Lake States Research Articles

Interactions between suspended sediments and submerged macrophytes-epiphytic biofilms under water flow in shallow lakes

Suspended sediments (SS) pollution is one of the factors affecting the transfer from turbid water state to clear water state in shallow lakes. However, the interactions between suspended sediments and submerged plants are far from clear. In this study, we investigated the settlement laws of SS in overlying water and its impact on the epiphytic biofilm of Myriophyllum verticillatum and Vallisneria natans under water flow. At least 90% of turbidity can be removed from overlying water, and the decreasing trend of water turbidity fitted the logarithmic decay model in all treatments. The size distribution of SS fit the log-normal distribution model in the first 240 min after SS addition. It should be noted that the main peak particle sizes were lower in treatments with submerged macrophytes (8.71-13.18 μm) than without plants (15.14-19.95 μm). Water flow and SS addition significantly increased the thickness of biofilms attached to M. verticillatum (p < 0.05), but they together significantly reduced the biofilm thickness on V. natans (p < 0.05). SS increased the bacterial α-diversity but decreased eukaryotic one in epiphytic biofilms. However, water flow had a more significant impact on microbial communities (especially eukaryotes) than SS and plant species. The relative abundances of dominant phylum Proteobacteria, class Alphaproteobacteria and Betaproteobacteria, and class Verrucomicrobiae increased in epiphytic biofilms after SS addition. Co-occurrence networks reveal that photosynthetic microbes in epiphytic biofilms played an important role in microbial communities under water flow and SS, and many hub microbes were increased by SS addition but reduced by water flow. These data highlight that SS decline can be predicted by the logarithmic decay model and, SS and water flow can affect the epiphytic-biofilm on submerged macrophytes.

Coprecipitation of Organic Matter, Phosphate With Iron: Implications for Internal Loadings of Phosphorus in Algae-Dominated and Macrophyte-Dominated Lakes

Coprecipitation with iron (Fe) plays an essential role in the biogeochemical cycles of organic carbon (OC) and phosphorus (P) in lakes. The sources and composition of organic matter (OM) mediate its association with iron, which could thus influence the immobilization of phosphorus. In this study, water-soluble organic matter from the sediments of two typical states of shallow lakes, macrophyte-dominated zones (M-WSOM) and algae-dominated zones (A-WSOM), was extracted, and the ternary coprecipitation of WSOM, phosphate with Fe(III), was investigated. The ternary coprecipitation process was enhanced with increasing Fe(III) or decreasing pH value. It was found that pH of 6.5 was more favorable for coprecipitation than a pH of 7.5 or 8.5. At pH 6.5, the complexation between WSOM and Fe(III) occurred at the low Fe(III) inputs, while the coprecipitation of phosphate, WSOM with Fe(III) took place when Fe(III) inputs reached 40 μM. The presence of A-WSOM showed stronger inhibition on the coprecipitation of phosphate than that by M-WSOM. The formed ternary coprecipitates with A-WSOM had lower C/Fe ratios (0.13–2.78) than those with M-WSOM (1.28–4.05), which was because A-WSOM had lower aromaticity than M-WSOM. In addition, more functional groups in A-WSOM could complex with Fe(III), resulting in less immobilization of OC and P during the coprecipitation of A-WSOM, phosphate, and Fe(III). Our results demonstrated that in algae-dominated zones, more phosphorus remained soluble during the ternary coprecipitation, which could perform positive feedback on the growth of phytoplankton and provide a novel explanation for the difficulty in restoring eutrophic lakes.

Effects of natural surfactants on the spatial variability of surface water temperature under intermittent light winds on Lake Geneva

