Past Fluctuations Research Articles

Pursuing China's provincial sustainable development goals within a safe and just operating space: Past, present and future

As emphasized by the challenging sustainable development agenda, countries are facing a complicated combination of environmental stress and social challenges, leading the Earth system towards an unsustainable path. Therefore, it is crucial to accurately assess past fluctuations contributing to current situations and apprehend plausible future implications. This study integrates safe and just operating space (SJOS) with Sustainable Development Goals to depict multiple “windows” of environmental and social evolution in different historical periods, with 31 provinces in China as a case study. Then, we track the spatiotemporal evolution trajectory of environmental performance and social well-being in each province from 2012 to 2021. The Long Short-Term Memory (LSTM) model is utilized to capture the temporal relationships between various indicators and to forecast the spatial trends of SJOS in the provinces from 2022 to 2030. Research findings indicate that: (1) over the 2012–2021 period, the environmental performance of the majority of provinces far exceeds the warning thresholds, with no province falling within all threshold boundaries simultaneously. The phosphorus cycle is the most challenging boundary, with only 6.8% of provinces within the safe boundary over the past 10 years. In comparison, freshwater use performs the best, with 80% of provinces staying within the threshold. (2) Social well-being generally improves across all provinces from 2012 to 2021, but the spatial and temporal trajectories are more varied. All provinces meet the thresholds for the food security and employment indicators. However, none of the provinces meet the standard for the social equity indicator. (3) Over the 2022–2030 projection period, environmental performance and social well-being trend in opposite directions across provinces. This culminates in no province being entirely within the safe and just space by 2030. Sanitation shows the most significant change compared to other indicators. Xinjiang had the largest improvement at 59.12%, while Tianjin had the most significant downward trend at 53.88%. Adjustments in national policies and priorities are essential if China wants to accomplish the sufficiency of biophysical resources whilst ensuring social equity in the access and exploitation of these resources.

Recent hummock establishment in the margin of a subarctic fen, Finnish Lapland

Northern fens, that host unique biota and form a remarkable carbon stock, are sensitive to changes in the moisture balance and, therefore, may be strongly affected by climatic fluctuations. However, long‐term monitoring and palaeoecological studies of fens are relatively rare and, as a result, their responses to past and current climatic fluctuations are poorly known. In this study, we examined the recent vegetation change as well as changes in testate amoeba communities in the mire margin of a subarctic fen in Finnish Lapland with four peat profiles. Testate amoebae were used as indicators of past fluctuations in water table depth. The vegetation showed a drastic shift from sedge‐dominated fen to Sphagnum‐dominated communities during the late 20th and the early 21st centuries. This shift was accompanied by a turnover in the testate amoeba community. Testate amoeba‐based water table reconstructions indicated recent drying. This may be due to the lowering of the water table either from accelerated Sphagnum increment or enhanced evaporation. The observed hummock establishment concurs with the documented hemisphere‐wide expansion trend of hummock communities in fens. This change may strengthen the carbon sink and storage capacity of these peatlands, which could be viewed as a welcome negative feedback process to the ongoing climate warming. However, the change also poses a threat to biodiversity since fens are not only species‐rich habitats but are also endangered ecosystems.

Deep-sea response to interglacial-glacial variability on the South Australian margin over the last 94 ka

The continuous record offered by deep-sea sediments has been extensively used to constrain shifting continental and oceanographic conditions. Yet, past fluctuations in deep-sea benthic conditions and bottom-currents are in numerous parts of the globe scarcely documented, one such example being the South Australian margin. Indeed, though variations in surface water masses and continental aeolian dust and river outflow are well documented in the area, little is known about benthic environments and their dynamics during the last interglacial-glacial cycle. We focus here on benthic foraminiferal assemblages sampled from a sediment core recovered at 2420 m depth from a small plateau south of Kangaroo Island within the underwater Murray Canyons Group (South Australian margin). Benthic foraminiferal assemblages show a distinct separation between interglacial and glacial periods over the last 94 ka, and indicate that the benthic environment was well-ventilated and oligotrophic during glacial periods, whilst being rather marked by reduced oxygenation associated to higher food input during the Holocene and Marine Isotope Stage 5a-c. We demonstrate that autochtonous deep-sea benthic foraminiferal communities neither respond to changes in the Murray River's discharges, nor do they follow variations in aeolian dust input from South Australia. Instead, the deep-sea and the terrestrial realm appear decoupled. Moreover, our observations suggest that bottom-water slope currents were stronger during the Holocene and Marine Isotope Stage 5a-c. We propose that this strengthening was triggered by an intensification of the poleward-circulating deep eastern boundary current transporting carbon-rich Indian Deep Water. In contrast, glacial seafloor conditions, especially during the Last Glacial Maximum, may reflect a greater influence and a shoaling of oxygen-rich Antarctic Bottom Water of South Australia. This bottom-water shift would follow the northward displacement of the Subtropical and Subantarctic Fronts and coincide with a withering influence of the Leeuwin Current within surface waters.

