Temperate Lakes Research Articles

Potential impact of cold water immersion on arrhythmogenesis: a pilot exploratory study surrounding the Geneva christmas cup

Abstract Background Cold-water immersion (CWI) is gaining popularity and is regulated by sports federations with guidelines for various cold temperature ranges. Small studies suggest cardiovascular and stress reduction benefits from regular CWI, yet acute effects and cardiac risks remain underexplored. Purpose This study aimed to assess the impact of CWI on arrhythmogenesis among participants of the 2023 Geneva Christmas Cup, the world's largest cold-water swimming event. Methods Volunteers aged 45 and older were recruited through the organizing committee. Each underwent baseline cardiovascular risk assessment 10 days prior to the event, including medical interviews, physical exams, blood tests, and 12-lead ECGs. A waterproof ECG recorder (BodyGuardian Mini®) was attached to participants, monitoring them for 10 days up to the end of the race. An activity diary recorded training sessions, CWI exposure, and any symptoms. Data from BodyGuardian Mini® were analyzed for CWI-induced arrhythmias and conduction disturbances. The local ethics committee approved the study. Results Twenty volunteers (11 women, mean age 56 ± 6.4 years) participated. Their mean SCORE2/SCORE2-OP was 4 ± 1.8%, with 60% at low to moderate and 40% at high cardiovascular risk. Average weekly training was 5.5 ± 2.9 hours. Lake temperature was 7.0 degrees. One participant could not race but all completed CWI training and wore ECG recorders for an average of 226 ± 32 hours. Sixteen participants (80%) exhibited non-sustained atrial tachycardia (average 12.4 ± 8.8 events), and four (20%) had non-sustained ventricular tachycardia events (average 1.2 ± 0.5), with no significant pauses or >1st degree AV block observed. No arrhythmic events were directly linked to CWI. Conclusion This exploratory study of active, middle-aged participants with moderate cardiovascular risk found no association between CWI and arrhythmias. Further, larger-scale studies are necessary to conclusively determine CWI's safety.

Characteristics and Correlation Study of Mountainous Lake Ice Phenology Changes in Xinjiang, China Based on Passive Microwave Remote Sensing Data

Lake ice phenology directly reflects local climate changes, serving as a key indicator of climate change. In today’s rapidly evolving climate, utilizing advanced remote sensing techniques to quickly extract long-term lake ice phenology features and studying their correlation with other climate factors is crucial. This study focuses on lakes in Xinjiang, China, with a mountainous area greater than 100 km2, including Sayram Lake, Ayahkum Lake, Achihkul Lake, Jingyu Lake, and Ahsaykan Lake. The Bayesian ensemble change detection algorithm was employed to extract lake ice phenology information, and the Mann–Kendall (MK) non-parametric test was used to analyze trends. The visual interpretation method was used to interpret the spatial evolution characteristics of lake ice, and the Pearson correlation coefficient was used to explore the driving factors of lake ice phenology. Results indicate the following: (1) Jingyu Lake exhibited the most significant delay in both freezing and complete freezing days, while Ayahkum Lake showed the most stable pattern. Ahsaykan Lake demonstrated the least delay in both starting and complete melting days. (2) Sayram Lake’s ice evolution was unstable, with wind causing variability in the locations where freezing begins and melting spreading from the west shore. Ayahkum Lake, Ahsaykan Lake, and Jingyu Lake exhibited similar seasonal variations, while Achihkul Lake’s ice spatial changes spread from the east to the center during freezing and from the center to the shore during melting. (3) The study found that the freeze–thaw process is influenced by a combination of factors including lake area, precipitation, wind speed, and temperature.

