Lake Morphometry Research Articles

Lake morphometry underlies physical and chemical parameters affecting the distribution of phytoplankton functional groups in lakes of the Sakarya River Basin (Turkey)

To test the effects of lake morphometry (lake size and depth) on water quality parameters which affect the phytoplankton functional groups (FG) distribution, phytoplankton and some environmental parameters were sampled in November 2017 and May 2018 at the two or three monitoring stations in nine Lakes of Sakarya River Basin (Turkey). Lake size and depth affected phytoplankton FG distribution in both large-sized and small-sized lakes by affecting light availability which was mainly driven by the mixing events during the studied period. Al- though PO4 -P and alkalinity were the other main environmental constraints influencing phytoplankton distribution, they were not directly affected by lake morphometry. Codon Lo was mainly found in small-sized and shallow lakes, whereas coda B, C, D, J, R, and T, which do not have active buoyancy regulation and adapt to high Zmix/Zeu con- ditions, occurred with high relative biovolume in large-sized water bodies.

Relationships of total phosphorus and chlorophyll in lakes worldwide

AbstractLakes around the world are sensitive to water quality degradation and eutrophication through increases in primary production. Understanding the drivers of primary production has been a fundamental question in limnology since its early days. Here, we conducted a systematic review to develop a dataset of water chemistry and lake morphometry for 3874 lakes distributed across 47 countries around the world to answer: (1) What is the global relationship between chlorophyll a (Chl a) and total phosphorus (TP) in lakes? (2) Are there inflection points at which the TP–Chl a relationship is no longer linear? and (3) What explains the inflection points and nonlinearities in the TP–Chl a relationship? We found that a sigmoidal relationship between TP and Chl a explained 44% of the variation. We also found physical characteristics of the lake mediated the TP–Chl a relationship such as mean depth, Secchi depth, and elevation. The nonlinear segments of this relationship best described lakes located in very cold (mean annual temperature = −10°C) and hot (> 25°C) climates, which also dominated the high and low ends of TP concentrations, respectively. A positive linear TP–Chl a relationship existed at intermediate concentrations of TP (0.004–0.23 mg L−1). A high degree of variability in Chl a exists between lakes at similar TP levels, highlighting the difficulty in simply decreasing nutrient inputs to manage eutrophication in lakes worldwide. Moreover, as global temperatures continue to rise, the Chl a–TP relationship in lakes located in very cold or warm temperate regions of the world may shift in response to these warmer temperatures.

Local and Regional Drivers of Environmental Changes in Two Subtropical Montane Ponds (Central China) Over the Last Two Centuries

Central China, one of the Earth’s distinctive ecoregions due to its endemic subtropical biota, has been subjected to enhanced nitrogen deposition and climate warming during recent decades. However, the extent and timescale of ecological changes are largely unexplored. Multiproxy analyses (diatoms, photosynthetic pigments and geochemistry) of 210Pb-dated sediment cores from two shallow ponds within an alpine basin (central China) were used to investigate the response of primary producer communities to external stressors during the last two centuries. The study sites include one drainage pond and one seepage pond. Both ponds exhibited unambiguous changes in production and composition of photoautotrophs since the early twentieth century, which are linked to climate warming, nitrogen deposition and local factors (for example, lake morphometry, desiccation and macrophyte). Although primary producers responded to regional warming and nitrogen deposition, the ecological responses differed among ponds due to local factors. In the deeper seepage pond, light attenuation due to terrestrial organic matter input caused recent decreases in carotenoids and small fragilarioid taxa. In contrast, the co-occurrence of euterrestrial and tychoplanktonic diatoms in the shallower drainage pond was indicative of its hydrological instability. Our results indicate that subtropical montane ponds in the East Asian monsoon region appear to be strongly influenced by a combination of local (for example, catchment-lake connectivity) and regional driving forces (for example, warming and nitrogen deposition).

