Antimicrobial efficacy of copper surfaces against spores and vegetative cells of Clostridium difficile: the germination theory

OBJECTIVES: Persistent contamination of surfaces by spores of Clostridium difficile is a major factor influencing the spread of C. difficile-associated diarrhoea (CDAD) in the clinical setting. In recent years, the antimicrobial efficacy of metal surfaces has been investigated against microorganisms including methicillin-resistant Staphylococcus aureus. This study compared the survival of C. difficile on stainless steel, a metal contact surface widely used in hospitals, and copper surfaces. METHODS: Antimicrobial efficacy was assessed using a carrier test method against dormant spores, germinating spores and vegetative cells of C. difficile (NCTC 11204 and ribotype 027) over a 3 h period in the presence and absence of organic matter. RESULTS: Copper metal eliminated all vegetative cells of C. difficile within 30 min, compared with stainless steel which demonstrated no antimicrobial activity (P < 0.05). Copper significantly reduced the viability of spores of C. difficile exposed to the germinant (sodium taurocholate) in aerobic conditions within 60 min (P < 0.05) while achieving a >or=2.5 log reduction (99.8% reduction) at 3 h. Organic material did not reduce the antimicrobial efficacy of the copper surface (P > 0.05).

The geochemistry of radioactive waste disposal

The present study attempted to identify the significant parameters which affect radionuclide migration from a low level radioactive waste disposal site located in a clay deposit. From initial sorption studies on smectite minerals, increased Kd with decreasing initial cation concentration was observed, and three sorption mechanisms were identified. The observation of anion dependent sorption was related to the existence of a mechanism in which an anion-cation pair are bound to the clay surface through the anion. The influence of competing cations, typical of inorganic groundwater constituents, depended on: (1) Ni/Co:Mn+(Mn+ = competing cation) ratio, (2) nature of M^n+, (3) total solution ionic strength. The presence of organic material in groundwater is well documented, but its effect on cation sorption has not been established. An initial qualitative investigation involving addition of simple organic ligands to Ni(Co)-hectorite samples demonstrated the formation of metal complexes in the clay interlayers, although some modified behaviour was observed. Further quantitative examination involving likely groundwater organic constituents and more comprehensive physical investigation confirmed this behaviour and enabled separation of the organic compounds used into two classes, according to their effect on cation sorption; (i) acids, (ii) amine compounds. X-ray photoelectron spectroscopy, scanning electron microscopy and Mossbauer spectroscopy were used to investigate the nature of transition metal ions sorbed onto montmorillonite and hectorite. Evidence strongly favoured the sorption of the hexaaquo cation, although a series of sorption sites of slightly different chemical characteristics were responsible for broadened peak widths observed in XPS and Mossbauer investigations. The surface sensitivity of XPS enabled recognition of the two surface sorption sites proposed in earlier sorption studies. Although thermal treatment of Fe^3+/Fe^2+-hectorite samples left iron atoms bonded to the silicate sheet structure, Mossbauer evidence indicated the presence of both ferric and ferrous iron in all samples.

UV-stable paper coated with APTES-modified P25 TiO2 nanoparticles

In order to inhibit the photocatalytic degradation of organic material supports induced by small titania (TiO2) nanoparticles, highly photocatalytically active, commercially available P25-TiO2 nanoparticles were first modified with a thin layer of (3-aminopropyl) triethoxysilane (APTES), which were then deposited and fixed onto the surface of paper samples via a simple, dip-coating process in water at room temperature. The resultant APTES-modified P25 TiO2 nanoparticle-coated paper samples exhibit much greater stability to UV-illumination than uncoated blank reference paper. Very little, or no, photo-degradation in terms of brightness and whiteness, respectively, of the P25-TiO2-nanoparticle-treated paper is observed. There are many other potential applications for this Green Chemistry approach to protect cellulosic fibres from UV-bleaching in sunlight and to protect their whiteness and maintain their brightness. © 2014 Elsevier Ltd.

