Varied patterns of DNA methylation change between different satellite regions in bovine preimplantation development

Global reduction of DNA methylation, a part of genome reprogramming processes, occurs in a gradual manner until before implantation and is recognized as a conserved process in mammals. Here, we reported that in bovine, satellite regions exhibited varied patterns of methylation changes when one-cell egg advanced to the blastocyst; a maintenance methylation was observed in satellite I sequences, a decrease in alpha satellites, and an increase in satellite II regions. Cloned embryos exhibited similar changes for DNA methylation in the satellite I and alpha. We also observed that the satellite I and alpha sequences were methylated more in inner cell mass region of the blastocyst whereas the satellite II showed selective demethylation in this region. Together, these findings point that individual satellite sequences carry their own methylation patterns under the pressure of global demethylation, suggesting that local methylation control system acts on the satellite regions in early bovine embryos.     

Modelling sediment transport in shallow lakes — interactions between sediment transport and sediment composition

In shallow, wind exposed lakes, the light conditions, the cycling of nutrients, heavy metals and organic micro-pollutants and changes in the local composition of the sediment top layer can be dominated by resuspension/erosion of bottom sediment and sedimentation of suspended solids. A 2 dimensional model for Sediment Transport, Resuspension and Sedimentation in Shallow lakes (STRESS-2d), based on an existing transport model, is discussed. In the model, mass balance equations for the water compartment and the bottom sediment are solved numerically. Up to 7 sediment fractions can be taken into account, each having a specific set of resuspension/erosion and sedimentation parameter values. Several options for modelling the changes in the bottom sediment composition are available.A simulation experiment for Lake Veluwe (The Netherlands), in which model options with and without the distinction of sediment fractions were used, showed that using sediment fractions to account for the variability in the sediment composition leads to an improvement of the model results, particularly the simulated phosphorus sediment-water exchange fluxes. For Lake Ketel (The Netherlands) two options for modelling changes in the bottom sediment composition are compared. It is shown that an option in which a thin water-sediment layer on top of the more consolidated bottom sediment is simulated provides an improvement in the simulation of the suspended solids concentration.     

Evaluating climatic and non-climatic influences on ion chemistry in natural and man-made lakes of Nebraska,USA

Conductivity and major ion chemistry data were analyzed for a suite of Nebraska (USA) natural lakes, reservoirs, sand pits, and barrow pits to evaluate the magnitude of climatic versus non-climatic influence on ionic concentration and composition. In both natural lakes and sand and barrow pits, conductivity is positively related to longitude and reflects decreasing effective moisture from east to west. Reservoirs showed no relationship between lake conductivity and location, probably because the reservoirs are very strongly influenced by groundwater and surface water inflow and have shorter residence times relative to the other lake types. At smaller spatial scales, conductivity among natural lakes is variable. Lakes that are at low elevation within a groundwater flow system were fresh, because of substantial input of fresh groundwater. In contrast, lakes at high elevation exhibited a wide range of conductivity, probably because of differences in the degree of connection to groundwater and surface to volume ratio impacts on evaporation rates. Differences also were evident among natural lakes in terms of their response to seasonal changes in precipitation. Sub-saline and saline lakes showed more seasonal variation in conductivity than freshwater lakes, and lakes in the more arid part of the state showed larger responses to precipitation change than those in areas to the east that receive higher precipitation.     

Shoreline urbanization interrupts allochthonous subsidies to a benthic consumer over a gradient of lake size

The role of resource subsidies across ecosystem boundaries has emerged as an important concept in contemporary ecology. For lake ecosystems, this has led to interest in quantifying the contribution of terrestrial allochthonous carbon to aquatic secondary production. An inverse relationship between habitat area and the role of allochthonous subsidies has been documented on marine islands and assumed for lakes, yet there have been no tests of this pattern among benthic (lake bottom) consumers. Here, we used carbon stable isotopes to trace terrestrial allochthonous and benthic autochthonous carbon use by the crayfish Pacifastacus leniusculus over a gradient of lake area, productivity and urbanization. Consistent with findings from terrestrial islands, habitat size dictated the importance of allochthonous subsidies, as P. leniusculus transitioned from using predominantly terrestrial carbon in small lakes to an increased reliance on autochthonous production in larger lakes. However, shoreline urbanization interacted with this pattern, particularly for small lakes where greater urbanization resulted in reduced use of allochthonous resources. As such, we provide, to our knowledge, the first confirmation of the predicted relationship between habitat size and importance of allochthonous subsidies to lake benthic consumers, but found that urbanization can interfere with this pattern.     

The human TTAGGG repeat factors 1 and 2 bind to a subset of interstitial telomeric sequences and satellite repeats

The study of the proteins that bind to telomeric DNA in mammals has provided a deep understanding of the mechanisms involved in chromosome-end protection. However, very little is known on the binding of these proteins to nontelomeric DNA sequences. The TTAGGG DNA repeat proteins 1 and 2 (TRF1 and TRF2) bind to mammalian telomeres as part of the shelterin complex and are essential for maintaining chromosome end stability. In this study, we combined chromatin immunoprecipitation with high-throughput sequencing to map at high sensitivity and resolution the human chromosomal sites to which TRF1 and TRF2 bind. While most of the identified sequences correspond to telomeric regions, we showed that these two proteins also bind to extratelomeric sites. The vast majority of these extratelomeric sites contains interstitial telomeric sequences (or ITSs). However, we also identified non-ITS sites, which correspond to centromeric and pericentromeric satellite DNA. Interestingly, the TRF-binding sites are often located in the proximity of genes or within introns. We propose that TRF1 and TRF2 couple the functional state of telomeres to the long-range organization of chromosomes and gene regulation networks by binding to extratelomeric sequences.     

Summer zooplankton dynamics in the limnetic and littoral zones of a humic acid lake

The limnetic and littoral zooplankton were studied during summer 1989 in Triangle Lake, a humic acid (pH 4.9) bog lake in Ohio, USA. The limnetic zooplankton showed low species richness and biomass, and dominance by the rotifers Kellicottia bostoniensis and Polyarthra vulgaris. In the littoral, species richness and biomass were markedly higher, and the crustaceans Alona guttata, Ceriodaphnia quadrangula, Chydorus sphaericus, Simocephalus serrulatus and Tropocyclops prasinus, and the rotifer Ascomorpha ecaudis were the dominants. The extreme rotifer dominance and lack of cladocerans in the limnetic zone were likely the result of Chaoborus predation. A pronounced mid-summer decline in cladoceran biomass in the littoral was likely due to predation by T. prasinus and Utricularia (bladderwort).     

Measurement and verification of rates of sediment phosphorus release for a hypereutrophic urban lake

The contribution of sediment release to the phosphorus budget of hypereutrophic Onondaga Lake was determined through laboratory measurements made on intact cores. Rates ranged from 9–21 mg P m^–2 d^–1 with a mean of 13 mg P m^–2 d^–1, values similar to those observed in other lakes of comparable trophic state. There was no statistically significant trend in rates in time (July versus September) or in space (location along the major N/S axis of the lake). Rates of sediment phosphorus release measured in the laboratory compared favorably with the observed rate of soluble reactive phosphorus accumulation in the lake's hypolimnion. The sediments are the second largest source of phosphorus for Onondaga Lake, contributing 24% of the overall phosphorus load to the system.     

Movement patterns of the White-tailed Sea Eagle (Haliaeetus albicilla): post-fledging behaviour,natal dispersal onset and the role of the natal environment

Exploratory movements and natal dispersal form essential processes during early life history stages of raptors, but identifying the factors shaping individual movement decisions is challenging. Global positioning system (GPS) telemetry thereby provides a promising technique to study movement patterns on adequate spatio-temporal scales. We analysed data of juvenile White-tailed Sea Eagles Haliaeetus albicilla (WTSE) in north-east Germany (n = 24) derived from GPS tracking to extensively analyse movements between fledging and emigration from the natal territory. Our goal was to determine the time point of fledging, characterize pre-emigration movements and the onset of natal dispersal while investigating the influence of the natal environment. WTSE fledged at an average age of 72 days and showed strong excursive behaviour during the post-fledging period regarding the number, distance and duration of excursions, yet with high individual variability. Excursive behaviour did not differ between sexes. On average, WTSE left the parental territory 93 days after fledging. The quantity of excursive behaviour delayed the timing of emigration and WTSE tended to postpone their emigration when foraging water was accessible within the boundaries of their parental territory. The overall results suggest that young WTSE assess the quality of the natal environment via pre-emigration movements and stay in their territory of origin for as long as internal and external conditions allow for it. Our study is one of the first to characterize post-fledging and natal dispersal movements of young WTSE to such an extent and applies modern techniques to understand related movements in relation to the natal environment. The results emphasize the urgent necessity for the extension of currently existing nest protection periods and guaranteeing sustainable management of potential breeding and foraging grounds for WTSE. Ultimately, the results are relevant for all large raptor species sensitive to human-related disturbance, as they support the increasing importance of regulations with spatio-temporal specifications for breeding populations of large raptors in densely human-inhabited areas with increasing alteration of land.