The Relationship of Lake Morphometry and Phosphorus Dynamics of a Tropical Highland Lake: Lake Tana, Ethiopia

Lakes hold most of the world’s fresh surface water resources. Safeguarding these resources from water quality degradation requires knowledge of the relationship between lake morphometry and water quality. The 3046-km2 Lake Tana in Ethiopia is one of the water resources in which the water quality is decreasing and water hyacinths have invaded. The objective of this study is to understand the interaction between the lake morphometry and water quality and specifically the phosphorus dynamics and their effect on the water hyacinths. A bathymetric survey was conducted in late 2017. Various morphometric parameters were derived, and both these parameters and sediment available phosphorus were regressed with the dissolved phosphorus. The results show that, with a wave base depth that is nearly equal to a maximum depth of 14.8 m, the bottom sediments were continuously suspended in the water column. As a result of the resuspension mixing, we found that the dissolved phosphorus in the water column decreased with lake depth and increased with sediment available phosphorus (R2 = 0.84) in the northern half of the lake. This relationship is not as strong in the south due to a large flow of Gilgel Abay to the outlets. Water hyacinths were found where the lake was shallow and the available phosphorus was elevated. The large reservoir of sediment phosphorus will hamper any remedial efforts in removing the water hyacinths.

The effects of extreme drought events on the morphometry of shallow lakes: Implications for sediment resuspension and littoral and pelagic zone distribution

Shallow lakes, because of their depth, are more vulnerable to the effects of wind and changes in precipitation and evaporation that deeper lakes and thus respond more dramatically to extreme climatic events, such as drought. The morphology of shallow lakes influences many of their physical, chemical, biological and sedimentological processes including sediment resuspension. Sediment resuspension can trigger undesired effects such as eutrophication, increase in turbidity, cyanobacterial blooms, and also affects the distribution and extent of the littoral and pelagic zones (habitat distribution) with potentially negative consequences on biodiversity and loss of native species. These problems are an increasing concern in the face of global warming. To understand how changes in lake' morphometry, triggered by extreme drought events influence sediment resuspension and habitat distribution, we studied four shallow lakes located in the southwest of the Argentinean Pampas. Each lake was characterized by its bathymetry, morphometric parameters (including area, shore development, dynamic ratio, critical depth), the spatial distribution of the littoral and pelagic areas, and the effect of the waves on sediment resuspension. We measured the Area and Shore development again during selected extreme drought periods identified through the Standardized Precipitation-Evapotranspiration Index. Then, for the given drought period, we calculated the extent and distribution of littoral and pelagic areas and the critical depth at which sediment resuspension occurred and then estimated the percentage of the lake that would be affected by it. We found that Pampean lakes are profoundly affected by sediment resuspension triggered by wind during extreme dry events. Droughts have different effects depending on lake morphology. Dry periods caused not only a decrease in water volume, but also modified the extension of littoral and pelagic zones and increased sediment resuspension. These results have significant implications for the preservation of these rich ecosystems, especially in the context of global warming.

Intrarift fault fabric, segmentation, and basin evolution of the Lake Malawi (Nyasa) Rift, East Africa

AbstractThe Lake Malawi (Nyasa) Rift, in the East African Rift System (EARS), is an ideal modern analogue for the study of extensional tectonic systems in low strain rate settings. The seismically active rift contains the 700-m-deep Lake Malawi, one of the world’s oldest and largest freshwater lakes with one of the most diverse endemic faunal assemblages on Earth. Modern and reprocessed legacy multichannel seismic-reflection data are constrained by velocity information from a wide-angle seismic experiment to evaluate variability in extension, segmentation, and timing of fault development along the 550-km-long rift zone. Fault geometries and patterns of synrift sediment fills show that the Lake Malawi Rift is composed of three asymmetric rift segments, with intervening accommodation zone morphologies controlled by the degree of overlap between segment border faults. Most extension occurs on the basin border faults, and broadly distributed extension is only observed at one accommodation zone, where no border fault overlap is observed. Structural restorations indicate a weakly extended rift system (∼7 km), with diminishing values of extension and thinner rift fill from north to south, suggesting a progressively younger rift to the south. There is no evidence of diking, sill injection, or extrusives within the synrift fill of the Lake Malawi Rift, although the volcanic load of the Rungwe magmatic system north of the lake and related subsidence may explain the presence of anomalously thick synrift fill in the northernmost part of the lake. The thickest synrift depocenters (∼5.5 km) are confined to narrow 10- to 20-km-wide zones adjacent to each rift segment border fault, indicating concentration of strain on border faults rather than intrarift faults. Intrarift structures control axial sediment delivery in the North and Central rift segments, focusing sediment into confined areas resulting in localized overpressure and shale diapirs. The asymmetric, basement-controlled relief was established early in rift development. When overprinted with frequent high-amplitude hydroclimate fluctuations, which are well documented for this basin, the resulting highly variable landscape and lake morphometry through time likely impacted the diverse endemic faunas that evolved within the basin. New seismic-reflection data, augmented by wide-angle seismic data and age constraints from drill core, offer the most highly resolved 3D view to date of latest Cenozoic extensional deformation in East Africa and provide a foundation for hazards analysis, resource assessments, and constraining deformation in a low strain rate, magma-poor active rift.

