The present paper is the result of a workshop sponsored by the DFG Research Center/Cluster of Excellence MARUM "The Ocean in the Earth System", the International Graduate College EUROPROX, and the ...Alfred Wegener Institute for Polar and Marine Research. The workshop brought together specialists on organic matter degradation and on proxy-based environmental reconstruction. The paper deals with the main theme of the workshop, understanding the impact of selective degradation/preservation of organic matter (OM) in marine sediments on the interpretation of the fossil record. Special attention is paid to (A) the influence of the molecular composition of OM in relation to the biological and physical depositional environment, including new methods for determining complex organic biomolecules, (B) the impact of selective OM preservation on the interpretation of proxies for marine palaeoceanographic and palaeoclimatic reconstruction, and (C) past marine productivity and selective preservation in sediments. It appears that most of the factors influencing OM preservation have been identified, but many of the mechanisms by which they operate are partly, or even fragmentarily, understood. Some factors have not even been taken carefully into consideration. This incomplete understanding of OM breakdown hampers proper assessment of the present and past carbon cycle as well as the interpretation of OM based proxies and proxies affected by OM breakdown. To arrive at better proxy-based reconstructions "deformation functions" are needed, taking into account the transport and diagenesis-related molecular and atomic modifications following proxy formation. Some emerging proxies for OM degradation may shed light on such deformation functions. The use of palynomorph concentrations and selective changes in assemblage composition as models for production and preservation of OM may correct for bias due to selective degradation. Such quantitative assessment of OM degradation may lead to more accurate reconstruction of past productivity and bottom water oxygenation. Given the cost and effort associated with programs to recover sediment cores for paleoclimatological studies, as well as with generating proxy records, it would seem wise to develop a detailed sedimentological and diagenetic context for interpretation of these records. With respect to the latter, parallel acquisition of data that inform on the fidelity of the proxy signatures and reveal potential diagenetic biases would be of clear value.
Continuous multiyear records of sediment-trap-gained microorganism fluxes are scarce. Such studies are important to identify and to understand the main forcings behind seasonal and multiannual ...evolution of microorganism flux dynamics. Here, we assess the long-term flux variations and population dynamics of diatoms, coccolithophores, calcareous and organic dinoflagellate cysts, foraminifera and pteropods in the eastern boundary upwelling ecosystem of the Canary Current. A multiannual, continuous sediment trap experiment was conducted at the mooring site CBeu (Cap Blanc eutrophic; â¼20.sup." N, 18.sup." W; trap depth is ca. 1300 m) off Mauritania (northwest Africa), between June 2003 and March 2008. Throughout the study, the reasonably consistent good match of fluxes of microorganisms and bulk mass reflects the seasonal occurrence of the main upwelling season and relaxation and the contribution of microorganisms to mass flux off Mauritania. A clear successional pattern of microorganisms, i.e., primary producers followed by secondary producers, is not observed. High fluxes of diatoms, coccolithophores, organic dinoflagellate cysts, and planktonic foraminifera occur simultaneously. Peaks of calcareous dinoflagellate cysts and pteropods mostly occurred during intervals of upwelling relaxation. A striking feature of the temporal variability of population occurrences is the persistent pattern of seasonal groups contributions. Species of planktonic foraminifera, diatoms, and organic dinoflagellate cysts typical of coastal upwelling, as well as cooler-water planktonic foraminifera and the coccolithophore Gephyrocapsa oceanica, are abundant at times of intense upwelling (late winter through early summer). Planktonic foraminifera and calcareous dinoflagellate cysts are dominant in warm pelagic surface waters, and all pteropod taxa are more abundant in fall and winter when the water column stratifies. Similarly, coccolithophores of the upper and lower photic zones, together with Emiliania huxleyi, and organic dinoflagellate cysts dominate the assemblage during phases of upwelling relaxation and deeper layer mixing.
Sea level oscillation during the Quaternary played a
major role in the geomorphology and vegetation dynamics of coastal areas in
southern Brazil, encompassing ecosystems that often have a unique
...biodiversity. Understanding the natural evolution of these areas is
essential for decision making regarding land use regulations towards sustainable
development, as well as to preserve the uniqueness of the coastal ecosystems.
The southern Brazil coastal plain is formed by marine, transitional and
continental Quaternary deposits controlled by past variations of the sea
level. These variations shaped the coastal landscape and influenced the
development of different Atlantic rainforest formations, such as mangroves
and restingas. In particular, the restinga formation corresponds to a
specific ecosystem that covers sandy soils of marine and fluvial–marine
origin formed during the Quaternary on the Brazilian coastal plain. In this
contribution, we present high-resolution palynological and stable isotope
data from a Holocene core retrieved from the coastal plain of Santa
Catarina Island (southern Brazil). We were able to identify four different
environmental zones for the last 6520 yr BP. The first zone (6520–2920 cal yr BP) is characterized by a lagoon with large marine-water influence.
Notably, the observed dinoflagellate cyst association suggests that marine
waters entering the region had their origin in the relatively warm and saline
Brazil Current waters. During the second zone (2920–1520 cal yr BP), marine-water contribution to the lagoon decreased until it became disconnected from
the sea. The third zone (1520–550 cal yr BP) was marked by the decrease of
the water level until it dried out and led to the colonization of herbaceous
vegetation over the palaeo-lagoon. The last zone (550 cal yr BP–recent) is
characterized by the consolidation of the coastal-plain Atlantic rainforest
(restinga vegetation). Our results form an example of the strong sensitivity
of southern Brazilian ecosystem change caused by relative sea level
variations. As such, this study might contribute to the debate about the potential
effects of current climate change induced by global sea level variations.
Proxies based on long-chain alkane-1, mid-chain diols (diol for short) are obtaining increasing interest to reconstruct past upper ocean temperature and productivity. Here we evaluate performance of ...the sea surface temperature proxies (long-chain diol index (LDI), diol saturation index (DSI), and diol chain length index (DCI)), productivity and upwelling intensity proxies (two diol indices DI.sub.R and DI.sub.W and the combined diol index (CDI)), and the nutrient diol index (NDI) as a proxy for phosphate and nitrate levels. This evaluation is based on comparison of the diols in sediment trap samples from the upwelling region off NW Africa collected at 1.28 km water depth with daily satellite-derived sea surface temperatures (SSTs), subsurface temperatures, productivity, the plankton composition from the trap location, monthly phosphate and nitrate concentrations, wind speed, and wind direction from the nearby Nouadhibou airport. The diol-based SST reconstructions are also compared the long-chain-alkenone-based SST reconstructions.
Anoxic sediments, as compared to oxic settings, encompass a much higher proportion of relatively labile and thus more reactive organic matter, naturally giving rise to structural changes of the ...organic molecules themselves, as well as cross-linking between them (e.g., through reactive sulfur species). Both processes transform the original biomolecules into geomolecules. For the oxic environment, these intermolecular and intramolecular transformations also operate, but cross-linking may be less important since the labile, reactive component is rapidly removed. As such, one may expect a structurally better preservation of the more refractory initial biomolecules in the oxic environment. To test this hypothesis, initially identical biomolecules need to be compared between different preservational environments. Here, we use the species-specific morphology of organic microfossils to assure a single initial biosynthetic product (the cysts of the fossil dinoflagellate species Thalassiphora pelagica) for comparison. We assess the macromolecular structures of cysts from the Eocene (∼40 Ma) sulfidic Rhine Graben and the oxic Kerguelen Plateau and compare them with each other and the structures of recent cysts. While between the sites the T. pelagica cysts are morphologically identical and show no signs of morphological modification, pyrolysis gas chromatography mass spectroscopy and micro Fourier transform infrared analyses show that their macromolecular characteristics are strongly different. Comparison with recent cysts shows that the cysts deposited in the sulfidic Rhine Graben show a strong additional contribution of long-chain aliphatic moieties and thus less diagenetic intermolecular cross-linking. The presence of organic sulfur identifies natural volcanization as one of the diagenetic processes. Furthermore, we observe a loss of bound oxygen and no trace of the original carbohydrate signature of the cyst wall biomacromolecule. The material deposited in the oxic sediments of the Kerguelen Plateau shows no traces of sulfurization. It shows a minor contribution of short carbon chains only and thus less diagenetic intermolecular cross-linking. Furthermore, a carbohydrate signature was still preserved evidencing a better molecular preservation of the initial biomacromolecule, supporting our initial hypothesis. This shows that excellent morphological preservation does not imply excellent chemical preservation. It also leads to the conclusion that the best preservation of molecular structure is not necessarily where most organic matter gets preserved, which, in turn, is important for understanding the nature and fate of sedimentary organic matter and its isotopic signature.
