Die Dynamik von Vitaminen und Spurenmetallen im Südpolarmeer: Bildungs- und Abbauprozesse von B-Vitaminen, Eisen, Zink und Kobalt mit Hilfe eines neuen Massenbilanz Verfahrens
Zusammenfassung der Projektergebnisse
Iron (Fe) is a strong driver of primary production and plankton ecology of the Southern Ocean. Recently it has come to light, however, that other trace nutrients such as Mn, Zn, Co and B-vitamins, may limit or, with Fe, co-limit the plankton community in the high nutrient low chlorophyll (HNLC) regions of the worlds oceans. Also, since the solubility and bioavailability of trace metals change depending on the pH of seawater, increases in pCO2 and resulting ocean acidification may also be important. Little is known on how the changes in availability of one trace nutrient impacts the cellular stoichiometry of the others and how changes a high CO2 ocean may influence these. Even though grazing by meso- and microzooplankton has long been acknowledged as an important factor in resupplying TMs to the dissolved pool, few studies have quantified these rates. Lastly, methodologies to measure B-vitamins and estimate resupply/production of TMs/B12 in the field are scarce. ViTMeD aimed at answering these questions through method development and a combination of laboratory and field experiments. Laboratory experiments revealed that the ecologically important species Phaeocystis antarctica responded strongly to Fe limitation by reducing its growth rate and particular organic carbon (POC) production. Even though OA stimulated growth in Fe-limited and -replete treatments, the slight reduction in cellular POC resulted in no net effect on POC production. Cellular concentrations of all TMs, not just Fe, were greatly reduced, suggesting that Fe limitation may drive cells into secondary limitation by another TM. Similarly, the diatom Chaetoceros simplex, and the cryptophyte Geminigera cryophila responded to various TM and vitamin limitation scenarios by reducing their growth and particulate organic carbon production rates. Also, limitation by one TM resulted in a significant decrease of the cellular quotas of other TMs measured. Field Experiments revealed that the biomass at two stations in the Drake Passage was primarily limited by Fe availability. The experiments did, however reveal that all of the different TM/B12 amendments forced changes in the community composition and revealed that B12 colimitation was prevalent in most of the plankton groups examined, followed by Zn and Mn. Uptake of TMs and B12 varied greatly around the WAP. Uptake of Fe and Zn occurred mostly in to the >2µm size fraction while the picoplankton were responsible for >70% of B12 uptake. This is despite the fact that primary production was equally distributed between both size fractions at most of the stations. Incubation experiments using salp and krill fecal pellets as an iron source showed that both, krill and salp pellets release similar amounts of Fe (per fecal pellet carbon). However, ~5 times higher Fe uptake by plankton in the salp fecal pellet compared to the krill fecal pellet treatment suggested a higher bioavailability of the Fe released form the former. Microzooplankton grazing experiments highlighted that heterotrophic picoplankton play a significant role in carbon cycling around the WAP and that high C:N seem to be targeted, driving the observed increases in C:N ratios when the grazing pressure was released. Finally, while the original approach of measuring recycling/production of TM/B12 for this project was limited due to flawed, existing methods, innovative new approaches developed during ViTMeD are promising. Together these findings provide new insights into drivers of SO plankton ecology and improve our understanding of biogeochemical cycles in this climate sensitive region.
Projektbezogene Publikationen (Auswahl)
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The impacts of iron limitation and ocean acidification on the cellular stoichiometry, photophysiology, and transcriptome of Phaeocystis antarctica. Limnology and Oceanography, 64(1), 357-375.
Koch, Florian; Beszteri, Sara; Harms, Lars & Trimborn, Scarlett
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Limitation by Fe, Zn, Co, and B12 Results in Similar Physiological Responses in Two Antarctic Phytoplankton Species. Frontiers in Marine Science, 6(c(2019, 8, 20)).
Koch, Florian & Trimborn, Scarlett
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Salp Fecal Pellets Release More Bioavailable Iron to Southern Ocean Phytoplankton than Krill Fecal Pellets. SSRN Electronic Journal (2020).
Böckmann, Sebastian; Koch, Florian; Meyer, Bettina; Pausch, Franziska; Iversen, Morten; Driscoll, Ryan; Laglera, Luis Miguel; Hassler, Christel & Trimborn, Scarlett
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Krill and salp faecal pellets contribute equally to the carbon flux at the Antarctic Peninsula. Nature Communications, 12(1).
Pauli, Nora-Charlotte; Flintrop, Clara M.; Konrad, Christian; Pakhomov, Evgeny A.; Swoboda, Steffen; Koch, Florian; Wang, Xin-Liang; Zhang, Ji-Chang; Brierley, Andrew S.; Bernasconi, Matteo; Meyer, Bettina & Iversen, Morten H.
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Iron and manganese co-limit the growth of two phytoplankton groups dominant at two locations of the Drake Passage. Communications Biology, 5(1).
Balaguer, Jenna; Koch, Florian; Hassler, Christel & Trimborn, Scarlett
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Method optimization of the simultaneous detection of B12 congeners leading to the detection of a novel isomer of hydroxycobalamin in seawater. Rapid Communications in Mass Spectrometry, 36(23).
Möller, Kristof; Krock, Bernd & Koch, Florian