Heterogeneous response of diatom assemblages since ca. 1945 in lakes from boreal regions of northern Alberta and Saskatchewan, Canada

The degree to which climate variability and anthropogenic stressors have impacted the rich array of boreal lakes in northern Saskatchewan and Alberta was explored in a dataset of 42 lakes from previous paleolimnological investigations of this region. This dataset was used to evaluate the extent of change in diatom assemblages over the past ~ 60 to 70 years in relation to lake and watershed characteristics. Similarity analysis was used to define the degree of change in diatom composition in lake sediment cores from each lake with a focus on post ca. 1945 changes to establish a common time frame to compare across all lakes. This time frame incorporates pre- and post-development of the Athabasca Oil Sands Region and additionally integrates pre- and post-periods of distinct changes in temperature and precipitation. Beta regression analysis was used to identify potential links between diatom assemblage change and lake physical–chemical and landscape characteristics (limno and landscape models, respectively). Similarity analysis indicated nearly 80% of the lakes showed only a very low degree of change (0–25%) since ca. 1945. Lakes with larger percent change in similarity (> 25%) showed increases in planktonic diatoms, although the specific taxa that changed varied from oligotrophic Discostella spp. to meso-eutrophic taxa, such as Asterionella formosa and Stephanodiscus minutulus. Lake volume and percent peat in the catchment were the most important limno and landscape explanatory variables, respectively, albeit the models had low predictive power. The lakes with large diatom compositional change were dispersed across the region, located in various geological and ecological zones and varying degrees of human disturbance. The interplay of climate and morphometric features of lakes is likely an influential driver of these changes, with larger heat-storage capacity in higher-volume lakes that potentially increases the sensitivity to warming. The small surface areas and shallow morphometry of most lakes, a heterogeneous hydrological and geological landscape, and frequent dominance of diatom assemblages by benthic generalists may explain the minimal responses of diatom assemblages over the past ~ 70 years to anthropogenic influences and climate.

Predicting lake dissolved organic carbon at a global scale

The pool of dissolved organic carbon (DOC), is one of the main regulators of the ecology and biogeochemistry of inland water ecosystems, and an important loss term in the carbon budgets of land ecosystems. We used a novel machine learning technique and global databases to test if and how different environmental factors contribute to the variability of in situ DOC concentrations in lakes. In order to estimate DOC in lakes globally we predicted DOC in each lake with a surface area larger than 0.1 km2. Catchment properties and meteorological and hydrological features explained most of the variability of the lake DOC concentration, whereas lake morphometry played only a marginal role. The predicted average of the global DOC concentration in lake water was 3.88 mg L−1. The global predicted pool of DOC in lake water was 729 Tg from which 421 Tg was the share of the Caspian Sea. The results provide global-scale evidence for ecological, climate and carbon cycle models of lake ecosystems and related future prognoses.

Lakes at Risk of Chloride Contamination.

Lakes in the Midwest and Northeast United States are at risk of anthropogenic chloride contamination, but there is little knowledge of the prevalence and spatial distribution of freshwater salinization. Here, we use a quantile regression forest (QRF) to leverage information from 2773 lakes to predict the chloride concentration of all 49 432 lakes greater than 4 ha in a 17-state area. The QRF incorporated 22 predictor variables, which included lake morphometry characteristics, watershed land use, and distance to the nearest road and interstate. Model predictions had an r2 of 0.94 for all chloride observations, and an r2 of 0.86 for predictions of the median chloride concentration observed at each lake. The four predictors with the largest influence on lake chloride concentrations were low and medium intensity development in the watershed, crop density in the watershed, and distance to the nearest interstate. Almost 2000 lakes are predicted to have chloride concentrations above 50 mg L-1 and should be monitored. We encourage management and governing agencies to use lake-specific model predictions to assess salt contamination risk as well as to augment their monitoring strategies to more comprehensively protect freshwater ecosystems from salinization.

