Multidecadal declines in particulate mercury and sediment export from Russian rivers in the pan-Arctic basin.

SignificanceRussian rivers are the predominant source of riverine mercury to the Arctic Ocean, where methylmercury biomagnifies to high levels in food webs. Pollution controls are thought to have decreased late-20th-century mercury loading to Arctic watersheds, but there are no published long-term observations on mercury in Russian rivers. Here, we present a unique hydrochemistry dataset to determine trends in Russian river particulate mercury concentrations and fluxes in recent decades. Using hydrologic and mercury deposition modeling together with multivariate time series analysis, we determine that 70 to 90% declines in particulate mercury fluxes were driven by pollution reductions and sedimentation in reservoirs. Results suggest that Russian rivers likely dominated over all other sources of mercury to the Arctic Ocean until recently.

Increasing benthic vent formation: a threat to Japan's ancient lake.

An autonomous underwater vehicle (AUV) was deployed in Lake Biwa from 2000 to 2012. In December 2009, ebullition of turbid water was first found in the deepest area (> 90 m) of the North Basin. Follow-up investigations in April and December 2010 and January 2012 confirmed the existence of benthic vents similar to the vents observed in other deep lakes. Importantly, vent numbers per unit travel distance in Lake Biwa dramatically increased from only two vents (0.37 vents km-1) in December 2009 to 54 vents (5.28 vents km-1) in January 2012, which could be related to recent tectonic activity in Japan, e.g., the M9.1 Tohoku earthquake in March 2011 and slow earthquakes along the Nankai Trough from 2006 to 2018. Continuous back-up investigations from 2014 to 2019 revealed additional benthic vents in the same area. The sudden increase in benthic vent activity (liquid and gaseous ebullitions) have significant potential to alter lake biogeochemistry and, ultimately, degrade Japan's major drinking water source and may be a harbinger of major crustal change in the near future.

Temporal and Longitudinal Mercury Trends in Burbot (Lota lota) in the Russian Arctic.

Current understanding of mercury (Hg) dynamics in the Arctic is hampered by a lack of data in the Russian Arctic region, which comprises about half of the entire Arctic watershed. This study quantified temporal and longitudinal trends in total mercury (THg) concentrations in burbot (Lota lota) in eight rivers of the Russian Arctic between 1980 and 2001, encompassing an expanse of 118 degrees of longitude. Burbot THg concentrations declined by an average of 2.6% annually across all eight rivers during the study period, decreasing by 39% from 0.171 µg g-1 wet weight (w.w.) in 1980 to 0.104 µg g-1 w.w. in 2001. THg concentrations in burbot also declined by an average of 1.8% per 10° of longitude from west to east across the study area between 1988 and 2001. These results, in combination with those of previous studies, suggest that Hg trends in Arctic freshwater fishes before 2001 were spatially and temporally heterogeneous, as those in the North American Arctic were mostly increasing while those in the Russian Arctic were mostly decreasing. It is suggested that Hg trends in Arctic animals may be influenced by both depositional and postdepositional processes.

Low and declining mercury in arctic Russian rivers.

Mercury (Hg) dynamics in the Arctic is receiving increasing attention, but further understanding is limited by a lack of studies in Russia, which encompasses the majority of the pan-Arctic watershed. This study reports Hg concentrations and trends in burbot (Lota lota) from the Lena and Mezen Rivers in the Russian Arctic, and assesses the extent to which they differ from those found in burbot in arctic rivers elsewhere. Mercury concentrations in burbot in the Lena and Mezen Rivers were found to be generally lower than in 23 other locations, most of which are in the Mackenzie River Basin (Canada). Mercury concentrations in burbot in the Lena and Mezen Rivers also were found to have been declining at an annual rate of 2.3% while they have been increasing in the Mackenzie River Basin at annual rates between 2.2 and 5.1% during roughly the same time period. These contrasting patterns in Hg in burbot across the pan-Arctic may be explained by geographic heterogeneity in controlling processes, including riverine particulate material loads, historically changing atmospheric inputs, postdepositional processes, and climate change impacts.

Long-term changes of heavy metal and sulphur concentrations in ecosystems of the Taymyr Peninsula (Russian Federation) North of the Norilsk Industrial Complex.