The use of hyphenated spectrometric techniques for the environmental forensic assessment of non-traditional pollutants and degradates in the greater Florida Everglades

A comprehensive investigation of sensitive ecosystems in South Florida with the main goal of determining the identity, spatial distribution, and sources of both organic biocides and trace elements in different environmental compartments is reported. This study presents the development and validation of a fractionation and isolation method of twelve polar acidic herbicides commonly applied in the vicinity of the study areas, including e.g. 2,4-D, MCPA, dichlorprop, mecroprop, picloram in surface water. Solid phase extraction (SPE) was used to isolate the analytes from abiotic matrices containing large amounts of dissolved organic material. Atmospheric-pressure ionization (API) with electrospray ionization in negative mode (ESP-) in a Quadrupole Ion Trap mass spectrometer was used to perform the characterization of the herbicides of interest. ^ The application of Laser Ablation-ICP-MS methodology in the analysis of soils and sediments is reported in this study. The analytical performance of the method was evaluated on certified standards and real soil and sediment samples. Residential soils were analyzed to evaluate feasibility of using the powerful technique as a routine and rapid method to monitor potential contaminated sites. Forty eight sediments were also collected from semi pristine areas in South Florida to conduct screening of baseline levels of bioavailable elements in support of risk evaluation. The LA-ICP-MS data were used to perform a statistical evaluation of the elemental composition as a tool for environmental forensics. ^ A LA-ICP-MS protocol was also developed and optimized for the elemental analysis of a wide range of elements in polymeric filters containing atmospheric dust. A quantitative strategy based on internal and external standards allowed for a rapid determination of airborne trace elements in filters containing both contemporary African dust and local dust emissions. These distributions were used to qualitative and quantitative assess differences of composition and to establish provenance and fluxes to protected regional ecosystems such as coral reefs and national parks. ^

Carbon and nitrogen stable isotopic patterns in South Florida coastal ecosystems: Modern and paleoceanographic perspectives

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, δ 15N 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 δ 15N values ranged on a quarterly basis by 7‰, while δ 13C 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. ^

Multidecadal climate oscillations detected in a transparency record from a subtropical Florida lake

Synchronous interannual variability in water transparency observed in neighboring lakes has been linked to regional precipitation and resultant runoff of dissolved organic material, but many climate forcings oscillate over time scales longer than most limnological records can detect. A strong relationship (R2 5 0.86) between transparency and the previous two years’ rainfall and lake stage in a 25-yr record from a Florida lake enabled us to hindcast transparency from a longer 75-yr record of rainfall and lake stage. Predictions revealed a ,30-yr cycle in transparency linked to the Atlantic Multidecadal Oscillation (AMO). Transparency was greatest (4–8 m) in the cool phase of the AMO (,1962–1993) associated with below-average rainfall in south Florida and lowest (0.1– 3.0 m) during two warm phases (,1932–1961, 1994–present) associated with above-average, but more variable, annual rainfall. Models that predict effects of large-scale hydrologic restoration projects on solute export from South Florida’s expansive wetlands need to account for recent entry into a warm AMO phase, where teleconnections between the AMO phases and runoff are opposite of those shown for the U.S. interior.

The Use of Hyphenated Spectrometric Techniques for the Environmental Forensic Assessment of Non-Traditional Pollutants and Degradates in the Greater Florida Everglades

A comprehensive investigation of sensitive ecosystems in South Florida with the main goal of determining the identity, spatial distribution, and sources of both organic biocides and trace elements in different environmental compartments is reported. This study presents the development and validation of a fractionation and isolation method of twelve polar acidic herbicides commonly applied in the vicinity of the study areas, including e.g. 2,4-D, MCPA, dichlorprop, mecroprop, picloram in surface water. Solid phase extraction (SPE) was used to isolate the analytes from abiotic matrices containing large amounts of dissolved organic material. Atmospheric-pressure ionization (API) with electrospray ionization in negative mode (ESP-) in a Quadrupole Ion Trap mass spectrometer was used to perform the characterization of the herbicides of interest. The application of Laser Ablation-ICP-MS methodology in the analysis of soils and sediments is reported in this study. The analytical performance of the method was evaluated on certified standards and real soil and sediment samples. Residential soils were analyzed to evaluate feasibility of using the powerful technique as a routine and rapid method to monitor potential contaminated sites. Forty eight sediments were also collected from semi pristine areas in South Florida to conduct screening of baseline levels of bioavailable elements in support of risk evaluation. The LA-ICP-MS data were used to perform a statistical evaluation of the elemental composition as a tool for environmental forensics. A LA-ICP-MS protocol was also developed and optimized for the elemental analysis of a wide range of elements in polymeric filters containing atmospheric dust. A quantitative strategy based on internal and external standards allowed for a rapid determination of airborne trace elements in filters containing both contemporary African dust and local dust emissions. These distributions were used to qualitative and quantitative assess differences of composition and to establish provenance and fluxes to protected regional ecosystems such as coral reefs and national parks.

Radiocarbon dating of mumiyo samples from Antarctica

Radiocarbon dating is a nimportant tool for reconstructing Late Quaternary paleoenvironmental history of the Antarctic continent. Because of the scarcity of datable material, new suitable substances are welcomed. We present here novel paleoenvironmental records subfosil stomach oil deposits (mumiyo). This waxy organic material is found in petrel breeding colonies, especialy in those of snow petrels, Pagodroma nivea. The substance is formed by acumulation and solidifica tion of stomach oil regurgitated for the purpose of defense. We demonstrate and outline the usefulnes and limitations of 14C dating mumiyo for determining dates of local ice retreat, moraines and petrel ocupation history.

Os efeitos das queimadas na Amazônia em nível celular e molecular

The Amazon holds over half of the planet's remaining tropical forests and comprises the largest biodiversity in the world, accounting for approximately 60 % of the Brazilian territory. However, deforestation fires in the region causes serious problems to exposed human. The aim of this study was to evaluate the chemical compounds as well as the cellular and molecular effects after exposure to organic material extracted from particulate matter less than 10 µm (PM10) in the Amazon region. As for the chemical composition, n-alkanes analysis showed a prevalence of anthropogenic influence during the fires in the region. In addition, there was a predominance of monosaccharides from biomass burning markers. Also, the Polycyclic Aromatic Hydrocarbons (PAH) and their derivatives have also been identified in samples collected in the Amazon. By using the PAH concentrations was possible to calculate the BaP-equivalent and it was found that the dibenz(a) anthracene contributes with 83% to potential carcinogenic risk. As for the potential mutagenic risk, the benzo (a) pyrene is the HPA that has a major contribution in this analysis. It may be noted that the retene was the most abundant PAH. This compound was genotoxic and cause death by necrosis in the human lung cells. In biological tests, the data showed that organic PM10 is capable of causing genetic damage in both plant cells and in human lung cells. This damage cause an arrest in the G1 phase of the cell cycle exposed, increasing the expression of p53 and p21. Additionally, the PM10 caused cell death by apoptosis, increasing the foci of histone - H2AX. Given these results, it is important to emphasize the reduction and better control of biomass burning in the Amazon region thus improving the quality of health of the population being exposed. As clearly stated recently by the World Health Organization, the reduction of air pollution could save millions of lives annually.