Arctic freshwater fish productivity and colonization increase with climate warming

Climate warming at high latitudes has long been expected to exceed that predicted for tropical and temperate climes, but recent warming in the Arctic has exceeded even those expectations1. The geophysical consequences of this warming are reasonably well established2, but the impacts on freshwater fauna are poorly understood. Here we use a large-scale geospatial analysis of the population dynamics of one of the most abundant north temperate freshwater fish species to forecast increased demographic rates, productivity and colonization range in response to IPCC climate warming scenarios. Geospatial lake morphometry data were used to characterize 481,784 lakes in the Canadian Arctic capable of supporting lake trout (Salvelinus namaycush) populations. Lake trout productivity in existing habitat is projected to increase by 20% by 2050 due to climate change, but an expanded habitable zone may result in a 29% increase in harvestable biomass. Although many ecosystems are likely to be negatively impacted by climate warming, the phenotypic plasticity of fish will allow a rapid relaxation of the current environmental constraints on growth in the far north, as well as enhanced colonization of bodies of water in which there are few potential competitors. Arctic lakes and their resident fish species are warming rapidly. Geospatial analysis of Canadian Arctic lakes predicts a 20% increase in lake trout productivity by 2050 and a 29% increase in harvestable biomass across an expanded range.

Morphometry as tool to trace out the genealogy of oxbow lake

Morphometry of oxbow lakes is widely used as a tool for knocking the evolutionary history of geomorphology and hydraulics of the region concerned. Oxbow lakes are the treasury of abundant geomorphological records of yesteryears which could serve as important keys to the past fluvial environment. But in terms of morphometric magnitudes, today’s oxbow lakes differ significantly from the then river from which they were originated. That is why identifying the parent river and gauging the dimensions of past morphology of the parent river of the oxbow lakes is an important issue of fluvial geomorphology. That is why the present paper searches parent–daughter umbilical linkage between an oxbow lake and adjacent river and designs quantitative measures to find out the degree of similitude between an oxbow lake and adjacent rivers. We processed planimetric morphological variables (distance, width, amplitude, the radius of curvature and orientation angle) of 126 oxbow lakes and adjacent 13 rivers using statistical and mathematical tools. We found that there is a strong morphometric association between oxbow lakes and their parent river. Finally, we conclude that morphometrics of an oxbow lake can successfully be used for identifying its parent river. So, we suggested five indices to ascertain the degree of similitude for confirming the parent–daughter umbilical linkage between oxbow lake and adjacent river.

The significant contribution of lake depth in regulating global lake diffusive methane emissions

Global lakes have been identified as an important component of natural methane (CH4) sources. Given that lake CH4 emissions involve multiple, complex processes influenced by various environmental factors, estimates of global lake CH4 emissions are largely uncertain. In this study, we compiled global CH4 emission data on 744 lakes from published studies, and found a significantly negative correlation (R2 = 0.50, p < 0.01) between diffusive CH4 flux and lake maximum depth. Further analysis indicated that no significant differences in global sediment CH4 production were found for the different maximum depths investigated. Owing to the longer oxidation pathway, presence of oxycline layer, and the lower nutrient environment, deeper lakes yield less diffusive CH4 efflux compared to shallower lakes. Additionally, we also found that lake area was negatively correlated (R2 = 0.13, p < 0.01) to diffusive CH4 flux. Therefore, based on empirical correlations between lake morphometry (maximum depth and area) and diffusive CH4 emission, as well as the combination of two lake databases, we estimated that the annual diffusive CH4 emission from global lakes is approximately 11.2 (6.2–19.5) Tg CH4/yr, and greater than 84% is emitted from lakes with a mean depth of less than 5 m. Furthermore, two regions, 40–70° N (30.4%) and 20° S∼10° N (37.4%), were found to be the dominant contributors of global lake diffusive CH4 emissions, resulting from the considerable total lake area and the extensive shallow lakes in these regions. This study highlights the significance of the ‘depth-effect’ which controls the spatial distribution of lake diffusive CH4 flux and allows for the quantification of global lake diffusive CH4 emissions.

