Changes in marine production play a key role in determining the trophic structure of the northeastern Pacific Ocean. This is a region of great environmental fluctuations due to modern, historical, and paleo-environmental variability recorded throughout the Holocene. These fluctuations are recorded in the bone collagen of the marine mammals that reside in these waters. Marine mammal remains from four previously excavated archaeological deposits on Unalaska Island, Alaska are used as a proxy for marine production changes throughout the Holocene (4,500 BP to 350 BP). Historic and modern samples from museum collections, subsistence harvests, and previously published data provide a distinct contrast to prehistoric marine mammals. Stable carbon and nitrogen isotope ratios (δ13C and δ15N) derived from marine mammal bone collagen correlate to changes in marine production and food web length. The 13C and 15N of prehistoric marine mammal taxa covary through the Holocene, indicating no trophic level change with fluctuations in 13C. Changes in δ13C and δ15N of marine mammals are correlated to periods of environmental fluctuations within the Holocene. Cooler climatic periods (transitional interval, beginning of the Neoglacial Interval, and Little Ice Age) show enrichedδ13C, reflecting primary production increase, compared to warmer climate periods (end of the Neoglacial Interval into the Medieval Climatic Anomaly). Unidentified cetacean bones are isotopically distinguishable into orders Mysticeti (baleen) and Odontoceti (toothed) due to different feeding ecologies. The δ13C depletion in modern pinnipeds compared to prehistoric is likely caused by the effect of increased anthropogenic atmospheric CO2 and resulting decrease in primary production.

Establishing a chronology of variation in isotopic values can reveal frailty associated with biological and social age, as well as highlight individuals who vary from typical patterns. Although general dietary characteristics and infant feeding practices were previously unknown for subadults excavated from the cemetery at Alytus, Lithuania (14th-18th centuries), previous research concludes that Alytus' subadults experienced high rates of physiological, metabolic, non-specific stress, in addition to specific diseases like tuberculosis. To investigate nuanced relationships between diet and mortality, nitrogen and carbon stable isotopes from the femoral and humeral midshaft diaphyses of 70 subadults (32 weeks gestation to16 years) were analyzed. Dietary reconstruction reveals that on average, exclusive breastfeeding continued until around 2 years of age when enriched ?13C (-19.6‰) and ?15N values (12.7‰) begin to deplete suggesting introduction of C3 grain gruels and potential weaning-associated infirmity. Nitrogen values remained slightly elevated in children (3-5 years, 11.2‰) until the beginning of juvenility (5-8 years, 10.3‰) when ?15N more closely mirrored adult values (16 years, 10.2‰), consistent with predominant consumption of terrestrial animal protein, possibly with riverine influence. The difference between femoral to humeral ? F-H 13C (-0.05 ±0.25‰, 1?) and ? F-H 15N (- 0.01±0.45‰, 1?) was not significant, though humeral values were on average more enriched. Enrichments in humeral nitrogen and carbon coincided with estimated weaning age. Cohorts experiencing childhood and adolescent growth spurts experienced higher femoral ?13C and ?15N values. Examining dietary experience and physiological changes contributes a holistic understanding of subadult morbidity and mortality experiences in Medieval Lithuania.