Magnitude da morbidade relacionada ao trabalho no Rio Grande do Norte

Diseases and disorders related to work sets up an important public health problem in Brazil and worldwide. However, the reality of these diseases still constitutes a gap with regard to its characterization and epidemiological situation, especially in Brazil. In this context, this study aims to analyze the magnitude of morbidity related to work from the injuries and illnesses reported by Health the Diseases Notifiable of Health of the State Public River Health Department worker Reference Center Information System services Grande do Norte from 2007 to 2014. It is ecological study, quantitative cross-sectional study in which the analysis unit of the municipalities of Rio Grande do Norte. Data were collected from the state base of Diseases Notifiable Information System Centre of the Secretariat of State Workers' Health Reference Public Health of Rio Grande do Norte, between March and June 2015, after the approval of the Committee of Ethics in Research of the Federal University of Rio Grande do Norte, Opinion 014/2014. The population was represented by the universe of cases of diseases and disorders related to work that were reported and shut down the system from 2007 to 2014. Data were analyzed using descriptive and inferential statistics, presented in tables, graphs, charts and figures. For this, we used the Microsoft Excel 2007 and SPSS version 20.0. To check the significance level we opted for the application of the chi-square or Fisher tests. We adopted the significance level of p <0.05. Of the 10,161 cases of diseases related to the reported work, the biological work accidents had the highest percentage (52.84%) followed by serious occupational accidents (37.49%). For diseases, the highlights were musculoskeletal (4.82%), mental disorders (2.19%) and exogenous intoxication (1.97%). Among men, there was a predominance of major accidents (91.80%), mental disorders (70.00%) and exogenous poisoning (52.84%). Women were most affected by biological accidents (77.50%) and musculoskeletal diseases (64.10%). Among workers who have suffered injuries predominated mulatto (%), mean age of 35.86 years, low education (%) and workers in the formal sector (%). Among the accidents, biological (n = 5,369) accounted for 52.84% of cases occurred predominantly among nursing professionals (48.31%). The percutaneous exposure was the most frequent (73.05%) and the occurrence of circumstances was improper disposal of sharps (45.28%), the needle the most common agent (66.62%) and the organic material was blood (72.99%). Most injured workers were vaccinated against hepatitis B (68.13%), but no information as to the assessment of the vaccine response. In the course of the disease predominated ignored the situation with loss of monitoring of clinical follow-up (55.62%). There was also an increase in the notification of serious industrial accidents predominantly male (91.80%) workers aged 25-44 years (54.3%) and typical accidents (76.3%). The temporary disability was the most common outcome (55.53%) and hand the most affected part (33.00%); the mining and construction industry had the highest number of cases (25.1%) in registered employee (34.2%). The findings of this study show a positive result in relation to increased mandatory reporting of injuries and illnesses related to work together to health services that meet victimized workers, towards the occurrence of knowledge of these accidents for decision making in public plans and policies of health. However, the information system still needs improvement in both the coverage and the quality of the data to demonstrate with greater reliability the magnitude of events to support the planning of workers' health into shares in the state.

Radiocarbon age of bottom sediments from the Yenisei Gulf and the Kara Sea

Sedimentation rates and bottom sediment ages were determined by 14C method in the Kara Sea and the Yenisei River marginal filter. Age of carbon supplied by the Yenisei River is estimated to be 6.9 ka. As supplied carbon mixes with young biogenic carbon under influence of plankton and benthos young carbon flux (planktogenic) sharply diminishes. This has been inferred from studies of organic matter in sedimentary traps deployed along sections from the Yenisei River mouth to 76°N. The major part (70-80%) of organic carbon in bottom sediments of the Kara and Laptev Seas is ancient (Holocene). Planktogenic part comprises only 20-30%. In the Central Arctic Basin percentage of planktogenic organic matter in bottom sediments is still lower, the major part being associated with supply of ancient terrigenous organic material of low nutritional value for organisms. Determinations of sedimentation rates and recent matter fluxes from sedimentary traps served as a basis for locating a sedimentary depocenter in the Yenisei River both for present time and for geological past. Regularities of variations of sediment matter fluxes in the marginal filter were studied.

Weighted mean depth of zooplankton measured during various cruises to the Baltic Sea

The Baltic Sea is the largest brackish water area of the world. On the basis of the data from 16 cruises, we show the seasonal and vertical distribution patterns of the appendicularians Fritillaria borealis, Oikopleura dioica and the cyclopoid copepod Oithona similis, in the highly stratified Bornholm Basin. These species live at least temporarily below the permanent halocline and use different life strategies to cope with the brackish environment. The cold-water species F. borealis is abundant in the upper layers of the water column before the thermocline develops. With the formation of the thermocline abundance decreases and the specimens outlast higher temperatures below the halocline. Distribution and strategy suggest that F. borealis might be a glacial relict species in the Baltic Sea. Although Oikopleura dioica is only abundant during summer, O. similis is present all year round. Both species have in common that their vertical distribution is restricted to the waters below the halocline, most likely due to their requirements of higher salinities. We argue that the observed strategies are determined by ecophysiological constraints and life history traits. These species share an omnivorous feeding behaviour and the capability to utilise a spectra of small particles as food. As phytoplankton concentration is negligible below the halocline, we suggest that these species feed on organic material and heterotrophic organisms that accumulate in the density gradient of the halocline. Therefore, the deep haline waters in the Baltic Sea represent a habitat providing shelter from predation and food supply for adapted species that allows them to gather sufficient resources and to maintain populations.

