Nitrate supply and uptake in the Atlantic Arctic sea ice zone: seasonal cycle, mechanisms and drivers.

Nutrient supply to the surface ocean is a key factor regulating primary production in the Arctic Ocean under current conditions and with ongoing warming and sea ice losses. Here we present seasonal nitrate concentration and hydrographic data from two oceanographic moorings on the northern Barents shelf between autumn 2017 and summer 2018. The eastern mooring was sea ice-covered to varying degrees during autumn, winter and spring, and was characterized by more Arctic-like oceanographic conditions, while the western mooring was ice-free year-round and showed a greater influence of Atlantic water masses. The seasonal cycle in nitrate dynamics was similar under ice-influenced and ice-free conditions, with biological nitrate uptake beginning near-synchronously in early May, but important differences between the moorings were observed. Nitrate supply to the surface ocean preceding and during the period of rapid drawdown was greater at the ice-free more Atlantic-like western mooring, and nitrate drawdown occurred more slowly over a longer period of time. This suggests that with ongoing sea ice losses and Atlantification, the expected shift from more Arctic-like ice-influenced conditions to more Atlantic-like ice-free conditions is likely to increase nutrient availability and the duration of seasonal drawdown in this Arctic shelf region. The extent to which this increased nutrient availability and longer drawdown periods will lead to increases in total nitrate uptake, and support the projected increases in primary production, will depend on changes in upper ocean stratification and their effect on light availability to phytoplankton as changes in climate and the physical environment proceed. This article is part of the theme issue 'The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning'.

Adolescents' perceptions of health from disadvantaged urban communities: findings from the WAVE study.

The Well-being of Adolescents in Vulnerable Environments (WAVE) is a global study of young people living in disadvantaged urban communities from Baltimore, MD, Johannesburg, South Africa, Shanghai, China, New Delhi, India and Ibadan, Nigeria. WAVE was launched in the summer of 2011 to: 1) explore adolescents' perceived health and their top health challenges; and 2) describe the factors that adolescents perceive to be related to their health and health care utilization. Researchers in each site conducted in-depth interviews among adolescents; community mapping and focus groups among adolescents; a Photovoice methodology, in which adolescents were trained in photography and took photos of the meaning of 'health' in their communities; and key informant interviews among adults who work with young people. A total 529 participants from across the sites were included in the analysis. Findings from the study showed that gender played a large role with regards to what adolescents considered as their top health challenges. Among females, sexual and reproductive health problems were primary health challenges, whereas among males, tobacco, drug, and alcohol consumption was of highest concern, which often resulted into acts of violence. Personal safety was also a top concern among males and females from Baltimore and Johannesburg, and among females in New Delhi and Ibadan. Factors perceived to influence health the most were the physical environment, which was characterized by inadequate sanitation and over-crowded buildings, and the social environment, which varied in influence by gender and site. Regardless of the study site, adolescents did not consider physical health as a top priority and very few felt the need to seek health care services. This study highlights the need to focus on underlying structural and social factors for promoting health and well-being among adolescents in disadvantaged urban environments.