Metabolismus des Stickstoffs in der Amazonasfahne und dem westlichen, tropischen Nordatlantik (MeNARP)

• Antragstellerinnen: Dr. Natalie Loick-Wilde; Professorin Dr. Maren Voß
• Fachliche Zuordnung: Physik, Chemie und Biologie des Meeres ; Biochemie und Physiologie der Tiere ; Ökologie und Biodiversität der Tiere und Ökosysteme, Organismische Interaktionen
• Förderung: Förderung von 2020 bis 2024
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 439440452

• Erstellungsjahr: 2024

Zusammenfassung der Projektergebnisse

For the first time, the nitrogen cycle of the world's largest river and adjacent coastal ocean was studied incl. the plankton community and the food web. Although a zonation along the river plume had been described before, it was for the first time detailed including nutrient uptake and primary production. We described the sediment as a reactor, low primary production and high recycling rates in the high turbidity zone leading to the export of recycled N rather than riverine nitrogen. Interestingly, primary production was strongly ammonium driven in the northern plume, where nitrogen fixation rates remained low. Combining tracer and natural abundance data of bulk and compound specific stable nitrogen isotope data allowed for the first time to directly apply a mesozooplankton community production approach. This unexpectedly allowed for both, quantifying secondary production and identifying its physiological and environmental regulation, both of which have been unreached long term goals in marine science for the longest time now. In contrast to phytoplankton, which expresses high overall production rates, mesozooplankton production was strongly regulated by phytoplankton structure and function as well as habitat heterogenity. Contrary to the expectation that significant changes in the river loads due to the drastic human influences in the catchment area would be visible at the time of the cruise, these were not detected. However, this is to be expected in the coming years. Whether factors such as deforestation, dam construction, and global warming reinforce or cancel each other out is impossible to assess. In biogeochemical models, k2 (or NGE) and TP of mesozooplankton are constants e.g. set to 0.4 and 2.0 (herbivore), which leads to exponential errors in the estimation of secondary production and ammonium regeneration by mesozooplankton in models. We suggest to use adjusted TP and NGE or k2 values for mesozooplankton depending on the dominant phytoplankton in the habitat. Mixotrophy in phytoplankton seems to be an formerly unidentified strategie for optimal nutrient drawdown in the ARP.

Projektbezogene Publikationen (Auswahl)

• Nitrogen cycling and physical processes in the Amazon River plume, Cruise No. M 174, 12/04/2021 - 30/05/2021, Las Palmas (Spain) - Emden (Germany). In METEOR-Berichte (Vol. M174, pp. 1-40).
  Voss, M., Burtscher, E., Choisnard, N., Fernández Carrera, A., Fröhberg, N., Hollister, A., Loick- Wilde, N., Mohrholz, V., Montoya, J. P., Panthalil, B., Stelzer, M., Subramaniam, A., Umbricht, J. & Waggoner, E.
  
• Hydrographic properties of water masses in the Amazonas River plume obtained in April/May 2021 by CTD measurements during RV METEOR cruise M174 [dataset]. PANGAEA
  Mohrholz, V., Heene, T., Mars, R., Söder, J. & Subramaniam, A.
  
• Chemistry porewater nutrients and nutrient fluxes at sediment water interface
  Choisnard et al.
  
• Export of ice-nucleating particles from watersheds: results from the Amazon and Tocantins river plumes. Royal Society Open Science, 10(2).
  Einbock, Annika; Burtscher, Emma; Frey, Claudia & Conen, Franz
  
• The Amazon shelf sediments, a reactor that fuels intense nitrogen cycling at the seabed. Limnology and Oceanography, 68(10), 2211-2226.
  Choisnard, Noémie; Burtscher, Emma; Forster, Stefan; Frey, Claudia; Moros, Matthias & Voss, Maren
  
• Nitrate Uptake and Primary Production Along the Amazon River Plume Continuum. Journal of Geophysical Research: Biogeosciences, 129(8).
  Umbricht, Jacqueline; Burmeister, Christian; Dippner, Joachim W.; Liskow, Iris; Montoya, Joseph P.; Subramaniam, Ajit & Voss, Maren
  
• Nitrification in the Amazon River plume. Marine Ecology Progress Series, 730, 1-14.
  Choisnard, N.; Sperlea, T.; Liskow, I. & Voss, M.
  
• Nitrogen Turnover during Aging Cyanobacterial Blooms (NAC), Cruise No. EMB297, 19. AUGUST 2022 - 02. SEPTEMBER 2022, Rostock-Marienehe RFH (Germany) - Rostock-Marienehe RFH (Germany).
  Loick-Wilde, N., Mohrholz, V., Fernández-Carrera, A. & J. P. Montoya
  
• Planktonic habitats in the Amazon Plume region of the Western Tropical North Atlantic. Frontiers in Marine Science, 11.
  Pham, Anh H.; Choisnard, Noémie; Fernández-Carrera, Ana; Subramaniam, Ajit; Strope, Erica K.; Carpenter, Edward J.; Voss, Maren & Montoya, Joseph P.
  
• The Amazon River plume—a Lagrangian view. Limnology and Oceanography: Methods, 22(8), 572-589.
  Dippner, Joachim W.; Montoya, Joseph P.; Subramaniam, Ajit; Umbricht, Jacqueline & Voss, Maren