Dragonfly larvae as biosentinels of Hg bioaccumulation in Northeastern and Adirondack lakes: relationships to abiotic factors.

Mercury (Hg) is a toxic pollutant, widespread in northeastern US ecosystems. Resource managers' efforts to develop fish consumption advisories for humans and to focus conservation efforts for fish-eating wildlife are hampered by spatial variability. Dragonfly larvae can serve as biosentinels for Hg given that they are widespread in freshwaters, long-lived, exhibit site fidelity, and bioaccumulate relatively high mercury concentrations, mostly as methylmercury (88% ± 11% MeHg in this study). We sampled lake water and dragonfly larvae in 74 northeastern US lakes that are part of the US EPA Long-Term Monitoring Network, including 45 lakes in New York, 43 of which are in the Adirondacks. Aqueous dissolved organic carbon (DOC) and total Hg (THg) were strongly related to MeHg in lake water. Dragonfly larvae total mercury ranged from 0.016-0.918 μg/g, dw across the study area; Adirondack lakes had the minimum and maximum concentrations. Aqueous MeHg and dragonfly THg were similar between the Adirondack and Northeast regions, but a majority of lakes within the highest quartile of dragonfly THg were in the Adirondacks. Using landscape, lake chemistry, and lake morphometry data, we evaluated relationships with MeHg in lake water and THg in dragonfly larvae. Lakewater DOC and lake volume were strong predictors for MeHg in water. Dragonfly THg Bioaccumulation Factors (BAFs, calculated as [dragonfly THg]:[aqueous MeHg]) increased as lake volume increased, suggesting that lake size influences Hg bioaccumulation or biomagnification. BAFs declined with increasing DOC, supporting a potential limiting effect for MeHg bioavailability with higher DOC.

Organic carbon sequestration in sediments of subtropical Florida lakes.

Recent studies have shown that sediments of temperate and tropical lakes are sinks for organic carbon (OC), but little is known about OC burial in subtropical lakes. There are questions regarding the ability of subtropical lakes to store OC, given their relatively warmwater temperatures, lack of ice cover, frequent water-column mixing, and labile carbon forms. We used 210Pb-dated sediment cores from 11 shallow Florida (USA) lakes to estimate OC burial, i.e. net OC storage, over the last ~100 years. Shallow Florida water bodies average ~30% OC content in their sediments and displayed rates of net OC accumulation (63–177 g C m-2 a-1) that are similar to natural temperate lakes, but lower than temperate agricultural impoundments. We considered the influence of lake morphometry on OC storage in our study lakes, but did not observe an inverse relationship between lake size and OC burial rate, as has been seen in some temperate lake districts. We did, however, find an inverse relation between mean water depth and OC sequestration. Despite recent cultural eutrophication and the associated shift from macrophyte to phytoplankton dominance in the Florida study lakes, overall OC burial rate increased relative to historic (pre-1950 AD) values. Lakes cover >9000 km2 of the Florida landscape, suggesting that OC burial in sediments amounts to as much as 1.6 Mt a-1. The high rate of OC burial in Florida lake sediments indicates that subtropical lakes are important for carbon sequestration and should be included in models of global carbon cycling.

Winter Accumulation of Methane and its Variable Timing of Release from Thermokarst Lakes in Subarctic Peatlands

