Global assessment of species-specific habitats of planktonic foraminifera : an ecosystem modeling approach

Over the last few million years, the Eartha s climate system has changed continuously on decadal to millennial time scales. Past climate conditions have been reconstructed based on fossil evidence of marine microorganisms, such as planktonic foraminifera. Planktonic foraminifera exhibit species-specific seasonal production patterns and different preferred depth habitats. To precisely reconstruct past climate conditions these spatial and temporal variations within the individual species distribution have to be considered. In this regard, an ecosystem modeling approach can help to gain a better knowledge about species-specific habitat shifts under climate change. In this study, a planktonic foraminifera model is used to predict monthly concentrations of the colder-water species Neogloboquadrina pachyderma, Neogloboquadrina incompta, and Globigerina bulloides, and of the warm-water species Globigerinoides ruber (white) and Trilobatus sacculifer throughout the world ocean. In particular, the seasonal distribution of the polar species N. pachyderma in the surface mixed layer of the North Atlantic Ocean during the last glacial period was investigated. In response to changes in the sea ice cover and food supply, the peak timing of N. pachyderma is shifted from the last glacial period to modern conditions by several months. However, for a more realistic simulation of species-specific habitats, the planktonic foraminifera model PLAFOM was adapted to allow for resolving the vertical dimension. This new model version estimates the foraminiferal biomass of the colder- and warm-water species as a function of temperature, nutrition, competition, and in particular light. To predict the species concentration over different water depths the model code of the improved version of the planktonic foraminifera model was added to the code trunk of the ocean component of a global earth system model. This model produces seasonally and vertically coherent distribution patterns that are in good agreement with available observations without any explicit parameterization in the vertical dimension regarding their ontogeny. The colder-water species exhibit a seasonal cycle in their depth habitat in the polar and subpolar regions: during the warm season they occur at mid-depth, while during the cold season they ascend through the water column and are found in the near-surface layer. The warm-water species show a less variable depth habitat and occur almost consistently close to the sea surface throughout the year in the tropics and subtropics. This emergence of species-specific depth habitats in the model that are consistent with available observations indicates that the population dynamics of planktonic foraminifera species may be driven by the same factors. Here the impact of global warming on the speciesa spatial and seasonal distribution patterns has been investigated. In response to changes in the temperature and food supply, the habitat range as well as the peak timing of both the colder-water and warm-water species will likely shift. In general, planktonic foraminifera do not respond uniformly to climate change due to their different ecological preferences. Their habitat is altered in time and space, and depending on the ambient conditions either warm-water or colder-water species benefit strongly from these changes. Knowing how individual planktonic foraminifera species adapt to changing environmental conditions can help to obtain more precise estimates of the geological past and can provide implications for future climate change

Umweltprobleme des Borna-Leipziger Braunkohlereviers in der ersten Hälfte des 20. Jahrhunderts

Der Leipziger Südraum gehörte bis 1990 zu den europäischen Gebieten, die die größte Umweltbelastung aufwiesen. Die eingeleiteten Strukturveränderungen seit 1990 verringerten den Ausstoß beträchtlich. Das Industriegebiet bleibt dennoch mit Altlasten umfangreichen Ausmaßes behaftet. Der vorliegende Beitrag beschreibt die Hauptphasen der Entwicklung dieser Umweltzerstörung in der ersten Hälfte des 20. Jahrhunderts. Hauptsächlich die rücksichtslose Ausnutzung der Braunkohle während des Ersten Weltkriegs als Energieträger und Rohstoff für die Chemieindustrie ist für die heute schwierige Situation verantwortlich. Der Autor zeigt, wie die Entwicklung einer Industrieregion eine Eigendynamik entwickelt, die von Grenzen und den jeweiligen politischen Systemen unabhängig ist. (ICE)'Not only up to 1990 the Southern area of Leipzip has been one of the regions of Europe with the most devasting environmental pollution, even today this area is charged with an enormous amount of disused dump. This article checks the main stages of development of this environmental destruction at the field of brown coal in the Borna-Leipzig area during the first half of this century. Lack of raw materials during the First World-War led to an extensive mining of brown coal. In consequence villages were devastate , forests and land available for agriculture had to siappear, the water of rivers and other stretches of water were polluted, the air was charged with dust and toxic material; there was a pronounced leck of fresh water. The environmental pollution in this area grew with notable continuity, regardless of frontiers and political systems.' (author's abstract