Recent research using stable isotope analysis has shown a dependence on migrating or breeding populations of vertebrates as vectors for the transfer of marine-derived nutrients within coastal ecosystems. Sable Island, Nova Scotia, Canada supports numerous species of plants, a variety of seabird colonies (including common [Sterna hirundo] and Arctic [Sterna paradisaea] terns), the world’s largest grey seal (Halichoerus grypus) breeding colony, and a self-sustaining population of wild (feral) horses (Equus ferus caballus). I hypothesize that nitrogen cycling within this island ecosystem is highly influenced by the input of nutrients from seals and seabirds (‘biogenic vectors’), affecting primary production and potentially stabilizing higher trophic levels (i.e., horses). To examine this relation I developed a spatially-explicit isoscape for Sable Island through stable isotope analysis of nitrogen (δ15N) in samples (n = 282) of marram grass (Ammophila breviligulata). I incorporated significant variables (i.e., distance to vector colony and distance to shoreline, r2 = 0.41) into the final parsimonious interpolation model using universal co-kriging techniques. The greatest 15N enrichment occurred within the tips and along the perimeter of the island, coinciding with greater densities of grey seals, while the lowest values occurred within the centre of the island. I then identified individual contributions of seal-, tern- and horse-mediated transfer of marine-derived nutrients inland. Marram grass exhibited higher δ15N within seal (μ = 7.5‰) and tern (μ = 5‰) colonies, while horses and biogeochemical processes (i.e., volatilization, ammonification, etc.) most likely contributed to the homogeneity within the centre of the island (μ = 3.6‰). Due to the higher densities, wider distribution, and greater 15N enrichment of marram tissues, grey seals appear to be the most important vector species while seabirds have a more localized effect. The greater availability of N within vector colonies supplemented the local vegetation community, contributing to greater vegetation cover within colony boundaries. This relation had secondary effects on the horse population, which showed correspondingly higher horse δ15N values within the tips of the island (δ15N + 1.6‰) due to consumption of 15N enriched forage. I conclude that biogenic vector species promote nutrient transfer by establishing nutrient gateways which indirectly cause cascading effects throughout the food web.

The co-evolution of life and the environment stands as a cornerstone in Earth's 4.5-billion-year history. Environmental fluctuations have wielded substantial influence over biological evolution, while life forms have, in turn, reshaped Earth's surface and climate. This dissertation centers on a critical period in Earth's history—the Neoproterozoic Era—when profound environmental shifts potentially catalyzed pivotal eukaryotic evolutionary events. By delving deeper into Neoproterozoic paleoenvironments, I aim at a clearer understanding of life-environment co-evolution in this crucial era. The first chapter focuses on an important juncture—the transition from prokaryote to eukaryote dominance in marine ecosystems during the Tonian Period (1000 Ma to 720 Ma). To assess whether the availability of nitrate, an important macro-nutrient, played a critical role in this evolutionary event, nitrogen isotope compositions (δ¹⁵N) of marine carbonates from the early Tonian (ca. 1000 Ma to ca. 800 Ma) Huaibei Group in North China were measured. The data indicate nitrate limitation in early Neoproterozoic oceans. Further, a compilation of Proterozoic sedimentary δ¹⁵N data, together with box model simulations, suggest a ~50% increase in marine nitrate availability at ~800 Ma. Limited nitrate availability in early Neoproterozoic oceans may have delayed the ecological rise of eukaryotes until ~800 Ma when increased nitrate supply, together with other environmental and ecological factors, may have contributed to the transition from prokaryote-dominant to eukaryote-dominant marine ecosystems. Recognizing the spatial and temporal variations in Neoproterozoic oceanic environments, the second chapter lays the groundwork for a robust stratigraphic framework for the early Tonian Period. Employing the dynamic time warping algorithm, I constructed a global stratigraphic framework for the early Tonian Period using δ¹³C_carb data from the North China, São Francisco, and Congo