Influence of short-term temperature drops on sex-determination in sea turtles.

All sea turtles exhibit temperature-dependent sex-determination, where warmer temperatures produce mostly females and cooler temperatures produce mostly males. As global temperatures continue to rise, sea turtle sex-ratios are expected to become increasingly female-biased, threatening the long-term viability of many populations. Nest temperatures are dependent on sand temperature, and heavy rainfall events reduce sand temperatures for a brief period. However, it is unknown whether these short-term temperature drops are large and long enough to produce male hatchlings. To discover if short-term temperature drops within the sex-determining period can lead to male hatchling production, we exposed green and loggerhead turtle eggs to short-term temperature drops conducted in constant temperature rooms. We dropped incubation temperature at four different times during the sex-determining period for a duration of either 3 or 7 days to mimic short-term drops in temperature caused by heavy rainfall in nature. Some male hatchlings were produced when exposed to temperature drops for as little as 3 days, but the majority of male production occurred when eggs were exposed to 7 days of lowered temperature. More male hatchlings were produced when the temperature drop occurred during the middle of the sex-determining period in green turtles, and the beginning and end of the sex-determining period in loggerhead turtles. Inter-clutch variation was evident in the proportion of male hatchlings produced, indicating that maternal and or genetic factors influence male hatchling production. Our findings have management implications for the long-term preservation of sea turtles on beaches that exhibit strongly female-biased hatchling sex-ratios.

Mild Cognitive Impairment and Changes in Everyday Function Over Time: The Importance of Evaluating Both Speed and Accuracy.

OBJECTIVES: Research estimates that a significant percentage of individuals with mild cognitive impairment (MCI) experience functional difficulties. In addition to reduced accuracy on measures of everyday function, cross-sectional research has demonstrated that speed of performing instrumental activities of daily living (IADLs) is slowed in individuals with MCI. The present study investigated whether baseline and longitudinal changes in speed and accuracy of IADL performance differed between persons with MCI and cognitively normal peers. DESIGN: Linear mixed models were used to estimate the group differences in longitudinal performance on measures of IADLs. SETTING: Assessments were conducted at university and medical research centers. PARTICIPANTS: The sample consisted of 80 participants with MCI and 80 control participants who were enrolled in the Alzheimer's Disease Research Center's Measuring Independent Living in the Elderly Study. MEASUREMENTS: Instrumental activities of daily living speed and accuracy were directly assessed using selected domains of the Financial Capacity Instrument, the Timed IADL assessment, and driving-related assessments (Useful Field of View, Road Sign Test). RESULTS: Individuals with MCI performed worse on speed and accuracy measures of IADLs in comparison to cognitively normal peers and demonstrated significantly steeper rates of decline over three years in either speed or accuracy in all domains assessed. CONCLUSION: Both speed and accuracy of performance on measures of IADL are valuable indices for early detection of functional change in MCI. The performance pattern may reflect a trade-off between speed and accuracy that can guide clinical recommendations for maintaining patient independence.

Nitrogen critical loads for alpine vegetation and soils in Rocky Mountain National Park.

We evaluated the ecological thresholds associated with vegetation and soil responses to nitrogen (N) deposition, by adding NH(4)NO(3) in solution at rates of 5, 10 and 30 kg N ha(-1) yr(-1) to plots in a species rich dry meadow alpine community in Rocky Mountain National Park receiving ambient N deposition of 4 kg N ha(-1) yr(-1). To determine the levels of N input that elicited changes, we measured plant species composition annually, and performed one-time measurements of aboveground biomass and N concentrations, soil solution and resin bag inorganic N, soil pH, and soil extractable cations after 3 years of N additions. Our goal was to use these dose-response relationships to provide N critical loads for vegetation and soils for the alpine in Rocky Mountain National Park. Species richness and diversity did not change in response to the treatments, but one indicator species, Carex rupestris increased in cover from 34 to 125% in response to the treatments. Using the rate of change in cover for C. rupestris in the treatment and the ambient plots, and assuming the change in cover was due solely to N deposition, we estimated a N critical load for vegetation at 3 kg N ha(-1) yr(-1). Inorganic N concentrations in soil solution increased above ambient levels at input rates between 9 kg N ha(-1) yr(-1) (resin bags) and 14 kg N ha(-1) yr(-1) (lysimeters), indicating biotic and abiotic sinks for N deposition are exhausted at these levels. No changes in soil pH or extractable cations occurred in the treatment plots, indicating acidification had not occurred after 3 years. We conclude that N critical loads under 10 kg ha(-1) yr(-1) are needed to prevent future acidification of soils and surface waters, and recommend N critical loads for vegetation at 3 kg N ha(-1) yr(-1) as important for protecting natural plant communities and ecosystem services in Rocky Mountain National Park.

Translating science into policy: using ecosystem thresholds to protect resources in Rocky Mountain National Park.

Concern over impacts of atmospheric nitrogen deposition to ecosystems in Rocky Mountain National Park, Colorado, has prompted the National Park Service, the State of Colorado Department of Public Health and Environment, the Environmental Protection Agency, and interested stakeholders to collaborate in the Rocky Mountain National Park Initiative, a process to address these impacts. The development of a nitrogen critical load for park aquatic resources has provided the basis for a deposition goal to achieve resource protection, and parties to the Initiative are now discussing strategies to meet that goal by reducing air pollutant emissions that contribute to nitrogen deposition in the Park. Issues being considered include the types and locations of emissions to be reduced, the timeline for emission reductions, and the impact of emission reductions from programs already in place. These strategies may serve as templates for addressing ecosystem impacts from deposition in other national parks.