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Recent Arctic warming has major influences on biological communities, especially in freshwater environments. There is substantial evidence that lake ecosystems in the Canadian Arctic and Fennoscandia are undergoing changes that have been linked to human-induced climate warming during the past 150–100 years. However, only few data linking recent climatic changes with the changes in biological communities are available from the Russian Arctic. We investigated a short sediment core (bottom of the core dates to 1830 CE) from Lake Bolshoy Kharbey, the biggest lake of the Bol`shezemelskaya Tundra, western Russian Arctic, using chironomid, cladocera, diatom and palynological analyses. Variations in biological proxy were linked to regional meteorological data and compared with the available sub-recent palaeoecological and hydrobiological studies from the region. The overall change in species composition was the smallest for terrestrial vegetation (0.485 SD) followed by cladoceran communities (0.966 SD). Chironomid taxonomic turnover was 1.331 SD, and the greatest rate of change was observed in diatom assemblages (1.701 SD). Changes in biological communities demonstrated a correlation with meteorologically recorded climatic parameters (air temperature and precipitation). The strongest taxonomic shifts in biological communities took place in 1880 and 1980. Both dates can be linked with prominent and recent climatic events: 1880 can be related to the end of the Little Ice Age in the region and 1980 is the beginning of the modern accelerating warming.

In the Arabian Gulf, mangroves play a particularly important role in maintaining biodiversity. Water and intertidal sediments were collected from eight sampling locations in April 2017 to assess the environmental status of the mangrove forest in the Khor al Beida, Umm Al Quwain, which is one of the largest natural mangrove forests in the United Arab Emirates (UAE). Khor al Beida is also a breeding ground for the largest Gulf colony of a regionally endemic Socotra cormorant. Total metal concentrations of water and sediments were measured using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and ranged between 0.001&ndash, 2.873 mg/L and 0.08&ndash, 12683.02 mg/kg, respectively. Most metals were within permissible levels, except for copper, iron, aluminum, zinc, and nickel. Hazard Quotient calculations showed low risk to the ecosystem in relation to the presence of heavy metals, with the exception of zinc. Fifty-three diatom species of pennate benthic forms were identified in the intertidal sediments. For the first time in the UAE, diatom composition and diatom diversity values were quantitatively estimated in the surface sediments and a short sediment core. Overall, the assessment suggests that the mangrove forest is currently undisturbed and shows very little anthropogenic impact, yet, protection and conservation efforts are necessary in order to maintain its current status.

A lake sediment record from the north-eastern European Russian Arctic was examined using palaeolimnological methods, including subfossil chironomid and diatom analysis. The objective of this study is to disentangle environmental history of the lake and climate variability during the past 2000 years. The sediment profile was divided into two main sections following changes in the lithology, separating the limno-telmatic phase between ~2000 and 1200 cal. yr BP and the lacustrine phase between ~1200 cal. yr BP and the present. Owing to the large proportion of semi-terrestrial chironomids and poor modern analogues, a reliable chironomid-based temperature reconstruction for the limno-telmatic phase was not possible. However, the lacustrine phase showed gradually cooling climate conditions from ~1200 cal. yr BP until ~700 cal. yr BP. The increase in stream chironomids within this sediment section indicates that this period may also have had increased precipitation that caused the adjacent river to overflow, subsequently transporting chironomids to the lacustrine basin. After a short-lived warm phase at ~700 cal. yr BP, the climate again cooled, and a progressive climate warming trend was evident from the most recent sediment samples, where the biological assemblages seem to have experienced an eutrophication-like response to climate warming. The temperature reconstruction showed more similarities with the climate development in the Siberian side of the Urals than with northern Europe. This study provides a characteristic archive of arctic lake ontogeny and a valuable temperature record from a remote climate-sensitive area of northern Russia.

We investigated chironomid fauna of surface sediments and a short sediment core (Bol’shoy Kharbey Lake) from Pechora river basin, Northern Russia. Twenty three investigated lakes have thermokarst, glacial or floodplain origin and are characterised by low mineralization, mostly hydrocarbon-calcium type of water and low concentration of nutrients. Most of the lakes have circumneutral pH around ≤7 and only two lakes are slightly more acidic with pH ≤ 6. Ninety six chironomid taxa were identified in the surface sediments. Distribution of chironomids in the studied region is driven by continentality, mean TJuly and рН. Chironomid communities from the core of the B. Kharbei Lake demonstrate the highest similarity with the fauna of the deeper lakes of the glacial origin. The glacial lakes have the highest indices of continentality and the lowest winter temperatures within the investigated data set. The chironomid fauna of the glacial lakes is composed of the profundal, oligotrophic and cold-stenotherm taxa. The fauna of the floodplain and thermokarst lakes is more closely related to TJuly and is composed of littoral and phytophilic taxa of meso – or eutrophic waters and moderate temperature conditions. The fauna of the acidic thermokarst lakes considerably differs from the other lakes. Chironomid communities here are represented by tolerant to acidification taxa, and by the typically littoral and shallow water acid-tolerant taxa that apparently also can tolerate acidification. Studied sediment record covers ca last 200 years. The reconstructed TJuly during the entire period remain slightly below the modern temperatures. From 1970 reconstructed TJuly shows steady increase to the modern level. The reconstructed water depths (WDs) of the lake are higher than today till 1980. The highest WDs are reconstructed for ca 1970. After that the WDs gradually decrease to the modern level. Changes of the WDs are most probably related to changes in the precipitation rate.

