Shellfish Face Uncertain Future in High CO2 World: Influence of Acidification on Oyster Larvae Calcification and Growth in Estuaries

BACKGROUND: Human activities have increased atmospheric concentrations of carbon dioxide by 36% during the past 200 years. One third of all anthropogenic CO(2) has been absorbed by the oceans, reducing pH by about 0.1 of a unit and significantly altering their carbonate chemistry. There is widespread concern that these changes are altering marine habitats severely, but little or no attention has been given to the biota of estuarine and coastal settings, ecosystems that are less pH buffered because of naturally reduced alkalinity. METHODOLOGY/PRINCIPAL FINDINGS: To address CO(2)-induced changes to estuarine calcification, veliger larvae of two oyster species, the Eastern oyster (Crassostrea virginica), and the Suminoe oyster (Crassostrea ariakensis) were grown in estuarine water under four pCO(2) regimes, 280, 380, 560 and 800 microatm, to simulate atmospheric conditions in the pre-industrial era, present, and projected future concentrations in 50 and 100 years respectively. CO(2) manipulations were made using an automated negative feedback control system that allowed continuous and precise control over the pCO(2) in experimental aquaria. Larval growth was measured using image analysis, and calcification was measured by chemical analysis of calcium in their shells. C. virginica experienced a 16% decrease in shell area and a 42% reduction in calcium content when pre-industrial and end of 21(st) century pCO(2) treatments were compared. C. ariakensis showed no change to either growth or calcification. Both species demonstrated net calcification and growth, even when aragonite was undersaturated, a result that runs counter to previous expectations for invertebrate larvae that produce aragonite shells. CONCLUSIONS AND SIGNIFICANCE: Our results suggest that temperate estuarine and coastal ecosystems are vulnerable to the expected changes in water chemistry due to elevated atmospheric CO(2) and that biological responses to acidification, especially calcifying biota, will be species-specific and therefore much more variable and complex than reported previously

‘‘Beet-ing’’ the Mountain: A Review of the Physiological and Performance Effects of Dietary Nitrate Supplementation at Simulated and Terrestrial Altitude

Exposure to altitude results in multiple physiological consequences. These include, but are not limited to, a reduced maximal oxygen consumption, drop in arterial oxygen saturation, and increase in muscle metabolic perturbations at a fixed sub-maximal work rate. Exercise capacity during fixed work rate or incremental exercise and time-trial performance are also impaired at altitude relative to sea-level. Recently, dietary nitrate (NO3-) supplementation has attracted considerable interest as a nutritional aid during altitude exposure. In this review, we summarise and critically evaluate the physiological and performance effects of dietary NO3- supplementation during exposure to simulated and terrestrial altitude. Previous investigations at simulated altitude indicate that NO3- supplementation may reduce the oxygen cost of exercise, elevate arterial and tissue oxygen saturation, improve muscle metabolic function, and enhance exercise capacity/ performance. Conversely, current evidence suggests that NO3- supplementation does not augment the training response at simulated altitude. Few studies have evaluated the effects of NO3- at terrestrial altitude. Current evidence indicates potential improvements in endothelial function at terrestrial altitude following NO3- supplementation. No effects of NO3- supplementation have been observed on oxygen consumption or arterial oxygen saturation at terrestrial altitude, although further research is warranted. Limitations of the present body of literature are discussed, and directions for future research are provided

Production and Economic Comparisons of Two Calving Dates for Beef Cows in the Nebraska Sandhills

Calving date for 120 cows in the Nebraska Sandhills was changed from the traditional calving season beginning March 15 (d 75) to one beginning June 15 (d 167) to match increased nutrient needs for lactating cows to immature grazed forages that are high in protein and energy. The hypotheses being tested were that 1) less hay and purchased feeds would be required, 2) production costs would be reduced, and 3) net returns would be greater for June-calving cows compared with their March-calving counterparts. All steer calves from 75 March-calving cows were moved to a feedlot within 60 d of weaning (March calf-feds). Half the steer calves from the 120 June-calving herd were moved within 60 d of weaning to a feedlot to be finished (June calf-feds) and the other half were moved to a feedlot in September after summer grazing of Sandhills rangeland (June yearlings). Half of the June-calving cows were bred on sub-irrigated regrowth (Meadow) and half on upland range. Data on 4 consecutive calf crops were collected through harvest with an additional year collected to feedlot placement. Results showed that fed hay was reduced from 1.79 to 0.10 metric tons per cow annually for the June-calving system. Cost and return analyses were conducted by production phases on steer calves. Production costs for both June-calving groups were less and net returns higher when compared with the March-calved group. The highest net return for a calf group was for the June yearlings from cows bred on subirrigated regrowth

AREA-MEASURED CROP INSURANCE AND DISASTER AID FOR WHEAT AND GRAIN SORGHUM

Area crop insurance and disaster aid program designs are compared to an individual farm-yield insurance design like the current FCIC multiple peril program. Stochastic dominance analysis of net return distributions for 45 wheat and grain sorghum farms in southcentral Kansas is used to determine which strategy is preferred. The area disaster aid program is preferred by generally risk-averse managers over the individual farm-yield design for wheat and sorghum. When individual farm crop insurance is compared directly with ~rea crop insurance, given an equivalent level of government liability for each, individual insurance is usually preferred by risk-averse managers. When the premium for the area insurance is subsidized by 10 percent or more, slightly risk-averse managers usually prefer area insurance to full-cost individual insurance. For area crop insurance to be preferred by managers that are more strongly risk averse, a higher subsidy level is required