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In recent decades, the role of tumor biomechanics on cancer cell behavior at the primary site has been increasingly appreciated. However, the effect of primary tumor biomechanics on the latter stages of the metastatic cascade, such as metastatic seeding of secondary sites and outgrowth remains underappreciated. This work sought to address this in the context of triple negative breast cancer (TNBC), a cancer type known to aggressively disseminate at all stages of disease progression. Using mechanically tuneable model systems, mimicking the range of stiffness's typically found within breast tumors, it is found that, contrary to expectations, cancer cells exposed to softer microenvironments are more able to colonize secondary tissues. It is shown that heightened cell survival is driven by enhanced metabolism of fatty acids within TNBC cells exposed to softer microenvironments. It is demonstrated that uncoupling cellular mechanosensing through integrin β1 blocking antibody effectively causes stiff primed TNBC cells to behave like their soft counterparts, both in vitro and in vivo. This work is the first to show that softer tumor microenvironments may be contributing to changes in disease outcome by imprinting on TNBC cells a greater metabolic flexibility and conferring discrete cell survival advantages. [ABSTRACT FROM AUTHOR]

A bs tract: Climate change and anthropogenic activities mutually degraded global lake ecosystems during the Anthropocene. Nutrient mitigation via catchment management has been a constant priority for lake ecological restoration; however, the outcomes after mitigation remain uncertain. In particular, there is limited knowledge on the effects of large‐scale forest restoration and soil erosion reduction in catchments on the ecological dynamics of downstream aquatic systems.Here, we study a strategically chosen alpine lake from the Loess Plateau in northern China, which has been extensively afforested in the past decades. We present high‐resolution, multi‐proxy records to reconstruct environmental and ecological dynamics since 1960. To quantify the potential mechanisms, we combined evidence from palaeolimnological records, contemporary field observations and process‐based ecosystem modelling. We developed palaeorecord‐based proxies for water transparency, nutrient concentrations and algal composition, and applied these proxies to ecosystem modelling.Our results show that despite the concurrent decline in nutrient levels, the lake ecosystem has experienced large‐magnitude rapid shifts since 2000, characterised by unambiguously increased algae proliferation and community changes. The modelling results revealed that the reduction in soil erosion acts as a "double‐edged sword"; that is, lower external nutrient loading via soil erosion is ideal for in‐lake algae inhibition, whereas increasing light availability counteracts the reduced yet still sufficient nutrient concentrations and, ultimately, promotes temporary algal proliferation via extended habitats and intensive photosynthesis. Intriguingly, lake warming plays a secondary role in driving these ecological dynamics.Our results emphasised the unexpected algal proliferation when the nutrient level declined in lake ecosystems; thus, other compound factors, including water transparency and climate warming, need to be incorporated for reliable prediction and effective restoration. A multi‐disciplinary approach integrating palaeorecords as ecological indicators and process‐based ecosystem modelling holds great potential for investigating long‐term lake ecological dynamics in the context of rapid global changes. [ABSTRACT FROM AUTHOR]

Macrophyte invasive alien species (IAS) fitness is often hypothesised to be associated with beneficial environmental conditions (environmental matching) or species‐poor communities. However, positive correlations between macrophyte IAS abundance and native plant richness can also arise, due to habitat heterogeneity (defined here as variation in abiotic and native biotic conditions over space and time). We analysed survey and palaeoecological data for macrophytes in satellite lakes along the Upper Lough Erne (ULE) system (Northern Ireland, UK), covering a gradient of eutrophication and connectivity to partition how environmental conditions, macrophyte diversity and habitat heterogeneity explained the abundance of Elodea canadensis, a widely distributed non‐native macrophyte in Europe. E. canadensis abundance positively correlated with macrophyte richness at both the within‐ and between‐lake scales indicating coexistence of native and invasive species over time. E. canadensis was also more prolific in highly connected and macrophyte‐rich lakes, but sparser in the more eutrophic‐isolated ones. Partial boosted regression trees revealed that in eutrophic‐isolated lakes, E. canadensis abundances correlated with water clarity (negatively), plant diversity (positively), and plant cover (negatively) whereas in diverse‐connected lakes, beta diversity (both positively and negatively) related to most greatly E. canadensis abundance. Dense macrophyte cover and unfavourable environmental conditions thus appear to confer invasibility resistance and sufficient habitat heterogeneity to mask any single effect of native biodiversity or environmental matching in controlling E. canadensis abundance. Therefore, in shallow lake landscapes, habitat heterogeneity variously enables the coexistence of native macrophytes and E. canadensis, reducing the often‐described homogenisation effects of invasive macrophytes. [ABSTRACT FROM AUTHOR]

The onset of agriculture improved the capacity of ecosystems to produce food, but inadvertently altered other vital ecosystem functions. Plant traits play a central role in determining ecosystem properties, therefore we investigated how the onset of agriculture in Europe changed plant trait composition using 78 pollen records. Using a novel Bayesian approach for reconstructing plant trait composition from pollen records, we provide a robust method that can account for trait variability within pollen types. We estimate an overall four‐fold decrease in plant size through agriculture and associated decreases in leaf and seed size. We show an increase in niche space towards the resource‐acquisitive end of the leaf economic spectrum. Decreases in leaf phosphorus might have been caused by nutrient depletion through grazing and burning. Our results show that agriculture, from its start, has likely been gradually impacting biogeochemical cycles through altered vegetation composition. [ABSTRACT FROM AUTHOR]

Peatlands, an important carbon pool in terrestrial ecosystems, are often characterised by a hummock–hollow microtopography, which has important implications for hydrologic conditions, biotic community structure and carbon cycling. However, dynamics of microtopography formation are poorly understood. Moss‐inhabiting diatoms are sensitive to water table change and may be used to infer microtopography formation. Sixty‐three surface moss samples were collected from four Sphagnum peatlands in the Changbai Mountains (north‐eastern China), covering a water table gradient of 0–55 cm. Ordination analyses revealed that depth to the water table (DWT) was the determinant of diatom distribution, and its sole effect explained 15% of total variance in diatom composition. Accordingly, a diatom‐based water table transfer function was developed using a weighted averaging model with inverse deshrinking (R2 = 0.82, RMSEP = 5.63 cm with leave‐one‐out cross validation), and applied to diatom records of a Sphagnum hummock profile. Quantitative reconstruction of DWT showed that the height of the Sphagnum hummock increased obviously in the early stage and then remained relatively stable when the reconstructed height was more than 35 cm. The results suggested that annual addition of Sphagnum litter exceeded its decomposition during the early stage of hummock formation, and Sphagnum production and decomposition reached equilibrium when the hummock had grown to a certain height. This is the first study to explore dynamics of hummock height using moss‐inhabiting diatoms, and hence provides a novel tool for quantitative reconstruction of microtopography formation in Sphagnum peatlands. [ABSTRACT FROM AUTHOR]