Role of Lake Morphometric and Environmental Drivers of Ice Cover Formation and Occurrence on Temperate Lakes: A Case Study from the Eastern Baltic Lakeland, Poland

The presence of ice cover on temperate lakes is a crucial factor in determining the functioning of these ecosystems. The isolation of water from atmospheric influences significantly alters physical, chemical, and biological processes, and the intensity of this impact depends on the duration of the ice cover. This study analyzed the basic parameters of ice cover on several dozen lakes in Northeastern Poland. The aim of this study is to investigate the influence of morphometric parameters, alongside environmental factors, on the variation of ice cover characteristics in lakes located within the Eastern Baltic Lakeland. Characterization of ice conditions in the analyzed lakes was based on basic statistics such as minimum and maximum values, mean, standard deviation, coefficients of variation, skewness, and kurtosis. Given that the dataset contains variables describing ice phenomena in the studied lakes and data describing location, morphometric parameters, and land cover directly adjacent to the lake (treated as independent variables), a method of Spearman’s rank correlations and constrained ordination method were decided upon. Despite the relatively small study area, significant variability was observed, with average differences as follows: 26 days for the onset of ice cover, 17 days for the end date, 15 cm for ice thickness, and a 30-day difference in the average duration of ice cover. Key factors included parameters such as lake volume, average depth, and land use (urbanized and agricultural areas). Understanding parameters such as the onset and end of ice cover is essential for lake ecosystems, both from an ecological and economic perspective. This knowledge is crucial for interpreting the behavior of living organisms, water quality, and economic considerations.

Hatch timing of largemouth bass: implications for recruitment at the Northern edge of their native range

Climate-related shifts in hatch timing could mean that age-0 largemouth bass Micropterus salmoides in north temperate lakes reach larger sizes and experience higher survival, which may contribute to increased prevalence of this species in many lakes. However, information on age-0 largemouth bass life history is lacking for these lakes. We estimated hatch dates, daily growth rates (DGR), and length-based probability of piscivory of age-0 largemouth bass in Wisconsin lakes to: (1) provide baseline data on early life history; (2) compare hatch timing between years with different spring temperature regimes, and (3) project how shifts in hatch timing might influence total length (TL) distributions of age-0 bass if mean DGR remained constant. Most age-0 largemouth bass (>90%) collected from ten Wisconsin lakes (N = 746) hatched between 23 May and 24 June during 2012 and 2013 and did not switch to piscivory during their first summer. Prevalence of positive correlations (16 of 24 lake-year pairings) between TL in and age indicates hatch timing may influence TLs attained by age-0 largemouth bass in August in some lake-years. Mean daily water temperatures in May 2012 were 3.1 °C warmer than in May 2013 for the five of the six lakes where hatch dates were estimated in both years. On average, earliest and median hatch dates for age-0 largemouth bass in these six lakes were 10–11 d earlier in 2012 than in 2013 and hatch duration was approximately 8 d longer in 2012. Despite differences in hatch timing, mean DGR was relatively consistent (range = 0.61–0.74 mm/d) between lakes and years. Simple simulations suggest that earlier hatch dates could result in more age-0 largemouth bass reaching TLs associated with piscivory and overwinter survival by the end of their first summer if growth rates did not change, which could translate to higher recruitment.

Lake temperature and morphometry shape the thermal composition of recreational fishing catch

AbstractObjectiveManaging freshwater fisheries in warming lakes is challenging because climate change impacts anglers, fish, and their interactions.MethodsWe integrated recent models of current and future lake temperatures with recreational fisheries catch data from 587 lakes in three north‐central U.S. states (Michigan, Minnesota, and Wisconsin) to evaluate how the thermal composition of recreational fisheries catch varied as a function of temperature, ice coverage, and lake morphometry.ResultWe found that warmwater catch share (WCS), defined as the proportion of fish in recreational angling catch that belonged to the warmwater thermal guild (final temperature preferendum [FTP] > 25°C), increased with average annual lake surface temperature and decreased with survey ice coverage. However, we also found that WCS decreased with increased lake area and depth. Using mid‐century (2040–2060) water temperature and ice projections while holding all other variables constant, we predicted that WCS will likely increase as the climate warms but that significant thermal heterogeneity will persist.ConclusionLakes that are large (>100 ha) and deep (>10 m) and those with cooler (<3700 annual growing degree‐days) predicted future temperatures will likely hold thermal refugia for coolwater (FTP = 19–25°C) and coldwater (FTP < 19°C) fish even as average lake temperatures rise, creating the potential for management actions to resist the shift from coolwater to warmwater fisheries. Managers of smaller and more rapidly warming lakes may want to consider strategies that accept or direct emerging warmwater fishing opportunities. We suggest that the most viable path to climate adaptation in landscapes of diverse lakes may be to resist warmwater shifts where possible and to accept or direct the rise of warmwater fishing opportunities where necessary.