An ancient river landscape preserved beneath the East Antarctic Ice Sheet

The East Antarctic Ice Sheet (EAIS) has its origins ca. 34 million years ago. Since then, the impact of climate change and past fluctuations in the EAIS margin has been reflected in periods of extensive vs. restricted ice cover and the modification of much of the Antarctic landscape. Resolving processes of landscape evolution is therefore critical for establishing ice sheet history, but it is rare to find unmodified landscapes that record past ice conditions. Here, we discover an extensive relic pre-glacial landscape preserved beneath the central EAIS despite millions of years of ice cover. The landscape was formed by rivers prior to ice sheet build-up but later modified by local glaciation before being dissected by outlet glaciers at the margin of a restricted ice sheet. Preservation of the relic surfaces indicates an absence of significant warm-based ice throughout their history, suggesting any transitions between restricted and expanded ice were rapid.

A Brief History of Broomcorn Millet Cultivation in Lithuania

The eastern Baltic region represents the world’s most northerly limit of successful broomcorn millet (Panicum miliaceum) (hereafter, millet) cultivation in the past, yet this crop has been almost forgotten today. The earliest millet in the eastern Baltic region has been identified from macrobotanical remains which were directly dated to ca 1000 BCE. Between 800 and 500 BCE, millet was one of the major staple foods in the territory of modern-day Lithuania. Millet continued to play an important role in past agriculture up until the 15th century, with its use significantly declining during the following centuries. This paper analyses both the archaeobotanical records and written sources on broomcorn millet cultivation in Lithuania from its first arrival all the way through to the 19th century. The manuscript reviews the evidence of millet cultivation in the past as documented by archaeobotanical remains and historical accounts. In light of fluctuating records of millet cultivation through time, we present the hypothetical reasons for the decline in millet use as human food. The paper hypothesizes that the significant decrease in broomcorn millet cultivation in Lithuania from the 15th century onwards was likely influenced by several factors, which include climate change (the Little Ice Age) and the agricultural reforms of the 16th century. However, more detailed research is required to link past fluctuations in millet cultivation with climatic and historical sources, thus better understanding the roots of collapsing crop biodiversity in the past.

Fluctuations of health states in dementia diseases and their impact on the assessment of health today using the EQ-5D-5L: Protocol of a mixed-methods study.

The EQ-5D is a widely used health-related quality of life (HRQoL) instrument. The recall period "today" may miss out on recurrent health fluctuations often observed in people with dementia (PlwD). Thus, this study aims to assess the frequency of health fluctuations, affected HRQoL dimensions and the impact of the health fluctuations on the assessment of health today using the EQ-5D-5L. This mixed-methods study will base on n=50 patient and caregiver dyads and four main study phases: (1) Baseline assessment of patients' socio-demographic and clinical characteristics; (2) caregivers self-completion of a daily diary for 14 days, documenting patient's today's health compared to yesterday, the affected HRQoL dimensions, and events that could have caused the fluctuations; (3) administration of the EQ-5D-5L as self- and proxy-rating at baseline, day seven and day 14; (4) interviewing caregivers on patient's health fluctuation, the consideration of past fluctuations in the assessment of health today using the EQ-5D-5L, and the appropriateness of recall periods to capture health fluctuations on day 14. Qualitative semi-structured interview data will be analyzed thematically. Quantitative analyses will be used to describe the frequency and intensity of health fluctuations, affected dimensions, and the association between health fluctuation and its consideration in the assessment of health today. This study aims to reveal insights into the health fluctuation in dementia, the affected dimensions, and underlying health events, as well as whether individuals adhere to the recall period of health today using the EQ-5D-5L. This study will also provide information about more appropriate recall periods that could better capture health fluctuations. This study is registered in the German Clinical Trials Register (DRKS00027956).