cratons. This exercise confirms the generally narrow range of δ¹³C_carb fluctuations in the early Tonian, but also confirms the presence of a negative δ¹³C_carb excursion of notable magnitude (~9 ‰) at ca. 920 Ma in multiple records, suggesting that it was global in scope. This negative excursion, known as the Majiatun excursion, is likely the oldest negative excursion in the Neoproterozoic Era and marks the onset of the dynamic Neoproterozoic carbon cycle. Shifting focus to the late Neoproterozoic, the third chapter delves into the origins of Neoproterozoic superheavy pyrite, whose bulk-sample δ³⁴S values are greater than those of contemporaneous seawater sulfate and whose origins remain controversial. Two supervised machine learning algorithms were trained on a large LA-ICP-MS pyrite trace element database to distinguish pyrite of different origins. The analysis validates that two models built on the co-behavior of 12 trace elements (Co, Ni, Cu, Zn, As, Mo, Ag, Sb, Te, Au, Tl, and Pb) can be used to accurately predict pyrite origins. This novel approach was then used to identify the origins of pyrite from two Neoproterozoic sedimentary successions in South China. The first set of samples contains isotopically superheavy pyrite from the Cryogenian Tiesi'ao and Datangpo formations. The second set of samples contains pyritic rims from the Ediacaran Doushantuo Formation; these pyrite rims are associated with fossiliferous chert nodules and do not have superheavy sulfur isotopes. For the superheavy pyrite, the models consistently show high confidence levels in identifying its genesis type, and three out of four samples were inferred to be of sedimentary origins. For the pyritic nodule rims, the models suggest that early diagenetic pyrite was subsequently altered by hydrothermal fluids and therefore shows mixed signals. The third chapter highlights the importance of pyrite trace elements in deciphering and distinguishing the origins of pyrite in sedimentary strata. / Doctor of Philosophy / Understanding how life and the environment have shaped our planet's story over 4.5 billion years is like piecing together an intricate puzzle. On the one hand, changes in the environment kickstarted big shifts in how life evolved. On the other hand, living creatures have also left their mark on Earth's landscapes and climate. This dissertation focuses on unraveling the mysterious Neoproterozoic Era (1 billion to 538 million years ago), a time when Earth saw some of its most dramatic changes. A significant aspect of my investigation delves into the evolutionary dynamics within ancient marine ecosystems. Specifically, I'm exploring a critical juncture when organisms with more complex cellular structures, known as eukaryotes, became ecologically more important than prokaryotic life forms in many aspects of Earth systems. By examining ancient rock formations from China, I have found evidence suggesting that nitrate, a vital nutrient, was scarce in the Neoproterozoic oceans. However, around 800 million years ago, there appears to have been a significant surge in nitrate availability. This surge potentially catalyzed a pivotal phase in evolution, possibly driving the shift from prokaryote to eukaryote dominance in these ancient waters. Second, there is a challenge to delineate a robust timeline for the early Neoproterozoic Era. Imagine trying to piece together a story from a time when there were no calendars or clear dates. Employing advanced statistical methods and comparing chemical signals preserved in carbonate rocks from disparate global locations, I endeavor to craft a coherent timeline for this crucial period. Within this timeline, a noteworthy anomaly in the carbon cycle emerged around 920 million years ago known as the Majiatun excursion. This anomaly represents a significant shift in the Neoproterozoic carbon cycle. Furthermore, my investigation plunges into the geochemistry of sulfur, an important element in shaping ancient marine environments. Certain sedimentary rocks harbor anomalous sulfur isotope signatures in the mineral pyrite (also known as fool's gold), hinting at dramatic environmental transformations during the late Neoproterozoic. Employing advanced analytical techniques and machine learning methodologies, I seek to discern the origins and implications of these anomalous sulfur isotope signals found in pyrite, unraveling their significance in reconstructing the environmental dynamics of ancient oceans.

This research is associated to the FAPESP 2011/0095-7 thematic project, \"Interdisciplinary palaeoenviromental studies at Espirito Santo coast\" and to the FAPESP Research Program about Climate Global Change (PFPMCG-FAPESP). The objectives were: (1) to characterize the late Pleistocene connection between Atlantic and Amazon rainforest and possible routes of interaction (coast, continent or both); (2) to identify environmental characteristics that indicates the Northeastern Espírito Santo and Southern Bahia as a stable forest since the late Pleistocene; (3) reconstitute the vegetation dynamics and infer climate fluctuations. Three sedimentary cores were collected: at northern Espirito Santo (ES) state, southern Bahia (BA) and eastern Minas Gerais (MG). Carbon and nitrogen isotope analyses and bioindicators in sediments/ soils, chronologically determined by radiocarbon dating, contributed to the local palaeoenvironmental reconstitution. At ES, from ~33,460 to ~13,740 cal yr BP the vegetation was composed of arboreal/ shrub cold adapted species and the organic matter recorded the dominance of C3 plants (?13C ~-28?), suggesting a cold and humid forest domain. From ~13,740 to ~9500 cal yr BP vegetation changes, with the increase of grasses and decrease of arboreal types. Between ~9500 and to ~4000 cal yr BP herbs were abundant with a probable mixture of C3 and C4 plants (?13C ~-24?) and algae, suggesting a higher seasonality between humid and dry season. From ~7300 cal yr BP until present the peat layer initiates its deposition, and the pollen records represents the current vegetation. At BA, radiocarbon dating in high-resolution, C and N isotopes and palynology each ~150 years from ~6400 to ~3400 cal yr BP showed detailed vegetational dynamics. From ~6400 to ~5620 cal yr BP the pollen record indicates abundance of trees and shrubs (up to 96%). From ~5620 to ~4850 cal yr BP occurred a slightly increase of herbs (28%) but the ?13C of ~-28% indicate C3 plants domain. From 4850 to ~3400 cal yr BP trees and shrubs abundance increases up to 94%, indicating the forest domain. The results confirm the forest stability and high local humidity, allowing to recognize the area as a probable refugee since 6500 cal yr BP. Vegetation, climate and the landscape has changed at MG since ~10,000 cal yr BP. From 10,600 to ~9500 cal yr BP, pollen was not preserved, C/N values (2 to 11) reveal the algal contribution, the ?13C (~-20?) indicate the mixture of C3 and C4 plants and radiocarbon date inversions indicate that the material was reworked. From 9,500 to 7,500 cal yr BP the vegetation was predominantly herbaceous with mixture of C3 and C4 plant sources (?13C ~-17?). From 7,500 to 7,000 cal yr BP C3 plants (?13C ~-30?) as trees/shrubs domains the polen record. From ~7,000 to ~6500 cal yr BP the pollen records the herbaceous abundance, dominated by C4 plants (?13C ~-12 to 18?). Peat deposition starts at ~6500 cal yr BP composed by C3 plants, mainly dominated by trees. Pollen records since at least early Holocene and the floristics of current vegetation did not show any disjunct specie with Amazon / Este projeto está associado ao temático FAPESP 2011/00995-7, \"Estudos paleoambientais interdisciplinares na costa do Espírito Santo\", e ao Programa FAPESP de Pesquisas sobre Mudanças Climáticas Globais (PFPMCG-FAPESP). Os objetivos foram: (1) caracterizar a conexão da Mata Atlântica e Floresta Amazônica e possíveis rotas de interação (litorânea, continental ou ambas); (2) identificar padrões que caracterizem a região da costa norte do Espírito Santo e sul da Bahia como refúgios florestais; (3) reconstituir a dinâmica da vegetação e inferir flutuações climáticas desde o Pleistoceno tardio. Três testemunhos sedimentares foram coletados: ao norte do Espírito Santo (ES), ao sul da Bahia (BA) e ao leste de Minas Gerais (MG). Análises isotópicas de carbono e nitrogênio e bioindicadores em sedimento/solos, cronologicamente determinados por datação 14C, contribuíram para a reconstituição paleoambiental nestas regiões. No ES, de ~33.460 a ~13.740 anos cal AP, a vegetação era composta