Maria T. (Maite) Maldonado

-Physiological mechanisms and regulation of trace metal acquisition by marine phytoplankton -The role of trace metal availability in controlling the ecology and evolution of marine phytoplankton and bacteria -Interactive effects of N metabolism and Fe acquisition in microorganisms -The role of the biota in controlling biogeochemical cycles of trace elements in the ocean Trace elements regulation of harmful algal blooms -Substitution of trace metals in Fe-limited marine phytoplankton and bacteria -Elucidating the mechanistic link between variations in glacial-interglacial oceanic Fe bioavailability & phytoplankton assemblages, and the potential impact of phytoplankton productivity/assemblages in past and present climate. On an annual basis, marine phytoplankton reduce ~45 Gigatons of carbon dioxide to organic carbon, accounting for roughly half of total C fixation on Earth. A fraction of the organic carbon produced in marine surface waters (~ 16 GT) is exported to the deep ocean as sinking particles. Variations in the magnitude of this so-called 'biological carbon pump' affect the carbon dioxide content of the upper ocean, which in turn regulates atmospheric carbon dioxide levels—and hence climate—on time scales ranging from hundreds to thousands of years. In order to understand the regulation of the global carbon cycle, it is thus imperative to determine the factors that control oceanic primary productivity. In the last few decades, it has become apparent that the availability of certain micronutrients, such as the trace elements Fe, Mn, Zn, and Co may affect the species composition, functioning and growth of plankton communites. My research program is directed towards understanding trace metal acquisition, metabolism and nutrition of marine bacteria and phytoplankton. My research aims to addresses fundamental questions in microbial physiology, ecology and evolution in order to better understand how trace metal distribution and speciation may control global primary productivity in the present day and over glacial-interglacial cycles. In turn, these findings will elucidate how marine microorganisms may affect trace metal biogeochemical distribution and cycling in the ocean. My research approach is multidisciplinary, combining cell physiology, ecology, and ocean biochemistry, and applying state-of-the -art analytical techniques to the study of marine microbial/algal processes. Laboratory physiological and biochemical investigations are complemented with field research in oceanic regions, such as in the Subarctic Pacific and the Southern Ocean, in order to elucidate the occurrence of these physiological mechanisms in the ocean.