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Nearshore (littoral) habitats of clear lakes with high water quality are increasingly experiencing unexplained proliferations of filamentous algae that grow on submerged surfaces. These filamentous algal blooms (FABs) are sometimes associated with nutrient pollution in groundwater, but complex changes in climate, nutrient transport, lake hydrodynamics, and food web structure may also facilitate this emerging threat to clear lakes. A coordinated effort among members of the public, managers, and scientists is needed to document the occurrence of FABs, to standardize methods for measuring their severity, to adapt existing data collection networks to include nearshore habitats, and to mitigate and reverse this profound structural change in lake ecosystems. Current models of lake eutrophication do not explain this littoral greening. However, a cohesive response to it is essential for protecting some of the world's most valued lakes and the flora, fauna, and ecosystem services they sustain.

Lake Baikal, an ancient lake in Siberia, contains more endemic species than any other lake in the world with most of them residing in the benthic littoral zone. Explosive growth of benthic Spirogyra, a filamentous green alga, began approximately in 2011 in localized coastal areas, with the most severe examples occurring near coastal towns that lack a wastewater treatment facility or have a malfunctioning system. At other sites (small settlements, harbors), however, the cause of its excess growth is less obvious. Multiple hypotheses have been offered including lake level fluctuations, climate warming, a relaxation of grazing pressure, and coastal eutrophication. We assessed these hypotheses using data on historical lake levels, water temperature, the spatial-temporal distribution of Spirogyra along inhabited and non-inhabited shorelines, and measurements of fecal coliform bacteria and nutrients in ground water, interstitial water, and lake water. These data suggest that groundwater contamination is the primary cause of coastal eutrophication. Most houses and buildings in small settlements around Lake Baikal lack septic tanks but use unlined cesspools to collect human waste. This untreated human waste enters groundwater via passive filtration through permeable soils and flows to the coastal zone where it drives excess growth of Spirogyra. Remediation — including installation of septic systems, modernization of existing sewage treatment plants in coastal towns, and the adoption of non-phosphate containing detergents — as well as a reconsideration of the federal monitoring system regarding the coastal zone is urgently needed to protect this extraordinary lake.

Even though the interaction between water movements and aquatic plant is crucial for the aquatic ecosystem management, the importance of water turbulence in this regard is not well documented. To add to our knowledge on the interaction between aquatic plant communities and water turbulence, this study examined turbulence, plant, sediment and water quality at the reed community (Phragmites australis) in the Lake Shinji, Japan. Observations were conducted along transects perpendicular to the shoreline. For each transect, reed communities were observed at land ward side, centre, water ward and the outside of the reed community. An elevated level of turbulence was observed outside compared to inside reed community, where the magnitude of turbulence decreased with distance into the community interior. A significant positive correlation was observed for turbulence and surface-dissolved oxygen where the latter was negatively correlated to reed density. Sediment composition was affected by water turbulence where the content of coarse particles positively correlated to turbulence. Accumulation of organic matter in anoxic sediments together with fine particles was observed under low turbulence. Our findings can offer insight into understanding the interactions between turbulence and aquatic plant communities.

Cascading effects of pesticide use It is now well known that neonicotinoids negatively affect pollinators. As research has expanded, it has become clear that these globally used insecticides directly affect other ecosystem components, including vertebrates. Yamamuro et al. now show that these compounds are indirectly affecting species through trophic cascades (see the Perspective by Jensen). Since the application of neonicotinoids to agricultural fields began in the 1990s, zooplankton biomass has plummeted in a Japanese lake surrounded by these fields. This decline has led to shifts in food web structure and a collapse of two commercially harvested freshwater fish species. The authors argue that such dynamics are likely occurring widely. Science , this issue p. 620 ; see also p. 566

