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Mudanças na taxa de acumulação e na natureza da matéria orgânica sedimentar, e suas relações com as variações climáticas e flutuações do nível relativo do mar durante os últimos 8.500 anos cal. A.P. foram investigadas em dois testemunhos provenientes do Saco de Ribeira, Enseada do Flamengo, e junto à praia do Lázaro, Enseada da Fortaleza, na região de Ubatuba, litoral norte do Estado de São Paulo. Para o estudo as amostras coletadas foram submetidas a diversas análises - granulometria, teor de CaCO3, teores de Carbono orgânico, Nitrogênio e Enxofre totais, e razões isotópicas de carbono. Datações 14C, calibradas para a idade calendário, permitiram estabelecer um modelo de idades para as variações sedimentares detectadas. Intervalos de clima mais quente, 8.000-6.000 anos cal. A.P., foram acompanhados de um aumento na taxa de acumulação de carbono T.A.C. (10-13 g m-2 ano-1), seguida de diminuição após 5.000 anos cal. A.P., para valores inferiores a 2 g m-2 ano-1. Variações climáticas regionais, possivelmente relacionadas a chuvas torrenciais, próximos ao máximo transgressivo, de 5.100 anos 14C A.P., foram detectadas pelo aumento nos valores de T.A.C. (10-12 g. m- 2 ano-1), aumento nas taxas de acumulação de massa (T.A.M.) e deposição de sedimentos mais grossos, acompanhados de aumento na tendência continental da natureza da matéria orgânica. As maiores tendências continentais da matéria orgânica sedimentar, registradas aproximadamente entre 1.500-1.200 anos cal. A.P., podem ser decorrentes de uma oscilação negativa do nível do mar. No geral, todos os resultados estão de acordo com as curvas de variação do nível relativo do mar, já descritas na literatura. As análises sedimentares da região estudada revelaram um evento regressivo-trangressivo, que ainda não havia sido referido para o Estado de São Paulo. A partir de ~2.000 anos cal. A.P., o mar teria atingido um nível mais baixo que o atual, com o mínimo provavelmente entre 1.500-1.200 anos cal. A.P., e encontra-se em ascensão até os dias atuais. As características anóxicas e a matéria orgânica sedimentar de origem planctônica registradas junto à praia do Lázaro, em meio a condições de energia relativamente mais alta, em ~900 anos cal. A.P., foram consideradas como resultado de condições óxicas das águas, acompanhadas de altas taxas de produtividade, e subseqüente degradação da matéria orgânica, existentes no período anterior. / Changes in the organic carbon accumulation rates (Corg A.R.) and organic matter source characteristics and their relation to climate and relative sea level changes during the last 8.500 cal. yr. B.P. were investigated in two sediment cores from 2 embayments - Flamengo and Fortaleza inlets - northern coast of São Paulo State. Sediment samples were analysed for grain size, organic Carbon, total Nitrogen and Sulphur contents, and ?13C ratio. Radiocarbon datings provided a model age to the sedimentary deposits. The warm climate interval 8.000-6.000 cal. yr. B.P. was accompanied by an increase in the Corg A.R. (10-13 g.m.-2 yr -1) and a decrease (~2 g.m.-2 yr -1) in the last ~5.000 cal. yr. B.P. Regional climate changes, as stormy weather, that may have ocurred near the maximum transgressive period called Santos Transgression at 5.100 yr. B.P., were recorded in the sedimentary profiles by relatively hight T.A.C. and T.A.M. values, coaser grain size sediment delivery, and enhanced terrestrial organic matter source characteristics. Improvement of terrestrial origin of the sedimentary organic matter recorded between 1.500-1.200 cal. yr. B.P in the studied area was mainly related to a negative sea-level oscillation. All the results are in general agreement with the existing sea level change curves. The sedimentary profiles suggest a negative sea-level fall event, that had\'nt been described yet for São Paulo State. It\'s proposed that the negative oscillation would have begun at ~2.000 cal. yr. B.P.and reached a minimum probably between 1.500-1200 cal. yr. B.P. The relative sea level has been rising since then. Anoxic conditions accompanied by algal origins of sedimentary organic matter, observed in the sedimentary profile from Fortaleza inlet at 900 cal. yr. B.P, during a more oxidizing environment are considered as a result of a previous well oxygencontaining water column and high productivity rates.