The Norilsk industrial ore smelting complex (Taymyr Peninsula, Russian Federation) has significantly impacted many components of local terrestrial and aquatic environments. Whether it has had a major impact on the wider Russian Arctic remains controversial as studies are scarce. From 1986 to 2004, data on heavy metal (Cu, Ni, Zn, Hg, Cd and Hg) concentrations in fish (burbot), moss, lichens, periphyton, hydric soils and snow in and around Norilsk and the most northern parts of the Taymyr Peninsula were analysed. Very high concentrations of Cu (203 µg L⁻¹ ± 51 µg L⁻¹) and Ni (113 µg L⁻¹ ± 15 µg L⁻¹) were found in the water of the Schuchya River close to Norilsk. Heavy metal concentrations in burbot liver were highest in Lake Pyasino near Norilsk compared to other study regions that were >100 km distant. From 1989-1996, Cu (121 µg L⁻¹ ± 39 µg L⁻¹ SD), Zn (150 µg L⁻¹) ± 70 µg L⁻¹) and Ni (149 µg L⁻¹ ± 72 µg L⁻¹) snow concentrations were greatest in Norilsk, but were low elsewhere. By 2004, these concentrations had dropped significantly, especially for Cu-74 µg L⁻¹ (±18.7 µg L⁻¹ SD), Zn-81.7 µg L⁻¹ (± 31.3 µg L⁻¹ SD) and Ni-80 µg L⁻¹(±18.0 µg L⁻¹ SD). Norilsk and its surroundings are subject to heavy pollution from the Norilsk metallurgical industry but these are absent from the greater Arctic region due to the prevailing winds and the Byrranga Mountains. Pollution abatement measures have been made so further investigations are necessary in order to assess their efficiency.

Measurements of Cd, Cu, Pb and Zn in the lower reaches of major Eurasian arctic rivers using trace metal clean techniques.

Concentrations of dissolved and particulate Cd, Cu, Pb and Zn were determined in samples collected in summer 1998 from the lower reaches of six major Eurasian arctic rivers: the Onega, Severnaya Dvina, Mezen, Pechora, Ob and Yenisey. These data comprise some of the earliest measurements of trace metals in Eurasian arctic rivers above the estuaries using recognized clean techniques. Significant (alpha = 0.05) differences were observed among mean concentrations of particulate metals in the individual rivers (F < or = 0.006), with highest levels overall observed in the Severnaya Dvina and Yenisey. No significant differences were observed among mean concentrations of dissolved metals in the individual rivers (F = 0.10-0.84). Contributions from anthropogenic sources are suggested by comparison of trace metal ratios in the samples to crustal abundances. These results establish a baseline for assessing future responses of Eurasian arctic river systems to climate-related environmental changes and shifting patterns of pollutant discharge.

Impacts of tetracycline on planktonic bacterial production in prairie aquatic systems.

In view of antibiotics being detected in surface waters, experiments were conducted to determine the impacts of tetracycline on planktonic bacteria in wetland and river waters. The minimum inhibitory concentration (MIC) method is often used to measure for resistance or susceptibility of microbes to antibiotics with typical concentrations of antibiotics being mg L(-1). Moreover, there is the belief that antibiotics in the lower microg L(-1) range are unlikely to affect bacteria. We examined this assumption by measuring the effects of a broad range of tetracycline concentrations on bacterial protein production by the incorporation of L-[4,5-3H]leucine method. Tetracycline significantly (P < 0.05) inhibited production in river water bacteria at a "free" concentration of 5 microg L(-1), but the inhibition was significant only at 1000 microg L(-1) in wetland water. The data indicate that planktonic bacteria can be very sensitive to tetracycline at extremely low concentrations and that microbial production is seriously affected.

Behaviour and fate of tetracycline in river and wetland waters on the Canadian Northern Great Plains.

Very little is known about the factors affecting the behaviour, degradation and persistence of tetracycline in sensitive Prairie freshwater aquatic systems in Canada. Reported are results of studies conducted for the first time of tetracycline behaviour in Prairie river and wetland waters. For comparison, studies were also conducted using distilled water as a control. Different amounts of spiked tetracycline (0, 50 and 80 percent) was adsorbed by distilled, river and wetland water, respectively. These different amounts are likely due to the differences in the matrixes of the three waters. In wetland water, the addition of EDTA generally promoted the release of tetracycline indicating that a portion of the tetracycline was bound to metal ions. Decreasing the pH of the wetland water led to increased adsorption of tetracycline suggesting either that tetracycline epimerizes or binds, by hydrogen bonding, to acidic portions of organic material in the water. However, in wetland water, a significant portion of the spiked tetracycline (approximately =50%) was irreversibly bound to the water matrix and was not released by adding EDTA and/or by varying the pH. In laboratory experiments, the t1/2 of "free-form" tetracycline exposed to light (L+) in non-sterile waters was 32, 2 and 3 days in distilled, river and wetland water respectively, while in waters with no light exposure (L-), they were 83, 18 and 13 days. Similarly, t1/2 of tetracycline in L+ sterile waters treatments was 9, 1 and 1 day for distilled, river and wetland water, respectively, and 18, 11 and 7 days in the L-. In the experiment conducted in natural sunlight, tetracycline t1/2 in the presence of ultraviolet radiation (UV) treatments was 26, 17 and 18 min in distilled, river and wetland water and 39, 28 and 32 min in the absence of UV treatment. The combination of the effects of matrixes of the water, light and UV radiation therefore play a significant role in catalyzing the removal of tetracycline from different Prairie waters. In deep waters and in systems where sunlight is highly attenuated, the effects of light on tetracycline may be considerably reduced.

A review of riverine fluxes of hexachlorocyclohexane and DDT to the Azov and Black seas from the former USSR and Russian Federation.

While the Azov and Black seas are subject to anthropogenic pollution to a much higher extent than any other seas, this has been little studied with only a few critical reviews of contaminant fluxes to these seas. Riverine fluxes of the organochlorine pesticides (OCPs) hexachlorocyclohexane (HCH) and DDT to the Azov and Black seas from the former Soviet Union and Russian Federation were thus reviewed for 1986 to 1996. The review was based on official data and data obtained by independent specialists. The amount of HCH used, and the intensity of usage, in these river catchments decreased during the review period. Concurrently, OCP concentrations in the rivers and their fluxes also decreased according to both official and independent data. A comparison of the official and the independent data sets for 1988 revealed significant differences, reflecting the need for more rigorous sampling and analytical protocols for both data sets. According to the OGSNK/GSN data, the flux rates of the five largest rivers were ranked (from largest to smallest) as follows: Don > Dnestr > Danube > Kuban > Dnepro (alpha-HCH); Danube > Don > Dnestr > Dnepro > Kuban (gamma-HCH); Dnestr > Danube > Don > Dnepro-Kuban (DDT+DDE). For rivers with lower annual riverine discharges, the DDT fluxes were surprisingly high (0.43 to 1.49 tonnes a(-1)). According to independent data for 1988 the rankings of the rivers was: Danube > Don > Dnepro > Dnestr > Kuban (alpha-HCH); Danube > Don > Dnestr > Dnepro > Kuban (gamma-HCH); Danube > Dnepro > Dnestr > Don > Kuban (DDT); Danube > Dnepro > Don > Kuban > Dnestr (DDE). The DDT flux estimates for small rivers derived from independent data were 19 to 46 times lower than those calculated using OGSNK/GSN data. According to the independent data, the total riverine OCP transport from the Russian Federation into the Azov Sea from 1988 to 1996 was 1.288 tonnes of gamma-HCH+alpha-HCH and 1.693 tonnes of DDT+DDE while for the Black Sea they were 3.830 tonnes and 5.116 tonnes for gamma-HCH+alpha-HCH and DDT+DDE, respectively.

Seasonal changes in fungal production and biomass on standing dead Scirpus lacustris litter in a northern prairie wetland.

Decaying macrophytes are an important source of carbon and nutrients in fungal and bacterial communities of northern prairie wetlands. Dead macrophytes do not collapse into the water column immediately after death, and decomposition by fungi and bacteria begins while the plants are standing. The seasonal variations in fungal biomass and production on Scirpus lacustris stems, both above and below water, were measured to assess which environmental factors were dominant in affecting these variations in a typical prairie wetland. Fungal biomass and production were measured from early May to November, just prior to freeze-up. Fungal decomposition began and was greatest in the spring despite low water temperatures. The fungal production, as measured by the incorporation of [1-(14)C]acetate into ergosterol, ranged from 1.8 to 376 microg of C g of ash-free dry mass (AFDM)(-1) day(-1), and the biomass, as estimated by using ergosterol, ranged from nondetectable to 5.8 mg of C g of AFDM(-1). There was no significant difference in biomass or production between aerial and submerged portions of Scirpus stems. The water temperature was correlated with fungal production (r = 0.7, P < 0.005) for aerial stem pieces but not for submerged pieces. However, in laboratory experiments water temperature had a measurable effect on both biomass and production in submerged stem pieces. Changes in fungal biomass and productivity on freshly cut green Scirpus stems decaying in the water either exposed to natural solar radiation or protected from UV radiation were monitored over the summer. There was no significant difference in either fungal biomass (P = 0.76) or production (P = 0.96) between the two light treatments. The fungal biomass and rates of production were within the lower range of the values reported elsewhere, probably as a result of the colder climate and perhaps the lower lability of Scirpus stems compared to the labilities of the leaves and different macrophytes examined in other studies performed at lower latitudes.

Mass spectrometric determination of ergosterol in a prairie natural wetland.