A valid assessment of selective aerobic degradation on organic matter (OM) and its impact on OM-based proxies is vital to produce accurate environmental reconstructions. However, most studies ...investigating these effects suffer from inherent environmental heterogeneities. In this study, we used surface samples collected along two meter-scale transects and one longer transect in the northeastern Arabian Sea to constrain initial OM heterogeneity, in order to evaluate selective aerobic degradation on temperature, productivity and alteration indices at the sediment-water interface. All of the studied alteration indices, the higher plant alkane index, alcohol preservation index, and diol oxidation index, demonstrated that they are sensitive indicators for changes in the oxygen regime. Several export production indices, a cholesterol-based stanol/stenol index and dinoflagellate lipid- and cyst-based ratios, showed significant (more than 20%) change only over the lateral oxygen gradients. Therefore, these compounds do not exclusively reflect surface water productivity, but are significantly altered after deposition. Two of the proxies, glycerol dibiphytanyl glycerol tetraether-based TEX86 sea surface temperature indices and indices based on phytol, phytane and pristane, did not show any trends related to oxygen. Nevertheless, unrealistic sea surface temperatures were obtained after application of the TEX86, TEX86L, and TEX86H proxies. The phytol-based ratios were likely affected by the sedimentary production of pristane. Our results demonstrate the selective impact of aerobic organic matter degradation on the lipid and palynomorph composition of surface sediments along a short lateral oxygen gradient and suggest that some of the investigated proxies may be useful tracers of changing redox conditions at the sediment-water interface.
Simultaneous pancreas–kidney transplantation (SPK) is an advanced treatment option for type 1 diabetes mellitus (DM) patients with microvascular disease including nephropathy. Sidestreamdarkfield ...(SDF) imaging has emerged as a noninvasive tool to visualize the human microcirculation. This study assessed the effect of SPK in diabetic nephropathy (DN) patients on microvascular alterations using SDF and correlated this with markers for endothelial dysfunction. Microvascular morphology was visualized using SDF of the oral mucosa in DN (n = 26) and SPK patients (n = 38), healthy controls (n = 20), DM1 patients (n = 15, DM ≥ 40 mL/min) and DN patients with a kidney transplant (KTx, n = 15). Furthermore, 21 DN patients were studied longitudinally up to 12 months after SPK. Circulating levels of angiopoietin‐1 (Ang‐1), angiopoietin‐2 (Ang‐2) and soluble thrombomodulin (sTM) were measured using ELISA. Capillary tortuosity in the DN (1.83 ± 0.42) and DM ≥ 40 mL/min (1.55 ± 0.1) group was increased and showed reversal after SPK (1.31 ± 0.3, p < 0.001), but not after KTx (1.64 ± 0.1). sTM levels were increased in DN patients and reduced in SPK and KTx recipients (p < 0.05), while the Ang‐2/Ang‐1 ratio was normalized after SPK and not after KTx alone (from 0.16 ± 0.04 to 0.08 ± 0.02, p < 0.05). Interestingly, in the longitudinal study, reversal of capillary tortuosity and decrease in Ang‐2/Ang‐1 ratio and sTM was observed within 12 months after SPK. SPK is effective in reversing the systemic microvascular structural abnormalities in DN patients in the first year after transplantation.
Labial microvasular tortuosity, a surgate measure of generalized microvascular disease, is reversed after simultaneous pancreas—kidney transplantation.
