Comments and inputs for the PRIMO project

1. Comments and inputs for the PRIMO project

2. Physics in the OMZ of the ESP • Main Research questions • What is the transport of the PCU and what is its spatio-temporal variability?. • What are the main mechanisms transporting oxygen to the OMZ?. Evaluation of advection associated with different flows of the ESPCS, the role of the turbulent diffusivity on the oxygen transport toward the OMZ. • What prevents the southward extend of the ZMO and what is therefore the role of Chile-Peru Current? • The tropic-subtropics connections in the SEP • Role of the Coastal Trapped Waves on the vertical structure of the OMZ. • Role of Rossby waves on the offshore extension of the OMZ.

3. Variability of upwelling in the OMZ • How does the upwelling contribute to the vertical structure of the OMZ? • Mesoscale activities and the OMZ • Document processes associated with mesoscale eddies (eddy transports + lateral diffusion). • Subducted intermediate waters and the OMZ • Document vertical and horizontal mixing processes. • - Does the strong salinity vertical gradient (low salinity water near the surface and high salinity at OMZ level) prevent the mixing of low O2 waters? • Which other mechanisms (e.g. thermal stratification) prevent the vertical mixing of surface oxic and low O2 subsurface waters? • What is the contribution of the horizontal mixing to the OMZ spatial heterogeneity?.

4. National and international context National programs Some of the objectives related to PRIMO are associated to the ongoing Research Programs in IMARPE : “Dynamics of Coastal Upwelling, Biogeochemical Cycles and Paleo-oceanography of the Humboldt Current Ecosystem”. This program comprises the following projects: - “Seasonal and interannual variability of bio-oceanographic parameters in selected areas”, - “Interactions of the OMZ with organic carbon sedimentation and benthis processes” - “Paleo-oceanographic studies in the continantal margin”. “Effects of ENSO and decadal changes on the regional circulation, water masses and biological communties” - “Spatial and Temporal Variability of the Surface and Subsurface Circulation off the Peruvian coast in association to ENSO”.

5. The PRIMO oceanographic cruise Sampling strategy for the PRIMO oceanographic cruise between 10°S (Peru) and 30°S (Chili),: 195 hydrographic stations and 4 3-day fixed stations in two legs, Callao-Iquique, Iquique-Coquimbo.

6. The main components of the cruise are : a series of four 3-day fixed stations in the Humboldt current system (Paita, Chimbote, Pisco, Iquique and Coquimbo). During the whole cruise, continuous records of surface temperature (SST), salinity (SSS), fluorometry, pCO2, pN2O, 0-700m ADCP currents as well as surface classical meteorological parameters will be obtained. Stations will include CTDO2 casts to the bottom or 1000m, whichever shallowest, and 24 10-liter bottle Rosette samples. Station spacing may vary from 10 nm on sections to 30 or 60nm on transects between sections. In addition, sediment sampling will be carried out as follows: Paita 1 multicore (instead of Chala) Chimbote: 5 multicores Pisco: 5 multicores Iquique: 5 multicores Antofagasta : 1 multicore Coquimbo: 5 multicores Concepcion : 5 multicores

7. Callao-Paita-Chimbote 540+200+450mn=5 d 15 stat. (1d) Paita fixed stat. (3d) Sampling strategy for the PRIMO oceanographic cruise between 05°S (Peru) and 30°S (Chile),: 210 hydrographic stations and 4 3-day fixed stations in two legs, Callao-Paita-Iquique, Iquique-Coquimbo. ------------------------------------------ Paita, an upwelling centre where local forcing interacts with a recurrent regional forcing (e.g. pulses of advective transport of equatorial surface waters and of moderately oxygenated subsurface waters) is proposed due to its position as northern boundary of the Humboldt Ecosystem, and its long-term hydro-biochemical data base.

8. Table: Summary of necessary ship-time for the different operations. 2.4.3

9. BIOGEOCHEMICAL SECTION (1.2.2.1 Processes involved in sustaining the OMZ) Concerning the overall structure of this section it is necessary to rewriting, the following structure is suggested: 1.2.2. Biogeochemical processes The OMZ is sustained by different biogeochemical processes that occurs in the water column and sediments. These processes impact the oxygen concentration of these areas and, in turn, are strongly impacted by the presence of minimum oxygen conditions. They concern the following processes: 1.2.2.1 Production of organic matter 1.2.2.2 Remineralization of organic matter and nitrogen cycling 1.2.2.3 Trace metals speciation 1.2.2.4 Transfer and export of organic matter 1.2.2.5 Benthic biogeochemical processes

10. 1.2.2.1. Production of organic matter Should contain the topics related with new and regenerated primary production, community structure, carbon and nitrogen uptake (see PRIMO document). • 1.2.2.2. Remineralization of organic matter and nitrogen cycling. Should contain the section of biogenic elements mapping (the text was expanded with more background), OM respiration pathways (POM and DOM), Nitrogen processes (ammonium regeneration, nitrification, desnitrification, anammox) and the structure of the related community. • 1.2.2.3. Trace metals speciation (Fe, Zn, Co, Cd) - see PRIMO document • 1.2.2.4 Transfer and export of organic matter Should contain, studies with micro/meso zooplankton, grazing activity, sinking particles.

11. 1.2.2.5 (1.2.2.2) Benthic biogeochemical processes • The overall text structure and objectives are ok for us. • Should contain: • Transport rates • The text concerning the sedimentation rates was expanded, indicating the use of gamma and alpha spectrometry, as well as AMS-14C. It is suggested to evaluate the feasibility of using Ra226 as a tool within the time window of the past 1000 years. • b. Redox conditions, respiration pathways and sediment composition • Core and in vitro incubation experiments are proposed to measure rates of CO2 production, nitrogen trasformation and fluxes, and sulphate reduction in the sediment/water interface.

12. c. Benthic community structureand function • The text was expanded with more background information on benthic community features in the HCS. • For assessing bioturbation we suggest to combine indirect estimates from short-lived radionuclide profiles, vertical profiles of benthic biomass and functional groups, luminophore experiments, and image analyses from X-radiographies of the upper sediment layer. • Biological information (micro-, meio- and macrofauna) will also contribute to a better understanding of the imprint and interactions of the biological activity with biogeochemical processes and proxies preservation.

13. Peruvian participants in PRIMO • Physical Oceanography • Currentmeter moorings and data processing : Luis Pizarro, Luis Vásquez • Onboard CTD/ADCP hydrography and data processing: Luis Vásquez, José Tenorio • Remote sensing : Mario Ramírez, N. Domínguez • Biogeochemistry • Phytoplankton/flow citometry : Sonia Sánchez • Mesozooplankton/microzooplankton communities, diel migration :Patricia Ayón • Nitrogen cycling in the water column: Michelle Graco • Primary Production*: Georgina Flores, Jesús Ledesma • pCO2, TCO2 distribution and Alkalinity: Jesús Ledesma, G. Flores • Bioturbation (from radionuclide profiles): Dimitri Gutierrez • Sediment comm. respiration rates (from CO2 production): Dimitri Gutiérrez, M. Graco • Nitrogen cycling in the sediment/water interface: Michelle Graco • Benthic community structure: Luis Quipúzcoa (Macrofauna), Edgardo Enríquez (Meiofauna), • Luis Quipúzcoa, Wilbert Serrano (Microfauna, /DAPI, CTC and FISH?)

14. Proxy callibrations and Sediments • Sedimentation rates (from radionuclide profiles with Paleotropique and LSCE) : • Dimitri Gutiérrez • Bulk CNS, Rockeval and C, N isotopes (with Paleotropique):Dimitri Gutiérrez • Mineralogy (DRX, FTIR with Paleotropique): Federico Velazco • Mineralogy (Redox sensitive metals with Paleotropique): Juana Solís • Diatoms : Pedro Tapia (UPCH), F. Chang • Fish scales : Renato Salvatteci • Benthic forams : María Morales (INGEMMET), Sergio Mayor • Plankton forams : María Morales (INGEMMET) • ------------------------ • UPCH: Universidad Peruana Cayetano Heredia • INGENMET: Instituto Nacional Geologico y Metalurgico

15. Modelling • Numerical oceanographical modelling : José Pasapera, Augusto Ingunza • Numerical meteorological modelling/MM5 : Yamina Silva (IGP) • Subsurface current fields validation : Carmen Grados, Roberto Flores • Biogeochemical modelling validation: Georgina Flores • Biogeochemical dynamical modelling : Jorge Tam, Augusto Ingunza • Biogeochemical model parameterization : Michelle Graco • --------------- • IGP : Instituto Geofisico del Peru