por espécies de árvores/arbustos típicas de regiões frias com o domínio de plantas C3 (?13C ~-28?), sugerindo a presença de uma floresta fria e úmida. De ~13.740 a ~9500 anos cal AP ocorreu o aumento das herbáceas e diminuição dos tipos arbóreos. Entre ~9500 e ~4000 anos cal AP, as herbáceas tornaram-se abundantes com mistura de plantas C3 e C4 (?13C~-24?) e algas, sugerindo maior sazonalidade entre as estações seca e úmida. De ~7300 anos cal AP até o presente, iniciou-se a deposição da turfa e pólen da vegetação atual. Na BA, a alta resolução de datação C-14, isótopos de C e N e palinologia a cada ~150 anos entre ~6400 e ~3400 anos cal AP revelaram a dinâmica da vegetação. Entre 6400 e 5620 anos cal AP arbóreas/arbustivas (96%) são abundantes. De ~5620 até ~4850 anos cal AP ocorreu um pequeno aumento de herbáceas (28%), e os valores de ?13C ~-28% indicam o domínio de plantas C3. De 4850 a ~3400 anos cal AP, a abundância de arbóreas/arbustivas (94%), indica domínio florestal. Os resultados confirmam a estabilidade florestal e a umidade local, permitindo reconhecer esta área como um possível refúgio florestal desde pelo menos 6500 anos cal AP. Em MG, desde ~10.000 anos cal AP ao presente, a vegetação, o clima e a paisagem modificaram consideravelmente. De 10.600 a ~9500 anos cal AP não houve preservação de pólen, os valores de C/N (~2 e 11) revelam a contribuição algal, o ?13C (~-20?) indica mistura de plantas C3 e C4 e inversões nas datações indicam o retrabalhamento do material. De 9500 a 7500 anos cal AP a vegetação era predominantemente herbácea, com mistura de C3 e C4 (?13C ~-17?). De 7500 a 700 anos cal AP, plantas C3 (?13C ~-30?) arbustivo-arbóreas dominam o registro polínico. De ~7000 a 6500 anos cal AP as herbáceasC4 (?13C ~-12?) são abundantes. A deposição de turfa iniciou em ~6500 anos cal AP, composta por plantas C3 arbóreas. Registros palinológicos desde o Holoceno inferior e a avaliação florística atual não revelaram a presença de espécies de distribuição disjunta com a Amazônia

This research is associated to the FAPESP 2011/0095-7 thematic project, \"Interdisciplinary palaeoenviromental studies at Espirito Santo coast\" and to the FAPESP Research Program about Climate Global Change (PFPMCG-FAPESP). The objectives were: (1) to characterize the late Pleistocene connection between Atlantic and Amazon rainforest and possible routes of interaction (coast, continent or both); (2) to identify environmental characteristics that indicates the Northeastern Espírito Santo and Southern Bahia as a stable forest since the late Pleistocene; (3) reconstitute the vegetation dynamics and infer climate fluctuations. Three sedimentary cores were collected: at northern Espirito Santo (ES) state, southern Bahia (BA) and eastern Minas Gerais (MG). Carbon and nitrogen isotope analyses and bioindicators in sediments/ soils, chronologically determined by radiocarbon dating, contributed to the local palaeoenvironmental reconstitution. At ES, from ~33,460 to ~13,740 cal yr BP the vegetation was composed of arboreal/ shrub cold adapted species and the organic matter recorded the dominance of C3 plants (?13C ~-28?), suggesting a cold and humid forest domain. From ~13,740 to ~9500 cal yr BP vegetation changes, with the increase of grasses and decrease of arboreal types. Between ~9500 and to ~4000 cal yr BP herbs were abundant with a probable mixture of C3 and C4 plants (?13C ~-24?) and algae, suggesting a higher seasonality between humid and dry season. From ~7300 cal yr BP until present the peat layer initiates its deposition, and the pollen records represents the current vegetation. At BA, radiocarbon dating in high-resolution, C and N isotopes and palynology each ~150 years from ~6400 to ~3400 cal yr BP showed detailed vegetational dynamics. From ~6400 to ~5620 cal yr BP the pollen record indicates abundance of trees and shrubs (up to 96%). From ~5620 to ~4850 cal yr BP occurred a slightly increase of herbs (28%) but the ?13C of ~-28% indicate C3 plants domain. From 4850 to ~3400 cal yr BP trees and shrubs abundance increases up to 94%, indicating the forest