Sampling planktic foraminifera from dysoxic conditions

The overall goal of this project is to understand the strategies planktic foraminifera use to survive in low-oxygen environments in the pelagic ocean, and if relevant, assess the contribution of planktic foraminifera to nitrogen cycling. To accomplish that goal, the proposed research would test three interrelated hypotheses: (1) OMZ-dwelling planktic foraminifera are capable of performing denitrification; (2) Denitrification is widespread among planktic foraminifera, within and beyond OMZ-affiliated taxa; and (3) Planktic foraminifera capable of nitrate respiration do so regardless of macroenvironmental oxygen concentrations. These hypotheses would be addressed via materials collected on two short research cruises sampling four stations from Monterey Bay to the California Borderlands in two different seasons. Three OMZ-associated species will be targeted (Hastigerinella digitata, Hastigerina parapelagica, Globorotaloides hexagonus) along with one species associated with marine snow (Neogloboquadrina incompta) and one species not associated with low-oxygen conditions (Globigerina bulloides). Metatranscriptomics will be used to gather information on the metabolic capabilities of each species and their symbionts, if present. Shipboard incubations testing for active denitrification under three conditions (anoxic, dysoxic, and normoxic) and analyses of intracellular nitrate content and stable N and O ratios of the foraminiferal intracellular nitrate will be carried out on all five species (H. digitata, H. parapelagica, G. hexagonus and N. incompta) and cellular ultrastructural analysis on the three OMZ-associated species. Additionally, the latitudinal and onshore/offshore populations of the full planktic foraminiferal assemblages will be determined through the water column from ~1200 m to the surface.