Objective: The objective was to provide an overall assessment of genetic linkage data of BMI and BMI‐defined obesity using a nonparametric genome scan meta‐analysis.
Research Methods and Procedures: ...We identified 37 published studies containing data on over 31,000 individuals from more than >10,000 families and obtained genome‐wide logarithm of the odds (LOD) scores, non‐parametric linkage (NPL) scores, or maximum likelihood scores (MLS). BMI was analyzed in a pooled set of all studies, as a subgroup of 10 studies that used BMI‐defined obesity, and for subgroups ascertained through type 2 diabetes, hypertension, or subjects of European ancestry.
Results: Bins at chromosome 13q13.2‐ q33.1, 12q23‐q24.3 achieved suggestive evidence of linkage to BMI in the pooled analysis and samples ascertained for hypertension. Nominal evidence of linkage to these regions and suggestive evidence for 11q13.3‐22.3 were also observed for BMI‐defined obesity. The FTO obesity gene locus at 16q12.2 also showed nominal evidence for linkage. However, overall distribution of summed rank p values <0.05 is not different from that expected by chance. The strongest evidence was obtained in the families ascertained for hypertension at 9q31.1‐qter and 12p11.21‐q23 (p < 0.01).
Conclusion: Despite having substantial statistical power, we did not unequivocally implicate specific loci for BMI or obesity. This may be because genes influencing adiposity are of very small effect, with substantial genetic heterogeneity and variable dependence on environmental factors. However, the observation that the FTO gene maps to one of the highest ranking bins for obesity is interesting and, while not a validation of this approach, indicates that other potential loci identified in this study should be investigated further.
Saturation‐anomaly measurements of methyl bromide (CH3Br) were made in the eastern Pacific (3/30–4/27, 2010) and the eastern Atlantic (10/25–11/26, 2010) to assess the oceanic saturation state as the ...phaseout of fumigation ‐ non‐Quarantine and Pre‐Shipment (non‐QPS) uses of CH3Br nears completion and atmospheric concentrations continue to decline. These cruises occurred 16 years after the Bromine Latitudinal Air‐Sea Transect (BLAST) cruises, which were conducted in the same regions and first established a global oceanic net sink of −12.6 Gg yr−1 for atmospheric CH3Br in 1994. Results from this study suggest saturation anomalies of CH3Br in the surface ocean have become less negative than those observed 16 years ago as the atmospheric burden has declined over the past decade. The global net sea‐to‐air flux was estimated at 0 to 3 Gg yr−1 in 2010, suggesting that the ocean may become a net small source to atmospheric CH3Br. There are no significant differences between this study and previous studies for measured biological loss rate constants and calculated annual production rates, suggesting that annual production rates and biological degradation rate constants for CH3Br in the surface ocean have likely remained relatively constant over the past 16 years. When including the biological loss rate constants from this study and all previous studies, the mean global biological loss rate constant is constrained to 0.05 ± 0.01 d−1 (at a 95% confidence level). Combining chemical and eddy degradation rate constants, and using an updated gas transfer velocity, we estimate the CH3Br partial atmospheric lifetime with respect to oceanic loss to be 3.1 (2.3 to 5.0) years. Although the new partial atmospheric lifetime is about 1.3 years longer than the best prior estimate, it does not change the overall atmospheric lifetime of CH3Br, 0.8 (0.7–0.9) years.