Anthropogenic and climatic stressors on freshwater ecosystems are of global concern. However, the interactions and effects of multiple stressors (e.g., nutrient enrichment, climate warming, altered wind and precipitation) acting over different spatial and temporal scales are often complex and remain controversial. Here, we reconstructed one‐century dynamics of eutrophication and primary producer communities in algal‐dominated and macrophyte‐dominated zones of a large shallow lake (Taihu, China), by integrating sedimentary photosynthetic pigments and geochemical records with water monitoring and historical archives. We aimed to explore the long‐term underlying mechanisms of the responses of water quality and lake biota to multiple environmental perturbations. We found that water quality degradation and algal community modification showed similar trends but distinct timings and trajectories in contrasting ecological zones. Onset and intensity of eutrophication in north Meiliang Bay (since the 1950s) exceeded far beyond that of macrophyte‐dominated Eastern Taihu (~1990s). Anthropogenic nutrients overtook past climatic control on production and composition of phototrophic assemblages. More importantly, lake phytoplankton responded markedly to climate warming, decreasing wind speed, and extreme weathers after cultural eutrophication. Synergistic interactions of nutrients and climate on lake ecosystems became increasingly significant in promoting harmful algal blooms (HABs) dominated by Microcystis, close to the hyper‐eutrophic north lake zones. The asynchronous limnological and ecological responses also indicated the modulating roles of lake ecological regime and catchment hydrogeomorphic characteristic. Collectively, our findings suggest that mitigation of eutrophication and HABs calls for a triple management strategy integrating anthropogenic nutrients, climate change, and lake‐catchment setting. [ABSTRACT FROM AUTHOR]

This paleolimnological study aims to investigate how natural processes and anthropogenic land‐use changes have affected sedimentary phosphorus (P) forms and primary producers in a small, temperate lake (Lake Fuglsø, Denmark) throughout the Holocene. Our multi‐proxy approach uses pollen, X‐ray fluorescence scanning, carbon (C) and nitrogen contents and stable isotopes, sequential P extraction, 31P nuclear magnetic resonance spectroscopy, pigments, diatoms, and plant macrofossils from a 14C‐dated sediment record. We found three periods of human impact: (1) low disturbance from domestic grazing during the early/mid Neolithic (~3600 to ~2600 BC), (2) higher disturbance because of animal husbandry and some grain cultivation during the Late Bronze and Pre‐Roman Iron Age (~800 BC to AD ~100), and (3) strong disturbance caused by domestic grazing, intensified crop cultivation and, in particular, by retting of fiber plants during the Middle Ages and Renaissance (AD ~1000 to ~1700). Cultural eutrophication during the latter phase caused unprecedented changes in the lake, including altered species composition, high production, and strongly accelerated sediment accumulation rates. Generally, catchment deforestation was related to elevated proportions of metal (iron, aluminum, calcium)‐bound P forms in the sediment, while high tree cover correlated with elevated proportions of P forms associated with organic material ("organic" P, humic‐bound P, refractory organic P) and loosely bound P. During phases with forest in the catchment, silicon (Si) inputs to the lake were insufficient and diatom frustules were mostly absent in the sediments. In contrast, diatoms thrived in the lake when the landscape was open and erosional Si influx was high. This study is the first to show long‐term (~eight millennia) and recurring Si limitation of diatoms, a finding that may explain the absence of diatoms in sediment records of other sites too. In summary, human land‐use with preceding deforestation accelerated the transport of nutrients and elements from the terrestrial to the aquatic environment, leading to substantial and irreversible changes in Lake Fuglsø. Our study is a good example of the tight links between catchment processes and lake status, indicating that catchment dynamics should be considered in lake restoration projects, particularly for lowland lakes with high catchment : lake area ratios. [ABSTRACT FROM AUTHOR]

This paper uses multimedia to showcase the narratives and lived experiences of those who live and work in tropical Asian mega‐deltas, and as such is the first journal article of its kind in the field of Regional Geography. Using videos, photography and audio this paper describes the characteristics of ponds and their place in the intrinsically connected human‐environmental fabric of these delta regions. The aim is to bring to life descriptive inventories and provide greater weight in support of our conclusion that tropical Asian mega‐delta ponds are important and threatened systems. River deltas comprise just 1% of land cover worldwide but support the livelihoods of more than 500 million people. Delta research has historically focused on the major river channels and the socio‐ecological role of ponds has been overlooked despite their large number and surface area. Ponds are intrinsically linked to daily life (potable water, sanitation, bathing, washing), industry (aquaculture, agriculture) and the natural‐cultural heritage (religion, folklore) of deltas. In contrast to the larger river channels, ponds are likely to be significant stores and processors of nutrients, including carbon, and pollutants at annual to decadal scales, on account of their heavy anthropogenic use and smaller individual sizes. Consequently, they are severely polluted water sources and pose significant public health risks. In this review, we use case studies from three Asian mega‐deltas (the Red River Delta and the Mekong River Delta, Vietnam, and the Ganges‐Brahmaputra‐Meghna Delta, India and Bangladesh) to highlight the importance of Asian mega‐delta ponds as important socio‐ecological systems in their own right. We discuss future environmental challenges, knowledge gaps on the ecological function and biodiversity of these habitats, management and policy practices, and the capacity of ponds to achieve the UN Sustainable Development Goals.The role of Asian mega‐delta ponds as important socio‐ecological systems is investigated in this review. These systems have the capacity to deliver food and water provisional services but their intrinsic link to wider Asian mega‐delta socio‐ecological stressors and impacts, such as over‐population and intensification of human activity challenges the ability of these systems to deliver services such as water security and satisfy UN Sustainable Development Goals such as Goal 6. Clean Water and sanitation. [ABSTRACT FROM AUTHOR]

