Time filter

Source Type

Idrizaj A.,Estonian University of Life Sciences | Laas A.,Estonian University of Life Sciences | Anijalg U.,Estonian Environmental Research Center | Noges P.,Estonian University of Life Sciences
Journal of Hydrology | Year: 2016

The causes of horizontal differences in metabolic activities between lake zones are still poorly understood. We carried out a two-year study of lake metabolism in two contrasting parts of a large shallow lake using the open-water technique based on high-frequency measurements of dissolved oxygen concentrations. We expected that the more sheltered and macrophyte-rich southern part of the lake receiving a high hydraulic load from the main inflow will exhibit equal or higher rate of metabolic processes compared to the open pelagic zone, and higher temporal variability, including anomalous metabolic estimates such as negative gross primary production (GPP) or community respiration (CR) due to rapid water exchange. Our results showed that anomalous metabolic estimates occurred at both stations with a similar frequency and were related rather to certain wind directions, which likely contributed to stronger water exchange between the littoral and pelagic zones. Periods of auto and heterotrophy (daily mean NEP> or <0) had a 50:50 distribution at the Central Station while the proportions were 30:70 at the Southern Station. High areal GPP estimated in our study exceeding nearly twice the long-term average 14C primary production, showed the advantages of the free-water technique in integrating the metabolism of all communities, a large part of which has remained undetected by the traditional bottle or chamber incubation techniques. © 2016 Elsevier B.V. Source

Keis M.,University of Tartu | Remm J.,University of Tartu | Ho S.Y.W.,University of Sydney | Davison J.,University of Tartu | And 8 more authors.
Journal of Biogeography | Year: 2013

Aim: Using sequences of complete mitochondrial genomes, our aims were: (1) to investigate the matrilineal phylogeographical structure, migration patterns and lineage coalescence times in a large, continuous population of brown bears (Ursus arctos); and (2) to develop a novel spatial genetic method to identify migration corridors and barriers. Location: North-western Eurasia: from eastern European Russia to the Baltic Sea. Methods: We sequenced the complete mitochondrial genomes of 95 brown bears. The phylogeographical resolution of complete genomes was compared to that derived from subsets of the genome, including the most commonly used shorter sequences. We conducted network and Bayesian phylogeographical analyses and developed a novel, spatially explicit, individual-based approach (called DResD) for identifying migration corridors and barriers. Results: Analysis of mitogenome sequences revealed five haplogroups, specific to particular geographical areas, exhibiting far greater resolving power than shorter sequences. Estimated coalescence times for the haplogroups ranged from 7.7 to 15.2 ka, suggesting that their divergence took place after the last glaciation. We found several migration trends, including a large westward migration from eastern European Russia towards Finland. We also found evidence of a potential barrier and a migration corridor in the south-west of the study area. Main conclusions: The use of complete mitochondrial genomes from a brown bear population in north-western Eurasia allowed us to identify phylogeographical structure, signatures of demographic history and spatial processes that had not previously been detected using shorter sequences. These findings have implications for studies on other species and populations, especially those exhibiting low mtDNA diversity. The relatively recent divergence estimates for haplogroups highlight the significance not only of the last glaciation but also of climatic fluctuations during the post-glacial period for the divergence of mammal populations in Europe. Our spatial genetic method represents a new tool for the analysis of genetic data in a geographical context and is applicable to any data that yield genetic distance matrices, including microsatellites, amplified fragment length polymorphisms (AFLPs) and single-nucleotide polymorphisms (SNPs). © 2012 Blackwell Publishing Ltd. Source

Iital A.,Tallinn University of Technology | Pachel K.,Tallinn University of Technology | Pachel K.,Estonian Environmental Research Center | Loigu E.,Tallinn University of Technology | And 2 more authors.
Journal of Environmental Monitoring | Year: 2010