Sedimentology and faunal compositions of surface sediments from the southern Florida Strait

The water masses in the Florida Straits and Bahamas region are important sources for the Northern Atlantic surface ocean circulation. In this study, we analyse carbonate preservation in surface sediments located above the chemical lysocline in the Florida Straits and Bahamas region and discuss possible reasons for supralysoclinal dissolution. Calcite dissolution proxies such as the variation of the foraminiferal assemblage, Fragmentation Index, Benthic Foraminifera Index, and Resistance Index displayed a good preservation in both areas. The pteropod species Limacina inflata showed very good preservation in sediments of inter-platform channels from the Great Bahama Bank (Providence Channel, Exuma Sound) above the aragonite lysocline. Supralysoclinal aragonite dissolution, however, was observed at two water depth levels (800-1000 m and below 1500 m) in the Florida Straits. Our observations suggest that the supralysoclinal dissolution in the Florida Straits is due to the degradation of organic material. The presence of Antarctic Intermediate Water (AAIW) may be a contributing factor for the significant aragonite dissolution in 800-1000 m. The comparison of modern preservation patterns of the surface sediments with hydrographical measurements shows that the L. inflata Dissolution Index (LDX) might be an adequate proxy to reconstruct paleo-water mass conditions in an area which is highly saturated with respect to calcium carbonate.