The spatial variability of lake surface water temperature (LSWT) between smooth and rough surface areas and its potential association with the natural surfactant distribution in the surface microlayer were investigated for the first time in a lake. In spring 2019, two different field campaigns were carried out in Lake Geneva to measure: i) the enrichment factor of fluorescent dissolved organic matter (FDOM) as a proxy for biogenic surfactants, and ii) LSWT and near-surface water temperature profiles while simultaneously monitoring water surface roughness in both cases. Results indicate that, under intense incoming short-wave radiation and intermittent light wind conditions, the atmospheric boundary layer (ABL) was stable and the accumulation of heat due to short-wave radiation in near-surface waters was greater than heat losses by surface cooling, thus creating a diurnal warm layer with strong thermal stratification in the water near-surface layer. A threshold wind speed of 1.5 m s-1 was determined as a transition between different dynamic regimes. For winds just above 1.5 m s-1, the lake surface became patchy, and smooth surface areas (slicks) were more enriched with FDOM than rough areas (non-slick) covered with gravity-capillary waves (GCW). Sharp thermal boundaries appeared between smooth and rough areas. LSWT in smooth slicks was found to be more than 1.5°C warmer than in rough non-slick areas, which differs from previous observations in oceans that reported a slight temperature reduction inside slicks. Upon the formation of GCW in non-slick areas, the near-surface stratification was destroyed and the surface temperature was reduced. Furthermore, winds above 1.5 m s-1 continuously fragmented slicks causing a rapid spatial redistribution of LSWT patterns mainly aligned with the wind. For wind speeds below 1.5 m s‑1 the surface was smooth, no well-developed GCW were observed, LSWT differences were small, and strong near-surface stratification was established. These results contribute to the understanding and the quantification of air-water exchange processes, which are presently lacking for stable Atmospheric Boundary Layer conditions in lakes.

Genome Analysis of Enterobacter asburiae and Lelliottia spp. Proliferating in Oligotrophic Drinking Water Reservoirs and Lakes.

Surface waters are one of the main sources for drinking water production, and thus microbial contamination should be as minimal as possible. However, high concentrations of coliform bacteria were detected in reservoirs and lakes used for drinking water production during summer months due to autochthonous proliferation processes. Here, we present the genomic analyses of 17 strains of Enterobacter asburiae and Lelliottia spp. proliferating in reservoirs and lakes with special focus on the hygienic relevance, antibiotic resistance, and adaptations to the oligotrophic environments. The genomes contain neither genes for the type III secretion system nor cytotoxins or hemolysins, which are considered typical virulence factors. Examination of antibiotic resistance genes revealed mainly efflux pumps and β-lactamase class C (ampC) genes. Phenotypically, single isolates of Enterobacter asburiae showed resistance to fosfomycin and ceftazidime. The genome analyses further suggest adaptations to oligotrophic and changing environmental conditions in reservoirs and lakes, e.g., genes to cope with low nitrate and phosphate levels and the ability to utilize substances released by algae, like amino acids, chitin, alginate, rhamnose, and fucose. This leads to the hypothesis that the proliferation of the coliform bacteria could occur at the end of summer due to algae die-off. IMPORTANCE Certain strains of coliform bacteria have been shown to proliferate in the oligotrophic water of drinking water reservoirs and lakes, reaching values above 104 per 100 mL. Such high concentrations challenge drinking water treatment, and occasionally the respective coliform bacteria have been detected in the treated drinking water. Thus, the question of their hygienic relevance is of high importance for water suppliers and authorities. Our genomic analyses suggest that the strains are not hygienically relevant, as typical virulence factors are absent and antibiotic resistance genes in the genomes most likely are of natural origin. Furthermore, their presence in the water is not related to fecal contamination. The proliferation in reservoirs and lakes during stable summer stratification is an autochthonic process of certain E. asburiae and Lelliottia strains that are well adapted to the surrounding oligotrophic environment.

Lake-land breezes over a small elongated lake (Kozjak, Plitvice Lakes, Croatia)

The temperature of a small elongated lake (2.3 km by 0.1-0.6 km; maximum depth of 46 m) located in a mountaneous area was measured during July-September period over three years (2018-2020) at the depth close to the lake surface (0.2 m). Concurrent standard meteorological variables were measured in the vicinity of the lake. Criteria based on atmospheric and lake conditions were defined to detect the days with persistent lake-land breeze (LLB) events. The results showed that 17.7% of the investigated days were associated with LLB events. These days were accompanied by elevated energy in the normalized wavelet spectra for the wind speed at period of 24 hours. Daytime onshore lake breezes were mainly channeled in the along-lake direction due to the surrounding topography. Accordingly, during the daytime, diurnal wind veering was distorted. However, during the nighttime, a clear clockwise wind rotation was present. In addition, the results exhibited a clear relationship between the lake-land temperature difference and the strength of the LLBs.

Harnessing aquatic plant growth forms to apply European nutrient-enrichment bioindicators to Canadian waters.

PremiseAquatic macrophyte species abundance and nutrient affinity are used in metrics to assess the trophic condition of lakes and rivers. The development of these indices is often regional, with inter‐regional comparisons being complicated by the lack of taxonomic overlap. Here, we use a traits‐based approach to expand the geographic scope of existing metrics.MethodsWe generalized European trophic affinity values using the response of plant growth form to the light–nutrient gradient, then applied these values to sites in Canada. We evaluated the method's performance against the measured total phosphorus concentration (TP).ResultsFree‐floating and emergent growth forms were associated with enriched waters (>0.2 mg/L TP), whereas rosette forms were associated with oligotrophic conditions (<0.05 mg/L TP). The responses were longitudinally consistent, and the site scores among indices were highly collinear. Growth form–based scores were more strongly correlated with TP than were species‐based scores (0.42–0.56 versus 0.008–0.25).DiscussionWe leveraged the ecological relationship between increased surface water nutrient enrichment and the dominance of particular aquatic plant growth forms to generalize aquatic plant trophic indices. We demonstrated an approach for adapting species‐based indices to plant traits to facilitate a broader geographic application and simpler data collection, which could be used to develop an easily applied trait‐based method of assessing water nutrient status.

INFLUENCE OF BENTHIC FAUNA ON HYDROCHEMISTRY ANDSEDIMENT IN SASTHAMKOTTA LAKE IN SOUTHERN KERALA, INDIA

Sasthamkotta Lake is the largest freshwater water body of Kerala with great ecological significance, playing also pivotal role in the supply of water for drinking, agriculture, fishery exploitation, industrial activities, frivolous navigation and water tourism. Due to their importance, the environmental conditions in the Sasthamkotta lake have engrossed an better public attention in present society. The concentrations of various physico-chemical parameters of water and sediment are not exceeding environmental standards. Benthic samples revealed 8 species belonging to Order Diptera, Order Trichoptera and Order Tubificida. The results obtained from the study showed good ecological condition despite numerous local and regional natural and anthropogenic interventions.

Ecological Conditions of Luetshokha Lake and its Recharge Potential using Rooftop Rainwater Harvesting, Samtengang, Wangdue Bhutan

Luetshokha lake is noted to harbour invasive aquatic plants and experience reduction in water level. This research assessed the floristic and macroinvertebrate composition of Luetshokha lake in Samtengang, Wangdue and its potential to increase water level using rooftop rainwater harvesting (RWH). Presence of aquatic plants such as Brasenia schreberi, Schnoeplectus pungens and Potamogeton distinctus indicate organic pollution of water in the lake. Coenagrionidae and Baetidae families were the most dominant macroinvertebrate communities present in the lake. There was a positive relationship between aquatic plants and macroinvertebrate diversity indices (rs = 0.20, p = 0.25), richness (rs = 0.24, p = 0.16) and evenness (rs = 0.29, p = 0.04). The relationships between aquatic plants and physico-chemical variables were negative; pH (rs = -0.02, p = 0.90), conductivity (rs = -0.45, p = 0.00), Total Dissolved Solids (TDS) (rs = -0.43, p = 0.01) and salinity (rs = -0.34, p = 0.56). However, temperature was positively correlated (rs = 0.25, p = 0.14) with aquatic plants. Similarly, macroinvertebrate diversity was negatively correlated with pH (rs = -0.31, p = 0.07), temperature (rs = -0.11, p = 0.54), conductivity (rs = -0.24, p = 0.17), TDS (rs = -0.24, p = 0.16) and salinity (rs = -0.27, p = 0.12). Family Biotic Index (FBI) indicated good physical condition of lake water with some organic pollution. The lake water level was estimated to rise by 0.05 m through a potential RWH of 1,784.37 m3 from the roof catchment area of 2,221.01 m2.

