Dissolved gases in the deep North Atlantic track ocean ventilation processes.

Gas exchange between the atmosphere and ocean interior profoundly impacts global climate and biogeochemistry. However, our understanding of the relevant physical processes remains limited by a scarcity of direct observations. Dissolved noble gases in the deep ocean are powerful tracers of physical air-sea interaction due to their chemical and biological inertness, yet their isotope ratios have remained underexplored. Here, we present high-precision noble gas isotope and elemental ratios from the deep North Atlantic (~32°N, 64°W) to evaluate gas exchange parameterizations using an ocean circulation model. The unprecedented precision of these data reveal deep-ocean undersaturation of heavy noble gases and isotopes resulting from cooling-driven air-to-sea gas transport associated with deep convection in the northern high latitudes. Our data also imply an underappreciated and large role for bubble-mediated gas exchange in the global air-sea transfer of sparingly soluble gases, including O2, N2, and SF6. Using noble gases to validate the physical representation of air-sea gas exchange in a model also provides a unique opportunity to distinguish physical from biogeochemical signals. As a case study, we compare dissolved N2/Ar measurements in the deep North Atlantic to physics-only model predictions, revealing excess N2 from benthic denitrification in older deep waters (below 2.9 km). These data indicate that the rate of fixed N removal in the deep Northeastern Atlantic is at least three times higher than the global deep-ocean mean, suggesting tight coupling with organic carbon export and raising potential future implications for the marine N cycle.

Sero-immunity and serologic response to pandemic influenza A (H1N1) 2009 virus in Hong Kong.

To study the serologic response to the new pandemic influenza A (H1N1) 2009 virus in Hong Kong, the level of immunity was measured before and after the occurrence of the outbreak, and the titer of antibody to the pandemic influenza A (H1N1) 2009 virus in serum samples of laboratory confirmed cases. The presence of pre-outbreak pandemic influenza A (H1N1) 2009 virus antibodies in 37% of individuals older than >65 years suggested previous exposures to heterologous virus strains may have elicited cross-reacting antibody. Following large outbreaks of pandemic influenza A 2009 virus that peaked in September 2009, there is a change in immunity level in various age groups consistent with the attack rates among population in Hong Kong. Among individuals with mild clinical presentation, the antibody response to pandemic influenza A (H1N1) 2009 virus was stronger in those individuals aged ≤ 24 years but took more time to reach a titer of 40 when compared with those aged >24 years; however, the antibody level declined slower among individuals aged ≤ 24 years. Regardless of age, the antibody response rose rapidly and reached much higher titer among individuals with severe clinical presentation. Further study is required to collect additional data on antibody persistence and determine how much protection is conferred by previous exposure to seasonal influenza A (H1N1) viruses.

Phylogenetic relationships among the true porpoises (Cetacea:Phocoenidae).

Portions of the cytochrome b gene and control region of the mitochondrial DNA molecule were sequenced to investigate systematic relationships among the six extant species of true porpoises, (Cetacea: Phocoenidae). Phylogenetic analyses of mitochondrial cytochrome b sequences support a close relationship between Burmeister's porpoise, Phocoena spinipinnis, and the vaquita, Phocoena sinus, and the association of these two species with the spectacled porpoise, Australophocaena dioptrica. The latter result is not in concordance with a recent morphological reclassification which groups A. dioptrica with Dall's porpoise, Phocoenoides dalli, in the subfamily Phocoenoidinae. The molecular analysis found no support for this grouping. A. dioptrica was originally described as a member of the genus Phocoena, and our results support returning it to that genus at this time. Finally, the data suggest that the tropical species Neophocaena phocaenoides, the finless porpoise, may represent the most basal member of the family. The control region sequences corroborated the relationships among the closely related taxa P. sinus, P. spinipinnis, and A. dioptrica, but were unable to resolve the deeper branches of the tree, probably as a result of a high level of saturation of these sequences.

Hypoxia and auditory thresholds.

This paper reports the effects of hypoxia on hearing. Pure tone hearing and speech discrimination were tested at ground level and during hypoxic states at simulated altitudes of 4,600 m (15,000 ft) and 6,100 m (20,000 ft) in a high-altitude chamber. Pure tone hearing was not significantly altered during hypoxia produced by this method. Speech discrimination showed alterations, possibly due to central nervous system hypoxia. It was concluded that hypoxia does not cause significant deterioration of hearing for pure tones.