Carbonate preservation of sediment cores from the Great Bahama Bank

The oceanic carbon cycle mainly comprises the production and dissolution/ preservation of carbonate particles in the water column or within the sediment. Carbon dioxide is one of the major controlling factors for the production and dissolution of carbonate. There is a steady exchange between the ocean and atmosphere in order to achieve an equilibrium of CO2; an anthropogenic rise of CO2 in the atmosphere would therefore also increase the amount of CO2 in the ocean. The increased amount of CO2 in the ocean, due to increasing CO2-emissions into the atmosphere since the industrial revolution, has been interpreted as "ocean acidification" (Caldeira and Wickett, 2003). Its alarming effects, such as dissolution and reduced CaCO3 formation, on reefs and other carbonate shell producing organisms form the topic of current discussions (Kolbert, 2006). Decreasing temperatures and increasing pressure and CO2 enhance the dissolution of carbonate particles at the sediment-water interface in the deep sea. Moreover, dissolution processes are dependent of the saturation state of the surrounding water with respect to calcite or aragonite. Significantly increased dissolution has been observed below the aragonite or calcite chemical lysocline; below the aragonite compensation depth (ACD), or calcite compensation depth (CCD), all aragonite or calcite particles, respectively, are dissolved. Aragonite, which is more prone to dissolution than calcite, features a shallower lysocline and compensation depth than calcite. In the 1980's it was suggested that significant dissolution also occurs in the water column or at the sediment-water interface above the lysocline. Unknown quantities of carbonate produced at the sea surface, would be dissolved due to this process. This would affect the calculation of the carbonate production and the entire carbonate budget of the world's ocean. Following this assumption, a number of studies have been carried out to monitor supralysoclinal dissolution at various locations: at Ceara Rise in the western equatorial Atlantic (Martin and Sayles, 1996), in the Arabian Sea (Milliman et al., 1999), in the equatorial Indian Ocean (Peterson and Prell, 1985; Schulte and Bard, 2003), and in the equatorial Pacific (Kimoto et al., 2003). Despite the evidence for supralysoclinal dissolution in some areas of the world's ocean, the question still exists whether dissolution occurs above the lysocline in the entire ocean. The first part of this thesis seeks answers to this question, based on the global budget model of Milliman et al. (1999). As study area the Bahamas and Florida Straits are most suitable because of the high production of carbonate, and because there the depth of the lysocline is the deepest worldwide. To monitor the occurrence of supralysoclinal dissolution, the preservation of aragonitic pteropod shells was determined, using the Limacina inflata Dissolution Index (LDX; Gerhardt and Henrich, 2001). Analyses of the grain-size distribution, the mineralogy, and the foraminifera assemblage revealed further aspects concerning the preservation state of the sediment. All samples located at the Bahamian platform are well preserved. In contrast, the samples from the Florida Straits show dissolution in 800 to 1000 m and below 1500 m water depth. Degradation of organic material and the subsequent release of CO2 probably causes supralysoclinal dissolution. A northward extension of the corrosive Antarctic Intermediate Water (AAIW) flows through the Caribbean Sea into the Gulf of Mexico and might enhance dissolution processes at around 1000 m water depth. The second part of this study deals with the preservation of Pliocene to Holocene carbonate sediments from both the windward and leeward basins adjacent to Great Bahama Bank (Ocean Drilling Program Sites 632, 633, and 1006). Detailed census counts of the sand fraction (250-500 µm) show the general composition of the coarse grained sediment. Further methods used to examine the preservation state of carbonates include the amount of organic carbon and various dissolution indices, such as the LDX and the Fragmentation Index. Carbonate concretions (nodules) have been observed in the sand fraction. They are similar to the concretions or aggregates previously mentioned by Mullins et al. (1980a) and Droxler et al. (1988a), respectively. Nonetheless, a detailed study of such grains has not been made to date, although they form an important part of periplatform sediments. Stable isotopemeasurements of the nodules' matrix confirm previous suggestions that the nodules have formed in situ as a result of early diagenetic processes (Mullins et al., 1980a). The two cores, which are located in Exuma Sound (Sites 632 and 633), at the eastern margin of Great Bahama Bank (GBB), show an increasing amount of nodules with increasing core depth. In Pliocene sediments, the amount of nodules might rise up to 100%. In contrast, nodules only occur within glacial stages in the deeper part of the studied core interval (between 30 and 70 mbsf) at Site 1006 on the western margin of GBB. Above this level the sediment is constantly being flushed by bottom water, that might also contain corrosive AAIW, which would hinder cementation. Fine carbonate particles (<63 µm) form the matrix of the nodules and do therefore not contribute to the fine fraction. At the same time, the amount of the coarse fraction (>63 µm) increases due to the nodule formation. The formation of nodules might therefore significantly alter the grain-size distribution of the sediment. A direct comparison of the amount of nodules with the grain-size distribution shows that core intervals with high amounts of nodules are indeed coarser than the intervals with low amounts of nodules. On the other hand, an initially coarser sediment might facilitate the formation of nodules, as a high porosity and permeability enhances early diagenetic processes (Westphal et al., 1999). This suggestion was also confirmed: the glacial intervals at Site 1006 are interpreted to have already been rather coarse prior to the formation of nodules. This assumption is based on the grain-size distribution in the upper part of the core, which is not yet affected by diagenesis, but also shows coarser sediment during the glacial stages. As expected, the coarser, glacial deposits in the lower part of the core show the highest amounts of nodules. The same effect was observed at Site 632, where turbidites cause distinct coarse layers and reveal higher amounts of nodules than non-turbiditic sequences. Site 633 shows a different pattern: both the amount of nodules and the coarseness of the sediment steadily increase with increasing core depth. Based on these sedimentological findings, the following model has been developed: a grain-size pattern characterised by prominent coarse peaks (as observed at Sites 632 and 1006) is barely altered. The greatest coarsening effect due to the nodule formation will occur in those layers, which have initially been coarser than the adjacent sediment intervals. In this case, the overall trend of the grain-size pattern before and after formation of the nodules is similar to each other. Although the sediment is altered due to diagenetic processes, grain size could be used as a proxy for e.g. changes in the bottom-water current. The other case described in the model is based on a consistent initial grain-size distribution, as observed at Site 633. In this case, the nodule reflects the increasing diagenetic alteration with increasing core depth rather than the initial grain-size pattern. In the latter scenario, the overall grain-size trend is significantly changed which makes grain size unreliable as a proxy for any palaeoenvironmental changes. The results of this study contribute to the understanding of general sedimentation processes in the periplatform realm: the preservation state of surface samples shows the influence of supralysoclinal dissolution due to the degradation of organic matter and due to the presence of corrosive water masses; the composition of the sand fraction shows the alteration of the carbonate sediment due to early diagenetic processes. However, open questions are how and when the alteration processes occur and how geochemical parameters, such as the rise in alkalinity or the amount of strontium, are linked to them. These geochemical parameters might reveal more information about the depth in the sediment column, where dissolution and cementation processes occur.

Carbon and Nitrogen Stable Isotopic Patterns in South Florida Coastal Ecosystems: Modern and Paleoceanographic Perspectives

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.