Key Points
The ocean may currently be near equilibrium with atmospheric CH3Br
The old SA‐SST relationship for surface seawater CH3Br is no longer valid
Production rates and biological degree rate consistently remain constant
Atmospheric mixing ratios and seawater concentrations of bromoform (CHBr3), dibromomethane (CH2Br2), and other brominated very short‐lived substances (BrVSLS) were measured during five cruises from ...1994 to 2010. These cruises were conducted over large latitudinal (62°N–60°S) and longitudinal transects (11°W–86°W) in the Atlantic Ocean. Elevated seawater concentrations of CHBr3 and CH2Br2 were often observed in regions where chlorophyll a concentrations were also elevated, which suggests biogeochemical processes associated with photosynthetic biomass may be related to CHBr3 and CH2Br2 production. Our results suggest that, at least in the open ocean, several phytoplankton taxa may contribute to the production of these trace gases. While observed correlations between CHBr3 and CH2Br2 in different regions are usually interpreted as common sources for these compounds, results in this study suggest different biogeochemical processes may contribute separately to the production of these trace gases. Heterotrophic bacterial abundance was significantly correlated with CH2Br2, but not with CHBr3, which suggests the biogeochemical processes associated with heterotrophic bacteria may be related to CH2Br2 in seawater but probably not to CHBr3. In general, the Atlantic Ocean is a net source for CHBr3 and CH2Br2, except for a few locations where these trace gases were undersaturated in seawater. Assuming fluxes measured in the Atlantic open ocean are globally representative, the resulting extrapolated, global open‐ocean annual net sea‐to‐air fluxes calculated from data from the five cruises was estimated at 0.24–3.80 Gmol Br yr−1 for CHBr3 and 0.11–0.77 Gmol Br yr−1 for CH2Br2.
Key Points
Bromoform exhibits significant temporal and spatial variations.
BrVSLS distributions in the ocean are related to photosynthetic biomass.
CHBr3 and CH2Br2 production is controlled by different biogeochemical processes.
The atmospheric methyl bromide (CH3Br) burden has declined in recent years, in response to the phaseout of agricultural and structural fumigation consumption under the amendments to the Montreal ...Protocol. The timing and magnitude of this decrease represents an opportunity to examine our current understanding of the CH3Br budget, the phaseout schedule, and recent estimates of interannual variability in biomass burning and global OH. In this study, simulations obtained from a time-dependent global model of atmospheric CH3Br emissions and uptake are compared to observations from the NOAA flask network. The model includes an updated global methyl bromide source inventory that includes biofuel combustion emissions estimated at 6.1±3 Gg yr−1 globally. The phaseout of CH3Br production for agricultural uses began in 1998, concurrent with the pulse in biomass burning associated with the 1998 El Niño. The combined effects of three factors (biomass burning, global OH, and anthropogenic phaseout) appear to explain most of the observed atmospheric methyl bromide trend over the 1997–2005 period. The global budget remains imbalanced, with a large missing source. These results suggest that more than 80% of the missing source does not exhibit significant interannual variability during the phaseout period and, therefore, does not result from underestimating agricultural CH3Br emissions.
Marine hydrocarbon seeps are sources of methane and carbon dioxide to the ocean, and potentially to the atmosphere, though the magnitude of the fluxes and dynamics of these systems are poorly ...defined. To better constrain these variables in natural environments, we conducted the first high-resolution measurements of sea surface methane and carbon dioxide concentrations in the massive natural seep field near Coal Oil Point (COP), California. The corresponding high resolution fluxes were calculated, and the total dissolved phase air–sea fluxes over the surveyed plume area (∼363 km2) were 6.66 × 104 to 6.71 × 104 mol day–1 with respect to CH4 and −6.01 × 105 to −5.99 × 105 mol day–1 with respect to CO2. The mean and standard deviation of the dissolved phase air–sea fluxes of methane and carbon dioxide from the contour gridding analysis were estimated to be 0.18 ± 0.19 and −1.65 ± 1.23 mmol m–2 day–1, respectively. This methane flux is consistent with previous, lower-resolution estimates and was used, in part, to conservatively estimate the total area of the dissolved methane plume at 8400 km2. The influx of carbon dioxide to the surface water refutes the hypothesis that COP seep methane appreciably influences carbon dioxide dynamics. Seeing that the COP seep field is one of the biggest natural seeps, a logical conclusion could be drawn that microbial oxidation of methane from natural seeps is of insufficient magnitude to change the resulting plume area from a sink of atmospheric carbon dioxide to a source.