Southwestern United States drought of the 21st century presages drier conditions into the future

Intense drought has occurred in the United States Southwest this century, causing unprecedented stress to water resources. Here we use paleoclimate and instrumental records to establish that the recent temperature rise is incompatible with random draws from past fluctuations, including the current period of warming. Consistent with and extending previous reconstructions, we find that the ongoing drought is the most intense at the 21-year scale back to 600 CE. Evaluation using standardized regression coefficients shows that recent warming damps the effect of moisture delivery on the Standardized Precipitation-Evaporation Index by approximately one-third. The probability of full recovery of the current moisture deficit is unlikely even by mid-century and about five percent in 10-15 years. Evaluation of future climate simulations indicates increasing regional temperature stress and soil moisture depletion, and coupled with long recovery periods for moisture delivery, very low chance for regional mega-reservoirs to regain full-capacity levels assuming current demand.

Habitat change alters the expression and efficiency of a female ornament.

Anthropogenic habitat changes are disrupting the mate choice process in a range of organisms, with consequences for populations and communities. Research has so far focused on male sexually selected traits and female mate choice, given their conspicuousness, whereas effects on female ornaments and male mate choice have been largely overlooked. Yet, females of many species develop ornaments that males use in mate choice. These ornaments can be costly and reduce female fecundity and viability and, hence, influence population growth rate. Thus, attention should be paid to changes in female ornaments and the consequences the changes have for populations. Here, we show that declining visibility in aquatic ecosystems reduces the investment of female three-spined stickleback in a melanin-based ornament in favor of increased mate search activity. The adjustment appears adaptive as males pay less attention to the ornament under poor visibility, and as melanin-based ornaments are generally physiologically costly. It is likely that past fluctuations in visibility have promoted the evolution of environment-dependent plasticity in female ornamentation. More attention should be paid to changes in female ornaments and their adaptive value, across taxa, given the impact that female investment in ornaments can have on fecundity and population growth rate. Environments are changing at an accelerating rate because of human activities and knowledge of the responses of both males and females is needed to evaluate and predict the ultimate impact on populations and biodiversity.

Simplified calculations of time correlation functions in non-stationary complex financial systems

For complex dynamic systems in non-stationary states, we develop a useful method to simplify the calculation of time correlations. The method is particularly applied to the financial dynamic systems, with focus on how the past fluctuation drives the future motion of the dynamic variables. The results are important both theoretically and practically. Further, we demonstrate how to construct an investment strategy based on the time correlations.

A history of tourism at the Mer de Glace: Adaptations of glacier tourism to glacier fluctuations since 1741

Climate change induces profound changes in mountain territories that affect the activities pursued there. Tourism is one activity that is strongly impacted by these changes. Most research on tourism in mountain regions has focused on winter sports tourism, but glacier tourism, a summer activity, is also severely affected by climate change-induced phenomena, including glacier retreat and other geomorphological processes. Given that Alpine glacier tourism has been pursued since the 18th century and glaciers have been changing throughout this period, this article aims to examine the adaptations implemented by glacier tourism operators since the activity’s beginnings. Through analysis of historical documents, glaciological surveys and semi-structured interviews, this paper reveals how tourism activities around the Mer de Glace (the largest French glacier) have been impacted by glacier fluctuations since the first visit to the area in 1741. The study reveals that these developments have mainly been driven by glacier retreat and associated paraglacial dynamics. More recently, the shortening of the period of snow cover on the glacier has also impacted tourism activities. Most of the adaptation strategies implemented by tourism operators during the period in question are found to be reactive, consisting in the installation of safety equipment, the renovation of access points or the building of new structures to allow tourist activities to continue despite the consequences of glacier retreat. Other strategies, such as the adoption of new activities by workers previously specialised in another, are identified that could be considered transformative strategies, although these were only adopted by workers when their activity was no longer feasible. The analysis of materials from 1741 to the present also reveals that the recent impacts of climate change on glacier tourism are much more significant and diverse than those produced by past fluctuations. Therefore, it is important that stakeholders take suitable measures to ensure the sustainable future of the Mer de Glace and other glacier tourism destinations.

Revisiting the abandoned shorelines of Lake George, Australia: a refined optical dating framework

ABSTRACTAbandoned shorelines are an important archive used to constrain past fluctuations in the hydrological balance of lakes around the globe. Within Australia, the shorelines preserved at Lake George, NSW, form one of the few shoreline archives in the south‐east of the continent that record palaeoenvironmental conditions throughout the late Quaternary. Here, we examined and tested the lake‐level record for Lake George constructed in the 1970s by dating a well‐preserved shoreline sequence at Luckdale, on the lake's eastern shore, using single‐grain optically stimulated luminescence (OSL) dating. Ten stratigraphic units were identified, and these suggest a late Quaternary highstand for Lake George in MIS 3, with fluctuations superimposed upon an overall drying trend throughout MIS 2 and into the present. At Luckdale, the highest four shoreline‐associated units were deposited ~13 to 19 m above lake base and date to between 39 ± 2 and 29 ± 1 ka ago. Our study pushes back the timing of maximum lake depth at Lake George to at least MIS 3, rather than MIS 2. The overall drying trend is supported by similar reductions in both Riverine Plain fluvial activity and other associated lake‐level records from within the Murray basin.

Glacial geomorphology of the Ahuriri River valley, central Southern Alps, New Zealand

ABSTRACT Detailed geomorphological mapping of ice-related and post-glacial landforms is widely used to explain past glacial fluctuations and dynamics. Here we present the first detailed glacial geomorphological description of the landform assemblages produced by the former Ahuriri Glacier, Southern Alps, New Zealand (44° 15′ S, 169° 36′ E). The Southern Alps of New Zealand experienced multiple episodes of glaciation during the Late Quaternary with large mountain glaciers in many valleys, but very little is known about the Ahuriri River valley, one of the main tributaries of the Waitaki River. We selected a region extending approximately 45 km downstream from the headwaters of the Ahuriri River covering an area of about 532 km2. Our goal was to create a detailed 1:38,000 scale glacial geomorphological map of this area and provide a geomorphological context to support future geochronological work. Glacial geomorphological mapping was performed by combining several field investigations and remote sensing surveys. We provided high-resolution spatial information for all the glacial-related landforms shown on the map (see main Map). The distribution of post-glacial landforms in the middle and lower section of the main valley outline at least three advances or stillstand phases of past glaciers and suggesting the maximum length (∼41 km) of the former glacier during the Last Glacial Maximum. Most of the tributary valleys were also probably covered by ice at this time. Other prominent but smaller size moraine landforms, mostly in the tributary river valleys, also suggest relatively small, post-glacial advance phases of former glaciers.

Transfer Learning-Based State of Charge Estimation for Lithium-Ion Battery at Varying Ambient Temperatures

Accurate and reliable state of charge (SoC) estimation becomes increasingly important to provide a stable and efficient environment for Lithium-ion batteries (LiBs) powered devices. Most data-driven SoC models are built for a fixed ambient temperature, which neglect the high sensitivity of LiBs to temperature and may cause severe prediction errors. Nevertheless, a systematic evaluation of the impact of temperature on SoC estimation and ways for a prompt adjustment of the estimation model to new temperatures using limited data has been hardly discussed. To solve these challenges, a novel SoC estimation method is proposed by exploiting temporal dynamics of measurements and transferring consistent estimation ability among different temperatures. First, temporal dynamics, which is presented by correlations between the past fluctuation and the future motion, are extracted using canonical variate analysis. Next, two models, including a reference SoC estimation model and an estimation ability monitoring model, are developed with temporal dynamics. The monitoring model provides a path to quantitatively evaluate the influences of temperature on SoC estimation ability. After that, once the inability of the reference SoC estimation model is detected, consistent temporal dynamics between temperatures are selected for transfer learning. Finally, the efficacy of the proposed method is verified through a benchmark. Our proposed method not only reduces prediction errors at fixed temperatures (e.g., reduced by 24.35% at -20 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C, 49.82% at 25 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C) but also improves prediction accuracies at new temperatures.

