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Slow Particle Remineralization, Rather Than Suppressed Disaggregation, Drives Efficient Flux Transfer Through the Eastern Tropical North Pacific Oxygen Deficient Zone
Author(s) -
Cram Jacob A.,
Fuchsman Clara A.,
Duffy Megan E.,
Pretty Jessica L.,
Lekanoff Rachel M.,
Neibauer Jacquelyn A.,
Leung Shirley W.,
Huebert Klaus B.,
Weber Thomas S.,
Bianchi Daniele,
Evans Natalya,
Devol Allan H.,
Keil Richard G.,
McDonnell Andrew M. P.
Publication year - 2022
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2021gb007080
Subject(s) - flux (metallurgy) , particle (ecology) , photic zone , oxygen minimum zone , water column , oceanography , environmental science , anoxic waters , mesopelagic zone , atmospheric sciences , geology , chemistry , upwelling , ecology , pelagic zone , nutrient , phytoplankton , biology , organic chemistry
Models and observations suggest that particle flux attenuation is lower across the mesopelagic zone of anoxic environments compared to oxic environments. Flux attenuation is controlled by microbial metabolism as well as aggregation and disaggregation by zooplankton, all of which shape the relative abundance of differently sized particles. Observing and modeling particle spectra can provide information about the contributions of these processes. We measured particle size spectrum profiles at one station in the oligotrophic Eastern Tropical North Pacific Oxygen Deficient Zone (ETNP ODZ) using an underwater vision profiler (UVP), a high‐resolution camera that counts and sizes particles. Measurements were taken at different times of day, over the course of a week. Comparing these data to particle flux measurements from sediment traps collected over the same time‐period allowed us to constrain the particle size to flux relationship, and to generate highly resolved depth and time estimates of particle flux rates. We found that particle flux attenuated very little throughout the anoxic water column, and at some time points appeared to increase. Comparing our observations to model predictions suggested that particles of all sizes remineralize more slowly in the ODZ than in oxic waters, and that large particles disaggregate into smaller particles, primarily between the base of the photic zone and 500 m. Acoustic measurements of multiple size classes of organisms suggested that many organisms migrated, during the day, to the region with high particle disaggregation. Our data suggest that diel‐migrating organisms both actively transport biomass and disaggregate particles in the ODZ core.