253 research outputs found
Beyond the Fe-P-redox connection: preferential regeneration of phosphorus from organic matter as a key control on Baltic Sea nutrient cycles
Patterns of regeneration and burial of phosphorus (P) in the Baltic Sea are strongly dependent on redox conditions. Redox varies spatially along water depth gradients and temporally in response to the seasonal cycle and multidecadal hydrographic variability. Alongside the well-documented link between iron oxyhydroxide dissolution and release of P from Baltic Sea sediments, we show that preferential remineralization of P with respect to carbon (C) and nitrogen (N) during degradation of organic matter plays a key role in determining the surplus of bioavailable P in the water column. Preferential remineralization of P takes place both in the water column and upper sediments and its rate is shown to be redox-dependent, increasing as reducing conditions become more severe at greater water-depth in the deep basins. Existing Redfield-based biogeochemical models of the Baltic may therefore underestimate the imbalance between N and P availability for primary production, and hence the vulnerability of the Baltic to sustained eutrophication via the fixation of atmospheric N. However, burial of organic P is also shown to increase during multidecadal intervals of expanded hypoxia, due to higher net burial rates of organic matter around the margins of the deep basins. Such intervals may be characterized by basin-scale acceleration of all fluxes within the P cycle, including productivity, regeneration and burial, sustained by the relative accessibility of the water column P pool beneath a shallow halocline
ΠΠΈΠ½Π°ΠΌΡΠΊΠ° ΠΌΡΡΠΎΡΠΈΡΠ½ΠΎΡ Π°ΠΊΡΠΈΠ²Π½ΠΎΡΡΡ ΠΊΠ»ΡΡΠΈΠ½ ΠΌΠ΅ΡΠΈΡΡΠ΅ΠΌΠΈ Ρ Π²ΠΎΡ ΠΌΠΎΠ΄ΡΠΈΠ½ΠΈ Π·Π°Ρ ΡΠ΄Π½ΠΎΡ (Larix occidentalis Nutt.)
Π£ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ Π΄ΠΎΡΠ»ΡΠ΄ΠΆΠ΅Π½Π½Ρ Π΄ΠΈΠ½Π°ΠΌΡΠΊΠΈ ΠΌΡΡΠΎΡΠΈΡΠ½ΠΎΡ Π°ΠΊΡΠΈΠ²Π½ΠΎΡΡΡ ΠΊΠ»ΡΡΠΈΠ½ ΠΌΠ΅ΡΠΈΡΡΠ΅ΠΌΠΈ Ρ
Π²ΠΎΡ ΠΌΠΎΠ΄ΡΠΈΠ½ΠΈ Π·Π°Ρ
ΡΠ΄Π½ΠΎΡ (Larix occidentalis Nutt.) Π²ΠΈΠ·Π½Π°ΡΠ΅Π½ΠΎ, ΡΠΎ ΠΌΠ°ΠΊΡΠΈΠΌΠ°Π»ΡΠ½Π° ΠΊΡΠ»ΡΠΊΡΡΡΡ ΠΊΠ»ΡΡΠΈΠ½, ΡΠΊΡ Π΄ΡΠ»ΡΡΡΡΡ, ΠΏΡΠΈΠΏΠ°Π΄Π°Ρ Π½Π° ΡΠ°Π½ΠΊΠΎΠ²Ρ Π³ΠΎΠ΄ΠΈΠ½ΠΈ Π΄ΠΎΠ±ΠΈ (6 β 9 Π³ΠΎΠ΄ΠΈΠ½ΠΈ). ΠΡΠ°ΡΡΠΊ Π΄ΠΈΠ½Π°ΠΌΡΠΊΠΈ ΠΌΠ°Ρ Π΄Π²ΠΎΠ²Π΅ΡΡΠΈΠ½Π½ΠΈΠΉ Ρ
Π°ΡΠ°ΠΊΡΠ΅Ρ Π· ΠΏΡΠΊΠ°ΠΌΠΈ ΠΎ 7-ΡΠΉ ΡΠ° ΠΎ 9-ΡΠΉ Π³ΠΎΠ΄ΠΈΠ½Π°Ρ
ΡΠ°Π½ΠΊΡ.Π ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠ΅ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠΉ Π΄ΠΈΠ½Π°ΠΌΠΈΠΊΠΈ ΠΌΠΈΡΠΎΡΠΈΡΠ΅ΡΠΊΠΎΠΉ Π°ΠΊΡΠΈΠ²Π½ΠΎΡΡΠΈ ΠΊΠ»Π΅ΡΠΎΠΊ ΠΌΠ΅ΡΠΈΡΡΠ΅ΠΌΡ Ρ
Π²ΠΎΠΈ Π»ΠΈΡΡΠ²Π΅Π½Π½ΠΈΡΡ Π·Π°ΠΏΠ°Π΄Π½ΠΎΠΉ (Larix occidentalis) ΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΎ, ΡΡΠΎ ΠΌΠ°ΠΊΡΠΈΠΌΠ°Π»ΡΠ½ΠΎΠ΅ ΠΊΠΎΠ»ΠΈΡΠ΅ΡΡΠ²ΠΎ Π΄Π΅Π»ΡΡΠΈΡ
ΡΡ ΠΊΠ»Π΅ΡΠΎΠΊ ΠΎΠ±Π½Π°ΡΡΠΆΠΈΠ²Π°Π΅ΡΡΡ Π² ΡΡΡΠ΅Π½Π½ΠΈΠ΅ ΡΠ°ΡΡ ΡΡΡΠΎΠΊ (6 β 9 ΡΠ°ΡΠΎΠ²). ΠΡΠ°ΡΠΈΠΊ Π΄ΠΈΠ½Π°ΠΌΠΈΠΊΠΈ ΠΈΠΌΠ΅Π΅Ρ Π΄Π²ΡΡ
Π²Π΅ΡΡΠΈΠ½Π½ΡΠΉ ΡΠΈΠΏ Ρ ΠΏΠΈΠΊΠ°ΠΌΠΈ Π² 7 ΠΈ 9 ΡΠ°ΡΠΎΠ² ΡΡΡΠ°.Results of researches for dynamics of mitotic activity of merystem cells of Western larch (Larix occidentalis Nutt.) needles show, that maximal amount of divided cells was found out at 6 β 9 o'clock in the morning. The graph of dynamics has bimodal type with the peaks at 7 and at 9 o'clock in the morning
Recovery from multiβmillennial natural coastal hypoxia in the Stockholm Archipelago, Baltic Sea, terminated by modern human activity