Seawater concentrations and distributions of brominated very short‐lived substances (BrVSLS), including bromoform (CHBr3), dibromomethane (CH2Br2), bromodichloromethane (CHBrCl2), ...chlorodibromomethane (CHClBr2), were measured in the upper water column (5–750 m) in the eastern Pacific. Inorganic nutrient, pigment concentrations, and picoplankton cell counts were measured to determine biogeochemical factors that affect the production and distribution of these BrVSLS. Elevated concentrations of BrVSLS were observed in coastal and tropical seawater. Concentration maxima for CHBr3, CH2Br2, and CHClBr2 were observed below the mixed layer, near the subsurface chlorophyll a maxima, which suggest BrVSLS production may be related to photosynthetic biomass production. Our results also suggest that heterotrophic bacteria may also contribute to CH2Br2 and CHBrCl2 production in the water column. The maximum CHBrCl2 concentration was observed at a depth much deeper than the euphotic zone, which suggests sources other than photosynthetic biomass. Elevated CHBrCl2 concentrations in deeper waters were coincident with elevated CHCl3 concentrations, which may be an evidence for successive chlorine substitution of CHBr3 in deeper and older water masses.
Key Points
BrVSLS maxima were observed near the subsurface chlorophyll a maxima.
BrVSLS production is in general related to ocean photosynthetic biomass.
CHBr3 and CH2Br2 production is controlled by different biogeochemical factors.
The atmospheric methyl bromide (CH3Br) burden has declined in recent years, in response to the phaseout of agricultural and structural fumigation consumption under the amendments to the Montreal ...Protocol. The timing and magnitude of this decrease represents an opportunity to examine our current understanding of atmospheric CH3Br and its budget, response to the phaseout, and response to interannual variability in biomass burning and global OH. In this study, simulations obtained from a time-dependent global model of atmospheric CH3Br emissions and uptake are compared to observations from the NOAA flask network. The model includes a detailed gridded ocean model coupled to a time-dependant atmospheric 2-box model. The phaseout of CH3Br production for agricultural uses began in 1998, concurrent with the pulse in biomass burning associated with the 1998 El Niño. The combined effects of three factors (biomass burning, global OH, and anthropogenic phaseout) appear to explain most of the observed atmospheric methyl bromide variability over the 1997–2008 period. The global budget remains imbalanced, with a large missing source indicated. The missing source does not exhibit a systematic decline during the phaseout period, and therefore, is not the result of significantly underestimating non-QPS agricultural CH3Br emissions. The model results suggest that the oceans should be less undersaturated than before the phaseout began.
Ship-based Multi-Axis Differential Optical Absorption Spectroscopy measurements of iodine monoxide (IO) and atmospheric and seawater Gas Chromatography – Mass Spectrometer observations of methyl ...iodide (CH3I) were made in the Eastern Pacific marine boundary layer during April 2010 as a part of the HaloCarbon Air Sea Transect-Pacific (HaloCAST-P) scientific cruise. The presence of IO in the open ocean environment was confirmed, with a maximum differential slant column density of 5 × 1013 molecules cm−2 (corresponding to approximately 1 pptv) measured in the oligotrophic region of the Southeastern Pacific. Such low IO mixing ratios and their observed geographical distribution are inconsistent with satellite estimates and with previous understanding of oceanic sources of iodine. A strong correlation was observed between reactive iodine (defined as IO + I) and CH3I, suggesting common sources. In situ measurements of meteorological parameters and physical ocean variables, along with satellite-based observations of Chlorophyll a (Chl a) and Chromophoric Dissolved Organic Matter (CDOM) were used to gain insight into the possible sources of iodine in this remote environment. Surprisingly, reactive iodine showed a negative correlation (>99% confidence) to Chl a and CDOM across the cruise transect. However, a significant positive correlation (>99% confidence) with sea surface temperature (SST) and salinity instead suggests a widespread abiotic source related to the availability of aqueous iodine and to temperature.
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