The aim of the study was assessment of changes in nutrient concentrations in Estonian rivers as a response to improved wastewater treatment and substantial reductions in the use of fertilisers and number of livestock during the past 15-20 years. A Mann-Kendall test and flow adjusted technique to assess recent trends have been used. Statistical analysis covered time series of 53 sampling sites on 40 rivers and streams in different hydro-geographical regions and varying human pressures. The results indicate a statistically significant downward trend in nitrogen concentration in 18 sampling stations during the studied period; only very few showed an upward trend. These decreases in total nitrogen (TN) relate mainly to (i) substantial reductions in the use of fertilisers, (ii) decreased area of agricultural land, (iii) decreased point source load and (iv) increased self-purification capacity of soil-water systems. The concentration of phosphorus decreased only in 13 locations, despite of efforts to improve the efficiency of wastewater treatment. Moreover, in seven locations the concentration of phosphorus was increasing. This increase in total phosphorus (TP) probably relates to the low treatment efficiency of small wastewater treatment facilities as well as to the raised ground water table due to insufficient maintenance of drainage systems that favour transport of soil P to water bodies. Accordingly, the ratio of nitrogen and phosphorus had both decreasing and increasing trends. © 2010 The Royal Society of Chemistry. Source

Hindrikson M.,University of Tartu | Mannil P.,Estonian Environmental Research Center | Ozolins J.,State Forest Research Institute Silava | Krzywinski A.,Wildlife Park Kadzidlowo | Saarma U.,University of Tartu
PLoS ONE | Year: 2012

Studies on hybridization have proved critical for understanding key evolutionary processes such as speciation and adaptation. However, from the perspective of conservation, hybridization poses a concern, as it can threaten the integrity and fitness of many wild species, including canids. As a result of habitat fragmentation and extensive hunting pressure, gray wolf (Canis lupus) populations have declined dramatically in Europe and elsewhere during recent centuries. Small and fragmented populations have persisted, but often only in the presence of large numbers of dogs, which increase the potential for hybridization and introgression to deleteriously affect wolf populations. Here, we demonstrate hybridization between wolf and dog populations in Estonia and Latvia, and the role of both genders in the hybridization process, using combined analysis of maternal, paternal and biparental genetic markers. Eight animals exhibiting unusual external characteristics for wolves - six from Estonia and two from Latvia - proved to be wolf-dog hybrids. However, one of the hybridization events was extraordinary. Previous field observations and genetic studies have indicated that mating between wolves and dogs is sexually asymmetrical, occurring predominantly between female wolves and male dogs. While this was also the case among the Estonian hybrids, our data revealed the existence of dog mitochondrial genomes in the Latvian hybrids and, together with Y chromosome and autosomal microsatellite data, thus provided the first evidence from Europe of mating between male wolves and female dogs. We discuss patterns of sexual asymmetry in wolf-dog hybridization. © 2012 Hindrikson et al. Source

Tammeleht E.,University of Tartu | Remm J.,University of Tartu | Korsten M.,University of Tartu | Davison J.,University of Tartu | And 5 more authors.
Molecular Ecology | Year: 2010

Knowledge of population structure and genetic diversity and the spatio-temporal demographic processes affecting populations is crucial for effective wildlife preservation, yet these factors are still poorly understood for organisms with large continuous ranges. Available population genetic data reveal that widespread mammals have for the most part only been carefully studied at the local population scale, which is insufficient for understanding population processes at larger scales. Here, we provide data on population structure, genetic diversity and gene flow in a brown bear population inhabiting the large territory of northwestern Eurasia. Analysis of 17 microsatellite loci indicated significant population substructure, consisting of four genetic groups. While three genetic clusters were confined to small geographical areas - located in Estonia, southern Finland and Leningrad oblast, Russia - the fourth cluster spanned a very large area broadly falling between northern Finland and the Arkhangelsk and Kirov oblasts of Russia. Thus, the data indicate a complex pattern where a fraction of the population exhibits large-scale gene flow that is unparalleled by other wild mammals studied to date, while the remainder of the population appears to have been structured by a combination of demographic history and landscape barriers. These results based on nuclear data are generally in good agreement with evidence previously derived using mitochondrial markers, and taken together, these markers provide complementary information about female-specific and population-level processes. Moreover, this study conveys information about spatial processes occurring over multiple generations that cannot be readily gained using other approaches, e.g. telemetry. © 2010 Blackwell Publishing Ltd. Source

Discover hidden collaborations