Author: Catherine Van Wie Davis Publisher: ISBN: 9781369311105 Category : Languages : en Pages :
Book Description
Foraminifera, marine protists, are ubiquitous throughout the worlds oceans, contributing to pelagic and benthic ecosystems, global carbon cycling and in producing an extensive fossil record ideal for paleoclimate reconstruction as well as for exploring macroevolutionary questions. As such, the morphology, species assemblages and geochemistry of fossil foraminifera each contain extensive information about their growth and depositional environment. Here, the responses of foraminifera along the California Margin are examined across a range of naturally occurring hydrographic variables and at differing time scales. Chapter 1 explores the potential for size and weight change in fossil calcareous benthic foraminifera across a temporal change in oxygen and inorganic carbon. Previous work has demonstrated that changes in both oxygen and pH can impact foraminiferal calcification. Four species of benthic foraminifera from a sediment core in Santa Barbara Basin were weighed and measured against a backdrop of well-resolved, decadal scale Oxygen Minimum Zone and corresponding Carbonate Maximum Zone fluctuations at the site over the last 15,000 years. The resulting record shows long-term species-specific fluctuations in size and size-normalized weight. Chapter 2 focuses on the species level planktic foraminiferal response to seasonal upwelling on the Central California shelf. The region off of Bodega Head, California experiences wind-driven coastal upwelling which seasonally brings deeper, colder, nutrient rich, oxygen poor, and CO2 enriched waters to the near surface. A distinct difference is observed in the relative abundances of species found during and outside of upwelling season, with Globigerina bulloides associated with non-upwelled waters, Turborotalia quinqueloba and Neogloboquadrina pachyderma found primarily during upwelling season, and Neogloboquadrina incompa present year-round but more relatively abundant outside of upwelling season. Chapter 3 builds from previous observations of decreased foraminifera calcification in response to low pH or [CO32−] to further probe the physiologic response of foraminifera to these conditions. Foraminifer G. bulloides was subjected in the laboratory to an ecologically relevant range of environmental pH treatments (7.5-8.3) and evaluated on both respirometry and calcification metrics. Results indicated a decrease in calcification with decreasing pH and reduced shell-repair at low pH, but a non-linear respiratory response, with metabolic depression at low pH, and the highest respiration rates observed at pH ~8.1. Chapter 4 presents species-specific Mg/Ca:temperature relationships for the cold-water planktic foraminifera species N. pachyderma and N. incompta. No significant pH effect on Mg/Ca is demonstrated at 12 °C in N. incompta. However, N. incompta did form a low Mg/Ca “crust” in culture at the same temperature as ontogenetic (higher Mg/Ca) calcite. This chapter therefore proposes a Mg/Ca:temperature relationship exclusive to ontogenetic calcite and presents a corroboration of this approach in fossil N. pachyderma and N. incompta. Through these chapters, the foraminiferal response in terms of morphology, species compositions, physiology and geochemistry is documented with respect the the range of conditions relevant to the modern California Margin. The results of each of these approaches inform the paleoceaongraphic interpretation of this and analogous regions, highlighting the importance of approaching paleoceaongraphic interpretations with species and regional specificity to the greatest extent possible. This necessitates relating the morphology and geochemistry of foraminiferal species to the environment in which they are endemic, and taking into account the ecology, physiology and life history or foraminifera populations when interpreting paleoclimate proxies.
Author: Inda Brinkmann Publisher: ISBN: 9789187847677 Category : Languages : en Pages : 0
Book Description
Climate changes, tightly linked to anthropogenic activities, are significantly altering environments and ecosystems globally, such as by increasing marine and coastal deoxygenation or occurrences of extreme weather events. The significance of paleoenvironmental and -climate reconstructions, as well as monitoring of current conditions, for unravelling baseline natural variation, today's changes and potential future impacts, has been recognised by the Intergovernmental Panel on Climate Change (IPCC) reports. However, to access past records of physical and chemical environmental variables, and comprehensively assess ecosystem reactions, reliable and sensitive proxies are critical. This thesis' focus lies on benthic foraminifera--unicellular protists with mineralised or organic test, abundantly inhabiting ocean and coastal sediments--and their calibration as indicator for a variety of environmental conditions in field-sampling approaches. The research projects follow two general strategic tracks: (I) a biogeochemical assessment of trace-elemental ratios in foraminiferal calcium-carbonate tests using high-resolution, micro-analytical techniques; (II) a molecular approach investigating foraminiferal environmental DNA derived from coastal sediments. Papers I and II concern the calibration of the benthic foraminiferal Mn/Ca proxy for marine oxygenation conditions in modern field studies. Trace-element concentrations and distributions were measured by plasma-, laser- and synchrotron-based analyses in a high-resolution, individual-foraminifera approach, and interpreted in the context of ambient physical and chemical conditions of the water column, pore-waters and sediments (including oxygen and manganese concentrations). Investigating two coastal systems with almost permanently severely oxygen-deficient bottom-waters (Santa Barbara Basin, Paper I), and undergoing a seasonal oxygenation cycle across the low- to well-oxygenated range (Gullmar Fjord, Paper II), respectively, demonstrated the utility of the Mn/Ca proxy for indicating low-oxygen conditions specifically. Continued calibration efforts under consideration