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Abstract. Diel vertical migration (DVM) can enhance the verticalflux of carbon (C), and so contributes to the functioning of the biologicalpump in the ocean. The magnitude and efficiency of this active transport ofC may depend on the size and taxonomic structure of the migrant zooplankton.However, the impact that a variable community structure can have onzooplankton-mediated downward C flux has not been properly addressed. Thistaxonomic effect may become critically important in highly productiveeastern boundary upwelling systems (EBUSs), where high levels of zooplanktonbiomass are found in the coastal zone and are composed by a diverse communitywith variable DVM behavior. In these systems, presence of a subsurfaceoxygen minimum zone (OMZ) can impose an additional constraint to verticalmigration and so influence the downward C export. Here, we address theseissues based on a vertically stratified zooplankton sampling at threestations off northern Chile (20–30∘ S) duringNovember–December 2015. Automated analysis of zooplankton composition andtaxa-structured biomass allowed us to estimate daily migrant biomass by taxaand their amplitude of migration. We found that a higher biomass aggregatesabove the oxycline, associated with more oxygenated surface waters and thiswas more evident upon a more intense OMZ. Some taxonomic groups, however,were found closely associated with the OMZ. Most taxa were able to performDVM in the upwelling zone withstanding severe hypoxia. Also, strongmigrants, such as eucalanid copepods and euphausiids, can exhibit a largemigration amplitude (∼500 m), remaining either temporarily orpermanently within the core of the OMZ and thus contributing to the releaseof C below the thermocline. Our estimates of DVM-mediated C flux suggestedthat a mean migrant biomass of ca. 958 mg C m−2 d−1 may contributewith about 71.3 mg C m−2 d−1 to the OMZ system through respiration,mortality and C excretion at depth, accounting for ca. 4 % of the netprimary production, and so implies the existence of an efficient mechanismto incorporate freshly produced C into the OMZ. This downward C fluxmediated by zooplankton is however spatially variable and mostly dependenton the taxonomic structure due to variable migration amplitude and DVMbehavior. 

ABSTRACT MotivationHere, we make available a second version of the BioTIME database, which compiles records of abundance estimates for species in sample events of ecological assemblages through time. The updated version expands version 1.0 of the database by doubling the number of studies and includes substantial additional curation to the taxonomic accuracy of the records, as well as the metadata. Moreover, we now provide an R package (BioTIMEr) to facilitate use of the database. Main Types of Variables IncludedThe database is composed of one main data table containing the abundance records and 11 metadata tables. The data are organised in a hierarchy of scales where 11,989,233 records are nested in 1,603,067 sample events, from 553,253 sampling locations, which are nested in 708 studies. A study is defined as a sampling methodology applied to an assemblage for a minimum of 2 years. Spatial Location and GrainSampling locations in BioTIME are distributed across the planet, including marine, terrestrial and freshwater realms. Spatial grain size and extent vary across studies depending on sampling methodology. We recommend gridding of sampling locations into areas of consistent size. Time Period and GrainThe earliest time series in BioTIME start in 1874, and the most recent records are from 2023. Temporal grain and duration vary across studies. We recommend doing sample‐level rarefaction to ensure consistent sampling effort through time before calculating any diversity metric. Major Taxa and Level of MeasurementThe database includes any eukaryotic taxa, with a combined total of 56,400 taxa. Software Formatcsv and. SQL.