Holocene glacier and ice cap fluctuations in southwest Greenland inferred from two lake records

Glaciers and ice caps (GICs) respond rapidly to changes in temperature and precipitation. Thus, records of their past fluctuations yield valuable information on past climate. However, relatively little is known about the long-term, Holocene history of Greenland’s local GICs, peripheral to the Greenland Ice Sheet. Here we report sediment records of Holocene glacier activity from two distally fed glacial lakes near Buksefjord, southwest Greenland. The two lakes’ watersheds host modern GICs of contrasting size. The Pers Lake (informal name) watershed drains part (3 km2) of a single small ice cap. In contrast, nearby Lake T3’s (informal name) watershed drains numerous GICs totaling 100 km2. At the time it emerged from the sea ∼8.6 ka BP, Pers Lake was receiving no glacial meltwater input. Sediment physical and geochemical properties indicate persistent meltwater input and regrowth of the ice cap within the Pers Lake catchment beginning at ∼1.4 ka BP, after almost 3000 years of sporadic meltwater input beginning ∼4.3 ka BP. The ice cap above Pers Lake reached a maximum late Holocene extent during the final phase of the Little Ice Age (LIA), ∼0.1 ka BP. The complementary Lake T3 sediment record suggests continued meltwater input from the larger suite of upstream GICs from the time of the lake’s isolation from the sea ∼8.4–7.5 ka BP through to the present. This indicates that some GICs here probably survived the Holocene Thermal Maximum (HTM), although were significantly reduced in size for an extended period (of unknown age and duration). Combined with evidence from Pers Lake and prior studies that show GICs at low and intermediate elevations in this region melted away completely during the HTM, and evidence for GIC presence at Lake T3, we provide lower and upper bounds on regional HTM equilibrium-line altitudes (ELAs). We estimate that regional ELAs were between ∼1370 and 1470 m above sea level in the early-to-middle Holocene. From the middle to late Holocene, our results, along with other regional GIC studies, indicate progressive lowering of regional glacier ELAs in response to Neoglacial summer cooling of ∼2.7 °C, assuming no change in precipitation.

Is there a common threshold to subfossil chironomid assemblages at 16 m water depth? Evidence from the Tibetan Plateau

Fluctuating lake levels are an important driver of ecosystem change, and changes in the precipitation/evaporation balance of a region can lead to undesirable changes in ecosystem functioning. Large-scale changes in hydrology will become increasingly more likely as a result of ongoing climate change in the coming century. This is especially true for the Tibetan Plateau, which plays a crucial role as the “Asian water tower” for the surrounding densely populated regions. Chironomids (Diptera: Chironomidae) have proven to be one of the most valuable bioindicators for monitoring and reconstructing the development of aquatic ecosystems. Besides temperature, water depth and salinity are two of the most important environmental factors affecting chironomids. To study the relationship between chironomids and water depth, we analyzed surface sediment samples of two large Tibetan lakes, Selin Co and Taro Co. These lakes have similar environmental conditions (e.g. elevation, temperature and oxygenation) but show strong differences in salinity (7–10 and 0.5 ppt, respectively). Our results show that the chironomid assemblages in both lakes have similar water depths at which the fauna abruptly changes in composition, despite different faunal assemblages. The most important boundaries were identified at 0.8 and 16 m water depth. While the uppermost meter, the “splash zone”, is characterized by distinctly different conditions, resulting from waves and changing water levels, the cause of the lower zone boundary remains enigmatic. Even though none of the measured water depth-related factors, such as water temperature, oxygen content, sediment properties, light intensity or macrophyte vegetation, show a distinct change at 16 m water depth, comparison to other records show that a similar change in the chironomid fauna occurs at 16 m water depth in large, deep lakes around the world. We propose that this boundary might be connected to water pressure influencing the living conditions of the larvae or the absolute distance to the surface that has to be covered for the chironomid larvae to hatch. We conclude that water depth either directly or indirectly exerts a strong control on the chironomid assemblages even under different salinities, resulting in distribution patterns that can be used to reconstruct past fluctuations in water depths.