Modeling the fate of methane hydrates under global warming

Large amounts of methane hydrate locked up within marine sediments are vulnerable to climate change. Changes in bottom water temperatures may lead to their destabilization and the release of methane into the water column or even the atmosphere. In a multimodel approach, the possible impact of destabilizing methane hydrates onto global climate within the next century is evaluated. The focus is set on changing bottom water temperatures to infer the response of the global methane hydrate inventory to future climate change. Present and future bottom water temperatures are evaluated by the combined use of hindcast high-resolution ocean circulation simulations and climate modeling for the next century. The changing global hydrate inventory is computed using the parameterized transfer function recently proposed by Wallmann et al. (2012). We find that the present-day world's total marine methane hydrate inventory is estimated to be 1146Gt of methane carbon. Within the next 100years this global inventory may be reduced by ∼0.03% (releasing ∼473Mt methane from the seafloor). Compared to the present-day annual emissions of anthropogenic methane, the amount of methane released from melting hydrates by 2100 is small and will not have a major impact on the global climate. On a regional scale, ocean bottom warming over the next 100years will result in a relatively large decrease in the methane hydrate deposits, with the Arctic and Blake Ridge region, offshore South Carolina, being most affected

Past and future decline of tropical pelagic biodiversity

Author's accepted version (postprint).This is an Accepted Manuscript of an article published by the National Academy of Sciences in PNAS on 26/05/2020.Available online: https://www.pnas.org/content/pnas/117/23/12891.full.pdfA major research question concerning global pelagic biodiversity remains unanswered: when did the apparent tropical biodiversity depression (i.e., bimodality of latitudinal diversity gradient [LDG]) begin? The bimodal LDG may be a consequence of recent ocean warming or of deep-time evolutionary speciation and extinction processes. Using rich fossil datasets of planktonic foraminifers, we show here that a unimodal (or only weakly bimodal) diversity gradient, with a plateau in the tropics, occurred during the last ice age and has since then developed into a bimodal gradient through species distribution shifts driven by postglacial ocean warming. The bimodal LDG likely emerged before the Anthropocene and industrialization, and perhaps ∼15,000 y ago, indicating a strong environmental control of tropical diversity even before the start of anthropogenic warming. However, our model projections suggest that future anthropogenic warming further diminishes tropical pelagic diversity to a level not seen in millions of years.acceptedVersio

Trace Metals and Their Isotopes in the Tropical Atlantic Ocean - Cruise No. M81/1, February 04 – March 08, 2010, Las Palmas (Canary Islands, Spain) – Port of Spain (Trinidad & Tobago)

Summary Meteor Cruise M81/1 was dedicated to the investigation of the distribution of dissolved and particulate trace metals and their isotopic compositions (TEIs) in the full water column of the tropical Atlantic Ocean and their driving factors including main external inputs and internal cycling and ocean circulation. The research program is embedded in the international GEOTRACES program (e.g. Henderson et al., 2007), which this cruise was an official part of and thus corresponds to GEOTRACES cruise GA11. This cruise was completely dedicated to the trace metal clean and contamination-free sampling of waters and particulates for subsequent analyses of the TEIs in the home laboratories of the national and international participants. Besides a standard rosette for the less contaminant prone metals, trace metal clean sampling was realized by using a dedicated and coated trace metal clean rosette equipped with Teflon-coated GO-FLO bottles operated via a polyester coated cable from a mobile winch that was thankfully made available by the U.S. partners of the GEOTRACES program for this cruise. The particulate samples were also collected under trace metal clean conditions using established in-situ pump systems. The cruise track led the cruise southward from the Canary Islands to 11°S and then continued northwestward along the northern margin of South America until it reached Port of Spain, Trinidad & Tobago. The track crossed areas of major external inputs including exchange with the volcanic Canary Islands, the Saharan dust plume, as well as the plume of the Amazon outflow. In terms of internal cycling the equatorial high biological productivity band, as well as increased productivity associated with the Amazon Plume were covered. All major water masses contributing the Atlantic Meridional Overturning Circulation, as well as the distinct narrow equatorial surface and subsurface east-west current bands were sampled. A total of 17 deep stations were sampled for the different dissolved TEIs, which were in most cases accompanied by particulate sampling. In addition, surface waters were continuously sampled under trace metal clean conditions using a towed fish

