SUBPROJECT - B8
The role of zooplankton in N-, P- and C- cycling and for the oxygen budget of tropical oxygen minimum zones
Zooplankton organisms are an essential component of pelagic biogeochemical cycles via their uptake and catabolism of particulate organic matter. Environmental oxygen levels exert significant controls on zooplankton abundance, biomass and activity. At the same time, zooplankton metabolism possibly impacts oxygen gradients at the oxycline, and thus potentially the physical supply of oxygen to the oxygen minimum zones (OMZ). We will contribute to the synthesis efforts in the 3rd phase of the SFB 754 to calculate the Eastern Tropical North Atlantic and Eastern Tropical South Pacific oxygen budget with estimates of zooplankton and particulate matter respiration rates as central constituents of the oxygen demand component. To better resolve the mutual interactions between oxygen, particulate matter distribution and zooplankton activity across the oxycline and in the OMZ, we will resolve the fine scale distribution of zooplankton with horizontal net catches that target different oxygen levels. Zooplankton also responds to phytoplankton community dynamics, and often controls phytoplankton biomass build-‐up. The mesocosm experiment conducted together with B2 will enable us to study the impacts of different nutrient supply regimes on zooplankton biomass build-‐up. Specifically it will be important to assess how much N and P are bound in zooplankton during the course of the experiment to allow budget calculations.
Furthermore, we will be able to study how zooplankton grazing impacts phytoplankton
dynamics. Already available and further planned observations of zooplankton abundance, biomass, food availability (detritus, marine aggregates, phytoplankton from UVP5 observations and in collaboration with B2) and grazing activity from oceanographic surveys will enable us to synthesize mesocosm study results and field observations regarding the role of zooplankton in controlling elemental cycles. We will also further improve biogeochemical models with respect to the representation of heterotrophic processes in the tropical ocean and their dependence on substrate supply via diel vertical migrations of zooplankton and particulate matter flux. We aim to improve our understanding of interactions between these processes in a consistent hydrographic context using global model experiments that include parameterizations for marine aggregates and zooplankton dynamics.
Franz, J., H. Hauss, U. Sommer, T. Dittmar and U. Riebesell (2012) Production, partitioning and stoichiometry of organic matter under variable nutrient supply during mesocosm experiments in the tropical Pacific and Atlantic Ocean. Biogeosciences, 9(11), 4629-‐4643, doi: 10.5194/bg-‐9-‐4629-‐2012
Hauss, H., J. Franz and U. Sommer (2012) Changes in N:P stoichiometry influence taxonomic composition and nutritional quality of phytoplankton in the Peruvian upwelling. J. Sea Res., 73, 74-‐85, doi: 10.1016/j.seares.2012.06.010
Hauss, H., J. Franz, T. Hansen, U. Struck, and U. Sommer (2013) Relative inputs of upwelled and atmospheric nitrogen to the eastern tropical North Atlantic food web: Spatial distribution of δ15N in mesozooplankton and relation to dissolved nutrient dynamics. Deep-Sea Res. Pt. I, 75, 135-‐145, doi: 10.1016/j.dsr.2013.01.010
Hauss, H., S. Christiansen, F. Schütte, R. Kiko, M.E. Lima, E. Rodrigues, J. Karstensen, C.R. Löscher, A. Körtzinger and B. Fiedler (2015) Dead zone or oasis in the open ocean? Zooplankton distribution and migration in low-oxygen modewater eddies. Biogeosciences Discuss, 12, 18315-18344, doi:
Kiko, R., H. Hauss, F. Buchholz and F. Melzner (2015) Ammonium excretion and oxygen respiration of tropical copepods and euphausiids exposed to oxygen minimum zone conditions. Biogeosciences Discuss., 12, 17329-17366, doi:
Kiko, R., H. Hauss, M. Dengler, S. Sommer and F. Melzner (2015) The squat lobster Pleuroncodes monodon tolerates anoxic “dead zone” conditions off Peru. Marine Biology, 1-9, doi: 10.1007/s00227-015-2709-6
Sandel, V., R. Kiko, P. Brandt, M. Dengler, L. Stemmann, P. Vandromme, U. Sommer and H. Hauss (2015) Nitrogen Fuelling of the Pelagic Food Web of the Tropical Atlantic. PloS one, 10, e0131258, doi: