Abstract:

Marine snow are macroscopic aggregates of organic and inorganic matter that originate in surface waters as a by-product of phytoplankton and bacterial activities. As the material sinks, it collects other floating debris including fecal material, dead and decaying animals, and suspended sediments from terrestrial runoff. It also incorporates marine pollutants such as microplastics and petroleum hydrocarbons from oil spills, affecting the fate of toxic substances in the ocean. Many animals in the deep ocean filter marine snow from the surrounding seawater or scavenge it from the seabed as their primary food source. Differences in the amount of marine snow falling through the water column, or density of this snowfall, is mainly influenced by biological and physical factors, including primary and secondary production, consumption and decomposition rates of the snow en route, and water mixing processes ranging from small-scale turbulence to larger scale currents. To adequately predict the fate of marine snow and its components, numerical models are required based on realistic measures of marine snow dynamics. Such measures include microbial activities on marine snow formed under controlled laboratory conditions. In this seminar I will present results from laboratory studies on the formation, sinking, and microbial decomposition of marine snow. I will also discuss the role of microbes in the formation and fate of oil-containing marine snow, also known as ‘marine oil snow’, following the 2010 BP oil spill in the northern Gulf of Mexico. My work on marine snow associated microbial dynamics emphasizes the importance of small-scale processes on larger scale elemental cycles in the ocean.

Speaker Biography:

Dr. Kai Ziervogel is currently a research associate professor at the University of New Hampshire, where he is the head of the marine biogeochemistry lab. A native German, Dr. Ziervogel graduated from Rostock University where he studied biogeochemical fluxes associated with marine snow in the Baltic Sea. He continued his research on marine snow at the University of North Carolina, focusing on the role of aggregate-associated microbial activities. His research has taken him on several expeditions into the Gulf of Mexico, the North Atlantic, and the northeast Pacific. One of his career highlights was a dive in the research submarine ‘Alvin’ to the bottom of Guaymas Basin, Gulf of California, where he studied microbial processes in deep ocean waters around hydrothermal vents.

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