AbstractPrevious studies of thermokarst lakes have drawn attention to the potential for accumulation of CH4 under the ice and its subsequent release in spring; however, such observations have not been available for thermokarst waters in carbon‐rich peatlands. Here we undertook a winter profiling of five black‐water lakes located on eroding permafrost peatlands in subarctic Quebec for comparison with summer profiles and used a 2‐year data set of automated water temperature, conductivity, and oxygen measurements to evaluate how the annual mixing dynamics may affect the venting of greenhouse gases to the atmosphere. All of the sampled lakes contained large amounts of dissolved CH4 under their winter ice cover. These sub‐ice concentrations were up to 5 orders of magnitude above air equilibrium (i.e., the expected concentration in lake water equilibrated with the atmosphere), resulting in calculated emission rates at ice breakup that would be 1–2 orders of magnitude higher than midsummer averages. The amount of CO2 dissolved in the water column was reduced in winter, and the estimated ratio of potential diffusive CO2 to CH4 emission in spring was half the measured summer ratio, suggesting a seasonal shift in methanogenesis and bacterial activity. All surface lake ice contained bubbles of CH4 and CO2, but this amounted to &lt;5% of the total amount of the dissolved CH4 and CO2 in the corresponding lake water column. The continuous logging records suggested that lake morphometry may play a role in controlling the timing and extent of CH4 and CO2 release from the water column to the atmosphere.

Comparison of ice‐on and ice‐off abiotic and biotic parameters in three eutrophic lakes

AbstractThe structure and abundance of winter planktonic communities are limited by environmental conditions that are unfavorable to life, but do not stop biological processes. The aim of the study was to test the hypothesis that the abundance of planktonic groups of organisms in temperate lakes can be higher during winter under ice cover than during the ice‐free seasons. Physical (ice/snow cover, temperature), chemical (organic carbon, chlorophyll a, phosphorus, nitrogen) and biological parameters (phytoplankton, protozooplankton, zooplankton) were investigated in three eutrophic lakes during two consecutive years in winter, spring, summer and autumn. The results of this study showed that in all lakes chlorophyll a concentrations were usually lower in winter than in other seasons, while total nitrogen concentrations were higher in winter than in autumn. All groups of planktonic organisms were able to reach similar or even higher abundances in winter under‐ice than in other ice‐free periods, depending on the lake morphometry and the year of the study. Winter taxonomic structure of phytoplankton was similar to the spring (medium‐sized Lake Dgał Wielki with the dominance of cryptophytes), summer (small‐sized Lake Dgał Mały with cyanobacteria as a dominant group) or autumn (the shallow lake with the dominance of diatoms) structure, depending on the lake. In all lakes, the structure of the ciliate community was the most similar to that of the spring with the clear dominance of Oligotrichida. Our results show that some species among all the studied groups of organisms can lead an active and dynamic life under the ice cover.

Alternative host identity and lake morphometry drive trematode transmission in brook charr.

Both biotic and abiotic factors have been invoked to explain the large variations observed in the prevalence and abundance of parasites in aquatic ecosystems. However, we have only a poor knowledge of the potential interplay among these factors in natural systems. It is, therefore, important to analyze the effects of multiple potential environmental drivers together to get an integrated view of their influence on the prevalence and abundance of parasites. To this end, we selected two genera of digenean trematode parasites that require at least two hosts to complete their life cycle and use two different transmission strategies. Crepidostomum moves through a trophic pathway via consumption of infected prey by the host, while Apophallus infects its hosts via direct penetration of their skin. This study was conducted in 23 Canadian Shield lakes exhibiting orthogonal gradients of biotic (fish species richness and biomass) and abiotic (morphometry, physico-chemical) variables. We quantified prevalence and abundance of these parasites in the skin and intestine of brook charr (Salvelinus fontinalis). Our results show that biotic factors are key drivers of parasite abundance and prevalence, with Apophallus being negatively associated with the fish species richness-biomass gradient, and Crepidostomum responding more to identity of host than to the diversity gradient. Among the abiotic variables, lake areawas found to be positively related to both prevalence and abundance in Apophallus. Our results suggest that taking into account the interplay of both biotic and abiotic factors is crucial for understanding patterns of parasite transmission success in boreal lakes.

Gas‐emission craters of the Yamal and Gydan peninsulas: A proposed mechanism for lake genesis and development of permafrost landscapes

