Characterization,Sources,and Transformations of Dissolved Organic Matter (DOM) in the Florida Coastal Everglades (FCE)

Dissolved organic matter (DOM) is one of the largest carbon reservoirs on this planet and is present in aquatic environments as a highly complex mixture of organic compounds. The Florida coastal Everglades (FCE) is one of the largest wetlands in the world. DOM in this system is an important biogeochemical component as most of the nitrogen (N) and phosphorous (P) are in organic forms. Achieving a better understanding of DOM dynamics in large coastal wetlands is critical, and a particularly important issue in the context of Everglades restoration. In this work, the environmental dynamics of surface water DOM on spatial and temporal scales was investigated. In addition, photo- and bio-reactivity of this DOM was determined, surface-to-groundwater exchange of DOM was investigated, and the size distribution of freshwater DOM in Everglades was assessed. The data show that DOM dynamics in this ecosystem are controlled by both hydrological and ecological drivers and are clearly different on spatial scales and variable seasonally. The DOM reactivity data, modeled with a multi-pool first order degradation kinetics model, found that fluorescent DOM in FCE is generally photo-reactive and bio-refractory. Yet the sequential degradation proved a “priming effect” of sunlight on the bacterial uptake and reworking of this subtropical wetland DOM. Interestingly, specific PARAFAC components were found to have different photo- and bio-degradation rates, suggesting a highly heterogeneous nature of fluorophores associated with the DOM. Surface-to-groundwater exchange of DOM was observed in different regions of the system, and compositional differences were associated with source and photo-reactivity. Lastly, the high degree of heterogeneity of DOM associated fluorophores suggested based on the degradation studies was confirmed through the EEM-PARAFAC analysis of DOM along a molecular size continuum, suggesting that the fluorescence characteristics of DOM are highly controlled by different size fractions and as such can exhibit significant differences in reactivity

Ultrasound Versus Contrast-Enhanced Magnetic Resonance Imaging for Subclinical Synovitis and Tenosynovitis: A Diagnostic Performance Study

OBJECTIVES: Radiographic manifestations of synovitis (e.g., erosions) can be observed only in the late stage of rheumatoid arthritis. Ultrasound is a noninvasive, cheap, and widely available technique that enables the evaluation of inflammatory changes in the peripheral joint. In the same way, dynamic contrast-enhanced magnetic resonance imaging (MRI) enables qualitative and quantitative measurements. The objectives of the study were to compare the sensitivity and accuracy of ultrasound in detecting subclinical synovitis and tenosynovitis with those of contrast-enhanced MRI. METHODS: The ultrasonography and contrast-enhanced MRI findings of the wrist, metacarpophalangeal, and proximal interphalangeal joints (n=450) of 75 patients with a history of joint pain and morning stiffness between 6 weeks and 2 years were reviewed. The benefits score was evaluated for each modality. RESULTS: The ultrasonic findings showed inflammation in 346 (77%) joints, while contrast-enhanced MRI found signs of early rheumatoid arthritis in 372 (83%) joints. The sensitivities of ultrasound and contrast-enhanced MRI were 0.795 and 0.855, respectively, and the accuracies were 0.769 and 0.823, respectively. Contrast-enhanced MRI had a likelihood of 0–0.83 and ultrasound had a likelihood of 0–0.77 for detecting synovitis and tenosynovitis at one time. The two imaging modalities were equally competitive for detecting synovitis and tenosynovitis (p=0.055). CONCLUSION: Ultrasound could be as sensitive and specific as contrast-enhanced MRI for the diagnosis of subclinical synovitis and tenosynovitis

Directional Selection from Host Plants Is a Major Force Driving Host Specificity in Magnaporthe Species

One major threat to global food security that requires immediate attention, is the increasing incidence of host shift and host expansion in growing number of pathogenic fungi and emergence of new pathogens. The threat is more alarming because, yield quality and quantity improvement efforts are encouraging the cultivation of uniform plants with low genetic diversity that are increasingly susceptible to emerging pathogens. However, the influence of host genome differentiation on pathogen genome differentiation and its contribution to emergence and adaptability is still obscure. Here, we compared genome sequence of 6 isolates of Magnaporthe species obtained from three different host plants. We demonstrated the evolutionary relationship between Magnaporthe species and the influence of host differentiation on pathogens. Phylogenetic analysis showed that evolution of pathogen directly corresponds with host divergence, suggesting that host-pathogen interaction has led to co-evolution. Furthermore, we identified an asymmetric selection pressure on Magnaporthe species. Oryza sativa-infecting isolates showed higher directional selection from host and subsequently tends to lower the genetic diversity in its genome. We concluded that, frequent gene loss or gain, new transposon acquisition and sequence divergence are host adaptability mechanisms for Magnaporthe species, and this coevolution processes is greatly driven by directional selection from host plants

Integrated Carbon Budget Models for the Everglades Terrestrial-Coastal-Oceanic Gradient: Current Status and Needs for Inter-Site Comparisons