The cities across the northern dry region of China are exposed to multiple sustainability challenges. Beijing‐Hebei‐Tianjin (BTH) urban agglomeration, for example, experiences severe water shortages due to rapidly expanding urban populations, industrial use, and irrigation‐intensive agriculture. Climate change has further threatened water resources security. Overuse of water resources to meet the demand of various water sectors has far‐reaching health and environmental implications including ecosystem sustainability. Surface water and groundwater pollution present public health risks. Despite the extraordinary policies and efforts being made and implemented by the Government of China, the BTH region currently lacks coordination among stakeholders leading to poor water governance. Consultation among scientists, engineers and stakeholders on regional water security issues is crucial and must be frequent and inclusive. An international symposium was held in Shijiazhuang in early November 2019 to identify some of the key water security challenges and scope of an idealized future eco‐city in the region by developing a sustainability framework. This work drew on experiences from across China and beyond. Scientists agree that integration of science, technology, and governance within an appropriate policy framework was particularly significant for combating the issue of water insecurity, including in the region's newly developed city, Xiong'an New Area. An emerging concept, "Healthy Waterways and Ecologically Sustainable Cities" which integrates social, ecological and hydrological systems and acts as an important pathway for sustainability in the 21st century was proposed in the symposium to tackle the problems in the region. This high level biophysical and cultural concept empowers development goals and promotes human health and wellbeing. The framework on healthy waterways and ecologically sustainable cities can overcome sustainability challenges by resolving water resource management issues in BTH in a holistic way. To implement the concept, we strongly recommend the utilization of evidence‐based scientific research and institutional cooperation including national and international collaborations to achieve the Healthy Waterways and Ecologically Sustainable Cities goal in the BTH in future. This article is categorized under:Water and Life > Conservation, Management, and Awareness [ABSTRACT FROM AUTHOR]

The young water fraction of streamflow (Fyw), an important hydrological variable, has been calculated for the first time, for a monsoon‐fed coastal catchment in northern Vietnam. Oxygen stable isotopes (δ18O) from six river sites in the Day River Basin (DRB) were analysed monthly, between January 2015 and December 2018. River δ18O signatures showed sine wave variability, reflecting the amount effect and tropical (dry‐rainy) seasonality of the region. The δ18O composition of precipitation ranged from −12.67 to +1.68‰, with a mean value of −5.14‰, and in‐streamflow signatures ranged from −11.63 to −1.37‰ with a mean of −5.02‰. Fractions of young water (Fyw) were calculated from the unweighted and flow‐weighted δ18O composition of samples. Unweighted Fyw ranged between 29 ± 8% and 82 ± 21% with a mean value of 51 ± 19%, and was not significantly different from flow‐weighted Fyw (range between 33 ± 25% and 92 ± 73%, mean 52 ± 36%). Both unweighted and flow‐weighted Fyw were highest in the middle of stream and lowest in downstream sites, capturing the impacts of landuse changes, hydrology and human activities in the catchment. Our calculations imply that more than a half of rainwater reaches the DRB river mainstream within the first 3 months. The Fyw is much higher than the global average (of one‐third) and insensitive to discharge due to the combination of a humid catchment with high rainfall, low storage capacity, flat landscape and an intensive drainage system in the DRB. Also the low discharge sensitivity of Fyw in the DRB implies that the regional hydrology is severely altered by humans. [ABSTRACT FROM AUTHOR]

Near‐surface wind speeds have changed over recent decades, raising questions about the extent to which these changes are altering the vertical thermal structure of lakes and affecting lake food webs. Neo‐ and paleolimnological techniques were used to assess wind‐driven changes in lake thermal habitat and resulting effects on primary producers in two lakes in Isle Royale National Park, an island archipelago located in Lake Superior, where wind speed has increased in recent decades. Responses in Siskiwit Lake, a large (16 km2 surface area), deep (Zmax = 49 m), oligotrophic lake, were compared to those of Lake Desor, a moderately large (4.3 km2) but shallower (Zmax = 13 m), mesotrophic lake. High‐frequency sensor data suggested that changes in wind speed affected epilimnion thickness in both lakes synchronously (ρ = 0.7, p < 0.001). Diatom‐inferred mixing depths suggested a coherent shift in both lakes to deeper mixing (an increase of 3 and 6 m) since 1920 (ρ = 0.8), which was correlated with an increase in regional wind speed during the 20th century at the decadal‐scale in Lake Desor and Siskiwit Lake (ρ = 0.6 and 0.4, respectively). In Lake Desor, algal biomass declined as mixing deepened from 1920 to 1980, and then cyanobacteria and cryptophyte pigments increased from 1980 to present, a period of inferred stable and deep mixing. Algal pigment concentrations in Siskiwit Lake were unchanged as mixing depth deepened. Although changes in wind speed altered lake physical structure similarly, the ecological consequences of these changes differed between lakes and were most likely influenced by lake‐specific variability in nutrient and light availability. [ABSTRACT FROM AUTHOR]

Regime shifts in ecology are characterised by major, often abrupt changes in ecosystem structure and functioning in response to one or more driving variables, or pressures. Changes in the provision of ecosystem services are a potential outcome. Despite the current combination of rapidly increasing pressures on what are often highly important socio‐ecological systems, the resilience of lakes in the warm tropics to human perturbation is far less well understood than those at higher latitudes. This paper focuses on evidence of aquatic ecosystem change from a cluster of three deep, freshwater, volcanic crater lakes (Yambo, Mohicap, and Sampaloc) at low altitude on the island of Luzon, Philippines. The lakes support different intensities of aquaculture, an important livelihood but also a driver of poor water quality throughout tropical Asia.Measured and monitored climate and water quality data, in addition to sedimentary evidence from sediment cores collected from the three study lakes, were used to determine the magnitude and trajectory of changes in lake water quality. Sediment cores were radiometrically dated and analysed for organic matter, spheroidal carbonaceous particles, and diatom remains. Diatom data were zoned numerically using cluster analysis. Diatom remains were also used to infer past variations in pH and possible relationships between potential driving climatic variables (temperature and rainfall). Diatom data sets were explored using detrended component analysis and principle component analysis.Despite differences in intensity of aquaculture, a common trajectory and timing of a potential regime shift, characterised by a replacement of benthic with planktonic diatoms and an increase in diatom accumulation rates from the early to mid‐1980s, is evident, and attests a low threshold for disturbance effects. A predominantly planktonic diatom flora has persisted even after recent improvements in environmental quality.The potential new regime may be less resilient and more susceptible to harmful algal blooms, abrupt expansions of anoxic conditions, and periodic mass fish kills when compared with its former state. The research further highlights the sensitivity of freshwater ecosystems in the warm tropics to disturbance pressures, and the risks to livelihoods, ecosystem services, and sustainable development. [ABSTRACT FROM AUTHOR]

