Coastal-ocean variability in primary production in the Canary Current upwelling region: comparison among in situ and satellite-derived estimates

Poster.-- Conferencia sobre los Sistemas de Afloramiento de Borde Oriental (EBUS): Pasado, Presente y Futuro & Segunda Conferencia Internacional sobre el Sistema de Corrientes de Humboldt, 19-23 de Septiembre de 2022, Lima, PerúThe Canary Current Eastern Boundary Upwelling Ecosystem (CanC-EBUE), unlike other EBUE, has been unabatedly warming, and decreasing (or at least not increasing) in wind intensity during the last 60 years. However, past trends in net primary production are uncertain, due to differences in the outputs of remote sensing models and the lack of in situ data to validate these models in the region. Here we compare four widely-used models – the Vertically Generalized Production Model (VGPM) and its variant based on Eppley’s description of the growth function (Eppley-VGPM), the Carbon-based Production Model (CbPM), and the Carbon, Absorption and Fluorescence Euphotic-resolving model (CAFE)- with in situ primary production (PP) data. Together with chlorophyll a concentration (Chl a) and phytoplankton biomass (B), we measured PP by 14C and 13C uptake, and oxygen evolution inside incubation bottles, along 11 stations across the transition zone expanding from the coastal upwelling to the open ocean waters at the Cape Verde Frontal Zone (17-23ºN; 16-26ºW). We compared in situ PP, Chl a and B with models’ outputs (NPP) and inputs (satellite derived Chl a and B), respectively. Although carbon and oxygen –based in situ PP estimates were frequently correlated, we found that only the Chl a-based VGPMs were significantly correlated with in situ estimates, yet these are among the the first-described models in the literature. Models based on B, however, did not correlate with in situ PP estimations, in spite that satellite-derived B presented better correlations than Chl a with the in situ dataN

KOSMOS 2020 Peru mesocosm study on ecosystem responses to different light and upwelling intensities: oxygen primary production rates of water samples

This data is part of the BMBF project CUSCO (Coastal Upwelling Systems in a Changing Ocean). Here we report oxygen primary production rates during a 35-day experiment, where we enclosed natural plankton communities in in-situ mesocosms off Peru. The experiment investigated the interactive effects of light and upwelling on the Humboldt upwelling ecosystem by mimicking a gradient of upwelling intensities (0%, 15%, 30%, 45% and 60%) under summer-time high light and winter-time low light. Integrated seawater samples from a depth between 0 and 10m were collected using a 5L Integrating Water sampler (IWS; Hydro-Bios, Kiel). Oxygen production as well as respiration rates were measured as described in Ortiz et al. (2022; doi:10.3389/fmars.2021.743105) using the Winkler method. For each mesocosm and sampling day samples for initial oxygen values fixed immediately after subsampling ("Initial"), dark incubations ("Dark") and light incubations ("Light") were measured. All samples were incubated with constant light dark/cycles and temperature was adjusted regularly to mesocosm values. After incubation samples were fixed and titrated by means of an automated, precise titration system with colorimetric end-point detection along with the initials (Dissolved Oxygen Analyzer, SIS Schwentinental, Germany). Community respiration (CR) was calculated as the oxygen consumption during dark incubation per hour. Net community production (NCP) was the oxygen production per hour in the light samples and gross production (GP) the sum of CR and NCP

Artificial Upwelling Intensity and Mode Have a Major Imprint in Dissolved Organic Matter Dynamics

VIII International Symposium on Marine Sciences, 6-8 July 2022, Las Palmas de Gran Canaria, EspañaIn the face of climate change there is a need to reduce atmospheric CO2 concentrations. Artificial upwelling of nutrient-rich deep waters has been proposed as a method to enhance the biological carbon pump in oligotrophic oceanic regions in order to fuel carbon sequestration. However, the fate of the newly produced organic matter, and specifically of its resulting dissolved fraction, is not clearly understood. In the present work, nutrient-rich deep water was introduced to large scale (~44 m3) mesocosms in the oligotrophic subtropical North Atlantic with the aim of studying how the intensity and mode of artificial upwelling (large single pulses vs recurring smaller pulses) affects the dissolved organic matter (DOM) pool. Artificial upwelling yielded marked increases in the concentration and shifts in the characteristics of DOM. The magnitude of the observed changes was mostly related to the upwelling intensity: more intense treatments led to higher accumulation of dissolved organic carbon (>70 μM of excess DOC over ambient waters for extreme treatments), as well as increases in the concentration and average molecular weight of chromophoric DOM (CDOM) and the intensification of humic-like fluorescent DOM, suggesting transformation of the DOM pool. The artificial upwelling mode also affected DOM, with singular treatments overall resulting in higher CDOM quantities and molecular weight than recurring treatments. Our results indicate that under artificial upwelling, large DOM pools may accumulate in the surface ocean without being remineralised in the shortterm. This persistence could be associated with a combination of the molecular diversification of DOM due to microbial reworking, nutrient limitation and reduced metabolic capabilities of the prokaryotic communities inside the mesocosms. The present study highlights the importance of considering DOC when assessing the carbon sequestration potential of artificial upwellingPeer reviewe

KOSMOS 2018 Gran Canaria mesocosm study: dissolved organic matter

This dataset contains the dissolved organic matter (DOM) quantification and optical characterisation results from a KOSMOS mesocosm experiment carried out in the framework of the Ocean Artificial Upwelling project. The experiment was carried out in the autumn of 2018 in the oligotrophic waters of Gran Canaria. During the 39 days of experiment nutrient-rich deep water was added to the mesocosms in two modes (singular vs recurring additions), with four levels of intensity. Dissolved organic carbon, nitrogen and phosphorus were quantified with a Shimadzu TOC-5000 and a QuAAtro AutoAnalyzer. The absorption and fluorescence proprieties of DOM were determined making use of an Ocean Optics USB2000+UV-VIS-ES Spectrometer and a Jobin Yvon Horiba Fluoromax-4 spectrofluorometer, respectively. The aim of this dataset was to study the effect of artificial upwelling on the dissolved organic matter pool and its potential implications for carbon sequestration