The availability of nutrients for primary producers has long been thought to be the main limiting factor for primary productivity in nutrient-poor lake ecosystems. However, recent studies have indicated that the availability of light energy is also important. On the other hand, the amount of phototroph was reported to decrease in summer in Antarctic lakes, furthermore, the light environment underwater was shown containing high amount of ultraviolet energy in small Antarctic lakes. Here, we hypothesized that primary productivity is limited by not only nutrients and simple light quantity but also light quality in nutrient-poor lakes. Then, we investigate factors influencing primary production by benthic phototrophic communities in shallow nutrient-poor lakes. We examine the relationships between primary production in 17 Antarctic freshwater lakes and nutrient concentrations in lake and benthic water, temperature and light energy. Primary production is decreased by ultraviolet energy reaching the lake bed, showing that production is determined by light quality. We also correlate ultraviolet energy in lake water with the catchment area of each lake. Our results show that the underwater light environment has an important influence on primary production as a key limitation factor and is sensitive to materials in runoff from the surrounding environment for pristine lakes.

This study aimed to evaluate the loading of nutrients of agricultural origin. We investigated monthly nutrient concentrations at 11 stations located in the Hii River, Japan. The nitrogen and oxygen stable isotope ratios in nitrate were applied to distinguish the origin of nitrogen, i.e., from fertilizers applied to paddy fields or from sewage. Although total nitrogen (TN), presumably from transboundary air pollution, was mainly loaded during the cooler season, nitrate originating from fertilizers applied to paddy fields became the main source of nitrogen in the river water during the warmer season. Phosphorus was mainly added in particulate form, and showed increased loading at the upstream stations in the warmer season, but not in the cooler season. Potassium and magnesium—components of fertilizers—showed an increasing trend in the downstream section of the paddy fields. Our results suggest that controlled application of fertilizers is necessary to decrease the nitrogen loads originating from farmlands, particularly from paddy fields. Since the nitrogen isotope of TN in fertilizer showed significantly lower values (mean value −4.6 ‰) than that in river water (mean value 1.8 ‰) or treated water (mean value 21.9 ‰), we could use these values to determine the contribution of TN from fertilizers to river water quality, and can use them to monitor fertilization levels in watersheds.

Most freshwater lakes in continental Antarctica are in a paradoxical situation as they are in nutrient-poor conditions despite luxuriant vegetation growth covering the entire lakebed. Although the phytobenthos possibly take up nutrients from inside lakebeds, the amount of nutrients and their utilization by these phytobenthos are unclear. Sediment cores were collected from 17 freshwater lakes in East Antarctica, then dissolved inorganic nitrogen (DIN) and phosphate of the lake waters, and the vertical profiles of the interstitial water in the sediment cores were analyzed. Here we revealed that there are abundant nutrients inside lakebeds surface with 3–220 times the amount of DIN and 2–102 times concentration of phosphate than those in lake water, and the nutrient profile inside the sediment suggested that the phytobenthos can utilize the much nutrients from lakebeds. We also show that nitrogen stable isotope ratios of shallower phytobenthos lying on the small amount of nutrients in a lake are similar to that of terrestrial cyanobacteria possessing N2 fixation ability.

Ecological degradation of the benthic littoral zone is an emerging, urgent problem at Lake Baikal (East Siberia), the most species-rich lake on Earth. Within the last 5 years, multiple changes have occurred in the nearshore benthos where most of the lake's endemic species reside. These changes include proliferation of benthic algae, death of snails and endemic sponges, large coastal wash-ups of dead benthic algae and macrophytes, blooms of toxin-producing benthic cyanobacteria, and inputs of industrial contaminants into parts of the lake. Some changes, such as massive coastal accumulations of benthic algae, are currently shared with the Laurentian Great Lakes (LGLs); however, the drivers of these changes differ between Lake Baikal and the LGLs. Coastal eutrophication from inputs of untreated sewage is causing problems at multiple sites in Lake Baikal, whereas in the LGLs, invasive dreissenid mussels redirect pelagic nutrients to the littoral substrate. At other locations in Lake Baikal, ecological degradation may have different causes including water level fluctuations and the input of toxic industrial contaminants. Importantly, the recent deterioration of the benthic littoral zone in both Lake Baikal and the LGLs has occurred while little change has occurred offshore. This highlights the necessity of monitoring both the littoral and pelagic zones of large lakes for assessing ecosystem health, change and conservation.

