Oceanography Seminar- Dr. Osvaldo Ulloa

“While the Ocean Suffocates, the Microbes Will Play”

Current data and models suggest that during the first half of Earth’s history, there was virtually no free oxygen in the atmosphere nor in the ocean water column, and the deep ocean remained dominantly anoxic until the Neoproterozoic. Obviously today, the situation is quite different, except in regions known as “anoxic marine zones (AMZs)”. In these oceanic pelagic environments, anaerobic or facultative anaerobic microbes thrive, impacting biogeochemical cycles on a planetary scale, and in particular, having a large influence on the ocean nitrogen cycle.

Our understanding of the microbial ecology and biogeochemistry of AMZs has improved significantly during the past few decades, with the identification of some of their key microbiota, and some unexpected biogeochemical processes they mediate. Also, recent genomic studies of OMZ relatives of the globally important cyanobacterium Prochlorococcus, suggest that it may have evolved in a realtively low-oxygen ocean.

Since climate-induced warming of the upper ocean contributes to the deoxygenation of the global ocean and the expansion of AMZs, there is an urgent need to assess the impact of AMZs on marine ecosystem structure —including the deep ocean— and associated global biogeochemical cycling.