Enhanced nutrient input and warming have led to the development of low oxygen (hypoxia) in coastal waters globally. For many coastal areas, insight into redox conditions prior to human impact is lacking. Here, we reconstructed bottom water redox conditions and sea surface temperatures (SSTs) for the coastal Stockholm Archipelago over the past 3000 yr. Elevated sedimentary concentrations of molybdenum indicate (seasonal) hypoxia between 1000b.c.e.and 1500c.e. Biomarker-based (TEX86) SST reconstructions indicate that the recovery from hypoxia after 1500c.e.coincided with a period of significant cooling (similar to 2 degrees C), while human activity in the study area, deduced from trends in sedimentary lead and existing paleobotanical and archeological records, had significantly increased. A strong increase in sedimentary lead and zinc, related to more intense human activity in the 18(th)and 19(th)century, and the onset of modern warming precede the return of hypoxia in the Stockholm Archipelago. We conclude that climatic cooling played an important role in the recovery from natural hypoxia after 1500c.e., but that eutrophication and warming, related to modern human activity, led to the return of hypoxia in the 20(th)century. Our findings imply that ongoing global warming may exacerbate hypoxia in the coastal zone of the Baltic Sea
Anthropogenic and climatic impacts on a coastal environment in the Baltic Sea over the last 1000 years
Coastal environments have experienced large ecological changes as a result of human activities over the last 100-200 years. To understand the severity and potential consequences of such changes, paleoenvironmental records provide important contextual information. The Baltic Sea coastal zone is naturally a vulnerable system and subject to significant human-induced impacts. To put the recent environmental degradation in the Baltic coastal zone into a long-term perspective, and to assess the natural and anthropogenic drivers of environmental change, we present sedimentary records covering the last 1000 years obtained from a coastal inlet (Gasfjarden) and a nearby lake (Lake Storsjon) in Sweden. We investigate the links between a pollen-based land cover reconstruction from Lake Storsjon and paleoenvironmental variables from Gasfjarden itself, including diatom assemblages, organic carbon (C) and nitrogen (N) contents, stable C and N isotopic ratios, and biogenic silica contents. The Lake Storsjon record shows that regional land use was characterized by small-scale agricultural activity between 900 and 1400 CE, which slightly intensified between 1400 and 1800 CE. Substantial expansion of cropland was observed between 1800 and 1950 CE, before afforestation between 1950 and 2010 CE. From the Gasfjarden record, prior to 1800 CE, relatively minor changes in the diatom and geochemical proxies were found. The onset of cultural eutrophication in Gasfjarden can be traced to the 1800s and intensified land use is identified as the main driver. Anthropogenic activities in the 20th century have caused unprecedented ecosystem changes in the coastal inlet, as reflected in the diatom composition and geochemical proxies. (c) 2018 Elsevier Ltd. All rights reserved.Peer reviewe
Iron-Phosphorus Feedbacks Drive Multidecadal Oscillations in Baltic Sea Hypoxia
Hypoxia has occurred intermittently in the Baltic Sea since the establishment of brackish-water conditions at similar to 8,000 years B.P., principally as recurrent hypoxic events during the Holocene Thermal Maximum (HTM) and the Medieval Climate Anomaly (MCA). Sedimentary phosphorus release has been implicated as a key driver of these events, but previous paleoenvironmental reconstructions have lacked the sampling resolution to investigate feedbacks in past iron-phosphorus cycling on short timescales. Here we employ Laser Ablation (LA)-ICP-MS scanning of sediment