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- Creators: Arizona Board of Regents
The global transport and deposition of anthropogenic nitrogen (N) to downwind ecosystems are significant and continue to increase. Indeed, atmospheric deposition can be a significant source of N to many watersheds, including those in remote, unpopulated areas. Bacterial denitrification in lake sediments may ameliorate the effects of N loading by converting nitrate (NO3-) to N2 gas. Denitrification also produces nitrous oxide (N2O), a potent greenhouse gas. The ecological effects of atmospheric N inputs in terrestrial ecosystems and the pelagic zone of lakes have been well documented; however, similar research in lake sediments is lacking. This project investigates the effects N of deposition on denitrification and N2O production in lakes. Atmospheric N inputs might alter the availability of NO3- and other key resources to denitrifiers. Such altered resources could influence denitrification, N2O production, and the abundance of denitrifying bacteria in sediments. The research contrasts these responses in lakes at the ends of gradients of N deposition in Colorado and Norway. Rates of denitrification and N2O production were elevated in the sediments of lakes subject to anthropogenic N inputs. There was no evidence, however, that N deposition has altered sediment resources or the abundance of denitrifiers. Further investigation into the dynamics of nitric oxide, N2O, and N2 during denitrification found no difference between deposition regions. Regardless of atmospheric N inputs, sediments from lakes in both Norway and Colorado possess considerable capacity to remove NO3- by denitrification. Catchment-specific properties may influence the denitrifying community more strongly than the rate of atmospheric N loading. In this regard, sediments appear to be insulated from the effects of N deposition compared to the water column. Lastly, surface water N2O concentrations were greater in high-deposition lakes compared to low-deposition lakes. To understand the potential magnitude of deposition-induced N2O production, the greenhouse gas inventory methodology of Intergovernmental Panel on Climate Change was applied to available datasets. Estimated emissions from lakes are 7-371 Gg N y-1, suggesting that lakes could be an important source of N2O.
Fisheries in the news: how the media sets the agenda for seafood sustainability in the United States
the past half century due to demographic changes. The increase in meat is visible in Mexico as well due to expanding economic interest in cattle production plus increased population and rising incomes. The worst consequences of our modern food system are in factory farming of animals, which requires a greater amount of resources than for producing grains, fruits, and vegetables. The specific effects of meat consumption highlight the importance of understanding humans as actors in the food system. In order to explore the drivers of consumer food and meat choice, my research answered the two questions: What factors influence meat consumption? and How do cultural and social norms influence decisions to consume certain types and amounts of meat?
Qualitative interviews were conducted with Mexican-American respondents between age 20 and 29 as the population of interest because of their regional dominance in the study area of Tempe, AZ and because of the high prevalence of meat in their cultural diets. Looking at millennials in particular is crucial because as the first generation born with technology and Internet as constants, they have formed unique characteristics like openness to change and new perspectives. My sample population communicated motivations and constraints to their overall consumption patterns and the frequency and types of meat consumed.
This study found that cost and convenience were the driving factors behind food choice, given the hectic schedules of the sample population, who were mostly students at Arizona State University. Culture played an important role in respondents' heavy meat consumption given their exposure to meat's centrality in traditional Mexican meals. Acculturation did not play an extensive role because prominent Mexican culture in the Southwest U.S. allowed respondents' families access to traditional food while living in the US. The lack of sustainability knowledge and its connection to food choice indicates the importance of marketing that contextualizes decreased meat consumption. Rather than focusing solely on environmental outcomes, marketing tools highlighting health, financial, and economic benefits of eating less meat would encourage more consumers to decrease consumption.