The natural conservation of coastal lagoons is important not only for their ecological importance, but also because of the valuable ecosystem services they provide for human welfare and wellbeing. Coastal lagoons are shallow semi-enclosed systems that support important habitats such as wetlands, mangroves, salt-marshes and seagrass meadows, as well as a rich biodiversity. Coastal lagoons are also complex social-ecological systems with ecosystem services that provide livelihoods, wellbeing and welfare to humans. This study assessed, quantified and valued the ecosystem services of 32 coastal lagoons. The main findings of the study are: (i) the definitions of ecosystem services are still not generally accepted; (ii) the quantification of ecosystem services is made in many different ways, using different units; (iii) the evaluation in monetary terms of some ecosystem service is problematic, often relying on non-monetary evaluation methods; (iv) when ecosystem services are valued in monetary terms, this may represent very different human benefits; and, (v) different aspects of climate change, including increasing temperature, sea-level rise and changes in rainfall patterns threaten the valuable ecosystem services of coastal lagoons. DEVOTES project, from the European Union's Seventh Framework Programme for research, technological development and demonstration [308392]; networks and communities of Eurolag; Future Earth Coasts; SCOR; Fundacao para a Ciencia e a Tecnologia (FCT) Investigador Programme [IF/00331/2013]; Fundacao para a Ciencia e a Tecnologia [UID/MAR/04292/2013]; CESAM by FCT/MEC national funds (PIDDAC) [UID/AMB/50017/2013 - POCI-01-0145-FEDER-007638]; FEDER; European Commission, under the 7th Framework Programme through the collaborative research project LAGOONS [283157]; FCT [SFRH/BPD/107823/2015, SFRH/BPD/91494/2012]

Deposition of atmospheric nutrients is known to alter oligotrophic ecosystems such as the open ocean, but the role of such nutrients in the further deterioration of eutrophic aquatic ecosystems is largely unknown. The Hii River watershed in Japan encompasses lagoons that have been eutrophic since 1980s. This study examined the atmospheric deposition of nitrogen and phosphorus in the Hii River watershed and the nitrogen and phosphorus concentrations in the Hii River over an 11-yr period. Total nitrogen (TN) concentrations of both precipitation and river water were significantly higher in cold months (November–March) than in warm months (April–October). Most of the TN was nitrate, which suggests that the TN source was atmospheric nitrogen from East Asia transported by seasonal winds. In contrast, total phosphorus (TP) concentrations of both precipitation and river water were significantly higher in warm months. Over time, the TN concentration in the river water showed a decreasing trend although the trend was not significant, while the TP concentration increased significantly. This was attributed to an increase in the atmospheric deposition of TP originating from East Asia since 2000. The increase in the deposition of atmospheric phosphorus might also have increased phosphorus leakage from the soils. In this work, the TN : TP ratios for both atmospheric deposition and river water indicate that changes in atmospheric nutrient deposition affect loading rates and N : P ratios. These changes, especially the latter, could have significant ecological effects in eutrophic systems by lowering the N : P ratios, which could induce cyanobacteria blooms.