Local glaciers record delayed peak Holocene warmth in south Greenland

Local glaciers and ice caps (GICs) respond sensitively and quickly, on the scale of decades to centuries, to climate variations. Continuous records of past fluctuations in GIC size provide information on the timing and magnitude of Holocene climate shifts, and a longer-term perspective on 21st century glacier retreat. Although there is broad-scale agreement on millennial-scale trends in Holocene climate variability and fluctuations in local GICs in Greenland, regional variations are only loosely constrained. Here we present three Holocene proglacial lake sediment records from South Greenland, an area with abundant local glaciers but few Holocene-length paleoclimate records. In addition, we use geospatial analysis to model past equilibrium-line altitudes (ELAs) and thereby constrain the magnitude of ablation-season temperature change during the warmest and coolest periods of the Holocene. Physical and geochemical sedimentary characteristics show that two of the proglacial lakes continued to receive glacial meltwater input until ∼7.3 and ∼7.1 ka BP. The survival of local glaciers implies that South Greenland remained relatively cool, and that summer temperatures gradually warmed, but did not warm well beyond 1.2 °C above present in the early Holocene. In the mid-Holocene, from ∼7.1 to 5.5 ka BP, organic sedimentation at these two sites indicates that local glaciers became very small, or more likely melted away completely. The glaciers within the third lake’s catchment melted away prior to ∼5.2 ka BP, as sediments deposited earlier in the Holocene could not be dated at this site. We estimate that summer temperatures increased by at least 1.2–1.8 °C above present by ∼7.3–7.1 ka BP. Our results are consistent with other observations that suggest a north-to-south gradient in the timing of Holocene thermal maximum conditions, with southern Greenland experiencing a delayed warming relative to other regions in Greenland. As summer temperatures cooled in the Neoglacial, our records show that sustained glacier regrowth began ∼3.1 ka BP with glaciers in the southernmost catchment, which at present, receive the most precipitation. In the other two catchments, which host smaller glaciers in a drier environment, regrowth began at ∼1.3 and ∼1.2 ka BP, the timing of which is in agreement with other glacial records from the Arctic Atlantic region. Local glaciers reached their maximum late Holocene extents during a cooler, second phase of the Little Ice Age (LIA) ∼0.2-0.1 ka BP, that we estimate was at least 0.4–0.9 °C cooler than present. Overall, these findings improve understanding of the spatio-temporal dynamics of Holocene glacier and climate change in Greenland, potentially yielding valuable information about their future response.

Bullish and Bearish Engulfing Japanese Candlestick patterns: A statistical analysis on the S&P 500 index

Technical analysts believe that by studying past price action, it is possible to forecast future prices of specific securities. Technical analysts rely on the use of charts, which graphically show the past fluctuations of prices. This study focuses on the chart style known as Japanese candlesticks, which relies on four pieces of information for every session: Open, High, Low and Close prices. It is believed that some candle patterns possess predictive capabilities that can alert investors of imminent price tops, bottoms, or price trend continuations. For this study, we performed a statistical analysis, using historical prices of the S&P 500 index, of the effectiveness of Bullish Engulfing and Bearish Engulfing patterns, which are believed to forecast bottoms and tops respectively. Results indicate that the Bearish Engulfing provide strong short-term forecasting power when using the Open and High criteria but not the Close criterion. Likewise, the Bullish Engulfing offered strong short-term forecasting power when using the Open and Low criteria but not the Close criterion.

Depth-distribution of lake benthic diatom assemblages in relation to light availability and substrate: implications for paleolimnological studies

We analyzed the depth distributions of benthic diatoms in two adjacent, but hydrologically distinct subalpine lakes (Lakes Soiernseen, S-Germany). Lake Unterer Soiernsee is affected by marked water-level fluctuations and is light-penetrated to the bottom most of the year, while Lake Oberer Soiernsee provides more stable conditions and an extended aphotic zone. Mixed samples of epiphytic, epilithic, epipsammic and epipelic periphyton were taken in one-meter depth steps by scuba divers. Most of the common benthic diatoms occurred in distinct depth-areas. RDA analyses showed that depth was strongly correlated with species distribution in both lakes. Depth-constrained cluster analyses indicated three distinct diatom community zones in each lake. A shallow littoral zone hosting mainly epiphytic and epilithic species and a deeper littoral zone with mainly epipsammic and epipelic taxa existed in both lakes. Additionally, a highly disturbed near-shore littoral zone with diatoms adapted to unstable conditions (aerophilic taxa, pioneer species) was found in Lake Unterer Soiernsee, and a deep-water pelagic zone with mainly planktonic taxa in Lake Oberer Soiernsee. Light availability, substrate, physical stressors and nutrient concentrations were linked closely with water depth. While light availability affected the ratio of benthic and planktonic diatoms, substrate type influenced benthic diatom assemblage structures. Diatoms occurring in surficial sediments of the aphotic zone represent an ideal cross-section of the recent diatom assemblage of the lake, including benthic and planktonic species. However, sediment samples taken in light-flooded depths are inappropriate for studies based on shifts between benthic and planktonic taxa, because in situ benthic species dominate the surface-sediment assemblages, while settled tychoplanktonic and planktonic species occur less frequently. A diatom-inferred depth model was created for each lake to prove the usability for down-core studies using weighted-averaging approaches. For both lakes these models are highly appropriate to reconstruct past fluctuations in water-transparency or lake-level. With regard to the development of diatom-based TP-transfer-functions for Bavarian mountain lakes, we found it is highly important to consider lake depth and transparency. Based on the findings of this study we recommend the creation of two different training-sets, one for deep or low-transparency lakes with an aphotic zone including both benthic and planktonic diatoms, and another one for shallow, clear water lakes solely using benthic diatoms.