Fungi are the main decomposers of plant material in an aquatic system. Levels of ergosterol, a compound generally specific to the cell membranes of fungi can be used as an indirect measure of their presence and biomass. Described is a procedure utilising reversed-phase liquid chromatography with positive-ion atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCI-MS-MS) for full quantification and confirmation of ergosterol in various wetland matrices. Solid and liquid samples (0.2-1 g dry weight and 10 ml) were subjected to alkaline saponification followed by serial extraction using pentane (3 x 10 ml). The procedure was applicable to quantitative analysis of wetland samples with little or no clean up. Under low energy (CID) collision induced dissociation conditions the major product-ion formed from m/z 379.4 [M + H-H2O]+ was m/z 69.4 [(CH3)2CHCH=CH]+. Selected reaction monitoring (SRM) of this transition along with the retention time were used to confirm that ergosterol was widely distributed at ppm levels (2.4 to 303 microg ash free dry mass (AFDM)) in matrices of decaying willow leaves, Scirpus stems (living and dead) and sediment collected at the water-sediment interface. Comparison between LC-APCI-MS-MS (SRM), LC-APCI-MS using selected ion monitoring (SIM) and liquid chromatography with ultraviolet absorption detection (LC-UV) indicated that SRM analysis was the most selective technique.

Levels of DDT and hexachlorocyclohexane in burbot (Lota lota l.) from Russian Arctic rivers.

The concentrations of organochlorine pesticides (OCPs =p,p'DDT, p,p'DDD, p,p'DDE, alpha-HCH and gamma-HCH) were measured in the sediments, water and burbot (whole liver and liver lipids) of eight Russian Arctic rivers near their outflows to the Arctic Ocean between 1988 and 1994. DDT was not detected in any river sediments above the limit of quantification (LOQ) of 2.5 ng g(-1) dry wt. Concentrations of DDD and DDE were only found in three of the river sediments above the LOQ of 0.75 ng g(-1) dry wt. DDT and DDE were present in only North Dvina and Pechora river water above the LOQ of 5 ng l(-1), while DDD was not found in any river above this limit. Both alpha- and gamma-HCH were found in all river sediments except for the Kolyma River at concentrations up to 2.4 and 3.5 ng g(-1) dry wt., respectively. In river water, alpha-HCH was as high as 8.6 ng l(-1) in the Ob River and gamma-HCH as high as 7.6 ng l(-1) in the Pechora River. The concentration of both sigmaDDT and sigmaHCH decreased to LOQ levels by about 1992 in both water and sediments. sigmaDDT (up to 70 ng g(-1) wet wt.) and sigmaHCH (maximum 18 ng g(-1) wet wt.) in burbot livers followed a similar temporal trend as in water and sediments. There is a scarcity of OCP data for Russia, but from what is available, we conclude that: (1) contamination of Russian rivers and burbot by OCPs is less severe in the Arctic than at lower latitudes; (2) contamination of Russian Arctic burbot is comparable to, or lower than, similar OCP contamination measured in burbot and other fish in other countries; and (3) the OCP concentrations in Russian burbot pose a negligible health risk to either humans or wildlife.

Zinc accumulation by the slime mold Fuligo septica (L.) Wiggers in the former Soviet Union and North Korea.

Samples of the slime mold Fuligo septica (L.) Wiggers were collected from an ecologically diverse selection of sites across the former USSR and in North Korea to determine their Zn concentrations. Plasmodia were collected from trees, rocks, soils, the walls of buildings and a variety of other materials and structures from 1990 to 1996. The biomass collected ranged from 305 to 968 mg, whereas Zn concentrations in plasmodia of F. septica ranged from 8400 to 23,000 mg kg(-1) dry wt. (mean and standard error = 14,200 +/- 860 mg kg(-1) dry wt.). No clear trend as to which areas produced F. septica with the highest Zn concentrations was discernable. Nor was it possible to identify any particular substrate on which F. septica grew that produced noticeably high Zn concentrations. For example, forest litter on which F. septica was found had Zn concentrations of only 25 to 130 mg kg(-1) dry wt. Our data confirm the only other study showing hyperaccumulation of Zn in F. septica, which was carried out in Finland. This ability seems to be unique to this species, but how or why it does this, or why such high Zn concentrations are not toxic to F. septica, are questions requiring future research.

Seasonal patterns of total and energy reserve lipids of dominant zooplanktonic crustaceans from a hyper-eutrophic lake.

Seasonal patterns of lipid reserves and lipid classes of dominant zooplankton in a hyper-eutrophic lake were examined in relation to algal food resources. Triacylglycerol was the principle lipid energy reserve in all five species examined. During the height of the yearlyAphanizomenon flos-aquae bloom, lipid levels of the principle herbivores (Daphnia pulex andLeptodiaptomus sicilis) and an omnivore (Diacyclops bicuspidatus thomasi), were at their lowest concentration, suggesting that this cyanobacterium is nutritionally inadequate. As the cyanobacterial bloom began to collapse, bacterial numbers increased rapidly. The increase in bacterial numbers coincided with a large increase in areal lipid energy reserves ofDiaphanosoma leuchtenbergianum andChydorus sphaericus. Examination of seasonal patterns in the biomass of different algal species suggested thatRhodomonas minuta andCryptomonas erosa played a key role in nutrition, lipid deposition, and reproduction ofD. pulex andL. sicilis.