This study is focused on the evaluation of a Digital Elevation Model (DEM) for Tokyo, Japan from data collected by the recently launched TerraSAR add-on for Digital Elevation Measurements (TanDEM-X), satellite of the German Aerospace Center (DLR). The aim of the TanDEM-X mission is to use Interferometric SAR techniques to generate a consistent high resolution global DEM dataset. In order to generate an accurate global DEM using TanDEM-X data, it is important to evaluate the accuracy at different sites around the world. Here, we report our efforts to generate a high-resolution DEM of the Tokyo metropolitan region using TanDEM-X data. We also compare the TanDEM-X DEM with other existing DEMs for the Tokyo region. Statistical techniques were used to calculate the elevation differences between the TanDEM-X DEM and the reference data. Two high-resolution LiDAR DEMs are used as independent reference data. The vertical accuracy of the TanDEM-X DEM evaluated using the Root Mean Square Error (RMSE) is considerably higher than the existing global digital elevation models. However, the local area DEM generated by Geospatial Information Authority of Japan (GSI DEM) showed the highest accuracy among all non-LiDAR DEM’s. The vertical accuracy in terms of RMSE estimated using the 2 m LiDAR as reference is 3.20 m for TanDEM-X, 2.44 m for the GSI, 7.00 m for SRTM DEM and 10.24 m for ASTER-GDEM. We also compared the accuracy of TanDEM-X with the other DEMs for different types of land cover classes. The results show that the absolute elevation error of TanDEM-X is higher for urban and vegetated areas, likewise to those observed for other global DEM’s. This is probably because the radar signals used by TanDEM-X tend to measure the first reflective surface that is encountered, which is often the top of the buildings or canopy. Hence, the TanDEM-X based DEM is more akin to a Digital Surface Model (DSM).

Metals are essential for human life and physiological functions but may sometimes cause disorders. Therefore, we conducted acute toxicity testing of 50 metals in Daphnia magna: EC50s of seven elements (Be, Cu, Ag, Cd, Os, Au and Hg) were 100,000 μgl 1 ; and. 7 elements (Ti, Zr, Bi, Nb, Hf, Re and Ta) did not show EC50 at the upper limit of respective aqueous solubility, and EC50s were not obtained. Ga, Ru and Pd adhered to the body of D. magna and physically retarded the movement of D. magna. These metals formed hydroxides after adjusting the pH. Therefore, here, we distinguished this physical effect from the physiological toxic effect. The acute toxicity results of 40 elements obtained in this study were not correlated with electronegativity. Similarly, the acute toxicity results of metals including the rare metals were also not correlated with first ionization energy, atomic weight, atomic number, covalent radius, atomic radius or ionic radius. Copyright © 2014 John Wiley & Sons, Ltd.

The most potent chemicals potentially causing adverse effects on fish species are estrogens in human waste.Sewage is a source of these estrogens and it is difficult to reduce. In particular, although the bioactivity of estrone is estimated to be about half of that of estradiol, multiple studies report that more than 100 ng l(–1) of estrone can be detected in urban rivers, including discharges from sewage treatment works; approximately two times as high as estradiol. Few studies have been conducted to investigate the long-term effects of estrone on wildlife; therefore, we conducted fish multigeneration test using Japanese medaka (Oryzias latipes). Medaka were exposed to estrone for 27 weeks across three generations in environmentally relevant concentrations, being 5.74, 11.4, 24.0, 47.1 and 91.4 ng l(–1). No effects on reproduction were observed in the first generation; however, a decline in egg production and fertility was observed in the second generation exposed to 91.4 ng l(–1) estrone, which is lower than some known environmental concentrations in urban environments. Furthermore, histopathological abnormalities were observed in the third generation exposed to both 47.1 and 91.4 ng l(–1), suggesting that estrone possibly exerts severe effects on the third or later generations. However, appearances of testis–ova were observed in the second and third generation they were not consistent with actual effects on reproduction, notwithstanding the testis-ovais regarded as the key evidence for endocrine disruption. Accordingly, we consider that qualitative measurement of abnormalities using histopathological observations is required for appropriate evaluation of endocrine disruption.

Juvenile hormone (JH) and JH agonists have been shown to induce male offspring production in various daphnids, including Daphnia magna using OECD TG211. The critical period (about 1h) for JH action on ova in the parent's ovary to induce male offspring is existing at 7-8h later from ovulation. Therefore, we considered that adult D. magna could be used to produce a short-term screening method for detecting JH analogs. Using this method, we successfully demonstrated male offspring induction in the second broods after exposure to JH or JH agonists. After investigating the exposure time, the number of repetitions and the exposure concentration, we established a short-term, in vivo screening method for detecting JH analogs using adult D. magna. We examined positive and negative control chemicals using a previously developed method and verified the validity of our new testing method. Copyright © 2014 John Wiley & Sons, Ltd.

‐4.6‰, whereas waters from the magnetite series area have positive δ 34 S values ranging from +1.7 to +8.0‰. The hot spring water quality of the Na‐Alk, Na‐SO 4 , Na‐SO 4 ·Cl·Alk, and Ca‐SO 4 types from the volcanic rocks area were estimated to be controlled by anhydrite dissolution, plagioclase weathering, cation exchange reaction of Na‐ montmorillonite, and precipitation of calcite during the fluid flow and mixing process. Different concentrations of SO 4 2‐ ions determined for these waters have a wide range of δ 34 S values ranging from ‐4.1 to +13.6‰, which is likely attributed to the dissolution of 34 S-rich and 34 S-poor anhydrite. The 34 S-rich SO4 2‐ ions were interpreted to be derived from sulfate in sulfuric acid, which arose from the disproportionation reaction of volcanic sulfur dioxide, whereas the 34 S-poor SO 4 2‐ ions were derived from the oxidation of ascending hydrogen sulfide in shallow ground waters during the active stage of past volcanism.

Various testing methods for the detection of the endocrine disruptive activities of chemicals have been developed in freshwater fish species. However, a few relatively easier specific methods for detecting anti-androgenic activities are available for fish. The aim of this study was to verify the papillary process in Japanese medaka (Oryzias latipes) as an indicator of the anti-androgenic activity of chemicals. Japanese medaka were exposed to two types of anti-androgenic compounds, vinclozolin and flutamide, using two short-term assays; one was conformed to the existing short-term reproduction assay using adult fish (adult test) and the other was a test based on the same methods but using juvenile fish at the beginning of exposure (juvenile test). Significant decreases in male papillary processes were observed in the juvenile test treated with the highest concentration of both antiandrogens (640 µg l(-1) vinclozolin and 1000 µg l(-1) flutamide); however, no significant effects were observed in the adult test. Consequently, our results indicate that papillary processes in Japanese medaka can be used as the end-point for screening the anti-androgenic activity of chemicals using juvenile fish for a specific period based on the existing short-term reproduction assay.

Estuarine ecosystems are easily deteriorated by organic pollution because of its high primary productivity. To identify chemical proxies for the possible sources of autochthonous organic matter [phytoplankton-derived particulate organic material (POM), macroalgae and seagrass], we measured C:N:P and the ratios of carbon and nitrogen stable isotopes (δ13C and δ15N values) in two estuarine environments, the polyhaline lagoon, Lake Nakaumi, and the oligohaline lagoon, Lake Shinji, in Japan. Due to vigorous photosynthesis, the δ13C of phytoplankton-derived POM in Lake Nakaumi was larger than what would normally be expected from estuarine salinity gradients. Concentrations of nitrogen and phosphorus did not affect the δ13C of phytoplankton-derived POM. The δ15N of all plants was uniform and was higher than the δ15N of sediments. The seagrass showed a higher C:N ratio than POM and macroalgae, while the macroalgae showed a higher N:P ratio. Thus, simultaneous evaluation of C:N and N:P ratios would distinguish these three plant groups, and it would be possible to identify the source plants from the elemental ratios of the sediments.

Although submerged vegetation is considered to be the most suitable refuge against predators and form of foraging habitat for small fishes, submerged plants are often scarce or lacking in turbid eutrophic lakes. To evaluate emergent (Zizania latifolia) and floating-leaved (Nelumbo nucifera) vegetation as refuge areas against predators and as foraging habitats for small fishes, we investigated the fauna, abundance, and size distribution of the fish community as well as the abundance of possible prey for small fishes in beds of each vegetation type in a eutrophic shallow lake: Lake Teganuma in Japan. The leaves and stems of N. nucifera occupied an area 4.2 times larger than that of Z. latifolia. The high coverage of the water surface with plants most likely induced the hypoxia found in the N. nucifera bed. The diversity of small fishes was greater in the Z. latifolia bed with piscivorous fish than in the N. nucifera bed without piscivorous fish. The diversity of fish species in the vegetation was enhanced when there was an increased diversity of possible food sources rather than an absence of predators. Some aquatic insects of the same species had a much lower δ13C signature at hypoxic locations than at less hypoxic locations in the N. nucifera bed. Such site differences within a bed were not observed in the organisms caught in the Z. latifolia bed. The insects in hypoxic zones with a δ13C signature lower than −30 ‰ were more depleted in 13C than the surface sediment or attached algae, suggesting that the larvae in the hypoxic zones incorporated the organic materials generated by methane-oxidizing bacteria. We can therefore conclude that floating-leaved vegetation, especially a N. nucifera bed, is not suitable as a replacement for submerged vegetation because of its potential to induce hypoxia, which can decrease the diversity of the fish fauna.

