Grant: Discovery Grants Program - Individual

Photosynthetic phytoplankton growth supports aquatic productivity, atmospheric gas balances and ultimately fishery harvests. Phytoplankton sinking velocity then determines their interactions with consumers, and their delivery of carbon and nutrients from the surface to the deep ocean. Now these phytoplankton face unprecedented change in their environments. The Campbell group grows diverse phytoplankton cells under multiple environments, while tracking their growth and sinking, to understand their interactions with changing environments. With climate change many phytoplankton are shifting polewards to keep within their preferred temperatures and water qualities, bringing species into new photoperiods. We hypothesize that photoperiod helps determine current phytoplankton distributions, and may limit their future distributions. Low oxygen zones are now spreading in ocean and coastal regions, while human activity imposes new nutrient conditions on coastal waters. We therefore apply matrices of photoperiod, temperatures, nutrients and oxygen to parallel microcultures, while monitoring their growth, sinking rates and physiology, to understand the limits on their current and future distributions. As a byproduct phytoplankton produce toxic Reactive Oxygen Species (ROS). We hypothesize that diffusion limits toxic ROS from leaving large cells, which must rely upon expensive ROS detoxification encoded by their own genes. In contrast small phytoplankton can rely upon ROS diffusion out of the cell for breakdown by co-occurring bacteria. This hypothesis predicts the loss of ROS detoxification genes across diverse small, but not large, phytoplankton, to be tested through genome comparisons. The hypothesis also predicts that small phytoplankton will cope better with internally generated ROS which can leave by diffusion, whereas large phytoplankton will cope better with ROS from outside sources, protected by the same diffusion limitation that renders them sensitive to internally produced ROS. The students in my group learn to apply growth, compositional, and biooptical analyses across the wide taxonomic range of phytoplankton groups, to understand their responses to complex, interacting environmental changes, and where they will grow (or fail to grow) in future. Through their projects students learn transferrable skills designing, analyzing and presenting high throughput, parallel data capture, applicable to many areas.