Monitoring the trophic state of shallow urban lakes using Landsat 8/OLI data: a case study of lakes in Hanoi (Vietnam)

Monitoring the trophic state of shallow urban lakes using Landsat 8/OLI data: a case study of lakes in Hanoi (Vietnam)

Piscivore stocking significantly suppresses small fish but does not facilitate a clear-water state in subtropical shallow mesocosms: A biomanipulation experiment

Biomanipulation by piscivore stocking has been widely used to combat eutrophication in north temperate lakes, but its applicability in warm lakes has not yet been well elucidated. Here, we used experimental mesocosms to test the effects of a native benthi-piscivore (snakehead, Channa argus Cantor) on water clarity under subtropical conditions where small omni-benthivorous fish like crucian carp (Carassius carassius L.) prevail. Our results showed that, despite of a great reduction of crucian carp biomass, snakehead stocking did not create a strong trophic cascade as neither (herbivorous) zooplankton biomass nor their grazing pressure, indicated by biomass ratio of (herbivorous) zooplankton to phytoplankton, changed significantly. Moreover, snakehead stocking significantly increased water non-algal turbidity as well as nutrient and chlorophyll-a concentrations, suggesting that these benthi-piscivores also disturbed sediments like crucian carp did. Our study showed that biomanipulation by stocking of snakehead does not facilitate clear-water state in warm shallow lakes, even on the short-term.

Physical Factors and Microbubble Formation Explain Differences in CH4 Dynamics Between Shallow Lakes Under Alternative States

Submerged macrophytes play a key role in maintaining clear vegetated states in shallow lakes, but their role on methane (CH4) dynamics is less explored. They might enhance methanogenesis by providing organic matter but they can also supply oxygen to the sediments increasing methanotrophy. They may also affect gas exchange by diminishing wind turbulence in the water column. We previously measured seasonal CO2 and CH4 partial pressure (pCO2 and pCH4) and diffusive fluxes from two clear vegetated and two turbid algal shallow lakes of the Pampean Plain, Argentina, and we reported that clear lakes had higher mean annual pCH4 despite states having similar mean annual CH4 diffusive flux. In this study we explore the contribution of physical and biological factors regulating surface pCH4. Mean annual CH4 diffusive fluxes and CH4 fraction of oxidation (Fox) were similar between states, implying a comparable mean annual CH4 input. kCH4 was significantly higher than kCO2, suggesting occurrence of CH4 microbubbles, yet kCH4 was higher in turbid lakes than in clear lakes, implying a higher microbubble formation in turbid lakes. Furthermore, in turbid lakes there were positive relationships between k and wind speed, and between k and pCH4, yet in clear lakes these relations were absent. Results suggest that submerged vegetation suppresses wind induced turbulence in clear vegetated lakes, decoupling kCH4 from wind and reducing microbubble formation, therefore augmenting pCH4 in their surface waters. Overall, physical rather than biological factors appear to control the observed differences in pCH4 between states.

Six decades of field observations reveal how anthropogenic pressure changes the coverage and community of submerged aquatic vegetation in a eutrophic lake

Six decades field observation data series on submerged aquatic vegetation (SAV), water level and water quality from Lake Taihu were compiled to reveal the dynamics in coverage and species composition of SAV and their anthropogenic drivers. We found that both SAV species composition and coverage area declined significantly in Lake Taihu during the period, and the increasing nutrient levels and water level as well as decreasing water clarity were responsible for these change trends. Specifically, the decrease in species richness could be particularly well predicted by total nitrogen (TN) and the ratio of water clarity (i.e., Secchi disk depth (SDD)) to water level (WL), contributing 47.3 % and 32.3 %, respectively, while the coverage of macrophytes was most strongly related to the water level, accounting for 70.1 % of the variation. A classification tree analysis revealed a threshold of TN of 3.2 mg/L and SDD/WL of 0.14 that caused a shift to a eutrophic low-macrophyte dominated state. Our results highlight that SDD/WL must be improved for SAV recolonization, rather than merely reducing nutrient input and regulating water level. Our findings provide scientific information for lake managers to prevent plant degradation in macrophyte-dominant lakes and facilitate a shift to a macrophyte-dominant state in eutrophic lakes.

Late Pleistocene and Holocene palaeoecological reconstruction of Lake Texcoco (Basin of Mexico) based on its ostracod record

AbstractWe present a palaeohydrological reconstruction of Lake Texcoco over the last 32.7 cal ka based on ostracod records consisting of two species, Candona patzcuaro and Limnocytherina axalapasco. Overall, the presence of these species suggests that Lake Texcoco was highly saline and experienced occasional desiccation periods. Moreover, this work helps improve our knowledge of L. axalapasco, an endemic species of central Mexico; their eggs could remain dormant‐resting to survive long dry periods. Four ostracod zones reflect the main environmental changes that occurred during the Late Pleistocene and Holocene. From 32.7 to 30 cal ka bp (Zone 4), Lake Texcoco's water levels were stable and alkaline with saline conditions. Zone 3, representing the period from 30 to 18 cal ka bp, includes a period of enhanced precipitation (greatest abundance of C. patzcuaro) from 30 to 26 cal ka bp. From 26 to 18 cal ka bp, an abundance of L. axalapasco reflects shallower and more saline conditions. The Last Glacial Maximum was characterised by cold and humid conditions with enhanced runoff, especially at 25.3, 21.9, and 20.7 cal ka bp. Zone 2 (18–7 cal ka bp) represents the driest period on record. Finally, shallow and saline lake conditions have prevailed over the last 7 cal ka (Zone 1).

Using an unmanned aerial vehicle (UAV) for lake management: ecological status, lake regime shift and stratification processes in a small Mediterranean karstic lake

High-resolution remote sensing imagery by unmanned aerial vehicles (UAVs) has been used as a tool for the environmental management of natural resources. Monitoring programmes that evaluate the ecological status of water bodies according to the Water Framework Directive (WFD) involve significant costs and sampling efforts that can be reduced by using UAVs. UAV imagery was used to measure some metrics of the “macrophytes and phytobenthos” biological quality element (BQE), which is required to assess the ecological status of European lakes; e.g. the percentage cover of hydrophytes and helophytes. Eight UAV flights took place during an annual cycle (July 2016 to July 2017) in a small karstic lake located in southeast Spain. Limnolog¬ical surveys of physicochemical (temperature, conductivity, dissolved oxygen, pH) and biological (pigments) parameters were simultaneously performed to correctly interpret the UAV images. For each flight performance, an orthomosaic of georeferenced RGB images was obtained, and the different features of interest were monitored and quantified by an automated identification and classification system (the LAIC software). The UAV images allowed us to not only evaluate the lake’s ecological status by measuring macrophyte metrics, but to also detect relevant ecological events for environmental management. A gradual burial process of charophyte meadows by the proliferation of periphytic cyanobacterial was detected in an early state by UAV images. Stratification processes, such as hypolimnetic sulphur bacteria blooms or metalimnetic white colloidal layers, were also ob¬served by UAV imaging. We conclude that UAV imagery is a useful tool for environmental lake management.

Water quality evaluation and ecological-health risk assessment on trace elements in surface water of the northeastern Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau is a unique area with water sources for approximately 40 % of the population in the world. Water resources and water quality are closely associated with ecological security and human health. Fifty-one trace elements in surface water samples (n = 40) were measured, and water quality, health and ecological risks were assessed. Trace elements showed significant variations in different surface water bodies in the study area. Concentrations of minor elements were relatively high in saline and salt lakes while those of REEs varied from 0.05 to 33.62 μg/L with an average value of 3.80 μg/L. The Nemerow pollution index (NP) values of trace elements ranged from 0.08 to 3.48, with an average value of 0.36 in rivers, fresh lakes and reservoir water samples; The heavy metal pollution index (HPI) values ranged from 3.70 to 21.18, indicating that most samples were within the critical limit; The heavy metal evaluation index (HEI) values and degree of contamination (DC) values indicated a free pollution status. The water quality index (WQI) values showed that 96 % of the samples belonged to excellent status in rivers, fresh lakes and reservoir water samples. More attention should be given to the Cr, Zn and Hg in the study area according to potential ecological risk assessment. Hazard quotients for residential children in 30 sites exceed 1.0 with maximal value of 10.97, suggesting the high non-carcinogenic risks for children in the study area. U, Zr and Cr for the ingestion pathway, Cr and U for the dermal pathway were primary contributors to the total health risk. Carcinogenic risk values of trace elements for residential and recreational receptors were in the range of 3.20 × 10−5-7.38 × 10−3 and 8.62 × 10−6-3.63 × 10−3, respectively. The carcinogenic risk values of Cr in surface water were higher than the target risk of 1 × 10−4, while the carcinogenic risk values of As were below the target risk. The results of this study provided information on trace elements for human health protection and water management in the northeastern Qinghai-Tibet Plateau.