Recent studies suggest that coastal ecosystems can bury significantly more C than tropical forests, indicating that continued coastal development and exposure to sea level rise and storms will have global biogeochemical consequences. The Florida Coastal Everglades Long Term Ecological Research (FCE LTER) site provides an excellent subtropical system for examining carbon (C) balance because of its exposure to historical changes in freshwater distribution and sea level rise and its history of significant long-term carbon-cycling studies. FCE LTER scientists used net ecosystem C balance and net ecosystem exchange data to estimate C budgets for riverine mangrove, freshwater marsh, and seagrass meadows, providing insights into the magnitude of C accumulation and lateral aquatic C transport. Rates of net C production in the riverine mangrove forest exceeded those reported for many tropical systems, including terrestrial forests, but there are considerable uncertainties around those estimates due to the high potential for gain and loss of C through aquatic fluxes. C production was approximately balanced between gain and loss in Everglades marshes; however, the contribution of periphyton increases uncertainty in these estimates. Moreover, while the approaches used for these initial estimates were informative, a resolved approach for addressing areas of uncertainty is critically needed for coastal wetland ecosystems. Once resolved, these C balance estimates, in conjunction with an understanding of drivers and key ecosystem feedbacks, can inform cross-system studies of ecosystem response to long-term changes in climate, hydrologic management, and other land use along coastlines

Impact of High Methane Flux on the Properties of Pore Fluid and Methane-Derived Authigenic Carbonate in the ARAON Mounds, Chukchi Sea

We investigated the pore fluid and methane-derived authigenic carbonate (MDAC) chemistry from the ARAON Mounds in the Chukchi Sea to reveal how methane (CH4) seepage impacts their compositional and isotopic properties. During the ARA07C and ARA09C Expeditions, many in situ gas hydrates (GHs) and MDACs were found near the seafloor. The fluid chemistry has been considerably modified in association with the high CH4 flux and its related byproducts (GHs and MDACs). Compared to Site ARA09C-St 08 (reference site), which displays a linear SO42- downcore profile, the other sites (e.g., ARA07C-St 13, ARA07C-St 14, ARA09C-St 04, ARA09C-St 07, and ARA09C-St 12) that are found byproducts exhibit concave-up and/or kink type SO42- profiles. The physical properties and fluid pathways in sediment columns have been altered by these byproducts, which prevents the steady state condition of the dissolved species through them. Consequently, chemical zones are separated between bearing and non-bearing byproducts intervals under non-steady state condition from the seafloor to the sulfate-methane transition (SMT). GH dissociation also significantly impacts pore fluid properties (e.g., low Cl-, enriched delta D and delta O-18). The upward CH4 with depleted delta C-13 from the thermogenic origin affects the chemical signatures of MDACs. The enriched delta O-18 fluid from GH dissociation also influences the properties of MDACs. Thus, in the ARAON Mounds, the chemistry of the fluid and MDAC has significantly changed, most likely responding to the CH4 flux and GH dissociation through geological time. Overall, our findings will improve the understanding and prediction of the pore fluid and MDAC chemistry in the Arctic Ocean related to CH4 seepage by global climate change

Characterization, sources, and transformations of dissolved organic matter (DOM) in Florida coastal Everglades (FCE)

Dissolved organic matter (DOM) is one of the largest carbon reservoirs on this planet and is present in aquatic environments as a highly complex mixture of organic compounds. The Florida coastal Everglades (FCE) is one of the largest wetlands in the world. DOM in this system is an important biogeochemical component as most of the nitrogen (N) and phosphorous (P) are in organic forms. Achieving a better understanding of DOM dynamics in large coastal wetlands is critical, and a particularly important issue in the context of Everglades restoration. In this work, the environmental dynamics of surface water DOM on spatial and temporal scales was investigated. In addition, photo- and bio-reactivity of this DOM was determined, surface-to-groundwater exchange of DOM was investigated, and the size distribution of freshwater DOM in Everglades was assessed. The data show that DOM dynamics in this ecosystem are controlled by both hydrological and ecological drivers and are clearly different on spatial scales and variable seasonally. The DOM reactivity data, modeled with a multi-pool first order degradation kinetics model, found that fluorescent DOM in FCE is generally photo-reactive and bio-refractory. Yet the sequential degradation proved a “priming effect” of sunlight on the bacterial uptake and reworking of this subtropical wetland DOM. Interestingly, specific PARAFAC components were found to have different photo- and bio-degradation rates, suggesting a highly heterogeneous nature of fluorophores associated with the DOM. Surface-to-groundwater exchange of DOM was observed in different regions of the system, and compositional differences were associated with source and photo-reactivity. Lastly, the high degree of heterogeneity of DOM associated fluorophores suggested based on the degradation studies was confirmed through the EEM-PARAFAC analysis of DOM along a molecular size continuum, suggesting that the fluorescence characteristics of DOM are highly controlled by different size fractions and as such can exhibit significant differences in reactivity