionally dispersed Y-3 and Y-5 tephra layers, dated at ca 30 and 39 cal ka BP. The cryptotephra at 310–315 cm has a mugearitic–benmoreitic composition, and was correlated with the FL eruption of Mt. Etna, dated at 3370±70 cal yr BP. These ages are in agreement with five 14C AMS measurements carried out on plant remains and macrofossils from the lake sediments at different depths along the core. The recognition of distal tephra from Italian volcanoes allows us to link the Lake Ohrid succession to other archives located in the Mediterranean area and in eastern Europe. The benmoreitic–mugearitic tephra layer at 310–315 cm is the first recognition in the Balkan area of a distal ash deposit from a mid-intensity explosive eruption of Mt. Etna, as far as 600 km from the source. [Copyright &y& Elsevier]

The Tibetan Plateau (TP) has the world's largest distribution of high-alpine and saline (generally hardwater) lakes, which are expected to affect regional carbon cycling profoundly. However, the variability, and especially underlying factors controlling CO 2 dynamics, across widespread hardwater lakes is poorly understood on the TP. Here, we present year-round records of surface water pCO 2 from a representative hardwater lake (Nam Co) on the TP, and analyze relationships between ambient variables and pCO 2 during open water (i.e., ice-free) and ice-covered months. Surface pCO 2 (233.3 μatm on average) was a little oversaturated to atmosphere (219 μatm on average) during the open water season. As a CO 2 source, Nam Co emitted 8.73 ± 1.06 Gg C annually, but this flux only accounted for 0.53 ± 0.06 ‰ of its total dissolved inorganic carbon pool (1.64 × 10 13  g C). Regression results indicate that, during open water months, both seasonal and diurnal varying patterns of surface pCO 2 were influenced predominantly by water temperature, in a quasi-marine mode, by controlling gas solubility and dissolved carbonate equilibria. Therefore, CO 2 evasion was elevated during summer months, despite the lake being autotrophic (i.e., CO 2 consumption via photosynthesis). By contrast, during ice-covered months the surface pCO 2 was strongly related to under-ice thermodynamics, and declined nonlinear with increased inversed stratification. In the hypolimnion, as a result of extremely weak metabolism (as indicated by low dissolved oxygen depletion rates) and a combined high carbonate buffering effect, accumulation of CO 2 was negligible, leading to an absence of peak effluxes of CO 2 during turnover periods, compared to eutrophic freshwater lakes. We argue that, under future global warming scenarios, consideration of the impact of gradually warming lake water on thermodynamics and dissolved carbonate equilibria are vital in order to understand the future CO 2 dynamics of these widespread high-altitude oligotrophic-hardwater lakes situated across the TP., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Although it is well known that humans substantially altered the Malagasy ecosystems, the timing of the human arrival as well as the extension of their environmental impact is yet not well understood. This research aims to study the influence of early human impact and climate change on rainforests and wildlife in northern Madagascar during the past millennia. Results obtained from the lake sediment in a montane environment showed significant changes in vegetation within the lake catchment associated with a major drought that started approximately 1100 years ago. Human impact, revealed by fires, began at roughly the same time and occurred outside the lake catchment. Although this does not dismiss the impacts that humans had at a regional scale, this result demonstrates that the late Holocene natural drought also significantly impacted the ecosystems independently of anthropogenic activities. At a regional scale, a review of species demographic history revealed a substantial number of population bottlenecks during the last millennia, probably resulting from this combination of human-related impact and natural climate changes. This research highlights the importance of a multi-site and multi-proxy comparison for deciphering the nature and succession of environmental changes., Competing Interests: We declare we have no competing interests., (© 2024 The Author(s).)

Quaternary climatic changes have been invoked as important drivers of species diversification worldwide. However, the impact of such changes on vegetation and animal population dynamics in tropical regions remains debated. To overcome this uncertainty, we integrated high-resolution paleoenvironmental reconstructions from a sedimentary record covering the past 25,000 years with demographic inferences of a forest-dwelling primate species (Microcebus arnholdi), in northern Madagascar. Result comparisons suggest that climate changes through the African Humid Period (15.2 - 5.5 kyr) strongly affected the demographic dynamics of M. arnholdi. We further inferred a population decline in the last millennium which was likely shaped by the combination of climatic and anthropogenic impacts. Our findings demonstrate that population fluctuations in Malagasy wildlife were substantial prior to a significant human impact. This provides a critical knowledge of climatically driven, environmental and ecological changes in the past, which is essential to better understand the dynamics and resilience of current biodiversity., (© 2021. The Author(s).)

The Tibetan Plateau (TP) is primarily influenced by the northern hemispheric middle latitude Westerlies and the Indian summer monsoon (ISM). The extent, long-distance effects and potential long-term changes of these two atmospheric circulations are not yet fully understood. Here, we analyse modern airborne pollen in a transition zone of seasonally alternating dominance of the Westerlies and the ISM to develop a pollen discrimination index (PDI) that allows us to distinguish between the intensities of the two circulation systems. This index is applied to interpret a continuous lacustrine sedimentary record from Lake Nam Co covering the past 24 cal kyr BP to investigate long-term variations in the atmospheric circulation systems. Climatic variations on the central TP widely correspond to those of the North Atlantic (NA) realm, but are controlled through different mechanisms resulting from the changing climatic conditions since the Last Glacial Maximum (LGM). During the LGM, until 16.5 cal kyr BP, the TP was dominated by the Westerlies. After 16.5 cal kyr BP, the climatic conditions were mainly controlled by the ISM. From 11.6 to 9 cal kyr BP, the TP was exposed to enhanced solar radiation at the low latitudes, resulting in greater water availability.

The Caribbean is highly vulnerable to coastal hazards. Based on their short recurrence intervals over the intra-American seas, high-category tropical cyclones and their associated effects of elevated storm surge, heavy wave impacts, mudslides and floods represent the most serious threat. Given the abundance of historical accounts and trigger mechanisms (strike-slip motion and oblique collision at the northern and southern Caribbean plate boundaries, submarine and coastal landslides, volcanism), tsunamis must be considered as well. This paper presents interdisciplinary multi-proxy investigations of sediment cores (grain size distribution, carbonate content, loss-on-ignition, magnetic susceptibility, microfauna, macrofauna) from Washington-Slagbaai National Park, NW Bonaire (Leeward Antilles). No historical tsunami is recorded for this island. However, an allochthonous marine layer found in all cores at Boka Bartol reveals several sedimentary criteria typically linked with tsunami deposits. Calibrated (14)C data from these cores point to a palaeotsunami with a maximum age of 3,300 years. Alternative explanations for the creation of this layer, such as inland flooding during tropical cyclones, cannot entirely be ruled out, though in recent times even the strongest of these events on Bonaire did not deposit significant amounts of sediment onshore. The setting of Boka Bartol changed from an open mangrove-fringed embayment into a poly- to hyperhaline lagoon due to the establishment or closure of a barrier of coral rubble during or subsequent to the inferred event. The timing of the event is supported by further sedimentary evidence from other lagoonal and alluvial archives on Bonaire.