Ancient lakes are among the best archivists of past environmental change, having experienced more than one full glacial cycle, a wide range of climatic conditions, tectonic events, and long association with human settlements. These lakes not only record long histories of environmental variation and human activity in their sediments, but also harbor very high levels of biodiversity and endemism. Yet, ancient lakes are faced with a familiar suite of anthropogenic threats, which may degrade the unusual properties that make them especially valuable to science and society. In all ancient lakes for which data exist, significant warming of surface waters has occurred, with a broad range of consequences. Eutrophication threatens both native species assemblages and regional economies reliant on clean surface water, fisheries, and tourism. Where sewage contributes nutrients and heavy metals, one can anticipate the occurrence of less understood emerging contaminants, such as pharmaceuticals, personal care products, and microplastics that negatively affect lake biota and water quality. Human populations continue to increase in most of the ancient lakes' watersheds, which will exacerbate these concerns. Further, human alterations of hydrology, including those produced through climate change, have altered lake levels. Co‐occurring with these impacts have been intentional and unintentional species introductions, altering biodiversity. Given that the distinctive character of each ancient lake is strongly linked to age, there may be few options to remediate losses of species or other ecosystem damage associated with modern ecological change, heightening the imperative for understanding these systems. [ABSTRACT FROM AUTHOR]

Abstract: Freshwater ecosystems are threatened by multiple anthropogenic stressors acting over different spatial and temporal scales, resulting in toxic algal blooms, reduced water quality and hypoxia. However, while catchment characteristics act as a ‘filter’ modifying lake response to disturbance, little is known of the relative importance of different drivers and possible differentiation in the response of upland remote lakes in comparison to lowland, impacted lakes. Moreover, many studies have focussed on single lakes rather than looking at responses across a set of individual, yet connected lake basins. Here we used sedimentary algal pigments as an index of changes in primary producer assemblages over the last ~200 years in a northern temperate watershed consisting of 11 upland and lowland lakes within the Lake District, United Kingdom, to test our hypotheses about landscape drivers. Specifically, we expected that the magnitude of change in phototrophic assemblages would be greatest in lowland rather than upland lakes due to more intensive human activities in the watersheds of the former (agriculture, urbanization). Regional parameters, such as climate dynamics, would be the predominant factors regulating lake primary producers in remote upland lakes and thus, synchronize the dynamic of primary producer assemblages in these basins. We found broad support for the hypotheses pertaining to lowland sites as wastewater treatment was the main predictor of changes to primary producer assemblages in lowland lakes. In contrast, upland headwaters responded weakly to variation in atmospheric temperature, and dynamics in primary producers across upland lakes were asynchronous. Collectively, these findings show that nutrient inputs from point sources overwhelm climatic controls of algae and nuisance cyanobacteria, but highlights that large‐scale stressors do not always initiate coherent regional lake response. Furthermore, a lake's position in its landscape, its connectivity and proximity to point nutrients are important determinants of changes in production and composition of phototrophic assemblages. [ABSTRACT FROM AUTHOR]

"Arctic greening" will alter vegetation quantity and quality in northern watersheds, with possible consequences for lake metabolic balance. We used paleolimnology from six Arctic lakes in Greenland, Norway, and Alaska to develop a conceptual model describing how climate‐driven shifts in terrestrial vegetation (spanning herb to boreal forest) influence lake autotrophic biomass (as chlorophyll and carotenoid pigments). Major autotrophic transitions occurred, including (1) optimal production of siliceous algae and cyanobacteria/chlorophytes at intermediate vegetation cover (dwarf shrub and Betula; dissolved organic carbon (DOC) range of 2–4 mg L−1), below and above which UVR exposure (DOC; < 2 mgL−1) and light extinction (DOC; > 4 mgL−1), respectively limit algal biomass, (2) an increase in potentially mixotrophic cryptophytes with higher forest cover and allochthonous carbon supply. Vegetation cover appears to influence lake autotrophs by changing influx of (colored) dissolved organic matter which has multiple interacting roles—as a photoprotectant—in light attenuation and in macronutrient (carbon, nitrogen) supply. [ABSTRACT FROM AUTHOR]

This study aimed to understand changes in the biogeochemical processing of organic matter (OM) in response to multiple stressors (e.g., littoral area expansion, wastewater input, and hydrological regulation) in East Dongting Lake (Central China) over the past 60 years, using analyses of total organic carbon (TOC), total nitrogen (TN), C/N ratios, δ13C, δ15N, and diatoms from 2 sediment cores collected from the littoral and central parts of the lake. OM mainly originated from phytoplankton and C3 plant-derived soil OM based on the ranges of C/N ratios (from 7 to 11) and δ13C (between −27‰ and −23‰). Littoral area expansion due to siltation caused an increasing influx of terrestrial soil OM in the 1980s and the 1990s, subsequently lowering δ13C values and rising C/N ratios in both sediment cores. Meanwhile, higher δ15N was linked to a high influx of isotopically heavy nitrate from urban and agricultural wastewaters. After 2000, slight decreases in TOC and TN in the littoral area were attributable to reducing inputs of external OM, likely linked to declining sediment influx from the upper reaches resulting from the Three Gorges Dam impoundment. Contrasting increases in TOC, TN, and C/N ratios in the central part indicated a high influx of terrestrial soil OM due to the declining distance from the shoreline with littoral area expansion. Declining δ15N values after 2000 indicated an increase in N2-fixing cyanobacteria with eutrophication. Changes in diatom assemblages in both the littoral and central zones reflected nutrient enrichment and hydrological alterations. These results indicate that littoral expansion, declining riverine influx, and anthropogenic nutrient inputs are potential driving forces for the biogeochemical processing of OM in floodplain lakes. This study provides sedimentary biogeochemical clues for tracking past limnological conditions of floodplain lakes that are subjected to increasing disturbances from hydrological regulation and eutrophication. [ABSTRACT FROM AUTHOR]