cores to generate ultra-high resolution geochemical records of past hypoxic events. We show that in-phase multidecadal oscillations in hypoxia intensity and iron-phosphorus cycling occurred throughout these events. Using a box model, we demonstrate that such oscillations were likely driven by instabilities in the dynamics of iron-phosphorus cycling under preindustrial phosphorus loads, and modulated by external climate forcing. Oscillatory behavior could complicate the recovery from hypoxia during future trajectories of external loading reductions.Peer reviewe
Associations between the LEP -2548G/A Promoter and Baseline Weight and between LEPR Gln223Arg and Lys656Asn Variants and Change in BMI z Scores in Arab Children and Adolescents Treated with Risperidone
Data on baseline (antipsychotic-naΓ―ve) age, weight, and height and change in these over three subsequent follow up time points up to 313.6 days (CI 303.5-323.7), were collected from 181 risperidone-treated children and adolescents (mean age 12.58 years, SD 4.99, range 2.17-17.7) attending a pediatric neurology clinic in Saudi Arabia. Owing to differences in genotypic distributions in subsamples, results are reported from the white Arabs (N=144). Age and gender-normed BMI-standardised z scores (BMI z) were calculated (lmsgrowth program). Linear regression was performed for baseline weight and BMI z, while change in BMI z was assessed using random effects ordered logistic regression. The following SNPs were analyzed: rs7799039 in the LEP promoter, rs1805094 (previously rs8179183), rs1137100 and rs1137101 in the LEPR, and rs1414334 in HTR2C. We found a nominally significant association between rs7799309 and baseline weight, adjusting for height, age, gender and diagnosis (A/G, P=0.035, Ξ²=-3.62, compared to G/G). rs1137101 (G/G, P=0.018, OR=4.13 compared to A/A) and rs1805094 C-allele carriers (P=0.019, OR=0.51) showed nominally significant associations with change in BMI z categories. Our data support and replicate previous relevant associations for these variants including with weight gain on risperidone, whilst being the first to report such associations in those of Arab ethnicity
Effects of redox variability and early diagenesis on marine sedimentary Hg records
Volcanism is a dominant natural source of mercury (Hg) to the atmosphere, biosphere, ocean and sediments. In recent years, sedimentary Hg contents have emerged as a tool to reconstruct volcanic activity, and particularly activity of (subaerially emplaced) large igneous provinces in geological deep time. More specifically, Hg has shown potential as a useful proxy to illuminate the previously elusive impact of such large-scale volcanism on marine and terrestrial paleo-environments. While Hg is now widely applied as volcanism tracer, non-volcanic factors controlling sedimentary Hg content are generally not well constrained. Part of this uncertainty stems from our inability to directly observe a natural unperturbed βsteady-stateβ environment as a baseline, as the modern Hg cycle is heavily influenced by anthropogenic activity. Here we focus on the effects of ambient redox conditions in the water column and shallow sediments (early diagenesis), quantify their influence on the geological Hg record and thereby contribute to constraining their potential impact on the use of Hg as a proxy for deep-time volcanic activity. Constraining these factors is of critical importance for the application of Hg as such a proxy. Many periods in the geological past for which records have been generated, such as the Mesozoic Oceanic Anoxic Events, are marked