of ambient oxygenation and redox regimes may open further possibilities of quantitative oxygen reconstructions. Paper III explores the use of coastal, benthic Ba/Ca records as indicator of riverine runoff and drought on land across the years 2018 and 2019, characterised by severe heat and drought, and warm and wet conditions, respectively. Benthic Ba/Ca correlated significantly with the hydroclimate conditions, as inferred from extensive meteorological and hydrological data sets of the region, highlighting qualitative proxy potential for paleo-drought reconstructions. Based on ambient sediment and pore-water geochemistry, we discuss mediation of water-column transport and pore-water Ba cycling by Fe and Mn oxides. All three investigations of these geochemical proxies (Paper I-III) highlighted the significance of biological controls on foraminiferal TE/Ca, which are species-specific and, thus, should be a deciding factor in choosing proxy candidate species. In particular the influences of micro-habitat distribution and utilised metabolic pathways by foraminifera are discussed in detail. In Paper IV foraminiferal biodiversity and assemblage responses to natural and anthropogenic environmental trends in a fjord system (Swedish west coast) are documented in a metabarcoding approach. Environmental DNA successfully tracked biodiversity and community composition changes associated with contrasting ecosystems but showed damped sensitivity to environmental variability on sub-annual time-scales. Overlaps and discrepancies between molecular and traditional, observation-based assessment techniques, as well as future trajectories to resolve uncertainties are discussed. Overall, this thesis solidifies and expands the currently available proxy toolbox for reconstructions of both coastal low-oxygen, as well as terrestrial hydroclimate conditions. The findings contribute towards filling current knowledge gaps pertaining to biotic impacts on foraminifera-derived biogeochemical signals and methodological uncertainties in metabarcoding approaches and highlight the significance of implementing molecular techniques in conventional foraminiferal assemblage studies.
Author: Roberta K. Smith Publisher: ISBN: Category : Science Languages : en Pages : 42
Book Description
While several papers exist on the small scale spatial distribution of living foraminifera, almost no work exists on the small scale spatial distribution of fossils. The present study took 24 (5 ml) replicates 10 cm apart along one bed of the Monterey Formation in California.The mean density for all replicates is 6084.96 with a standard deviation of 8776.95. Both inspection and a cluster analysis of the data indicate replicates 20-24 have a much higher density and different rank order of abundance than replicates 1-19. The mean density for the total of all species in replicates 1-19 is 2387.47 with a standard deviation of 1175.58. For replicates 20-24 the mean density is 20135.40 with a standard deviation of 11181.40. The spatial variability is so great that four replicates (more than commonly taken) would only allow us to be 95% confident that we are within 50% of the true mean. Because age determination is based on presence of particular taxa rather than on densities, stratigraphic assignment would still be possible.The three species dominating the 1-19 group make up from 86% to 99% of the fauna. The three species dominating the 20-24 group make up from 77% to 85% of the fauna. Two of these are also dominant in the 1-19 group, but the most dominant species in the 20-24 group constitutes only
Author: William E. N. Austin Publisher: Geological Society of London ISBN: 9781862392571 Category : Medical Languages : en Pages : 206
Book Description
Most of our information about the evolution of Earth's ocean-climate system comes from the analysis of sediments laid down in the past. For example, the microfossil assemblage reflects the temperature, salinity and nutrient abundance of the water in which the organisms lived, while the chemical and isotopic composition of biogenic carbonates may be used to reconstruct past variations in the operation of the carbon cycle, as well as changes in ocean circulation. Nevertheless, understanding the link between these sediment variables (or 'proxies') and environmental conditions is not straightforward. This volume adopts a novel approach by bringing together palaeontologists, geochemists and palaeoceanographers, who contribute evidence that is required to better constrain these proxies. Topics include: (i) processes of biomineralization, and their effect on the chemical and isotopic composition of different organisms; (ii) proxy validation, including field, laboratory and theoretical studies; (iii) the links between modern and fossil organisms
Author: Alexander Altenbach Publisher: Springer Science & Business Media ISBN: 9400718969 Category : Science Languages : en Pages : 642
Book Description
ANOXIA defines the lack of free molecular oxygen in an environment. In the presence of organic matter, anaerobic prokaryotes produce compounds such as free radicals, hydrogen sulfide, or methane that are typically toxic to aerobes. The concomitance of suppressed respiration and presence of toxic substances suggests these habitats are inhospitable to Eukaryota. Ecologists sometimes term such environments 'Death Zones'. This book presents, however, a collection of remarkable adaptations to anoxia, observed in Eukaryotes such as protists, animals, plants and fungi. Case studies provide evidence for controlled beneficial use of anoxia by, for example, modification of free radicals, use of alternative electron donors for anaerobic metabolic pathways, and employment of anaerobic symbionts. The complex, interwoven existence of oxic and anoxic conditions in space and time is also highlighted as is the idea that eukaryotic inhabitation of anoxic habitats was established early in Earth history.
Author: Catherine Van Wie Davis
Author: Inda Brinkmann
Author: Gregory Howard Blake
Author: 
Author: David Buursma Field
Author: Roberta K. Smith
Author: William E. N. Austin
Author: Maryke den Dulk
Author: Gabriel J. Valov (Graduate student)
Author: Alexander Altenbach