Groundwater in karst regions in the Philippines is inhabited by a diverse yet unique aquatic fauna. While this habitat is threatened by anthropogenic disturbances, basic physicochemical information is lacking. Here, we provide the first report of karst groundwater quality based on the characterization and assessment of samples collected from caves. Water samples from seven islands (Bohol, Calicoan, Luzon, Mindanao, Negros Oriental, Panglao, and Samar) were analyzed in order to obtain baseline information about and assess the environmental status of groundwater in karst areas. Although most of the sites showed no evidence of anthropogenic disturbance, excessive amounts of NO2 −, NO3 −, and Cl− were detected in the samples from a few areas, particularly Panglao Island, Bohol. These pollutants likely originate from human-related activities such as the use of water treatment chemicals, detergents, and bleach, as well as the leakage of septic tanks. Further investigations and in-depth studies aimed at clearly understanding the dynamics of the karst groundwater, thus preventing the aggravation of problems with the groundwater in the future, are highly recommended.

In this study, we used a new integrated measurement system that combines the acoustic imaging sonar of DIDSON (Dual-frequency IDentification SONar) with concentrator lenses, motion sensors, and GPS receivers to find and identify different species of aquatic plants. Two types of experiments were performed at two lakes in Japan: Lake Yamanaka and Lake Yunoko. In the first experiment at Lake Yamanaka, the image was captured with a one-degree concentrator lens. Multi-beam image processing was used to generate 3-D images of aquatic plants. The lens used in this experiment concentrated the vertical beam width within 1 degree. The second experiment at Lake Yunoko DIDSON with a 3-degree concentrator lens was applied, and histogram and spatial spectrum analyses were performed for plant species classification. Three species of aquatic plants, Myriophyllum spicatum, Chara globularis, and Elodea nuttallii, were classified by the parameters obtained from the current methods. The ability to visualize the features of each aquatic plant for species classification, e.g., leaf and branch dimensions, was attributed to spatial spectrum and scattering analyses of the acoustic images. The high spatial resolution of the integrated DIDSON measurement system will contribute protection of endangered species in rapidly changing underwater environment.

A method for determination of hydrogen sulfide in microsamples (200 μL) was developed by modifying the methylene blue method. Samples were collected using a micropipette and were combined with sulfide coloring reagent and 5 mL of 0.1 M HCl in test tubes. Absorbance of the solution was measured spectrophotometrically at 667 nm. This modified method did not require any special labware or technique, and can be used in a variety of research fields.

As expressed in the Ramsar Convention, the wise use of wetlands, including coastal lagoons, is one of the greatest environmental concerns across the globe. Seagrass beds are the key element for sustaining coastal lagoon ecosystems. Eutrophication, especially by nitrogen and phosphorus, has degraded many coastal waters and has been invoked as a major cause of seagrass disappearance worldwide. Seagrass had been used as fertilizer in Japan, and the removal of seagrass contributed to the decline of nutrients in the water. The shifts of primary producers from rooted macrophytes to phytoplankton occurred simultaneously between the mid-1950s and 1965 in Japan—presumably because of the wide use of herbicides for rice paddies. Increased phytoplankton induced the increase of fishery yield of clam on one hand and non-edible biofouling species on the other. Because a phytoplankton-dominated ecosystem is easily oxygen depleted at the bottom with the accumulation of organic matter of phytoplankton origin, preventing hypoxia is the key factor to maintain high secondary production for bivalve fisheries and sustainable use of the ecosystem of coastal lagoons.

