Award: PLR-1142049

Intellectual Merit: The Southern Ocean plays a critical role for carbon sequestration (that is, how carbon is removed from the atmosphere and stored) in the oceans. The flux of carbon (C) and nitrogen (N) export to the deep ocean depends on the efficiency of the mechanism by which biomass is transported to depth from the sunlit ocean. This study focused on understanding the biological mechanisms that drive carbon export, and specifically the impact of cell death, in the Ross Sea observed in the late austral summer during TRACERS (2013). While cell death controls the turnover of phytoplankton in the oceans, very few field data exist and show this. We present evidence of diatoms undergoing cell death and the causes in the Ross Sea. We also examined other primary groups of organisms undergoing cell death in the water column. We found that diatoms dying at the ocean surface, while other dying organisms were found at depth. In addition, we determined that cell death has an important role controlling carbon export in the Ross Sea through the production of exopolymer particles that quickly sink to the deep ocean, or as free biopolymers that assemble into bigger particles, which then consumed in the water column. Broader Impacts: Understanding the biological mechanisms driving the carbon export to the deep ocean, including the community structure that drives the export production allows us to predict the fate of the carbon exported from the euphotic zone. Furthermore, understanding the physical dynamics of polymers produced by cell death has an impact on the understanding of the dynamics of dissolved organic matter in other oceans. From this grant and in combination with other NSF grants we designed an education module to better understand ocean acidification. This high school curriculum is very popular and has an important impact on society. We believe that education brings awareness about ocean acidification and climate change. We believe that an educated public will be empowered to understand the issue, critically assess complex information, and make informed decisions on behaviors that could control and mitigate CO2 emissions. Last Modified: 05/29/2016 Submitted by: Monica Orellana