Eryhropoiesis‐stimulating agents have demonstrated tissue‐protective effects in experimental models of ischemia‐reperfusion injury. PROTECT was a 12‐month, randomized, double‐blind, ...placebo‐controlled, single center study with high‐dose recombinant human erythropoietin‐β (Epoetin) in 92 donation after cardiac death (DCD) kidney transplant recipients. Patients were randomized to receive an intravenous bolus of Epoetin (3.3 × 104 international unit (IU); n = 45) or placebo (saline 0.9% solution; n = 47) on 3 consecutive days, starting 3–4 h before the transplantation and 24 h and 48 h after reperfusion. The immunosuppressive regimen included an anti‐CD25 antibody, steroids, mycophenolate mofetil and delayed introduction of cyclosporine. Primary end point was a composite of the incidence of primary nonfunction and delayed graft function, either defined by spontaneous functional recovery or need for dialysis in the first week. Secondary objectives included duration of delayed function, renal function and proteinuria up to 1 year and thrombotic adverse events. Results showed no differences in the incidence or duration of delayed graft function and/or primary nonfunction (Epoetin 77.8 vs. placebo 78.7%, p = 1.00). Epoetin treatment significantly increased the risk of thrombotic events at 1 month and 1 year (Epoetin 24.4% vs. placebo 6.4%, p = 0.02).
This randomized controlled trial with high‐dose epoetin in donation after cardiac death kidney transplant recipients shows no benefit on the incidence and duration of delayed graft function and/or primary nonfunction.
A biometrical analysis of the dinoflagellate cyst
Lingulodinium machaerophorum Deflandre, G., Cookson, I.C., 1955. Fossil microplankton from Australia late Mesozoic and Tertiary sediments. Australian ...journal of Marine and Freshwater Research 6: 242–313. Wall, 1967 in 144 globally distributed surface sediment samples revealed that the average process length is related to summer salinity and temperature at a water depth of 30 m by the equation (salinity/temperature) = (0.078⁎average process length
+
0.534) with
R
2
=
0.69. This relationship can be used to reconstruct palaeosalinities, albeit with caution. The particular ecological window can be associated with known distributions of the corresponding motile stage
Lingulodinium polyedrum (Stein) Dodge, 1989. Confocal laser microscopy showed that the average process length is positively related to the average distance between process bases (
R
2
=
0.78), and negatively related to the number of processes (
R
2
=
0.65). These results document the existence of two end members in cyst formation: one with many short, densely distributed processes and one with a few, long, widely spaced processes, which can be respectively related to low and high salinity/temperature ratios. Obstruction during formation of the cysts causes anomalous distributions of the processes. From a biological perspective, processes function to facilitate sinking of the cysts through clustering.
Ischemia/reperfusion injury (IRI) is a central phenomenon in kidney transplantation and AKI. Integrity of the renal peritubular capillary network is an important limiting factor in the recovery from ...IRI. MicroRNA-126 (miR-126) facilitates vascular regeneration by functioning as an angiomiR and by modulating mobilization of hematopoietic stem/progenitor cells. We hypothesized that overexpression of miR-126 in the hematopoietic compartment could protect the kidney against IRI via preservation of microvascular integrity. Here, we demonstrate that hematopoietic overexpression of miR-126 increases neovascularization of subcutaneously implanted Matrigel plugs in mice. After renal IRI, mice overexpressing miR-126 displayed a marked decrease in urea levels, weight loss, fibrotic markers, and injury markers (such as kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin). This protective effect was associated with a higher density of the peritubular capillary network in the corticomedullary junction and increased numbers of bone marrow-derived endothelial cells. Hematopoietic overexpression of miR-126 increased the number of circulating Lin(-)/Sca-1(+)/cKit(+) hematopoietic stem and progenitor cells. Additionally, miR-126 overexpression attenuated expression of the chemokine receptor CXCR4 on Lin(-)/Sca-1(+)/cKit(+) cells in the bone marrow and increased renal expression of its ligand stromal cell-derived factor 1, thus favoring mobilization of Lin(-)/Sca-1(+)/cKit(+) cells toward the kidney. Taken together, these results suggest overexpression of miR-126 in the hematopoietic compartment is associated with stromal cell-derived factor 1/CXCR4-dependent vasculogenic progenitor cell mobilization and promotes vascular integrity and supports recovery of the kidney after IRI.
PDF