Appraisal on heavy metal contamination in tissues (gills, intestine, liver, and fillet) of <i>Parachanna obscura</i> and the physicochemical properties of Oguta Lake, South-Eastern Nigeria.

The aim of this study is to provide baseline data on the investigation of concentrations of copper (Cu), lead (Pb), iron (Fe), manganese (Mn), and zinc (Zn) in various tissues (gills, intestine, liver, and fillet) of Parachanna obscura in Oguta Lake, and to assess physicochemical properties of Oguta lake to determine level of pollution and contamination. Twenty fish samples in total were collected at the fishermen landing site of the lake and analyzed using the Atomic Absorption Spectroscopy (AAS). Dissolved oxygen and temperature were measured on site using dissolved Oxygen meter (model 5509) and Mercury-in-glass thermometer respectively, while other parameters were analyzed in the laboratory. Results indicated Fe had the highest concentrations (1.479±0.003 mg/kg) especially in the gills, while Mn recorded least concentrations (0.001±0.000) mg/kg) of all metals analyzed. Values for Cu (0.026±0.002 mg/kg), Mn (0.001±0.000 mg/kg), Zn (.782±0.015 mg/kg), and Fe (1.479±0.030 mg/kg) levels were within FAO/WHO permissible limits in all tissues, whereas Pb (1.438±0.015 mg/kg) exceeded standard limits especially in the gills and intestines, indicating potential contamination and threats to aquatic and human health. Heavy metal concentrations in the tissues followed the order: gills > intestine > fillet > liver. The physicochemical properties assessment of Oguta Lake indicated a stable temperature with mean value of (28.02±022 C). The lake's temperature supports aquatic life, but challenges like low transparency (1.22±0.13 m), acidic pH levels (5.83±0.09), elevated ammonium levels (0.63±0.03 mg/l), low nitrate-nitrogen levels (0.0±50.00 mg/l), and fluctuating dissolved oxygen (6.50±0.29 mg/l) levels suggests pollution from agricultural runoff or sewage. The findings proffer effective management through pollution control, enhanced buffering capacity, and rigorous monitoring to safeguard biodiversity and ensure longterm ecological health.

Process-based forecasts of lake water temperature and dissolved oxygen outperform null models, with variability over time and depth

Near-term iterative ecological forecasting has great potential for providing new insights into our ability to predict multiple ecological variables. However, true, out-of-sample probabilistic forecasts remain rare, and variability in forecast performance has largely been unexamined in process-based forecasts which predict multiple ecosystem variables. To explore how forecast performance varies for water temperature and dissolved oxygen, two freshwater variables important for lake ecosystem functioning, we produced probabilistic forecasts at multiple depths over two open-water seasons in Lake Sunapee, NH, USA. Our forecasting system, FLARE (Forecasting Lake And Reservoir Ecosystems), uses a 1-D coupled hydrodynamic-biogeochemical process model, which we assessed relative to both climatology and persistence null models to quantify how much information process-based FLARE forecasts provide over null models across varying environmental conditions. We found that FLARE water temperature forecasts were always more skillful than FLARE oxygen forecasts. Specifically, temperature forecasts outperformed both null models up to 11 days into the future, as compared to only two days for oxygen. Across different years, we observed variable forecast skill, with performance generally decreasing with depth for both variables. Overall, all temperature forecasts and surface oxygen, but not deep oxygen, forecasts were more skillful than at least one null model >80 % of the forecasted period, indicating that our process-based model was able to reproduce the dynamics of these two variables with greater reliability than the null models. However, process-based oxygen forecasts from deeper waters were less skillful than both null models during a majority of the forecasted period, which suggests that deep-water oxygen dynamics are dominated by autocorrelation and seasonal change, which are inherently captured by the null forecasts. Our results highlight that forecast performance varies among lake water quality metrics and that process-based forecasts can provide important information in conjunction with null models in varying environmental conditions. Altogether, these process-based forecasts can be used to develop quantitative tools which inform our understanding of future ecosystem change.