Global aquatic ecosystems are under increasing threat from anthropogenic activity, as well as being exposed to past (and projected) climate change, however, the nature of how climate and human impacts are recorded in lake sediments is often ambiguous. Natural and anthropogenic drivers can force a similar response in lake systems, yet the ability to attribute what change recorded in lake sediments is natural, from that which is anthropogenic, is increasingly important for understanding how lake systems have, and will continue to function when subjected to multiple stressors; an issue that is particularly acute when considering management options for aquatic ecosystems. The duration and timing of human impacts on lake systems varies geographically, with some regions of the world (such as Africa and South America) having a longer legacy of human impact than others (e.g., New Zealand). A wide array of techniques (biological, chemical, physical and statistical) is available to palaeolimnologists to allow the deciphering of complex sedimentary records. Lake sediments are an important archive of how drivers have changed through time, and how these impacts manifest in lake systems. With a paucity of 'real-time' data pre-dating human impact, palaeolimnological archives offer the only insight into both natural variability (i.e., that driven by climate and intrinsic lake processes) and the impact of people. While there is a need to acknowledge complexity, and temporal and spatial variability when deciphering change from sediment archives, a palaeolimnological approach is a powerful tool for better understanding and managing global aquatic resources. WIREs Water 2017, 4:e1195. doi: 10.1002/wat2.1195 For further resources related to this article, please visit the . [ABSTRACT FROM AUTHOR]

Sedentary herbivores may improve the food resources available to them by 'gardening', and most obviously by fertilising primary producers with excreted nutrients such as nitrogen. In five English lakes, spanning a gradient of nutrient availability, we predicted that fertilisation of the larval retreat by the littoral, gallery-building caddisfly Tinodes waeneri would result in: (a) a distinct algal assemblage from that in the background epilithon, and that (b) the difference would be greatest in the least productive lakes (where the importance of the nutrient subsidy from larvae should be greatest)., Classes of algae present in samples of galleries and epilithon were investigated using chlorophyll and carotenoid pigment analysis and diatoms were identified., Galleries were characterised by a greater content of pigments indicative of diatoms, including fucoxanthin, than the background epilithon (which contained a higher proportion of chlorophyte algae). Redundancy analysis (RDA) of diatom counts indicated a clear separation between gallery and epilithic assemblages in all lakes, supporting hypothesis (a)., Furthermore, in agreement with hypothesis (b), the assemblage of diatoms on galleries was most similar to that of the epilithon in the more productive lakes, with the greatest divergence in Windermere and Coniston, mainly due to a much greater relative proportion of Gomphonema in the epilithon than in the galleries, suggesting that fertilisation had a greater impact where background nutrient concentrations were low. Lakes in the RDA triplot were arranged in order of productivity along axis 1, with gallery assemblages in each case located towards the more productive end relative to the epilithon., This sedentary, retreat-building grazer, probably in common with many other taxa with such traits in aquatic ecosystems, improves its own food resources by gardening. Larvae can modify algal assemblages in their feeding patches by weeding and fertilisation. They create new surfaces for growth of the biofilm via continually adding to the front of their silken galleries and harvesting the biofilm (dominated by diatoms) that has developed on older parts of their galleries to the rear. It is also feasible that the physical structure of the gallery (separately from the effects of nutrients) plays some role in increasing the availability of algae within the territory. This behaviour is likely to extend the range of conditions under which such species can persist, raise the carrying capacity of their habitat, and has possible wider ecosystem consequences for productivity and nutrient cycling. [ABSTRACT FROM AUTHOR]

Planted forests are increasing in many upland regions worldwide, but knowledge about their potential effects on algal communities of catchment lakes is relatively unknown. Here, the effects of afforestation were investigated using palaeolimnology at six upland lake sites in the north-west of Ireland subject to different extents of forest plantation cover (4-64% of catchment area). 210Pb-dated sediment cores were analysed for carotenoid pigments from algae, stable isotopes of bulk carbon ( δ13C) and nitrogen ( δ15N), and C/N ratios. In lakes with >50% of their catchment area covered by plantations, there were two- to sixfold increases in pigments from cryptophytes (alloxanthin) and significant but lower increases (39-116%) in those from colonial cyanobacteria (canthaxanthin), but no response from biomarkers of total algal abundance ( β-carotene). In contrast, lakes in catchments with <20% afforestation exhibited no consistent response to forestry practices, although all lakes exhibited fluctuations in pigments and geochemical variables due to peat cutting and upland grazing prior to forest plantation. Taken together, patterns suggest that increases in cyanobacteria and cryptophyte abundance reflect a combination of mineral and nutrient enrichment associated with forest fertilization and organic matter influx which may have facilitated growth of mixotrophic taxa. This study demonstrates that planted forests can alter the abundance and community structure of algae in upland humic lakes of Ireland and Northern Ireland, despite long histories of prior catchment disturbance. [ABSTRACT FROM AUTHOR]

Dongting Lake, a wetland of international importance under the Ramsar Convention, is the hydrological lynchpin of the Yangtze floodplain. It is subjected to eutrophication and heavy metal pollution, but little is known of recent rapid degradation of its aquatic environment and potential causes. Here, we use sedimentary records of particle size, elements and pigments, combined with historical hydrological and limnological data, to assess aquatic environmental changes since ca 1960. Coarse particles in the sediments increased after 2003, while concentrations of K, Li, Al and Mg declined. These changes are probably linked to strong erosion of the downstream riverbed and declining supply of ion-rich material from the upper Yangtze reaches after the Three Gorges Dam (TGD) began to operate. Furthermore, enrichment of sedimentary heavy metals and total phosphorus since the 1990s can be attributed to the influx of anthropogenic pollutants. Biotic responses are manifested in higher concentrations of fossil algal pigments, especially those from chlorophytes and siliceous algae after the TGD impoundment. Multivariate analysis revealed that changes in fossil pigments were significantly correlated with total phosphorus and Pb and three indicators for hydrological conditions (i.e. coarse particles, water exchange ratio and sediment discharge), indicating that influx of anthropogenic pollutants and hydrological regulation by the TGD are main drivers of algal community change. Our results provide reference conditions for restoration of Dongting Lake and highlight the importance of hydrological connection with the mainstream and pollution control for continuing efforts to restore Dongting Lake, as well as other similar floodplain lakes worldwide. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Freshwater aquaculture is an important source of protein worldwide. Over‐exploitation of fisheries can, however, add severely to pressures on ecosystem functioning and services. In Southeast Asia, aquaculture in freshwater lakes contributes significantly to the economy and to reductions in poverty and nutritional insecurity. However, overstocking and excessive feeding of fish can lead to a degradation of affected water bodies, manifest as eutrophication, toxic algal blooms, losses of biodiversity and amenity, anoxia and, in extreme cases, collapse of fisheries. Projected increased warming and storminess associated with global climate change are likely to magnify existing problems. Matching levels of aquaculture production with ecological carrying capacity is therefore likely to become increasingly challenging, requiring levels of data and understanding that are rarely available, a problem that is impossible to rectify in the short term using standard limnological approaches. This paper reviews the development of freshwater aquaculture in the Philippines, associated environmental impacts, and relevant environmental regulations and regulatory bodies. The potential role of palaeolimnology, a science that is relatively under‐utilised in the tropics generally and in tropical Asia in particular, in complementing extant datasets, including monitoring records, is highlighted through reference to a preliminary study at Lake Mohicap. Lake Mohicap currently supports aquaculture and is one of a cluster of seven volcanic crater lakes on Luzon, the largest of the archipelago of islands forming the Philippines. [ABSTRACT FROM AUTHOR]