domain. The results confirm the forest stability and high local humidity, allowing to recognize the area as a probable refugee since 6500 cal yr BP. Vegetation, climate and the landscape has changed at MG since ~10,000 cal yr BP. From 10,600 to ~9500 cal yr BP, pollen was not preserved, C/N values (2 to 11) reveal the algal contribution, the ?13C (~-20?) indicate the mixture of C3 and C4 plants and radiocarbon date inversions indicate that the material was reworked. From 9,500 to 7,500 cal yr BP the vegetation was predominantly herbaceous with mixture of C3 and C4 plant sources (?13C ~-17?). From 7,500 to 7,000 cal yr BP C3 plants (?13C ~-30?) as trees/shrubs domains the polen record. From ~7,000 to ~6500 cal yr BP the pollen records the herbaceous abundance, dominated by C4 plants (?13C ~-12 to 18?). Peat deposition starts at ~6500 cal yr BP composed by C3 plants, mainly dominated by trees. Pollen records since at least early Holocene and the floristics of current vegetation did not show any disjunct specie with Amazon / Este projeto está associado ao temático FAPESP 2011/00995-7, \"Estudos paleoambientais interdisciplinares na costa do Espírito Santo\", e ao Programa FAPESP de Pesquisas sobre Mudanças Climáticas Globais (PFPMCG-FAPESP). Os objetivos foram: (1) caracterizar a conexão da Mata Atlântica e Floresta Amazônica e possíveis rotas de interação (litorânea, continental ou ambas); (2) identificar padrões que caracterizem a região da costa norte do Espírito Santo e sul da Bahia como refúgios florestais; (3) reconstituir a dinâmica da vegetação e inferir flutuações climáticas desde o Pleistoceno tardio. Três testemunhos sedimentares foram coletados: ao norte do Espírito Santo (ES), ao sul da Bahia (BA) e ao leste de Minas Gerais (MG). Análises isotópicas de carbono e nitrogênio e bioindicadores em sedimento/solos, cronologicamente determinados por datação 14C, contribuíram para a reconstituição paleoambiental nestas regiões. No ES, de ~33.460 a ~13.740 anos cal AP, a vegetação era composta por espécies de árvores/arbustos típicas de regiões frias com o domínio de plantas C3 (?13C ~-28?), sugerindo a presença de uma floresta fria e úmida. De ~13.740 a ~9500 anos cal AP ocorreu o aumento das herbáceas e diminuição dos tipos arbóreos. Entre ~9500 e ~4000 anos cal AP, as herbáceas tornaram-se abundantes com mistura de plantas C3 e C4 (?13C~-24?) e algas, sugerindo maior sazonalidade entre as estações seca e úmida. De ~7300 anos cal AP até o presente, iniciou-se a deposição da turfa e pólen da vegetação atual. Na BA, a alta resolução de datação C-14, isótopos de C e N e palinologia a cada ~150 anos entre ~6400 e ~3400 anos cal AP revelaram a dinâmica da vegetação. Entre 6400 e 5620 anos cal AP arbóreas/arbustivas (96%) são abundantes. De ~5620 até ~4850 anos cal AP ocorreu um pequeno aumento de herbáceas (28%), e os valores de ?13C ~-28% indicam o domínio de plantas C3. De 4850 a ~3400 anos cal AP, a abundância de arbóreas/arbustivas (94%), indica domínio florestal. Os resultados confirmam a estabilidade florestal e a umidade local, permitindo reconhecer esta área como um possível refúgio florestal desde pelo menos 6500 anos cal AP. Em MG, desde ~10.000 anos cal AP ao presente, a vegetação, o clima e a paisagem modificaram consideravelmente. De 10.600 a ~9500 anos cal AP não houve preservação de pólen, os valores de C/N (~2 e 11) revelam a contribuição algal, o ?13C (~-20?) indica mistura de plantas C3 e C4 e inversões nas datações indicam o retrabalhamento do material. De 9500 a 7500 anos cal AP a vegetação era predominantemente herbácea, com mistura de C3 e C4 (?13C ~-17?). De 7500 a 700 anos cal AP, plantas C3 (?13C ~-30?) arbustivo-arbóreas dominam o registro polínico. De ~7000 a 6500 anos cal AP as herbáceasC4 (?13C ~-12?) são abundantes. A deposição de turfa iniciou em ~6500 anos cal AP, composta por plantas C3 arbóreas. Registros palinológicos desde o Holoceno inferior e a avaliação florística atual não revelaram a presença de espécies de distribuição disjunta com a Amazônia

科学研究費補助金 研究種目:基盤研究(B)(2) 課題番号:06453006 研究代表者:才野 敏郎 研究期間:1994-1996年度