The premise of this article is that climate effects on lakes can be quantified most effectively by the integration of process-oriented limnological studies with paleolimnological research, particularly when both disciplines operate within a common conceptual framework. To this end, the energy (E)-mass (m) flux framework (Em flux) is developed and applied to selected retrospective studies to demonstrate that climate variability regulates lake structure and function over diverse temporal and spatial scales through four main pathways: rapid direct transfer of E to the lake surface by irradiance, heat, and wind; slow indirect effects of E via changes in terrestrial development and subsequent m subsidies to lakes; direct influx of m as precipitation, particles, and solutes from the atmosphere; and indirect influx of water, suspended particles, and dissolved substances from the catchment. Sedimentary analyses are used to illustrate the unique effects of each pathway on lakes but suggest that interactions among mechanisms are complex and depend on the landscape position of lakes, catchment characteristics, the range of temporal variation of individual pathways, ontogenetic changes in lake basins, and the selective effects of humans on m transfers. In particular, preliminary synthesis suggests that m influx can overwhelm the direct effects of E transfer to lakes, especially when anthropogenic activities alter m subsidies from catchments.

The Pechora Region (PR) has extensive natural resources supporting forestry, oil and gas industries. The objective of this integrated study was to identify if local and long range pollution and bio ...

Changes in diatom assemblages and spheroidal carbonaceous particle (SCP) profiles during the last 200 years in 210Pb-dated sediment cores from five remote arctic and sub-arctic lakes in the northern Urals were analysed. The study area covers a large territory from arctic tundra in the north to boreal forest on the western slopes of the Ural mountains in the south. pH was reconstructed using a diatom-based model. The degrees of compositional turn-over and rates-of-change were estimated numerically. The 20th century diatom floristic shifts, the rise in diatom accumulation rates and the rates of diatom compositional change in the northern Ural lakes correlate well with June temperature in the region and with the overall circum-arctic temperature increase from the 1970s. The main driving force behind diatom compositional shifts in the study lakes are the changes in the duration of ice-free season, timing of water turn-over and stratification periods and habitat availability. Changes in spheroidal carbonaceous particles show no pronounced effect on diatom assemblages. Pollution is restricted to regional sources originating mainly from the Vorkuta coal industry. Changes in diatom plankton are more pronounced than changes in diatom benthos. There is no clear north–south gradient in degree of compositional changes, with greatest changes occurring in Lake Vankavad situated in northern boreal forest. The degree of the 20th century diatom changes in Lake Vankavad is greater than in most circum-arctic and sub-arctic lakes from northern Europe and Canada.

Mid-Holocene changes in vegetation, palaeohydrology and climate were investigated from the sediments of Lake Vankavad in the northern taiga of the Usa Basin, NE European Russia, through the analysis of pollen, plant macrofossils, Cladocera and diatoms. Lake Vankavad was probably formed at ca. 5000 BP (ca. 5600 cal. BP) and initially it was shallow with a littoral cladoceran fauna. Macrofossil and pollen results suggest that dense Betula-Picea forests grew in the vicinity and the shore was close to the sampling point. At ca. 4600 BP (ca. 5400 cal. BP) the water level rose coincident with the decrease in the density and area of forests, probably caused by cooling climate and accelerated spread of mires. There was also a further rise in the water level at ca. 3500 BP (ca. 3800 cal. BP). The initiation of the lake, followed by two periods of rising water-level, as well as the increase in mire formation, was a consequence of a rise in groundwater level. This probably reflects lower evapotranspiration in a cooling mid-Holocene climate and/or higher precipitation in the lowland area. Also the decreased forest density and area may have contributed to the lower evapotranspiration. It is also possible that permafrost aggradation or changes in peat ecosystems might have affected the hydrological conditions in the area.

This study investigated Holocene tree-line history and climatic change in the pre- Polar Urals, northeast European Russia. A sediment core from Mezhgornoe Lake situated at the present-day alpine tree-line was studied for pollen, plant macrofossils, Cladocera and diatoms. A peat section from Vangyr Mire in the nearby mixed mountain taiga zone was analysed for pollen. The results suggest that the study area experienced a climatic optimum in the early Holocene and that summer temperatures were at least 2 � C warmer than today. Tree birch immi- grated to the Mezhgornoe Lake area at the onset of the Holocene. Mixed spruce forests followed at ca. 9500-9000 14 C yr BP. Climate was moist and the water level of Mezhgornoe Lake rose rapidly. The hypsithermal phase lasted until ca. 5500-4500 14 C yr BP, after which the mixed forest withdrew from the Mezhgornoe catchment as a result of the climate cooling. The gradual altitudinal downward shift of vegetation zones resulted in the present situation, with larch forming the tree-line. Copyright 2003 John Wiley & Sons, Ltd.

Fifty-five paleolimnological records from lakes in the circumpolar Arctic reveal widespread species changes and ecological reorganizations in algae and invertebrate communities since approximately anno Domini 1850. The remoteness of these sites, coupled with the ecological characteristics of taxa involved, indicate that changes are primarily driven by climate warming through lengthening of the summer growing season and related limnological changes. The widespread distribution and similar character of these changes indicate that the opportunity to study arctic ecosystems unaffected by human influences may have disappeared.