Prey selection and growth in 0+ Eurasian perch Perca fluviatilis L. in littoral zones of seven temperate lakes

AbstractWe studied the relationships between the planktonic food base and feeding patterns of juvenile mid‐summer/early autumn Eurasian perch Perca fluviatilis L., a common predatory freshwater fish in large parts of Europe and Asia. The feeding of 0+ perch was studied during summer and autumn in littoral habitats of seven lakes with different environmental conditions – four Latvian (Auciema, Riebinu, Vārzgūnes, Laukezers) and three Estonian (Kaiavere, Prossa and Akste) lakes. Simultaneously, the abundance, biomass and structure of zooplankton communities were examined. We focused on the littoral areas because many studies in lakes suggest that littoral habitats are particularly important for 0+ fish growth and survival. We were interested in the question: can the diet and growth of 0+ perch be explained by zooplankton community structure? We also presumed that if the amount of zooplankton is low, more benthic invertebrates will be consumed by 0+ perch. Opposite to expectations, we found that zooplankton always counted for over 90% of diet biomass in perch. There were also clear correlations between the zooplankton biomass in a given lake, the zooplankton biomass in 0+ perch stomachs, and the fish growth rate. The study also suggested that nutrient enrichment can positively impact the 0+ perch feeding conditions in lakes.

Analysis of the 2017-2018 Rift valley fever outbreak in Yirol East County, South Sudan: a one health perspective.

Introductionthe emergence and re-emergence of zoonotic diseases have threatened both human and animal health globally since their identification in the 20th century. Rift Valley fever (RVF) virus is a recurrent zoonotic disease in South Sudan, with the earliest RVF cases confirmed in 2007 in Kapoeta North County, Eastern Equatoria state.Methodswe analyzed national RVF outbreak data to describe the epidemiological pattern of the RVF outbreak in Yirol East county in Lakes State. The line list of cases (confirmed, probable, suspected, and non-cases) was used to describe the pattern and risk factors associated with the outbreak. The animal and human blood samples were tested using Enzyme-Linked Immunosorbent Assay (ELISA) (Immunoglobulin IgG and IgM) and Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). Qualitative data were collected from weekly RVF situation reports, and national guidelines and policies.Resultsbetween December 2017 and December 2018, 58 suspected human RVF cases were reported. The cases were reclassified based on laboratory and investigations results, such that as of 16th December 2018, there were a total of six (10.3%) laboratory-confirmed, three (5.2%) probable, one (1.7%) suspected, and 48 (82.8%) non-cases were reported. A total of four deaths were reported during the outbreak (case fatality rate (CFR) 6.8% (4/58). A total of 28 samples were collected from animals; of these, six tested positives for RVF (positivity rate of 32.1% (9/28). The outbreak was announced in March 2018, after four months of the first reported suspected RVF case. Several factors were attributed to the delayed notification and outbreak announcement such as lack of multi-sectorial coordination at the state and county level, multi-sectoral coordination at national level mostly attended by public health experts from human health, inadequate animal health surveillance, poor coordination between livestock disease surveillance and public health surveillance, limited in-country laboratory diagnostic capacity, the laboratory results for the animal health took longer than expected, and lack of a national One Health approach strategy.Conclusionthe outbreak demonstrated gaps to investigate and respond to zoonotic disease outbreaks in South Sudan.