Mudanças na taxa de acumulação e na natureza da matéria orgânica sedimentar, e suas relações com as variações climáticas e flutuações do nível relativo do mar durante os últimos 8.500 anos cal. A.P. foram investigadas em dois testemunhos provenientes do Saco de Ribeira, Enseada do Flamengo, e junto à praia do Lázaro, Enseada da Fortaleza, na região de Ubatuba, litoral norte do Estado de São Paulo. Para o estudo as amostras coletadas foram submetidas a diversas análises - granulometria, teor de CaCO3, teores de Carbono orgânico, Nitrogênio e Enxofre totais, e razões isotópicas de carbono. Datações 14C, calibradas para a idade calendário, permitiram estabelecer um modelo de idades para as variações sedimentares detectadas. Intervalos de clima mais quente, 8.000-6.000 anos cal. A.P., foram acompanhados de um aumento na taxa de acumulação de carbono T.A.C. (10-13 g m-2 ano-1), seguida de diminuição após 5.000 anos cal. A.P., para valores inferiores a 2 g m-2 ano-1. Variações climáticas regionais, possivelmente relacionadas a chuvas torrenciais, próximos ao máximo transgressivo, de 5.100 anos 14C A.P., foram detectadas pelo aumento nos valores de T.A.C. (10-12 g. m- 2 ano-1), aumento nas taxas de acumulação de massa (T.A.M.) e deposição de sedimentos mais grossos, acompanhados de aumento na tendência continental da natureza da matéria orgânica. As maiores tendências continentais da matéria orgânica sedimentar, registradas aproximadamente entre 1.500-1.200 anos cal. A.P., podem ser decorrentes de uma oscilação negativa do nível do mar. No geral, todos os resultados estão de acordo com as curvas de variação do nível relativo do mar, já descritas na literatura. As análises sedimentares da região estudada revelaram um evento regressivo-trangressivo, que ainda não havia sido referido para o Estado de São Paulo. A partir de ~2.000 anos cal. A.P., o mar teria atingido um nível mais baixo que o atual, com o mínimo provavelmente entre 1.500-1.200 anos cal. A.P., e encontra-se em ascensão até os dias atuais. As características anóxicas e a matéria orgânica sedimentar de origem planctônica registradas junto à praia do Lázaro, em meio a condições de energia relativamente mais alta, em ~900 anos cal. A.P., foram consideradas como resultado de condições óxicas das águas, acompanhadas de altas taxas de produtividade, e subseqüente degradação da matéria orgânica, existentes no período anterior. / Changes in the organic carbon accumulation rates (Corg A.R.) and organic matter source characteristics and their relation to climate and relative sea level changes during the last 8.500 cal. yr. B.P. were investigated in two sediment cores from 2 embayments - Flamengo and Fortaleza inlets - northern coast of São Paulo State. Sediment samples were analysed for grain size, organic Carbon, total Nitrogen and Sulphur contents, and ?13C ratio. Radiocarbon datings provided a model age to the sedimentary deposits. The warm climate interval 8.000-6.000 cal. yr. B.P. was accompanied by an increase in the Corg A.R. (10-13 g.m.-2 yr -1) and a decrease (~2 g.m.-2 yr -1) in the last ~5.000 cal. yr. B.P. Regional climate changes, as stormy weather, that may have ocurred near the maximum transgressive period called Santos Transgression at 5.100 yr. B.P., were recorded in the sedimentary profiles by relatively hight T.A.C. and T.A.M. values, coaser grain size sediment delivery, and enhanced terrestrial organic matter source characteristics. Improvement of terrestrial origin of the sedimentary organic matter recorded between 1.500-1.200 cal. yr. B.P in the studied area was mainly related to a negative sea-level oscillation. All the results are in general agreement with the existing sea level change curves. The sedimentary profiles suggest a negative sea-level fall event, that had\'nt been described yet for São Paulo State. It\'s proposed that the negative oscillation would have begun at ~2.000 cal. yr. B.P.and reached a minimum probably between 1.500-1200 cal. yr. B.P. The relative sea level has been rising since then. Anoxic conditions accompanied by algal origins of sedimentary organic matter, observed in the sedimentary profile from Fortaleza inlet at 900 cal. yr. B.P, during a more oxidizing environment are considered as a result of a previous well oxygencontaining water column and high productivity rates.