AbstractThis paper describes two gas‐emission craters (GECs) in permafrost regions of the Yamal and Gydan peninsulas. We show that in three consecutive years after GEC formation (2014–2017), both morphometry and hydrochemistry of the inner crater lakes can become indistinguishable from other lakes. Craters GEC‐1 and AntGEC, with initial depths of 50–70 and 15–19 m respectively, have transformed into lakes 3–5 m deep. Crater‐like depressions were mapped in the bottom of 13 out of 22 Yamal lakes. However, we found no evidence that these depressions could have been formed as a result of gas emission. Dissolved methane (dCH4) concentration measured in the water collected from these depressions was at a background level (45 ppm on average). Yet, the concentration of dCH4 from the near‐bottom layer of lake GEC‐1 was significantly higher (824–968 ppm) during initial stages. We established that hydrochemical parameters (dissolved organic carbon, major ions, isotopes) measured in GEC lakes approached values measured in other lakes over time. Therefore, these parameters could not be used to search for Western Siberian lakes that potentially resulted from gas emission. Temperature profiles measured in GEC lakes show that the water column temperatures in GEC‐1 are lower than in Yamal lakes and in AntGEC – close to values of Gydan lakes. Given the initial GEC depth &gt; 50 m, we suggest that at least in GEC‐1 possible re‐freezing of sediments from below might take place. However, with the present data we cannot establish the modern thickness of the closed talik under newly formed GEC lakes.

Linking landscape heterogeneity with lake dissolved organic matter properties assessed through absorbance and fluorescence spectroscopy: Spatial and seasonal patterns in temperate lakes of Southern Andes (Patagonia, Argentina)

Hydrological connectivity between terrestrial and aquatic systems is influenced by landscape features. Topography, vegetation cover and type, lake morphometry and climate (seasonality, precipitation) drive the timing, concentration and quality of allochthonous dissolved organic matter (DOM) inputs to lakes, influencing lake metabolism. The impact of climate changes on terrestrial-aquatic linkages depends on regional trends and ecosystems properties. We examined how landscape heterogeneity affects lake DOM in pristine temperate headwater lakes located in sharp bioclimatic gradients at the leeward side of the southern Andes (Patagonia, Argentina), and predicted their potential responses to forecasted changes in regional climate. We assessed DOM properties of deep and shallow lakes spotted along precipitation and altitudinal gradients which reflect on vegetation heterogeneity. Lake DOM (concentration, and chromophoric and fluorescent properties) was related to terrestrial bioclimatic conditions, addressing also DOM bio- and photodegradation processes. Co-effects of climate and vegetation determined the quantity and quality of allochthonous DOM inputs. Higher terrestrial signs showed up at the wettest extreme of the gradient and during the rainy season, being attributable to higher hydrological land-water connectivity, and dense vegetation cover. Under drier conditions, DOM displayed higher photobleaching signs at spatial and temporal scales. The ratio between non-humic and terrestrial humic substances indicated that DOM biodegradation dominates in shallow forested lakes and photodegradation prevails in deep ones, whereas coupled photo- and biological processing shaped the DOM pool of high altitude lakes. Overall, DOM optical metrics captured landscape heterogeneity. Under the forecasted climate changes for Patagonia (decreasing precipitation and increasing temperature), piedmont lakes may experience lower hydrological connectivity, lower terrestrial inputs and, enhanced photobleaching usually associated with longer water residence time. In high altitude lakes, terrestrial DOM inputs are expected to increase due to the upward expansion of native deciduous forests, thus becoming more similar to lakes located lower in the landscape.

Morphometry Study and Integrated Management of Dibawah Lake Watershed Solok Regency

Dibawah Lake is a tectonic lake located in Solok Regency, West Sumatra. It's functioned as the West Sumatra Government as a tourist area, besides that it was also used as an irrigation water source. This study aims to obtain information on the characteristics of lake morphometry and formulate the concept of integrated management of Dibawah Lake Catchment Area. From the results of bathymetry mapping produces a lake area of 10998.1 ha with a circumference of 17.2 km, a maximum length of 6.4 km, a maximum width of 3 km, a maximum depth of 326.8 m, an average depth of 164.3 m and volume of 1688 million m 3. The lake catchment area is 2881.7 ha and it is divided into 27 sub-catchments. The existing problems in the Dibawah Lake are (1) changes in lake area land cover into agricultural fields, (2) agricultural cropping patterns in slope areas, (3) lakefront settlements, (4) water quality degradation, (5) fish cages floating net and fishing ring. From the results of the SWOT analysis, the W-T (Weaknesses - Threats) strategy was chosen as the top priority. The W-T strategy focuses on strengthening and drafting rules, monitoring the implementation of rules, enforcing violations and socialization of the community.