Periphyton as a key diet source of essential fatty acids for macroinvertebrates across a nutrient and dissolved organic carbon gradient in boreal lakes

AbstractWe studied how physiologically important long‐chain polyunsaturated fatty acids (PUFA) in benthic macroinvertebrates (Asellus aquaticus, Chironomidae, and Oligochaeta) were related to those in periphyton and terrestrial organic matter (tree leaves), collected from littoral areas of 17 boreal lakes that differed in their dissolved organic carbon (DOC) and nutrient (phosphorus and nitrogen) concentrations. We also analyzed fatty acid (FA)‐specific stable carbon isotopes (δ13CFA) to investigate the dietary origin (periphyton vs. terrestrial organic matter) of PUFA in the consumers. In contrast to periphyton, terrestrial organic matter was deprived of long‐chain PUFA, such as eicosapentaenoic acid (EPA), but rich in short‐chain PUFA. The FA composition of macroinvertebrates was primarily taxon‐specific despite the large differences in DOC and nutrient concentrations of the lakes. An increase in DOC concentration had a negative impact on the EPA content of Asellus, chironomids, and oligochaetes as well as the total FA content of chironomids and oligochaetes. However, the FA content of macroinvertebrates was not related to lake total phosphorus concentrations, although the total FA and EPA content of periphyton increased with the trophic status of the study lakes. The δ13CPUFA values of macroinvertebrates were positively related with the δ13CPUFA of periphyton and weakly with δ13CPUFA of terrestrial leaf material. The results indicate that EPA in the studied macroinvertebrate taxa was mainly derived from an algal‐based diet and not via biosynthesis from allochthonous precursor FA. Thus, macroinvertebrate production in lakes may be limited by the available algae‐based food sources.

Lowstand lake conditions in NW Anatolia during the Little Ice Age: Multi-proxy evidence from Lake Sünnet

Despite global and local evidence of significant precipitation changes since the Little Ice Age (LIA), their impact upon lake hydrology and surrounding vegetation has yet to be investigated in NW Anatolia. Moreover, the LIA, as a trigger to the social/political recession of the Ottoman Empire in the 17th century is expected to have these impacts. To address this important gap, we studied three cores from Lake Sünnet, a landslide-dammed high altitude lake with extreme sedimentation rates, by using a wide range of proxies including lithology, stable isotopes of O and C, diatoms, pollen, and ostracods. The LIA timespan of AD 1510–1750 is represented by poorly preserved diatom flora and scarce ostracod fauna that collectively suggest very shallow aquatic conditions. The period AD 1640–1710 within the LIA is standing out with higher Abies and total herb pollen percentages that denotes considerably cooler conditions. During and soon after this cold and dry period precisely overlapping the Maunder Minimum, the currently deep Lake Sülüklü in close vicinity was a dry lowland where tall trees were growing. Progressive warming/lake level rise in Lake Sünnet after the AD 1750s is suggested based on a continuous diatom record with increasing planktonic share, increase in diverse and warm demanding arboreal cover, and a positive shift in δ18O of the lake muds. Following the relatively dry/cold period of AD 1800–1850 (Dalton Minimum) when the lake level was stationary and Artemisia cover became the most expanded of the whole record, a relatively warmer climate has dominated the area until the end of the 20th century.

Human impact on current environmental state in Chinese lakes

Anthropogenic and natural disturbance to inland aquatic ecosystems displays a notable spatial difference, yet data to measure these differences are scarce. This study encompasses 217 lakes distributed over five lake regions of China and elucidates the environmental factors determining the spatial variability of the water quality and trophic status. A significant correlation between human modification index in surrounding terrestrial systems (HMT) and trophic status of lake ecosystems (TSI) was found, and the regression slope in each region was similar except in the Qinghai-Tibet Plateau region. It was further noted that the pattern of environmental factor network (EF network) differed among freshwater and saline lakes. The EF network was complex for freshwater lakes in less human-influenced areas, but intensive man-made influence disrupted most relationships except for those between total nitrogen, total phosphorus, chlorophyll-a, and water turbidity. As for regions including saline lakes, correlations among water salinity and organic forms of carbon and nitrogen were apparent. Our results suggest that HMT and EF network can be useful indicators of the ecological integrity of local lake ecosystems, and integrating spatial information on a large scale provides conservation planners the option for evaluating the potential risk on inland aquatic systems.