Do the relationships between testate amoebae and fungi reflect the variability of past water table fluctuations in the ombrotrophic peatlands of Central Europe?

In this article, we examined the indicative value of a relationship between two non-pollen palynomorphs (NPPs), fungal HdV-10, related to the presence of Calluna vulgaris, and HdV-31A, which is testate amoeba – Archerella flavum. Both are frequently present on slides designated for pollen analysis, prepared from Sphagnum peat. We analysed three profiles from three extensive ombrotrophic peatlands in northern Poland, in which the content of testate amoebae (TA) was examined and TA-inferred depth to the water table (DWT) was reconstructed. The new analysis of palynological samples regarding NPPs revealed that strong increases in HdV-10 content were mostly simultaneous to HdV-31A declines. However, the relations between both types were not statistically significant. The rapid increases in HdV-10, despite the fact that this type of conidiospores is related to drier habitats on peatlands, were tentatively interpreted as an indicator of rapid rises in the water table level which, in consequence, might have stimulated the production of these spores by fungi. In addition, a negative correlation between HdV-31A and Arcella discoides and positive one, but weaker, in case of HdV-10 (attributed by some authors to species Trichocladium opacum (Corda) S Hughes) and A. discoides show a link between mutual fluctuations of both NPPs and hydrological instabilities on peatland. The Bagno Kusowo bog, the westernmost peatland subjected to the study, displayed an intriguing agreement between the presence of peat sections with strong increases in HdV-10 and cold climate events affecting Europe. Our study reveals that counting even a limited number of NPP types during the standard pollen analysis of Sphagnum peat may support the interpretation of results, especially, in cases when the investigation lacks testate amoeba analysis. When the reconstruction of TA-inferred DWT is provided, it may introduce additional information about the patterns of hydrological dynamics.

Dengue in Santander State, Colombia: fluctuations in the prevalence of virus serotypes are linked to dengue incidence and genetic diversity of the circulating viruses.

To investigate the link between fluctuations in the prevalence of dengue virus (DENV) serotypes and the number of dengue cases in the metropolitan area of Bucaramanga, Santander State, Colombia, in the 2007-2010 and 2014-2017 periods. Viruses were isolated from febrile patient samples by direct application to C6/36-HT cells and typed using monoclonal antibodies. We performed autocorrelation and cross-correlation analyses to determine whether fluctuations in the prevalence of DENV serotypes and dengue cases were correlated. Full envelope (E) gene sequences were employed to examine the genetic diversity of serotypes circulating by using a phylogenetic approach. All four dengue virus serotypes were detected. DENV-1 was the dominant serotype in both periods followed by DENV-3 or DENV-2 depending on the period; DENV-4 was the least prevalent virus in both periods. Cross-correlation analyses suggest a temporal relation between the fluctuations in the prevalence of DENV serotypes, which were almost simultaneous (lag=0) or related to recent past fluctuations (lag>1.0) in the number of dengue cases. Data suggest that a sustained predominance of DENV-1, an increase of the DENV-4 prevalence, and a switch from DENV-3 to DENV-2 could be linked to an outbreak. Circulating viruses were grouped into Genotype V, Asia/American III and II for DENV-1, -2, -3 and -4, respectively; intragenotypic diversity was detected. The present work highlights the need of comprehensive studies on dynamics of DENV in Colombia to understand transmission of dengue and evaluate the effectiveness of a vaccination programme.