Epigenetic Control of the foxp3 Locus in Regulatory T Cells

Compelling evidence suggests that the transcription factor Foxp3 acts as a master switch governing the development and function of CD4(+) regulatory T cells (Tregs). However, whether transcriptional control of Foxp3 expression itself contributes to the development of a stable Treg lineage has thus far not been investigated. We here identified an evolutionarily conserved region within the foxp3 locus upstream of exon-1 possessing transcriptional activity. Bisulphite sequencing and chromatin immunoprecipitation revealed complete demethylation of CpG motifs as well as histone modifications within the conserved region in ex vivo isolated Foxp3(+)CD25(+)CD4(+) Tregs, but not in naïve CD25(−)CD4(+) T cells. Partial DNA demethylation is already found within developing Foxp3(+) thymocytes; however, Tregs induced by TGF-β in vitro display only incomplete demethylation despite high Foxp3 expression. In contrast to natural Tregs, these TGF-β–induced Foxp3(+) Tregs lose both Foxp3 expression and suppressive activity upon restimulation in the absence of TGF-β. Our data suggest that expression of Foxp3 must be stabilized by epigenetic modification to allow the development of a permanent suppressor cell lineage, a finding of significant importance for therapeutic applications involving induction or transfer of Tregs and for the understanding of long-term cell lineage decisions

Globale Abschätzung artenspezifischer Lebensräume planktischer Foraminiferen : ein Ökosystemmodellierungsansatz

Over the last few million years, the Eartha s climate system has changed continuously on decadal to millennial time scales. Past climate conditions have been reconstructed based on fossil evidence of marine microorganisms, such as planktonic foraminifera. Planktonic foraminifera exhibit species-specific seasonal production patterns and different preferred depth habitats. To precisely reconstruct past climate conditions these spatial and temporal variations within the individual species distribution have to be considered. In this regard, an ecosystem modeling approach can help to gain a better knowledge about species-specific habitat shifts under climate change. In this study, a planktonic foraminifera model is used to predict monthly concentrations of the colder-water species Neogloboquadrina pachyderma, Neogloboquadrina incompta, and Globigerina bulloides, and of the warm-water species Globigerinoides ruber (white) and Trilobatus sacculifer throughout the world ocean. In particular, the seasonal distribution of the polar species N. pachyderma in the surface mixed layer of the North Atlantic Ocean during the last glacial period was investigated. In response to changes in the sea ice cover and food supply, the peak timing of N. pachyderma is shifted from the last glacial period to modern conditions by several months. However, for a more realistic simulation of species-specific habitats, the planktonic foraminifera model PLAFOM was adapted to allow for resolving the vertical dimension. This new model version estimates the foraminiferal biomass of the colder- and warm-water species as a function of temperature, nutrition, competition, and in particular light. To predict the species concentration over different water depths the model code of the improved version of the planktonic foraminifera model was added to the code trunk of the ocean component of a global earth system model. This model produces seasonally and vertically coherent distribution patterns that are in good agreement with available observations without any explicit parameterization in the vertical dimension regarding their ontogeny. The colder-water species exhibit a seasonal cycle in their depth habitat in the polar and subpolar regions: during the warm season they occur at mid-depth, while during the cold season they ascend through the water column and are found in the near-surface layer. The warm-water species show a less variable depth habitat and occur almost consistently close to the sea surface throughout the year in the tropics and subtropics. This emergence of species-specific depth habitats in the model that are consistent with available observations indicates that the population dynamics of planktonic foraminifera species may be driven by the same factors. Here the impact of global warming on the speciesa spatial and seasonal distribution patterns has been investigated. In response to changes in the temperature and food supply, the habitat range as well as the peak timing of both the colder-water and warm-water species will likely shift. In general, planktonic foraminifera do not respond uniformly to climate change due to their different ecological preferences. Their habitat is altered in time and space, and depending on the ambient conditions either warm-water or colder-water species benefit strongly from these changes. Knowing how individual planktonic foraminifera species adapt to changing environmental conditions can help to obtain more precise estimates of the geological past and can provide implications for future climate change

