Protist Community Ecology Across an Eddy Dipole in the North Pacific Subtropical Gyre

Jennifer Beatty, University of Southern California, Marine and Environmental Biology, Los Angeles, CA, United States, Brittany Stewart, University of Southern California, Los Angeles, United States, Lisa Y Mesrop, University of California Santa Barbara, Santa Barbara, CA, United States, Edward DeLong, Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawaii at Manoa, Honolulu, HI, United States and David A Caron, University of Southern California, Biological Sciences, Los Angeles, CA, United States
Oceanic eddies are common mesoscale features. At Station ALOHA in the North Pacific Subtropical Gyre, individual eddies can extend >100 km and maintain cohesiveness for months, potentially impacting biogeochemical cycles. Within the protistan plankton assemblages of this ecosystem, Rhizaria have recently been shown to be a significant component of sinking particle flux in some oceanic ecosystems, yet classical methods have failed to adequately document the contribution of this group. We used direct microscopy of sediment trap material, and imagery and sequence analysis of the planktonic community to investigate protistan standing stocks and sinking particle differences, with an emphasis on the role of Rhizaria, across an anti-cyclonic to cyclonic eddy-dipole during the SCOPE program MESO-SCOPE cruise off of Station ALOHA during July 2017. The water column was sampled at 4 depths from the surface to 500m and particle interceptor traps (PITs) were deployed at 150m. 18S sequencing revealed that protistan community structure was most affected by depth, not eddy type across the dipole. PIT material differed from water column communities, and revealed a substantial diversity of Rhizaria across the eddies.