Climate archives are of greatest significance when it comes to paleoclimate studies, since these types of archives in a natural way have registered and preserved the conditions of the past. There are several types of climate archives, one of the most commonly used are lake sediments, because lakes can reveal different types of information, for example weathering, vegetation and precipitation. Another reason why lakes are important in climate research is because they are widely spread over the world, and therefore they can be chosen depending on where the focus of the study will be. In this study, -the Lake Kuchi in the southern part of Taiwan, situated at the boundary between the Asian Mainland and the Western Pacific, was used. What makes this densely populated region of the world particularly interesting for climate research is because it is affected not only by monsoons, but also by typhoons and earthquakes. In this paleoclimate study, a total 16 core sections from three different coring points in the Kuchi Lake were analyzed. The main goal was to clarify if the lake could be used as a reliable climate archive, and also interpret the depositional environment of the sediment layers in the cores. All core sections were described and analyzed with the ITRAX XRF-scanner, which lead to the conclusion that the cores consist of a sedimentary sequence of alternating gray clay and dark gray gyttja clay layers, capped by peat, gyttja or clayey gyttja at topmost part.  By sieving samples from all different layers, it was observed that some dark gyttja clay layers contained terrestrial organic matter, and hard, angular clay clasts that suggest intense rain falls and flash floods as transportation mechanism. The uppermost part of the cores, from 310 cm to the top layers, consist of homogenous clay and in situ organic matter which indicate calmer depositional environments compared to the alternation between dark gyttja clay and homogenous gray clay. LOI-950 data indicate that the carbonate content of the Kuchi Lake is low, since the weight loss during this temperature is insignificant compared to LOI-550, which stood for the majority of the weight loss. Thus, the sediment sequence in the Kuchi Lake consist of alternation of clays deposited in a calm and relatively deep lake, mixed with layers apparently flushed in from land, possibly due to typhoons. This alternation is capped by organic rich layers, including peat, which indicating filling up of the basin, and shallower conditions.

O Antropoceno é marcado pelo aumento da demanda populacional e pelo desenvolvimento industrial. Essas alterações antrópicas têm tido como consequência mudanças ambientais e climáticas, principalmente nos últimos 200 anos. O Rio Guaíba, localizado no Estado brasileiro do Rio Grande do Sul, é considerado de extrema importância por diferentes atributos: (1) principal fonte de abastecimento de água potável para a população de Porto Alegre; (2) importante via de navegação, que liga a região central do Estado com a Lagoa dos Patos e, consequentemente, com o Oceano Atlântico; e (3) abriga o setor industrial da capital Porto Alegre. Este trabalho apresenta como objetivo principal a realização de um estudo de reconstrução ambiental em três testemunhos coletados ao longo do Rio Guaíba. Para atingir este objetivo, determinaram-se níveis de elementos traço (As, Cr, Cu, Ni, P, Pb, Sc e Zn), em conjunto com a geocronologia recente, obtida por meio das atividades dos radionuclídeos 210Pb e 137Cs, utilizando o modelo CRS (Constant Rate of Supply). Foram calculados os índices de geoacumulação: Fator de Enriquecimento, Pollution Load Index e Sediment Pollution Index. As colunas sedimentares G1 e G2 demonstraram resultados que expressam as consequências da mineração de areia que ocorre no rio Jacuí, principal fonte de sedimento para o Rio Guaíba. A partir de aproximadamente 1998, houve uma maior fiscalização das dragas operantes neste rio, e a dinâmica deposicional desses testemunhos foi novamente alterada. A reconstrução realizada no testemunho G3 demonstrou-se diferente das demais. Alterações no perfil granulométrico foram explicadas por eventos climáticos (El Niño e La Niña); e o aumento na concentração de elementos traço, principalmente Cr, Pb, P e Zn, está ligado a possíveis fontes antropogênicas. Neste estudo de reconstrução ambiental, a utilização do modelo CRS, de proxies de metais e da granulometria de finos mostrou-se adequada, principalmente no caso das consequências relacionadas à mineração de areia no rio Jacuí. / The new epoch Anthropocene is marked by the increase of population and industrial development. These anthropic alterations have had as consequences environmental and climatic changes, especially in the last two hundred years. The Guaíba River, located at the Brazilian State of Rio Grande do Sul, is extremely important for different attributes: (1) it is the main source of potable water to the capital Porto Alegre; (2) it is an important navigation route, that connects the State central region with the Patos Lagoon and the Atlantic Ocean; and (3) it harbors the main industries of Porto Alegre. The principal objective of this study was to obtain environmental reconstructions for three sediment cores from Guaíba River. To accomplish this goal, we determined the concentrations of trace elements (As, Cr, Cu, Ni, P, Pb, Sc and Zn) and proceeded the analysis of recent geochronology, which was acquired through 210Pb and 137Cs activities with the CRS model. Furthermore, we calculated geoaccumulation indices: Enrichment Factor, Pollution Load Index and Sediment Pollution Index. The sediment cores G1 and G2 presented results that expressed the consequences of the sand mining that occurs at Jacuí River. Approximately after 1998, there has been better control of the dredges that operate on the river and the depositional dynamics were changed again. The G3 reconstruction had different conclusions compared with the others. Grain size alterations were explained by climatic events, like El Niño and La Niña; and the concentration increase of trace elements, mainly Cr, Pb, P and Zn, was connected with possible anthropogenic sources. In this study of environmental reconstruction, the utilization of the CRS model and of metals concentrations and grain size as proxies proved to be adequate, especially in the case of the sand mining at Jacuí River and its consequences.