by a variety of high-amplitude environmental perturbations, including widespread deoxygenation and deposition of organic-rich sediments. We estimate the impact of redox changes and early diagenesis on the geological Hg record using a suite of (sub)recentβPleistocene and Upper Cretaceous sediments representing oxic to euxinic marine conditions. Our sample set includes a transect through an oxygen minimum zone and cores that record transient shifts in oxygenation state, as well as post-depositional effects β all unrelated to volcanism, to the best of our knowledge. We find substantial alterations to the Hg record and the total organic carbon and total sulfur content, which are typically assumed to be the most common carrier phases of Hg in marine sediments. Moreover, these biases can lead to signal alteration on a par with those interpreted to result from volcanic activity. Geochemical modifications are ubiquitous and their potential magnitude implies that the factors leading to biases in the geological record warrant careful consideration before interpretation. Factors of particular concern to proxy application are (1) the disproportionate loss of organic carbon and sulfur relative to Hg during oxidation that strongly modulates normalized Hg records, (2) the evasion of Hg in anoxic and mildly euxinic sediments and (3) sharp focusing of Hg during post-depositional oxidation of organic matter. We suggest that paired analyses of additional redox-sensitive trace elements such as molybdenum, and organic-matter characteristics, particularly the type of organic matter, could provide first-order constraints on the role that redox and diagenetic changes played in shaping the Hg record as part of checking the attribution of enrichments to volcanic activity
Warming, euxinia and sea level rise during the PaleoceneβEocene Thermal Maximum on the Gulf Coastal Plain: implications for ocean oxygenation and nutrient cycling
The PaleoceneβEocene Thermal Maximum (PETM, ~ 56 Ma) was a
~ 200 kyr episode of global warming, associated with massive
injections of 13C-depleted carbon into the oceanβatmosphere system.
Although climate change during the PETM is relatively well constrained,
effects on marine oxygen concentrations and nutrient cycling remain largely
unclear. We identify the PETM in a sediment core from the US margin of the
Gulf of Mexico. Biomarker-based paleotemperature proxies (methylation of
branched tetraetherβcyclization of branched tetraether (MBTβCBT) and
TEX86) indicate that continental air and sea surface temperatures
warmed from 27β29 to ~ 35 Β°C, although
variations in the relative abundances of terrestrial and marine biomarkers
may have influenced these estimates. Vegetation changes, as recorded from
pollen assemblages, support this warming.
The PETM is bracketed by two unconformities. It overlies Paleocene silt- and
mudstones and is rich in angular (thus in situ produced; autochthonous) glauconite
grains, which indicate sedimentary condensation. A drop in the relative
abundance of terrestrial organic matter and changes in the dinoflagellate
cyst assemblages suggest that rising sea level shifted the deposition of terrigenous
material landward. This is consistent with previous findings of eustatic sea
level rise during the PETM. Regionally, the attribution of the
glauconite-rich unit to the PETM implicates the dating of a primate fossil,
argued to represent the oldest North American specimen on record.
The biomarker isorenieratene within the PETM indicates that euxinic photic
zone conditions developed, likely seasonally, along the Gulf Coastal Plain.