Coassembly and binning of a twenty-year metagenomic time-series from Lake Mendota

The North Temperate Lakes Long-Term Ecological Research (NTL-LTER) program has been extensively used to improve understanding of how aquatic ecosystems respond to environmental stressors, climate fluctuations, and human activities. Here, we report on the metagenomes of samples collected between 2000 and 2019 from Lake Mendota, a freshwater eutrophic lake within the NTL-LTER site. We utilized the distributed metagenome assembler MetaHipMer to coassemble over 10 terabases (Tbp) of data from 471 individual Illumina-sequenced metagenomes. A total of 95,523,664 contigs were assembled and binned to generate 1,894 non-redundant metagenome-assembled genomes (MAGs) with ≥50% completeness and ≤10% contamination. Phylogenomic analysis revealed that the MAGs were nearly exclusively bacterial, dominated by Pseudomonadota (Proteobacteria, N = 623) and Bacteroidota (N = 321). Nine eukaryotic MAGs were identified by eukCC with six assigned to the phylum Chlorophyta. Additionally, 6,350 high-quality viral sequences were identified by geNomad with the majority classified in the phylum Uroviricota. This expansive coassembled metagenomic dataset provides an unprecedented foundation to advance understanding of microbial communities in freshwater ecosystems and explore temporal ecosystem dynamics.

Dynamics of the risk of algal blooms induced by surface water temperature in an alpine eutrophic lake under climate warming: Insights from Lake Dianchi

Climate change-induced higher water temperature is increasing the risk of algal blooms (ABs) in eutrophic water bodies. However, it is not well known how and to what extent warming affects ABs risk. In this work, with simple data input (satellite product, lake surface observation, and climate) and method structure (ensemble learning, statistical downscaling, and hierarchical clustering), a systematic lake surface water temperature (LSWT) and ABs risk evaluation system are constructed and applied in a typical eutrophic freshwater lake. The main results are as follows: 1. The warming rate of LSWT and air temperature from 2000 to 2023 reached 0.21 °C/10a and 0.30 °C/10a respectively, resulting in an extended ABs risk in the historical period. 2. The Nash–Sutcliffe efficiency between climate and LSWT reached 0.89, and LSWT showed a significant (p < 0.05) positive correlation with algal density. 3. The escalation of ABs risks mainly spread to spring and autumn in the forthcoming future, the adverse effect of high emission scenarios will evidently emerge in the mid-21st century. Policymakers and catchment managers should be cautious of lake warming and develop countermeasures in advance.

Seasonal Temperature and Circulation Patterns in a Hybrid Polar Lake, Great Bear Lake, Canada

Seasonal Temperature and Circulation Patterns in a Hybrid Polar Lake, Great Bear Lake, Canada

Nine Lessons about Aquatic Invasive Species from the North Temperate Lakes Long-Term Ecological Research (NTL-LTER) Program.

Freshwater ecosystems can serve as model systems that reveal insights into biological invasions. In this article, we summarize nine lessons about aquatic invasive species from the North Temperate Lakes Long-Term Ecological Research program and affiliated projects. The lessons about aquatic invasive species are as follows: Invasive species are more widespread than has been documented; they are usually at low abundance; they can irrupt from low-density populations in response to environmental triggers; they can occasionally have enormous and far-reaching impacts; they can affect microbial communities; reservoirs act as invasive species hotspots; ecosystem vulnerability to invasion can be estimated; invasive species removal can produce long-term benefits; and the impacts of invasive species control may be greater than the impacts of the invasive species. This synthesis highlights how long-term research on a freshwater landscape can advance our understanding of invasions.