Highly calcareous (marl) lakes are infrequent but important freshwater ecosystems, protected under the EU Habitats and Species Directive. Chara lakes have been considered resistant to eutrophication owing to the self-stabilising properties of charophyte meadows. However, the opposite is suggested by the large-scale biodiversity declines in marl lake taxa in Europe, and evidence of charophyte sensitivity to eutrophication. We combined contemporary, palaeolimnological and archival methods to investigate the eutrophication of Hawes Water, a shallow marl lake in north-west England ( U.K.)., Changes in aquatic macrophyte and invertebrate communities were reconstructed through the analysis of historical macrophyte surveys and sedimentary plant and animal macrofossils in two dated sediment cores from the littoral and deep zones of the lake. In addition, chlorophyll and carotenoid pigments were analysed to track changes in primary production from benthic and pelagic areas. Substantial changes in macrophyte communities were detected over centennial timescales, suggesting high ecosystem sensitivity considering the presently moderate phosphorus concentrations in Hawes Water (mean annual total phosphorus 20 μg L−1)., Two apparent periods of threshold-like change were identified from the sediment record: (i) changes in cyanobacteria (aphanizophyll + myxoxanthophyll to canthaxanthin + zeaxanthin) and potentially in nutrient stoichiometry, reductions in the maximum macrophyte colonisation depth and water clarity, reduced charophyte and Potamogeton diversity, and increases in Nymphaeaceae; and (ii) severe reductions in light availability inferred from subdecadal doubling in phytoplankton abundance, substantial increases in Daphnia abundance and the extinction of charophytes from higher water depths., Further, change in both the littoral and deeper water has confined key marl lake taxa to smaller niches. In the littoral, increasing siltation and reed and Nymphaeaceae densities caused extinction of Littorella uniflora in the early 1900s and have reduced the evenness of Characeae with suspected imminent extinction of two highly localised Chara spp. In the deeper water, upslope creep of maximum colonisation depth has reduced habitat for intermediate-depth marl lake taxa leading to the loss of four Potamogeton and one Chara species, and replacement of these taxa by Nuphar lutea., The large changes in macrophyte community composition and increased incidences of turbid water have reduced the distinctive and valued marl lake features of Hawes Water, indicating that marl lakes can, as a habitat type, be highly sensitive to eutrophication. The persistence of abundant generalist macrophyte species at considerable water depth may be a feature of high-alkalinity lakes in clearwater, macrophyte-dominated states, but is a distinct eutrophication response in marl lakes rather than an indication of resistance to eutrophication. [ABSTRACT FROM AUTHOR]

Increases in atmospheric temperature and nutrients from land are thought to be promoting the expansion of harmful cyanobacteria in lakes worldwide, yet to date there has been no quantitative synthesis of long-term trends. To test whether cyanobacteria have increased in abundance over the past ~ 200 years and evaluate the relative influence of potential causal mechanisms, we synthesised 108 highly resolved sedimentary time series and 18 decadal-scale monitoring records from north temperate-subarctic lakes. We demonstrate that: (1) cyanobacteria have increased significantly since c. 1800 ce, (2) they have increased disproportionately relative to other phytoplankton, and (3) cyanobacteria increased more rapidly post c. 1945 ce. Variation among lakes in the rates of increase was explained best by nutrient concentration (phosphorus and nitrogen), and temperature was of secondary importance. Although cyanobacterial biomass has declined in some managed lakes with reduced nutrient influx, the larger spatio-temporal scale of sedimentary records show continued increases in cyanobacteria throughout the north temperate-subarctic regions. [ABSTRACT FROM AUTHOR]

Disentangling the role of nutrient pollution and climate change on lake ecosystem functioning is paramount to protect water quality in lake catchments worldwide. For more effective management, however, we need to determine whether these two forcing factors interact at different spatial and temporal scales., This study compares centennial-scale archival data and lake sediment records of eutrophication from Blelham Tarn and previously published data from Lake Windermere's North Basin in the English Lake District. We aimed to quantify how lake morphometry, catchment characteristics and landscape position influence the relationship between climate, local land use and algal community change., Redundancy analysis revealed that increases in cyanobacterial pigments and stable isotopes of nitrogen and carbon in sediments of Blelham Tarn from the 1970s onwards correlate strongly with rising densities of sheep and cattle in the catchment. Concomitant installation of piped water and sewage processing facilities appeared to lead to the expansion of filamentous cyanobacteria. In contrast, elevated fossil pigments from siliceous algae after 1990 were related inversely to winter precipitation, suggesting seasonal changes in hydraulic flushing also influenced the algal community response to centennial-scale fertilisation., Abundance of vernal algae increased synchronously in Blelham Tarn and Lake Windermere's North Basin after regional agricultural intensification in the mid-nineteenth century. In contrast, differences in timing of wastewater disposal and treatment at each site led to asynchronous changes in summer taxa such as filamentous cyanobacteria., This study highlights that lake catchments can act as local filters to regional climate change, both due to differences in localised land-use and intrinsic hydrological features (e.g. catchment:lake area, flushing rate). Further, this paper highlights the ability of palaeolimnology to aid identification of significant nutrient sources over different spatial scales for effective catchment water management. [ABSTRACT FROM AUTHOR]