In the current study, sub-fossil Cladocera collected from the surface sediment of 44 shallow lakes spanning over five latitudes from north to south of Turkey using snap-shot methodology revealed strong impact of salinity on cladoceran community structure. To see the whole picture, sediment cores collected from six of the lakes and long-term monitoring data from two of the lakes were also investigated. Contemporary cladocerans and sub-fossil assemblages were compared to reveal that their responses to salinity changes were highly similar. This lead us to use sub-fossil cladocerans and salinity data from water column together while generating the calibration data set using ordination techniques. Salinity transfer function models were developed utilising weighted averaging techniques. The developed salinity transfer function was applied to cladocera assemblages from dated sediment cores. Hindcasting of the salinity inference model was performed using monitoring data and the reconstructed salinities from two central Anatolian lakes and reflected good linear correlation with the known lake salinity history. This thesis has confirmed that sub-fossil Cladocera is a valuable indicator of historical salinity change and marker for the monitoring of lakes. For the first time, the lake environmental variables and sub-fossil cladoceran species composition from the surface sediments of Turkish shallow lakes were studied and a salinity transfer function was developed to elucidate past salinity change. The approach of the current study has been proven to be reliable while interpreting past salinity conditions. Since monitoring programmes are scarce in Turkey, paleolimnological analyses would be beneficial especially when defining effective restoration strategies.

The fate and bioaccumulation of a contaminant entering the marine environment through wastewater outfalls depends on the contaminant’s persistence and affinity for particles. The physical characteristics of the receiving environment, e.g. current velocity, sedimentary processes, and the availability of organic carbon are also important. However, these latter effects are not usually evaluated quantitatively. This thesis investigates the near-field accumulation in sediment and biota of particle-reactive polybrominated diphenyl ethers (PBDEs) entering coastal waters via two municipal outfalls: one discharging into a high energy, low sedimentation environment near Victoria, B.C., Canada; the other into a low energy, high sedimentation environment near Vancouver, B.C. We used 210Pb profiles in sediment box cores together with an advection-diffusion model to determine surface mixing and sedimentation rates, and to model the depositional history of PBDEs at these sites. A particularly important finding of this study is that the very high energy environment to the southeast of the Victoria outfall accumulates PBDEs despite not having net sediment accumulation. Although the discharge of PBDEs was much lower from the Victoria outfall than from Vancouver, some sediment PBDE concentrations were higher near Victoria. Most PBDEs were dispersed beyond the near-field at both sites, but a greater proportion was captured in the sediment near the Vancouver outfall where rapid burial was facilitated by inorganic sediment supplied from the nearby Fraser River. Clearly, treating wastewater to the same level, regardless of local oceanographic conditions, will not result in a uniform environmental footprint. Total PBDE concentrations in benthic invertebrate communities were higher near Vancouver than Victoria, despite lower concentrations in sediments, and correlated with organic carbon normalized sediment concentrations. Principal Components Analysis suggested uptake of individual PBDE congeners was determined by sediment properties (TOC, grain size), whereas PCB congener uptake was governed by physico-chemical properties (octanol-water partitioning coefficient). Our results suggest that sediment quality guidelines for PBDEs and likely PCBs may be more relevant if corrected to TOC content in sediment. In addition, where enhanced wastewater treatment increases the ratio of PBDEs to particulate organic carbon in effluent, nearfield benthic invertebrates may face increased PBDE accumulation. This underlines the need for source control of persistent organic contaminants, which cannot be broken down by conventional wastewater treatment. / Graduate

