BIO Coffee Talks: June 2019
Who: Anya Waite
OFI Director, Dalhousie University
What: Mesoscale Eddies Perturb the Biological Pump
Ocean eddies (~10-100 km, or "mesoscale") have the capacity to transform the ecology of ocean ecosystems, shifting the nutritional status of higher tropic levels (zooplankton and fish/shellfish larvae), and significantly increasing vertical carbon fluxes moderated by the biological pump. Warm-core eddies (WCEs) carry higher surface chlorophyll signatures than cold-core eddies (CCEs), and have been considered historically as more productive as ecosystems overall. But, fish larvae often avoid WCEs, and their larvae have lipid stores and protein reserves than those in CCEs, suggesting a poorer nutritional status. We assess primary productivity and zooplankton isotopic data from eight Indian Ocean eddies across four research voyages (2003 - 11) to determine how this contradiction might occur. We show that high surface chlorophyll documented via satellite does not always indicate the most productive ecosystems, particularly for fish and shellfish larvae. We explore the consequence of these ecosystem changes for particle formation and sedimentation processes of the biological pump, using two new particle embedding techniques that illuminate the complex structure and highly diverse microbial environment of sinking particles. We show the first images of sulfur and nitrogen uptake in anoxic microzones within undisturbed porous particles. Underwater vision profiling (UVP) provides regional mapping of the particle field around eddies to 1000s of meters depth. We show new data from the South Atlantic Ocean, where we quantify particle formation and flux across an Atlantic CCE, concluding that zooplankton and internal waves both play a critical role in moderating the biological pump. We also use the Atlantic UVP data show a curious new optical signature emerging from particles in the deep sea.
When: Friday, June 14, 2019
Where: 10am, George Needler Boardroom, Room VS-427, van Steenburgh Building, Bedford Institute of Oceanography, Dartmouth, Nova Scotia