A global data compilation indicates that O2 concentrations dropped in
all ocean basins in response to warming, hydrological change, and carbon
cycle feedbacks. This culminated in (seasonal) anoxia along many continental
margins, analogous to modern trends. Seafloor deoxygenation and widespread
(seasonal) anoxia likely caused phosphorus regeneration from suboxic and
anoxic sediments. We argue that this fueled shelf eutrophication, as widely
recorded from microfossil studies, increasing organic carbon burial along
many continental margins as a negative feedback to carbon input and global
warming. If properly quantified with future work, the PETM offers the
opportunity to assess the biogeochemical effects of enhanced phosphorus
regeneration, as well as the timescales on which this feedback operates in
view of modern and future ocean deoxygenation
Differential Temporal and Spatial Progerin Expression during Closure of the Ductus Arteriosus in Neonates
Closure of the ductus arteriosus (DA) at birth is essential for the transition from fetal to postnatal life. Before birth the DA bypasses the uninflated lungs by shunting blood from the pulmonary trunk into the systemic circulation. The molecular mechanism underlying DA closure and degeneration has not been fully elucidated, but is associated with apoptosis and cytolytic necrosis in the inner media and intima. We detected features of histology during DA degeneration that are comparable to Hutchinson Gilford Progeria syndrome and ageing. Immunohistochemistry on human fetal and neonatal DA, and aorta showed that lamin A/C was expressed in all layers of the vessel wall. As a novel finding we report that progerin, a splicing variant of lamin A/C was expressed almost selectively in the normal closing neonatal DA, from which we hypothesized that progerin is involved in DA closure. Progerin was detected in 16.2%Β±7.2 cells of the DA. Progerin-expressing cells were predominantly located in intima and inner media where cytolytic necrosis accompanied by apoptosis will develop. Concomitantly we found loss of Ξ±-smooth muscle actin as well as reduced lamin A/C expression compared to the fetal and non-closing DA. In cells of the adjacent aorta, that remains patent, progerin expression was only sporadically detected in 2.5%Β±1.5 of the cells. Data were substantiated by the detection of mRNA of progerin in the neonatal DA but not in the aorta, by PCR and sequencing analysis. The fetal DA and the non-closing persistent DA did not present with progerin expressing cells. Our analysis revealed that the spatiotemporal expression of lamin A/C and progerin in the neonatal DA was mutually exclusive. We suggest that activation of LMNA alternative splicing is involved in vascular remodeling in the circulatory system during normal neonatal DA closure
Effects of external nutrient sources and extreme weather events on the nutrient budget of a Southern European coastal lagoon
The seasonal and annual nitrogen (N), phosphorus (P), and carbon (C) budgets of the mesotidal Ria Formosa lagoon, southern Portugal, were estimated to reveal the main inputs and outputs, the seasonal patterns, and how they may influence the ecological functioning of the system. The effects of extreme weather events such as long-lasting strong winds causing upwelling and strong rainfall were assessed. External nutrient inputs were quantified; ocean exchange was assessed in 24-h sampling campaigns, and final calculations were made using a hydrodynamic model of the lagoon. Rain and stream inputs were the main freshwater sources to the lagoon. However, wastewater treatment plant and groundwater discharges dominated nutrient input, together accounting for 98, 96, and 88 % of total C, N, and P input, respectively. Organic matter and nutrients were continuously exported to the ocean. This pattern was reversed following extreme events, such as strong winds in early summer that caused upwelling and after a period of heavy rainfall in late autumn. A principal component analysis (PCA) revealed that ammonium and organic N and C exchange were positively associated with temperature as opposed to pH and nitrate. These variables reflected mostly the benthic lagoon metabolism, whereas particulate P exchange was correlated to Chl a, indicating that this was more related to phytoplankton dynamics. The increase of stochastic events, as expected in climate change scenarios, may have strong effects on the ecological functioning of coastal lagoons, altering the C and nutrient budgets.Portuguese Science and Technology Foundation (FCT) [POCI/MAR/58427/2004, PPCDT/MAR/58427/2004]; Portuguese Science and Technology Foundation (FCT
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