O Antropoceno é marcado pelo aumento da demanda populacional e pelo desenvolvimento industrial. Essas alterações antrópicas têm tido como consequência mudanças ambientais e climáticas, principalmente nos últimos 200 anos. O Rio Guaíba, localizado no Estado brasileiro do Rio Grande do Sul, é considerado de extrema importância por diferentes atributos: (1) principal fonte de abastecimento de água potável para a população de Porto Alegre; (2) importante via de navegação, que liga a região central do Estado com a Lagoa dos Patos e, consequentemente, com o Oceano Atlântico; e (3) abriga o setor industrial da capital Porto Alegre. Este trabalho apresenta como objetivo principal a realização de um estudo de reconstrução ambiental em três testemunhos coletados ao longo do Rio Guaíba. Para atingir este objetivo, determinaram-se níveis de elementos traço (As, Cr, Cu, Ni, P, Pb, Sc e Zn), em conjunto com a geocronologia recente, obtida por meio das atividades dos radionuclídeos 210Pb e 137Cs, utilizando o modelo CRS (Constant Rate of Supply). Foram calculados os índices de geoacumulação: Fator de Enriquecimento, Pollution Load Index e Sediment Pollution Index. As colunas sedimentares G1 e G2 demonstraram resultados que expressam as consequências da mineração de areia que ocorre no rio Jacuí, principal fonte de sedimento para o Rio Guaíba. A partir de aproximadamente 1998, houve uma maior fiscalização das dragas operantes neste rio, e a dinâmica deposicional desses testemunhos foi novamente alterada. A reconstrução realizada no testemunho G3 demonstrou-se diferente das demais. Alterações no perfil granulométrico foram explicadas por eventos climáticos (El Niño e La Niña); e o aumento na concentração de elementos traço, principalmente Cr, Pb, P e Zn, está ligado a possíveis fontes antropogênicas. Neste estudo de reconstrução ambiental, a utilização do modelo CRS, de proxies de metais e da granulometria de finos mostrou-se adequada, principalmente no caso das consequências relacionadas à mineração de areia no rio Jacuí. / The new epoch Anthropocene is marked by the increase of population and industrial development. These anthropic alterations have had as consequences environmental and climatic changes, especially in the last two hundred years. The Guaíba River, located at the Brazilian State of Rio Grande do Sul, is extremely important for different attributes: (1) it is the main source of potable water to the capital Porto Alegre; (2) it is an important navigation route, that connects the State central region with the Patos Lagoon and the Atlantic Ocean; and (3) it harbors the main industries of Porto Alegre. The principal objective of this study was to obtain environmental reconstructions for three sediment cores from Guaíba River. To accomplish this goal, we determined the concentrations of trace elements (As, Cr, Cu, Ni, P, Pb, Sc and Zn) and proceeded the analysis of recent geochronology, which was acquired through 210Pb and 137Cs activities with the CRS model. Furthermore, we calculated geoaccumulation indices: Enrichment Factor, Pollution Load Index and Sediment Pollution Index. The sediment cores G1 and G2 presented results that expressed the consequences of the sand mining that occurs at Jacuí River. Approximately after 1998, there has been better control of the dredges that operate on the river and the depositional dynamics were changed again. The G3 reconstruction had different conclusions compared with the others. Grain size alterations were explained by climatic events, like El Niño and La Niña; and the concentration increase of trace elements, mainly Cr, Pb, P and Zn, was connected with possible anthropogenic sources. In this study of environmental reconstruction, the utilization of the CRS model and of metals concentrations and grain size as proxies proved to be adequate, especially in the case of the sand mining at Jacuí River and its consequences.

Discriminer l'influence des activités humaines de celle des processus naturels sur les changements environnementaux récents est un enjeu scientifique important. Dans ce but, les mollusques et les foraminifères fossiles des Pertuis Charentais (ouest de la France) ainsi que les sédiments déposés pendant l'Holocène dont ils sont issus ont été étudiés. L'objet d'étude central est un drapage vaseux qui constitue une grande partie du comblement sédimentaire terminal des Pertuis. Les résultats obtenus montrent qu'il est composé de sédiments fins d'origine continentale déposés à partir de 1400 AD. Il est la conséquence d'une augmentation de l'érosion des sols, favorisée par la déforestation entreprise au Moyen-Age. Le taux de sédimentation de cette vase a augmenté brutalement, suite à une période d'augmentation des précipitations hivernales à la fin du Petit Age Glaciaire qui a accéléré l'érosion des sols sur ces territoires fragilisés car déforestés. Le dépôt brutal de sédiments fins dans les Pertuis Charentais a eu peu de répercussions sur les communautés de mollusques benthiques, excepté l'extinction locale du bivalve \textit{Lepton squamosum} de la baie de Marennes-Oléron. En revanche, l'augmentation des apports sédimentaires a été à l'origine d'une succession écologique au sein des communautés de foraminifères (résistance - perturbation - adaptation). Les résultats obtenus démontrent comment des milieux perturbés par les activités humaines deviennent plus sensibles aux changements climatiques. Ils soulignent aussi le potentiel de la paléoécologie dans la compréhension des changements environnementaux récents dans les zones côtières à une échelle millénaire à séculaire. / Unraveling the respective influence of human activities and natural processes on recent environmental changes is a critical issue. In this respect, fossil molluscs and foraminifers of the Pertuis Charentais area (western France) as well as the sediments deposited during the Holocene they originate from have been studied. The study is focused on a mud drape that corresponds to the upper, most recent sediment infill of the area. The results show that it is composed of fine grained sediments originating from the adjacent catchments deposited from 1400 AD onwards. This major environmental change was the consequence of an increase in soil erosion promoted by intense deforestation started during the Middle Ages. Mud sedimentation rate increased suddenly in ca. 1760 AD, owing to a short-lived increase of winter rainfall which triggered more intense soil erosion on vulnerable deforested lands. The sharp deposition of fine grained sediments in the Pertuis Charentais has had few consequences on the past benthic mollusc communities, except the local extinction of the bivalve \textit{Lepton squamosum} in the Marennes-Oléron Bay. On the contrary, the increase in mud supply has triggered an ecological succession among benthic foraminifer communities (resistance - disturbance - adaptation). As a whole, the results demonstrate that environments disrupted by human activities become more sensitive to high-frequency climate changes. They also highlight the potential of paleoecology for a better understanding of recent environmental changes occurring within coastal areas at a millennial to centennial scale.

Long term management plans for restoration of natural flow conditions through the Everglades increase the importance of understanding potential nutrient impacts of increased freshwater delivery on coastal biogeochemistry. The present study sought to increase understanding of the coastal marine system of South Florida under modern conditions and through the anthropogenic changes in the last century, on scales ranging from individual nutrient cycle processes to seasonal patterns in organic material (OM) under varying hydrodynamic regime, to century scale analysis of sedimentary records. In all applications, carbon and nitrogen stable isotopic compositions of OM were examined as natural recorders of change and nutrient cycling in the coastal system. High spatial and temporal variability in stable isotopic compositions were observed on all time scales. During a transient phytoplankton bloom, ä15N values suggested nitrogen fixation as a nutrient source supporting enhanced productivity. Seasonally, particulate organic material (POM) from ten sites along the Florida Reef Tract and in Florida Bay demonstrated variable fluctuations dependent on hydrodynamic setting. Three separate intra-annual patterns were observed, yet statistical differences were observed between groupings of Florida Bay and Atlantic Ocean sites. The POM ä15N values ranged on a quarterly basis by 7‰, while ä13C varied by 22‰. From a sediment history perspective, four cores collected from Florida Bay further demonstrated the spatial and temporal variability of the system in isotopic composition of bulk OM over time. Source inputs of OM varied with location, with terrestrial inputs dominating proximal to Everglades freshwater discharge, seagrasses dominating in open estuary cores, and a marine mixture of phytoplankton and seagrass in a core from the boundary zone between Florida Bay and the Gulf of Mexico. Significant shifts in OM geochemistry were observed coincident with anthropogenic events of the 20th century, including railroad and road construction in the Florida Keys and Everglades, and also the extensive drainage changes in Everglades hydrology. The sediment record also preserved evidence of the major hurricanes of the last century, with excursions in geochemical composition coincident with Category 4-5 storms.