The south-east margin of Tibet is highly sensitive to global environmental change pressures, in particular, high contemporary reactive nitrogen (Nr) deposition rates (ca. 40 kg ha−1 yr−1), but the extent and timescale of recent ecological change is not well prescribed. Multiproxy analyses (diatoms, pigments and geochemistry) of 210Pb-dated sediment cores from two alpine lakes in Sichuan were used to assess whether they have undergone ecological change comparable to those in Europe and North America over the last two centuries. The study lakes have contrasting catchment-to-lake ratios and vegetation cover: Shade Co has a relatively larger catchment and denser alpine shrub than Moon Lake. Both lakes exhibited unambiguous increasing production since the late 19th to early 20th. Principle component analysis was used to summarize the trends of diatom and pigment data after the little ice age ( LIA). There was strong linear change in biological proxies at both lakes, which were not consistent with regional temperature, suggesting that climate is not the primary driver of ecological change. The multiproxy analysis indicated an indirect ecological response to Nr deposition at Shade Co mediated through catchment processes since ca. 1930, while ecological change at Moon Lake started earlier (ca. 1880) and was more directly related to Nr deposition (depleted δ15N). The only pronounced climate effect was evidenced by changes during the LIA when photoautotrophic groups shifted dramatically at Shade Co (a 4-fold increase in lutein concentration) and planktonic diatom abundance declined at both sites because of longer ice cover. The substantial increases in aquatic production over the last ca. 100 years required a substantial nutrient subsidy and the geochemical data point to a major role for Nr deposition although dust cannot be excluded. The study also highlights the importance of lake and catchment morphology for determining the response of alpine lakes to recent global environmental forcing. [ABSTRACT FROM AUTHOR]

Summary 1. Historical archives, published data sets and lake sediments from the North and South Basins of Windermere were analysed to reconstruct changes in the lake and catchment since 1850 and determine the drivers of limnological variability. 2. Pastoral sheep farming has remained the dominant form of agriculture since 1850, but there was a decline in horse numbers (because of agricultural mechanisation), an increase in nitrogen fertiliser use and a doubling in sheep numbers since the 1950s. The human population in the Windermere catchment almost quadrupled between 1801 and 1921 coincident with the arrival of the railway in 1847, which led to urban expansion, sewer and piped water installation (since ∼1860s) and the development of sewage treatment systems (after 1886). 3. C : N ratios and stable isotopes of carbon in 210Pb-dated sediment cores suggested that land disturbance increased the transport of terrestrial carbon to sediments of both basins after 1870, but algae increasingly contributed to the sediment matrix after ∼1890. Nitrogen-stable isotope ratios generally declined in both basins consistent with an increase in an isotopically light source such as atmospheric N deposition or synthetic fertilisers. 4. Chlorophyll and carotenoid pigments in sediment cores showed that algal production increased gradually in the North Basin from ∼1890 to 1940 to be maintained at higher abundance thereafter. South Basin pigments changed most markedly ∼1860 (increase in cyanobacterial pigments), ∼1945 (increase in siliceous algal and chlorophyte pigments) and ∼1987 (increase in cyanobacterial pigments). 5. Redundancy and variance partitioning analyses suggested that sewage influx and the modernisation of agriculture were strongly and positively correlated with algal abundance. However, climate variables were a secondary driver of algal change in both lake basins. 6. Enrichment of the lake was caused by a combination of increases in population (after 1847), more efficient sewage disposal, intensification of agriculture and atmospheric deposition of N, which led to a greater than fivefold increase in primary production in the North Basin and marked shifts in algal communities of the South Basin. 7. After enrichment, lake phytoplankton responded markedly to fluctuations in climate. High precipitation in January-March led to lower abundance of siliceous algae (mostly Asterionella formosa) in both lake basins, possibly because A. formosa inocula were diluted, thus limiting the spring diatom bloom. 8. This combined palaeolimnological and archival study has shown that eutrophication of Windermere occurred before the start of the lake monitoring programme in 1945, but that nutrient enrichment enhanced the lake response to meteorological change. Therefore, future management of Windermere should aim for baseline conditions similar to those existing c. 1850 and consider that the control of eutrophication is essential in building resilience to future climate change. [ABSTRACT FROM AUTHOR]

Human activities and climate change have greatly altered flooding regimes in many of the world's river deltas, but the impact of such changes remains poorly quantified on decadal to multidecadal timescales. This study identified the response of delta lake primary production (measured as the concentration of sedimentary pigments) to variations in flood frequency using spatial surveys and paleolimnological analyses of lakes in the Peace-Athabasca Delta (PAD), Canada. Surveys of 61 lakes spanning a range of hydrological conditions showed that those lakes that received flood waters less frequently were associated with elevated algal production (surface sedimentary pigments) and, in some lakes, increased growth of emergent macrophytes and epiphytic diatoms. Paleolimnological analyses of five lakes corroborated the contemporary spatial survey results by showing that production of pigments from most algal groups increased during recent periods of lower flood frequency in the 20th century as determined from increases in cellulose-inferred lake-water oxygen isotope composition and plant macrofossils, but remained stable in a 'reference' basin. In general, past periods of elevated algal production coincided with the increased abundance of submerged macrophytes or emergent vegetation that provide habitat for attached algae. These results suggest that interdecadal declines in river discharge arising from increased aridity, hydrologic regulation or consumptive water use will cause long-term increases in primary production and alter ecosystem processes (carbon sequestration, biological diversity) in aquatic delta ecosystems similar to the PAD where lakes become nutrient-rich in the absence of flooding. [ABSTRACT FROM AUTHOR]