A Biogeochemical Comparison of three Representative Lakes of Costa Rica

ABSTRACT Lakes are widely distributed across Costa Rica, from coasts to the highest elevation regions, and located in the main terrestrial biomes. However, updated biogeochemical information about the main types of lakes is still lacking. We present comparative biogeochemistry (water chemistry, stable isotopes, and picoplankton) for a coastal lake (Lake Madre de Dios, LMD), a volcanic lake (Lake Barva, LB), and a glacial lake (Lake Ditkevi, LD). Sampling was conducted between February-November 2022 including dry and rainy seasonal conditions. Hydrological and chemical conditions were evaluated using water and carbon stable isotopes, dissolved organic matter (DOM), major ions, and microbiota analysis. Isotopic data (δ18O, δ13CDIC) confirmed lower evaporative losses for the maar and tarn lakes and productivity response to precipitation inputs. Excitation/Emission matrices confirmed the prevalence of fulvic and humic acids in the coastal and glacial lakes, mainly aromatic proteins and soluble microbial by-products in the volcanic lake. Picophytoplankton (PPP, ∼0.2 to 10 μm) was mainly represented by phycocyanin-rich picocyanobacteria (PC-Pcy) events in the three lakes, but maar and tarn lakes had more representation of phycoerythrin (PE-Pcy) events. We confirmed fluctuations in PPP cell abundance in the lakes lower than in temperate lakes. Like in other eutrophic lakes, Pcy also dominated over picoeukaryotes (Peuk) algae abundance. This work seeks to promote adopting an ecosystem approach to study the biogeochemical functioning of tropical lakes using the combination of chemical, hydrological, and biological data and to provide baseline information for future studies (e.g., climate change and pollution impacts) on tropical lakes of Costa Rica.

Understanding the environmental drivers of summer dissolved carbon in lakes on the Qinghai-Tibetan Plateau

How environmental factors affecting dissolved carbon remains unclear in lakes on the Qinghai-Tibetan Plateau (QTP), which limits the understanding of the lake carbon cycle. In this study, 60 lakes on the QTP in summer were investigated to clarify the variation in dissolved carbon, estimate dissolved carbon storage, and reveal how environmental factors affect the variation in dissolved carbon. The average dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) contents of 60 lakes on the QTP in summer were 12.78 mg/L and 103.66 mg/L, respectively. Salinity and total nitrogen were the important drivers of variations in DIC and DOC, respectively. Lake salinity and temperature were reduced only when precipitation was >50 mm, thus affecting the variations in lake dissolved carbon. Importantly, the elevation and area of the lake also significantly affected the variation in lake dissolved carbon. The total storage amounts of DOC and DIC in the 60 lakes on the QTP in summer were 58.94 Tg and 6.22 Tg, respectively. Lake area was the most direct factor influencing dissolved carbon storage in lakes on the QTP. Moreover, the TN and pH of the lake water also affected the DOC and DIC storage in the lakes, respectively. Interestingly, the lake pH at 9.1 was an important turning point that caused variations in lake DIC storage. Surprisingly, we found that rivers were able to transport 30 % of the DIC into QTP lakes and were the main source of DIC in the lakes in summer. The findings of this study clarify the sources of dissolved carbon and its drivers and improve our understanding of the carbon cycling processes in the lake system on the QTP.

Influences of meteorological conditions, runoff, and bathymetry on summer thermal regime of a Great Lakes estuary

To better understand the primary drivers of the thermal regime in a Great Lakes estuary, and their implications for local biota, water temperature variations in the Milwaukee Estuary of Lake Michigan were studied between July and October of 2019 using a network of 25 sensors at 18 locations. Like Lake Michigan, the estuary was thermally stratified July to October, and historically dredged channels with water depths greater than 6 m allowed for the free movement of cold lake water into the estuary. However, temperatures in the estuary fluctuated rapidly both spatially and temporally, reflecting lake temperature fluctuations driven by changing meteorological conditions. Lake-driven upwelling and downwelling events influenced water temperature more than tributary contributions. Periodic upwelling and downwelling events caused temperature changes by up to 15 °C in less than 24 h. Nearshore upwelling events occasionally allowed cold, hypolimnetic lake water to reach tributary portions of the estuary beyond dredged areas, while downwelling events disrupted thermal stratification and caused the deep, dredged portions of the estuary to exceed 20 °C. Thermal impacts from these events were especially noticeable in transition zones between dredged and not dredged channels less than 2 m deep. The warming effects from downwelling persisted longer inside the estuary – up to two weeks – than cooling effects from upwelling, which typically lasted a few days. The predominantly lake-driven, rapid summer water temperature fluctuations observed in the Milwaukee Estuary serve as an important consideration in habitat restoration activities happening in Great Lakes estuaries.

