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Author: Joseph D. Ortiz Publisher: ISBN: Category : Foraminifera Languages : en Pages : 438
Book Description
MOCNESS plankton tows, sediment traps and sedimentary material are used to determine the linkage between bio-physical forcing and foraminiferal response over a range of time scales from the event scale to the glacial interglacial cycle. The annually averaged planktic foraminiferal fauna of the modem California Current is a diverse community composed of individuals from subarctic, transitional, and subtropical foraminiferal assemblages. This community is more diverse, but less abundant in total standing stock and shell flux than the subarctic community of the Gulf of Alaska. The use of plankton tow and isotopic data allow us to partition the foraminiferal community into shallow dwelling euphotic zone species and deep dwelling sub-thermocline species. On both the event and seasonal time scales, heterotrophic species were most abundant in cold, biomass rich coastal waters. In contrast, species which harbored endosymbionts were more abundant in oligotrophic waters with higher ambient light levels. During the Last Glacial Maximum (LGM), the diverse modern fauna was replaced with a low diversity, high flux, heterotrophic community similar to that of the modern Gulf of Alaska. Modern analog temperature estimates suggest the California Current was roughly 3°C cooler during the LGM than today. Coupled with oxygen isotopic results from G. bulloides, the surface thermal structure implies an equatorward flowing glacial California Current at these sites. The Polar Front thus remained north of these locations during the LGM. Comparison of glacial G. bulloides carbon isotopes and shell accumulation rates with organic carbon flux estimates implies the glacial California Current was (1) higher in nutrient content, (2) lower in plankton biomass, and (3) lower in export carbon flux than its modem counterpart. This description suggests that during the LGM the plankton community of the California Current was very similar to the modern plankton community of the Gulf of Alaska.
Author: Joseph D. Ortiz Publisher: ISBN: Category : Foraminifera Languages : en Pages : 438
Book Description
MOCNESS plankton tows, sediment traps and sedimentary material are used to determine the linkage between bio-physical forcing and foraminiferal response over a range of time scales from the event scale to the glacial interglacial cycle. The annually averaged planktic foraminiferal fauna of the modem California Current is a diverse community composed of individuals from subarctic, transitional, and subtropical foraminiferal assemblages. This community is more diverse, but less abundant in total standing stock and shell flux than the subarctic community of the Gulf of Alaska. The use of plankton tow and isotopic data allow us to partition the foraminiferal community into shallow dwelling euphotic zone species and deep dwelling sub-thermocline species. On both the event and seasonal time scales, heterotrophic species were most abundant in cold, biomass rich coastal waters. In contrast, species which harbored endosymbionts were more abundant in oligotrophic waters with higher ambient light levels. During the Last Glacial Maximum (LGM), the diverse modern fauna was replaced with a low diversity, high flux, heterotrophic community similar to that of the modern Gulf of Alaska. Modern analog temperature estimates suggest the California Current was roughly 3°C cooler during the LGM than today. Coupled with oxygen isotopic results from G. bulloides, the surface thermal structure implies an equatorward flowing glacial California Current at these sites. The Polar Front thus remained north of these locations during the LGM. Comparison of glacial G. bulloides carbon isotopes and shell accumulation rates with organic carbon flux estimates implies the glacial California Current was (1) higher in nutrient content, (2) lower in plankton biomass, and (3) lower in export carbon flux than its modem counterpart. This description suggests that during the LGM the plankton community of the California Current was very similar to the modern plankton community of the Gulf of Alaska.
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: Joseph D. Ortiz
Author: Joseph D. Ortiz
Author: David Buursma Field
Author: Gerard Johannes Augustinus Brummer
Author: Ronald Roy Schmidt
Author: John Stratlii Bradshaw
Author: 
Author: Stephen J. Culver
Author: Joseph J. Graham
Author: Catherine Van Wie Davis
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