{'fraction_non_alphanumeric': 0.022682053322721846, 'fraction_numerical': 0.025467568643056108, 'mean_word_length': 4.873831775700935, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Oxygen Minimum Zone in the highly productive upwelling region off

The daily vertical movement of zooplankton, known as diel vertical migration (DVM), can enhance the vertical 10 flux of carbon (C) and so contribute to the functioning of the biological pump in the ocean. The magnitude and efficiency of 11 this active transport of C may depend on the size and taxonomic structure of the migrant zooplankton. However, the impact 12 that a variable community structure can have on zooplankton-mediated downward C flux has not been properly addressed. 13 This taxonomic effect may become critically important in highly productive eastern boundary upwelling systems (EBUS), 14 where high levels of zooplankton biomass are found in the coastal zone and composed by a diverse community with variable 15 DVM behavior. In these systems, presence of a subsurface oxygen minimum zone (OMZ) can impose an additional 16 constraint to vertical migration and so influence the downward C export. Here, we address these issues based on a high17 resolution zooplankton sampling at three stations off northern Chile (20°S-30°S) during November-December 2015. 18 Automated analysis of zooplankton composition and taxa-structured biomass allowed us to estimate daily migrant biomass 19 by taxa and their amplitude of migration. We found that a higher biomass aggregates above the oxycline, associated with 20 more oxygenated surface waters and this was more evident upon a more intense OMZ. Some taxonomic groups, however, 21 were found closely associated with the OMZ. Most taxa were able to perform DVM in the upwelling zone withstanding 22 severe hypoxia. Also, strong migrants, such as Copepods Eucalanidae and Euphausiids, can exhibit a large migration 23 amplitude (~500 m), remaining either temporarily or permanently during the day or night condition within the core of the 24 OMZ and so contributing to the release of C below the thermocline. Our estimates of DVM-mediated C flux suggested that a 25 mean migrant biomass of ca. 958 mg C m-2 d-1 may contribute with about 71.3mg C m-2 d-1 to the OMZ system through 26 respiration, mortality and C excretion at depth, accounting for ca. 4% of the net primary production, and so implying the 27 existence of an efficient mechanism to incorporate freshly produced C into the OMZ. This downward C flux mediated by 28 zooplankton is however strongly variable in the space and mostly dependent on the taxonomic structure due to variable 29 migration amplitude and DVM behavior. 30