Phosphorus inactivation mitigates the effect of warm winters in a temperate shallow lake (Mielenko Lake, Poland)

Direct and indirect anthropopressure on water ecosystems is the serious problem throughout the world.. In the Northern Hemisphere, an increase in average air temperatures is observed, which implies the occurrence of a shorter period of snow and ice cover during the winter season. The winter 2019/2020 was unusual, because that was the first time in the record, that a complete lack of permanent ice cover was observed on numerous lakes in Poland. Such unusual conditions could influence lake functioning. Hence we analyzed the chemistry of the water–sediment interface (near-bottom and interstitial water and sediment) in the shallow, eutrophic Mielenko Lake (area 7.9 ha, max depth 1.9 m) in 2013 and 2019–2022 period to assess the influence of prolonged water circulation on the bottom zone. Mielenko Lake was subjected to a phosphorus inactivation procedure using Al and Fe salts (PAX 18, PIX 111) in 2020 and 2021. Our research revealed that unusually prolonged winter circulation caused a significant decrease in organic matter content in bottom sediment in 2020, as well as a decrease in NaOH-nrP fraction and TP amounts. That effect was short-term and it did not significantly influence the NaOH-rP fraction amounts. The released P was probably built in macrophytes biomass during vegetation season, because P inactivation has been limiting phytoplankton proliferation, and it favored shifting to a clearwater state with macrophytes domination. This was confirmed by decreasing in phytoplankton biomass, and a massive expansion of the macrophytes range noted in the second year of restoration. Our study shows, that P inactivation could mitigate the negative effects of warm winters in shallow lakes.

Probabilistic quantile multiple fourier feature network for lake temperature forecasting: incorporating pinball loss for uncertainty estimation

Probabilistic quantile multiple fourier feature network for lake temperature forecasting: incorporating pinball loss for uncertainty estimation

Evolution, sedimentation and thermal state of the emerging pro‐glacial lakes at Witenwasserengletscher, Switzerland

AbstractAs glaciers retreat worldwide, local basal depressions are exposed where new pro‐glacial lakes are forming. Although the formation of such new lakes has been mapped widely, the impact of their interaction with the glacier on sediment dynamics and the thermal state is rarely studied. At the example of Witenwasserengletscher, Switzerland, we use historic aerial imagery and a bathymetric survey to investigate in detail the interaction of glacier retreat, lake formation and sedimentation. Three lakes have emerged since the mid‐1990s with mean depths between 1.25 and 6 m. The deepest lake lost contact to the ice in 2009 with a delta forming from mobilized sub‐glacial sediment. Phases of direct contact of the glacier with the lakes are found to increase terminus retreat and affect the thermal state and sedimentation. In summer, lake water temperatures in these small ice‐contact lakes stay close to 0°C, whereas the disconnected eastern lake shows temperatures consistently over 6°C. Temperature profiles from 2021 show that after losing ice contact, warm sediment‐rich glacial water forms an underflow that is breaking through the summertime stratification with warm water over cold water. In this case, density stratification is dominated by suspended sediment rather than temperature. Sedimentation shows a high multiannual variability and is dependent on a multitude of factors, ultimately on the routing of glacial streams. These tend to migrate towards the centre of the valley as the glacier retreats. Our study shows that during deglaciation lake evolution, sediment redistribution and the thermal state are highly dynamic and pro‐glacial lakes strongly affect the sediment evolution and may thereby impact on the ecosystem in pro‐glacial streams.

Understanding zinc isotopic signatures in volcanic lakes

Magmatic activity can be monitored through the chemical variations of volcanic lakes. While those lakes can be influenced by direct magmatic input, water-rock interaction processes in hydrothermal system also have a large influence. Disentangling those effects is critical to use crater lakes for volcanic activity monitoring purposes. Zinc is a volatile metal that is easily degassed and can be incorporated into fluid circulation. During degassing, Zn isotopes can be fractionated and can thus be a potential tracer of magmatic input. Here we present a novel approach using stable Zn isotopic systems to understand how dissolution/precipitation processes affect isotopic compositions of volcanic lakes and if they can be used as tracers of magmatic activity. We investigate Zn isotopes expressed as δ66Zn for four volcanic lakes ranging from hyperacidic to neutral waters. Two of them, Kawah Ijen (Indonesia) and Santa Ana (El Salvador) volcanic lakes have been sampled from 2010 to 2012 and 2000–2002, respectively, and show a clear magmatic input with extremely low pH [0.1–1]. Taal (Philippines, pH ≈ 3) and Kelud (Indonesia, pH ≈ 6.5) volcanic lakes were sampled from 2017 to 2019 and 2003–2007 respectively, and are dominated by hydrothermal rather than magmatic inputs. Hyper-acidic lakes show minimal isotopic variation over the investigated time ranges, with δ66Zn values similar to their basalt-andesitic host rocks (0.26 ± 0.08 ‰). In contrast, we observe large δ66Zn fractionation for the Taal waters (0.4 ± 0.01 ‰) compared to their basalt-andesitic host rocks but no δ66Zn temporal variations. Kelud waters show significant δ66Zn (−0.08 ± 0.06 ‰ to 0.43 ± 0.06 ‰) temporal variation. This could be related to an evolution of the lake water chemistry as the sampling period occurred between two increases in lake temperature culminating into a lava dome eruption in 2007. For Taal and Kelud volcanic lakes, enrichment factors (EF) and PHREEQc modelling indicate that Zn is depleted and suggest that Zn could precipitate in the hydrothermal system, hence fractionating Zn isotopes during these precipitation processes. This contrasts to Zn elemental and isotope values from Kawah Ijen and Santa Ana with an EF ≈ 1 suggesting that Zn is derived from host rock dissolution, in agreement with their δ66Zn. These data are still limited and a longer observation is needed in the future to highlight significant geochemical changes in volcanic lakes and their relation to volcanic activity.

Lake Champlain Zooplankton Community Dynamics Following an Extreme Flood Event

Lake Champlain, the sixth largest freshwater lake in the U.S., is a deep thermally stratified temperate zone lake system. Recently, flood events have impacted the Northeastern U.S. more frequently than in past decades, resulting in increased turbidity and other impacts in northern temperate lakes. This study represents an unprecedented analysis of the impacts of major spring and summer flooding in 2011 on Lake Champlain zooplankton communities. Few studies exist on flood impacts on lake systems, especially in natural un-impounded lakes. Our results illustrate the impacts of large-scale flooding on planktonic communities in deep stratified temperate lakes and the differential responses among species based on autecological traits. Community responses include flood-adapted increase during the flood event (Ceriodaphnia reticulata and Eubosmina coregoni), a flood-intolerant decline (Asplanchna spp. and Keratella cochlearis) or a delayed flood intolerance (Daphnia retrocurva, Mesocyclops edax, and Polyarthra spp.). Our results suggest that large, temperate lakes such as Lake Champlain will experience community shifts in zooplankton composition during future extreme flood events associated with climate change-related weather patterns in the Northeastern U.S.

How Useful Are Moderate Resolution Imaging Spectroradiometer Observations for Inland Water Temperature Monitoring and Warming Trend Assessment in Temperate Lakes in Poland?

How Useful Are Moderate Resolution Imaging Spectroradiometer Observations for Inland Water Temperature Monitoring and Warming Trend Assessment in Temperate Lakes in Poland?