Methane emissions from subglacial meltwater of three alpine glaciers in Yukon, Canada

ABSTRACTSubglacial meltwater of land-terminating glaciers in Greenland and Iceland are sources of methane (CH4) to the atmosphere, but sparse empirical data exist about the spatial distribution of subglacial CH4 production and emission from glaciers in other regions of the world. This study presents the first measurements of CH4 emissions from the subglacial meltwater of three outlet glaciers of the St. Elias Mountains in Yukon, Canada. Dissolved CH4 concentrations were highly elevated at 45, 135, and 250 times compared to the atmospheric equilibrium concentration in the meltwater of Dusty, Kluane, and Donjek glaciers, respectively. Dissolved CO2 concentrations were depleted relative to the atmospheric equilibrium. This points to the meltwater being a source of CH4 and a sink of CO2. Stable carbon (13C) and hydrogen (2H) isotopic signatures of the subglacial CH4 were depleted compared to atmospheric CH4 at all sites, indicating both biotic and abiotic sources and possible alteration from bacterial CH4 oxidation in the meltwater. No relation was found between CH4 concentrations in the meltwater and the meltwater chemistry or the size of the glaciers in this study. These findings suggest that CH4 emissions from subglacial environments under alpine glaciers may be a more common phenomenon than previously thought

Juvenile stress increases cocaine-induced impulsivity in female rats

In humans, adverse childhood experiences are associated with an increased risk of developing a neuropsychiatric disorder. Changes in social behavior and cognitive function are hallmarks of numerous neuropsychiatric disorders. Here we examined the effects of exposure to variable stress during the juvenile period on social behavior, reward, and cognitive function (as measured in the 5-choice serial reaction time task (5CSRTT)) in rats. From postnatal days (PND) 25-29 male and female rats were exposed to a variable stress protocol. In adulthood, social interactions and sucrose preference were assessed prior to training on the 5CSRTT. Once successfully trained, rats were challenged with different task versions, and then the effects of cocaine (0, 10, or 20 mg/kg, IP) on performance were assessed. A follow-up experiment examined the ability of the D2 receptor antagonist eticlopride (0.0, 0.025, 0.05 mg/kg, IP) to block the effects of cocaine on 5CSRTT performance in female rats. Male rats exposed to juvenile stress tended to engage in less social behavior and had an increased correct response latency in the 5CSRTT following cocaine administration. Female rats exposed to juvenile stress exhibited a trend towards increased social behavior and demonstrated increased cocaine-induced impulsivity. The increase in impulsivity was not blocked by co-administration of eticlopride. Juvenile stress had minimal effects on adult behavior in male rats, but increased cocaine-induced impulsivity in female rats. Such an effect could contribute to the enhanced escalation of drug-use observed in females that experience juvenile stress. This possibility awaits further testing

Methane emissions from subglacial meltwater of three alpine glaciers in Yukon, Canada

Subglacial meltwater of land-terminating glaciers in Greenland and Iceland are sources of methane (CH4) to the atmosphere, but sparse empirical data exist about the spatial distribution of subglacial CH4 production and emission from glaciers in other regions of the world. This study presents the first measurements of CH4 emissions from the subglacial meltwater of three outlet glaciers of the St. Elias Mountains in Yukon, Canada. Dissolved CH4 concentrations were highly elevated at 45, 135, and 250 times compared to the atmospheric equilibrium concentration in the meltwater of Dusty, Kluane, and Donjek glaciers, respectively. Dissolved CO2 concentrations were depleted relative to the atmospheric equilibrium. This points to the meltwater being a source of CH4 and a sink of CO2. Stable carbon (13C) and hydrogen (2H) isotopic signatures of the subglacial CH4 were depleted compared to atmospheric CH4 at all sites, indicating both biotic and abiotic sources and possible alteration from bacterial CH4 oxidation in the meltwater. No relation was found between CH4 concentrations in the meltwater and the meltwater chemistry or the size of the glaciers in this study. These findings suggest that CH4 emissions from subglacial environments under alpine glaciers may be a more common phenomenon than previously thought.</p