Award: OCE-1658311

The phytoplankton community of the Pacific Sector of the Southern Ocean is dominated by diatoms, which produce a rigid shell made of silica, like glass. The concentrations of major nutrients like nitrate, phosphate, and silicate are relatively high in this region, but concentrations of the trace nutrient iron are extremely low, which restricts the growth of diatoms and other single-celled plants. Our research applied cutting-edge instrumentation to conclusively show that within these polar waters, diatoms actually embed another trace nutrient - zinc - inside their silica shells. Our evidence confirms that this zinc-silica relationship exists across the Southern Ocean, as observed in samples from the Ross Sea to the Western Antarctic Peninsula, and as deep as 1000 m (the deepest samples collected during this expedition). While the exact mechanism for this zinc-silica incorporation remains unknown, our findings help explain the global observation of a close relationship between the dissolved forms of zinc and silica (as silicic acid), which was first reported in 1978 but never fully understood. A rough draft of a manuscript describing the methods and significance of our projest, led by Dr. Erin Griffith, will be submitted in early 2024. Throughout our project, we included multiple undergraduate students in the research, from carefully preparing samples while avoiding contamination, to participating at the Argonne National Labs where the diatoms were analyzed, to writing an undergraduate Honor's Thesis summarizing the biology and chemistry of the Southern Ocean waters. We also regularly presented our project and results to the general public at annual "open house" events, attended by 7000 people, giving people access to our science through demos, tours, and one-on-one conversations. Last Modified: 01/15/2024 Submitted by: PeterMorton