The paper presents the first paleontological data (pollen, plant macrofossil, diatom and ostracod) on the sediments of Lake Beloye, which is situated in the forest-steppe zone of Western Siberia. Our study contributes to better understanding of the Middle–Late Holocene regional to local environmental changes. Regionally, we recognized a cold stage of 3.4–2.3 calibrated ka BP and a dry stage of 2.8–1.7 ka BP. The dry stage coincides with the climate-driven lowered level of the lake at 2.6–1.5 ka BP. Later, the climate changed to warmer and wetter, which resulted in a highest stand of the lake at 1.3–0.2 ka BP and was followed by the lowering of the lake. Forest-steppe persisted in this area during the whole period under consideration, but probably shifted southward. Such a shift is reflected in the environment around Lake Beloye similar to that of modern taiga, which existed at 3.2–1.3 ka BP, however, compared to the colder and wetter climate of taiga, the conditions were colder and drier. The local plant associations and the lake ecosystem were affected by those events of climate and lake level changes. The initial eutrophic sedge-reed swamp evolved to the oligo-mesotrophic sphagnum bog, which existed around the lake at 3.2–1.3 ka BP. Later, the bogging process was interrupted by the lake transgression, after which the dried bog around the lake was occupied by the birch forest. The lake ecosystem was strongly affected by the 3.4 ka BP climate change: the low-alkaline eutrophic lake with abundant water higher plants and diatoms changed to the alkaline oligotrophic lake with calcium-fixing macrophytic algae and angiosperms. This resulted in total change of lake's bio-geochemical and sedimentation patterns.

Sediment structure, rock-magnetic and bio-geochemical records obtained from sapropel core samples in Lake Beloye, southern Western Siberia, indicate an abrupt ecosystem change at 3.4 calibrated ka BP. The lake changed from eutrophic to oligotrophic, its vegetation — from carbon-fixing macrophytic angiosperms to calcium-fixing macrophytic algae and angiosperms, and, as a result, the type of sedimentation shifted from peaty sapropel to carbonate-rich sapropel. Those changes could be induced by climate, which was warmer and wetter before 3.4 ka BP and cooler and drier after this. Nevertheless, our data show that those ecosystem changes occurred when the lake became shallower to get about 1 m depth and started to freeze to the bottom in winter time. The full freezing of the lake led to the deposition of carbonates, which resulted in: i) death of carbon-utilizing macrophytic angiosperms; and ii) winter precipitation of calcium carbonate. In summer, additional portions of Ca 2+ and HCO 3 − ions come into the lake from the surrounding CaCO 3 rich loess sediments with ground water. The Beloye Lake thus represents an example of interrelated regional climatic and local ecological factors, which combination resulted in the 3.4 cal. ka BP dramatic change of its ecosystem.

Nitrogen compound deposition as a result of human activities on the terrestrial surface has increased sharply during the last one hundred years, causing ecological problems. One problem is nitrogen saturation in forest ecosystems, which results in the forest ecosystem receiving more nitrogen than required. In recent years, nitrogen oxide emissions have been decreasing in Japan; however, the total deposition of nitrogen is not decreasing because of cross-boundary emissions from other countries. As depositions in forest ecosystems increase, the likelihood of nitrogen saturation increases. At the same time, certain species of trees, geological conditions, and climate will affect nitrogen saturation. In Japan, there is heavy precipitation in summer; therefore, decreases in nitrate concentrations of stream water cannot be observed. Stable isotope analysis is the key to elucidating nitrogen dynamics between the atmosphere and rivers. From the atmosphere to stream water, nitrogen compounds have many chemical and biological reactions. Because a stable isotope is an indicator of the progress of these reactions, frequent analyses of stable isotope compositions reveals how nitrogen moves from the atmosphere to stream