We used stable isotopes (δ18O and δ²H) and water chemistry to characterize the water balance and hydrolimnological relationships of 57 shallow aquatic basins in the Peace-Athabasca Delta (PAD), northern Alberta, Canada, based on sampling at the end of the 2000 thaw season. Evaporation-to-inflow ratios (E/I) were estimated using an isotope mass-balance model tailored to accommodate basin-specific input water compositions, which provided an effective, first-order, quantitative framework for identifying water balances and associated limnological characteristics spanning three main, previously identified drainage types. Open-drainage basins (E/I < 0.4; n = 5), characterized by low alkalinity, low concentrations of nitrogen, dissolved organic carbon (DOC) and ions, and high minerogenic turbidity, include large, shallow basins that dominate the interior of the PAD and experience frequent or continuous river channel connection. Closed-drainage basins (E/I ≥ 1.0; n = 16), in contrast, possess high alkalinity and high concentrations of nitrogen, DOC, and ions, and low minerogenic turbidity, and are located primarily in the relict and infrequently flooded landscape of the northern Peace sector of the delta. Several basins fall into the restricted-drainage category (0.4 # E/I < 1.0; n = 26) with intermediate water chemistries and are predominant in the southern Athabasca sector, which is subject to active fluviodeltaic processes, including intermittent flooding from riverbank overflow. Integration of isotopic and limnological data also revealed evidence for a new fourth drainage type, mainly located near the large open-drainage lakes that occupy the central portion of the delta but within the Athabasca sector (n = 10). These basins were very shallow (<50 cm deep) at the time of sampling and isotopically depleted, corresponding to Eli characteristic of restricted- and open-drainage conditions. However, they are limnologically similar to closed-drainage basins except for higher conductivity and higher concentrations of Ca2+ and Na+, and lower concentrations of SiO2 and chlorophyll c. These distinct features are due to the overriding influence of recent summer rainfall on the basin water balance and chemistry. The close relationships evident between water balances and limnological conditions suggest that past and future changes in hydrology are likely to be coupled with marked alterations in water chemistry and, hence, the ecology of aquatic environments in the PAD. [ABSTRACT FROM AUTHOR]

Shallow lake ecosystems can shift between clear-water, macrophyte-rich conditions and turbid states with abundant phytoplankton. However, little is known about the controls of algal community composition and primary production before, during, and after ecosystem state change, because long time series that monitor biological change through the transition are scarce. Using proxy data sets derived from sediment cores from two shallow hypertrophic lakes in Denmark, variance-partitioning analysis (VPA) was used to determine the relative importance of changes in total phosphorus (diatom inferred), planktivorous fish density (zooplankton inferred), and submerged macrophyte communities (as macrofossil abundance) as determinants of algal abundance and community composition (as sedimentary pigments) over ecosystem state transitions since 1750 (CE) for Lake Lading and 1900 for Lake Søbygaard. Past variation in densities of planktivorous fish explained 12.3% and 18.2% of historical algal community change in lakes Lading and Søbygaard, respectively, while a further 22.3% and 6% of algal variability was explained by variation in macrophyte abundance. Total phosphorus (TP) alone explained nonsignificant amounts of variance (1.5%, 3.6%) but had a significant effect in combination with macrophytes and fish (27%, 13.4%). State transitions occurred ca. 1940 but were preceded by increases in benthic diatoms and macrophytes, suggesting that transitions were gradual rather than instantaneous. In contrast, green, colonial blue-green, and cryptophyte algae were abundant only during turbid states after ca. 1960 and were correlated to changes in planktivorous fish or fish-TP interactions. Contrary to expectations, the shift from predominantly benthic to pelagic algal production represented only a change in habitat and did not result in an increase in total abundance of primary producers. [ABSTRACT FROM AUTHOR]

Insight into the causes and consequences of changes in aquatic biodiversity requires an improved understanding of the nature of the relationships between species richness and ecosystem function over a much longer temporal perspective than we currently possess. We used high-resolution paleoecological records from two prairie lakes to show that diatom species richness (as fossil frustules) was negatively correlated (r² = 0.09-0.24, p < 0.001) with diatom production (as fossil pigments) during the past 2,000 yr. By comparing analyses from intervals of fresh and saline waters, we demonstrate that these significant richness-production relationships arose during freshwater periods (r² = 0.13-0.45, p < 0.001) and could be eliminated (r² < 0.02, p > 0.1) by abiotic disturbances such as droughts. Procrustes analyses of the concordance of species change within freshwater communities and the change in richness--production relationships through time revealed that shifts in diatom community composition could have a large influence in determining the negative relationship between richness and production. Finally, significant correlations (r² = 0.09-0.24, p < 0.0001) between past diatom species richness and ratios of stable isotopes (primarily δ15N) suggested that C and N biogeochemical cycles are also linked to changes in algal biodiversity. Taken together, these analyses suggest that the ongoing disruption of climate and biogeochemical systems by humans may obscure the relationship between aquatic biodiversity and ecosystem function in the future. [ABSTRACT FROM AUTHOR]

The cover image is based on the Focus Article Healthy waterways and ecologically sustainable cities in Beijing‐Tianjin‐Hebei urban agglomeration (northern China): Challenges and future directions by Giri Kattel et al., https://doi.org/10.1002/wat2.1500. [ABSTRACT FROM AUTHOR]

Evaluation of the effects of climate change and human activities on lakes requires improved understanding of how stressors interact and the degree to which individual sentinel lakes represent broad spatial patterns of ecosystem response to disturbance. We surveyed modern water chemistry (major ions, conductivity, salinity, lake volume) and sediments (algal pigments, stable isotopes) in 21 lakes that surround Humboldt Lake, Saskatchewan, site of a 2,000-yr climate reconstruction, to quantify spatial synchrony (S, the mean among-lake correlation coefficient) of prairie lake response to climate variability, land use, and their interactions. Whole-lake mass balances of total dissolved substances constructed at each site revealed that evaporation of water controlled seasonal changes in salt content only in years with dry summers (2003), leading to widespread spatial coherence of ecosystems (S = 0.78). In contrast, variations in hydrologic inputs (precipitation, groundwater) and solute fluxes regulated salt balances of lakes during years with wet summers (2004, 2005) and substantially reduced lake synchrony (S = 0.13-0.58). Furthermore, >25% of sites exhibited increased nitrogen influx (as d15N) and cyanobacterial production (as fossil pigments) between ca. 1920 and 2003, with particularly strong effects of land use recorded for northeastern sites, where evaporative forcing was greatest. Finally, principal component and canonical ordinations with redundancy analysis both explained ~50% of the variance in lake sensitivity to climate and land use and revealed that the effects of climate and land use interacted strongly, but that the unique effects of each factor remained identifiable in modern lake surveys. [ABSTRACT FROM AUTHOR]