Starter Grant: Ecophysiology of Marine Picoeukaryotic Primary Producers

University Of Miami, Coral Gables FL

Investigators

Abstract

Marine picophytoplankton are a key component of marine ecosystems. These microbes, which are only 0.2-2 mm in diameter, are highly abundant in marine ecosystems and responsible for up to 50-80% of total primary production in the open ocean. Despite their importance to global carbon cycling, the ecology of these organisms is not well understood. In particular little is known about one picophytoplankton group, the picoeukaryotes. It is critical that their physiology, as it relates to the environment, is elucidated in order to successfully model their ecology and global carbon cycles. This award is a postdoctoral starter grant as a follow-on activity to an NSF Microbial Biology Postdoctoral Fellowship. The goal of this project is to explore picoeukatyote photophysiology and the extent that photoprotective mechanisms differ, contributing to their relative success. For photosynthetic organisms the ability to regulate light absorption and control light damage (including UV) is extremely important. The project focuses on a newly discovered, environmentally important organism, Ostreococcus tauri, which is the smallest free-living eukaryote known in the world. Genome analysis, physiological growth studies and gene expression level studies will be used to better understand the photosynthetic capabilities of this organism. Genome sequencing of O. tauri is near completion and a survey of genes related to photosynthesis and light-stress responses has been conducted. Laboratory experiments will focus on the effects of high light versus UV light on cell growth. Expression level responses of the identified photosynthetic genes induced by high light and/or UV stress, especially stressful conditions akin to those of oceanic surface waters, will be analyzed by quantitative PCR. The extent of ecotypic differentiation, based on photophysiology, amongst Ostreococcus strains and other common picoeukaryotes will be explored. This research will contribute to knowledge of basic photosynthetic processes as well as the underlying mechanisms which shape the distribution and population dynamics of these important primary producers - allowing better understanding of microbial competition, dominance of certain groups, and global carbon cycling. A graduate student will be involved in the project from the outset, and will receive advanced research training.