SGER: Construction and Deployment of a High Pressure Chemostat System for the Culture of Deep Sea Bacteria and Nanoplankton Protists

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Approximately half of the area of the ocean floor is covered with water deeper than 4000 m making the deep sea the largest habitat on earth. The sheer size of the ocean interior makes it an important component of the global carbon cycle even though life occurs at much lower densities in the deep sea than at the ocean's surface. Organic nutrients arrive almost exclusively through the sinking of particles and the advection of dissolved matter from the surface. The degradation of bioavailable organic carbon by bacteria and the grazing on bacteria by protists are dominant biological processes in the deep ocean. Both groups of organisms seem to contribute to the production of refractory organic material reflected by the high 14C age of dissolved organic matter. Understanding these processes is limited by the inaccessibility of the deep sea ecosystem. One of the most challenging issues in deep sea research is the exposure of samples to large pressure and temperature gradients as they are retrieved. In an effort to eliminate this problem, Dr. Bochandsky will build a device to maintain in situ pressure and temperature while retrieving samples from the deep sea. The samples will allow measurements of growth, bacterial grazing and production of dissolved organic matter of deep sea organisms. Fundamental questions regarding the endemism in protists will also be addressed. The project is being done in collaboration with the Royal Netherlands Institute of Sea Research. Broader impacts include technology advancement, international collaboration and contributions to insights into the global carbon cycle.