Since the Industrial Revolution, human-caused (anthropogenic) emissions of greenhouse gases and pollutants, including sulfur, have changed the composition of the Arctic atmosphere. Greenhouse gas emissions and climate feedbacks have resulted in an Arctic amplification, the phenomenon of rapidly warming Arctic temperatures and of sea-ice extent declining at a rate of 7.2% per decade since the 1980s. Other anthropogenic emissions, such as sulfur aerosols, can reflect sunlight and increase cloud cover, temporarily decreasing temperatures. Since the 1980s, clean air policies have reduced the emissions of sulfur aerosols, which have contributed to Arctic amplification. The majority of Arctic sulfate aerosols come from anthropogenic emissions, but natural sources include sea salt, volcanoes, or biological activity. Sea-ice algae produce dimethylsulfide (DMS), which converts to sulfate aerosols through oxidation in the atmosphere. With the decline in sea-ice extent, the habitats of Arctic biota such as algae are diminishing, and it is unclear how declining sea ice will affect biogenic sulfate aerosols and DMS emissions in the future. Here we investigate the relationship between sea-ice extent decline and DMS emissions thorough analysis of an ice core collected in Summit, Greenland to understand the relative contribution of biological activity to Arctic aerosol abundance. To analyze the biogenic sulfate in the ice core, we concentrate ice core meltwater samples, precipitate sulfate in the concentrated sample solution, measure the sulfur isotopes on a stable isotope mass spectrometer, and run GEOS-Chem model simulations to interpret the observed trends. The isotopes of sulfur in sulfate indicate what portion of the atmospheric sulfate aerosols result from biological activity. We hypothesize that biogenic sulfate has decreased with declining sea-ice extent due to the reduction of sea-ice habitats for sea-ice algae. The response of Arctic sulfate aerosol abundance to the decline of sea ice holds implications for the future of Arctic amplification.

Throughout history, human-induced habitat loss, pollution, and hunting have pressured mammals to adapt to lifestyles that limit human interaction. When humans threaten wildlife, a fitness advantage is provided to animals who avoid human interaction. But what about in protected regions where these threats are limited? Cocha Cashu Biological Station, located in Manu National Park, is an example of one of these regions. While native communities continue to hunt within the research station, overall levels of hunting, deforestation, and pollution, are significantly lower than in the surrounding unprotected areas. Our research team chose to design a study in Cocha Cashu to analyze terrestrial mammal distribution in relation to human habitation in areas where human threats have historically been limited. Our hypothesis was that mammal abundance would increase with distance from human habitation. Our study design involved a northern and eastern transect with a near (N), medium-distanced (M), and far (F) trap location. Each trap location had both a sand and camera trap, and data was collected from the traps morning and night for four consecutive days. On the eastern transect, there was a positive linear relationship between distance from human habitation and number of mammals observed (N: 2 mammals, M: 4 mammals, F: 8 mammals). On the northern route, the highest number of mammals was observed at the medium-distanced location (N: 1 mammal, M: 7 mammals, F: 3 mammals). Overall, our data did not support our hypothesis that mammal abundance increases with distance from human habitation in protected areas. Our results do, however, provide a platform for further research on resource accessibility and its potentially larger influence on mammal distribution patterns than the influence of human habitation.