Assessment of planktonic metabolism in the artic and subtropical oceans by the 18O method

• Main Author: Mesa Cano, Elena
• Other Authors: Delgado Huertas, Antonio, Duarte Quesada, Carlos Manuel, Universidad de Granada. Programa Oficial de Doctorado en: Ciencias de la Tierra
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universidad de Granada 2018
• Subjects: Fitoplancton marino; Productividad primaria (Biología); Metabolismo; Biogeoquímica; Océanos; Respiración; Artico; Ecología marina; 55; 581.526.325; 2500; 2510; Arctic; Svalbard; Greenland; Pacific; Indian; artico; Phytoplankton
• Online Access: http://hdl.handle.net/10481/49076

The metabolism of oceanic phytoplankton, consisting of gross primary production (GPP) and respiration (R), regulates biogeochemical cycles and climate. Plankton photosynthesis is responsible for half of the world primary production and fuels the marine food web and the biological CO2 pump, which makes oceanic phytoplankton primary production a fundamental process at the global scale. However, there is a current debate over the estimations coming from different methods to assess GPP. The 18O method is the most accurate one and the only one that measures GPP directly, but has been used in very few studies (less than twenty, to the best of our knowledge) which are not representative of the global ocean. The other metabolic process, plankton respiration, is a major component of global CO2 production. At the ecosystem level, respiration integrates so many aspects of the functioning, that long-term shifts in respiration may provide the best warning system for global change. However, global respiration data are much more scarce than primary production data, there are around 20,000 estimates of oceanic production for each estimate of respiration rate. In addition, respiration is usually measured in dark conditions, assuming that it is equivalent to respiration in the light, which has not been proved and might thus be biasing global models of gas fluxes. The main aim of this PhD thesis is to go a step further in the global assessment of planktonic metabolism, by evaluating GPP18O (i.e. GPP measured with the 18O method) in the Arctic and in the tropical and subtropical ocean, and by testing the hypothesis of equal respiration in the dark and in the light. We assessed GPP18O in the context of three different studies: in the tropical and subtropical ocean (Malaspina Expedition); in the European Arctic Sector (to the west of Svalbard islands); and in a fjord in the east coast of Greenland (Young Sound). We evaluated GPP18O in 84 stations across the Atlantic, Pacific and Indian Oceans, in the framework of the 2010 Malaspina Expedition, occupying four of the five subtropical gyres. Tesis Univ. Granada. Programa Oficial de Doctorado en: Ciencias de la Tierra JAE Pre-doc fellowship from the Spanish National Research Council (CSIC). “Expedición de circunnavegación Malaspina 2010: Cambio Global y Exploración de la Biodiversidad del Océano Global” project, funded by Spanish Ministry of Education and Science (Ref. CSD2008-00077) “MALASPINOMICS y MALASPINA-ANALYTICS: Análisis de muestras de interés estratégico clave recogidas por la expedición Malaspina-2010”, funded by Spanish Ministry of Economy and Competitiveness (Ref. CMT-2011-15461-E). “Metabolismo del Océano: nuevas aproximaciones biogeoquímicas”, funded by Spanish Ministry of Economy, Industry and Competitiveness (Ref. CTM2013-49429R) “ARCTICMET: impacto del cambio climático sobre el metabolismo del Ártico” project, funded by the Spanish Ministry of Economy and Competitiveness (Ref. CTM2011-15792-E). ATOS project, funded by the Spanish Ministry of Economy and Competitiveness (Ref. POL2006-00550/CTM). ATP project, funded by the FP-7 of the EU (Ref. CTM2009-07781-E). CarbonBridge project, funded by the Norwegian Research Council (Ref. 226415). Greenland Ecosystem Monitoring (GEM) program. Carlsberg Foundation.