Global quantification of methane hydrates

Large amounts of methane hydrate are thought to be stored in marine sediments. Natural methane hydrate deposits have been found along the world's continental margins as the prevailing low ocean temperatures and high pressures guarantee their stability. Climate change could induce a destabilization of marine hydrates due to changes in bottom water temperatures and/or sea level. Once the hydrates are destabilized they could release methane into the water column and potentially into the atmosphere, enhancing global warming. In this study a comprehensive model analysis is performed to evaluate the impact of destabilizing methane hydrates onto global climate within the next century. Additionally, the focus is set on changing bottom water temperatures to infer the response of the global methane hydrate inventory to future climate change. This study provides a new estimate of the global methane hydrate inventory based on a transfer function, which was recently developed by Wallmann et al. (2012). Global bottom water temperatures and their future evolution are analyzed in detail, as over the past few decades bottom water temperatures changed considerably along the continental margins, owing to natural, but also to anthropogenic climate variability. The current variability of the global bottom water temperatures is investigated in a hindcast simulation of the global ocean-sea ice model configuration ORCA025. The future temperature trend is analyzed by using an ensemble of 22 100-year-long global warming experiments of the Kiel Climate Model (KCM). The resulting warming trend is found to be mostly confined to shallow and mid-depth regions. Especially the warming at mid-depth could destabilize methane hydrates. As a consequence, methane could be released into the ocean and could potentially reach the atmosphere, leading to a strong positive carbon climate feedback. Based on the temperature analyses the changes in the global abundance and distribution of methane hydrates under future climate conditions are inferred. By applying the transfer function of Wallmann et al. (2012) the present-day world's total methane hydrate inventory is estimated to be 1146 Gt of methane carbon. In a worst-case scenario, where steady state is reached by 2100, the global inventory could be reduced by ~0.6%, resulting in an additional average annual methane flux of ~89 Mt from the seafloor. Based on the results of this study, the amount of methane released from melting hydrates by 2100 will not have a major impact on the global climate

Temperaturentwicklungen in der Beaufort See: Implikationen für Methanemissionen aus dem Meeresboden

The effects of global warming on the stability of gas hydrates are investigated in the shelf regions of the Beaufort Sea. The mean conditions as well as the natural occuring variability of the bottom water temperatures in terms of the anthropogenic influences are examined. The analysis of the structure and variability of the bottom water temperature over the period from 1958 to 2004 was performed with the global ocean/sea-ice configuration ORCA05. The future climate trend was simulated with the Kiel Climate Model. An ensemble of eight 100-year long climate scenarios was available. The gas hydrate stability analyses are based on the calculations of the dissociation pressure. The gas hydrate stability mainly depends on pressure and temperature conditions in the water column. Therefore the temperature changes in the shelf regions of the Beaufort Sea had come into focus. The analysis of the bottom water temperatures resulted in a warming of the shelf of about 1.5 ◦C within the next 100 years. This can be ascribed to the influence of the Atlantic inflow. Due to the increasing warming in the boundary layers of the Beaufort Sea the possibly stored methane hydrate could be destabilised. As a consequence, methane gas could be released into the water column. This could lead to an interaction with the atmosphere and hence accelerate the natural greenhouse effect. A significant impact of the Atlantic inflow on the gas hydrate stability zone was verified. Especially in the shelf regions a phase shift from hydrate to gas can occur resulting in a possible gas release into the atmosphere. This would enhance global climate change