Award: OCE-2049297

Intellectual Merit: We determined the concentration and chemical composition of marine particles in the ocean in the South Pacific Ocean from Tahiti (20°S) south to 67°S along ~150°W,  eastward along 67°S to 100°W, and then in a final northeastward transect returning to Punta Arenas, Chile  (the “U.S. GEOTRACES GP17-OCE section”).  This includes the concentrations of the major particle components, which are particulate organic carbon (POC), the biologically-produced minerals calcium carbonate and opal, lithogenic (suspended sediment) particles, and reactive trace elements.  Marine particles play crucial roles in the chemical and biological cycling of most elements in the ocean, including how major elements such as carbon and trace elements are transformed and transported in the ocean.  For example, the production, destruction, and sinking of particulate organic carbon in the ocean, termed the biological pump, is an important set of processes by which the ocean takes up carbon dioxide from the atmosphere.  The presence of minerals such as calcium carbonate, opal, and lithogenic particles, affects how dense aggregates of marine particles are and therefore how quickly they sink to the deep ocean.  These minerals also affect the light scattering properties of marine particles. Indeed, one of our research products used measurements of these mineral components to show that commonly used satellite algorithms for predicting the amount of calcium carbonate particles from space overestimate this quantity in Antarctic waters (Li et al. 2025).  Another reason that particle concentration and composition matters is that marine particles are a key way in which trace elements, which include key micronutrients such as iron and pollution trace elements such as lead, are removed from seawater: many trace elements stick to particle surfaces and are then removed from seawater when particles sink to the deep ocean.  The amount of “scavenging” removal of trace elements depends on both particle concentration (more surfaces to stick to) and composition (some surfaces are stickier than others).  Our data allows us to better understand the scavenging process so that we can improve our models of how elements cycle in the ocean.

 

Broader Impacts: this project partially supported two Environmental Science undergraduate students, four graduate students, and an early career research scientist to pursue research in the Ocean Sciences department at the University of California, Santa Cruz.  Both undergraduates have graduated and are now employed in STEM fields (environmental consulting and as a marine geology research technician).  One graduate student has graduated and is now teaching marine geology at the college level.  The three other graduate students are making good progress in their degrees.

 

 

Last Modified: 12/08/2025
Modified by: Phoebe J Lam