Bacteria-zooplankton interactions: a key to understanding bacterial dynamics and biogeochemical processes in lakes?
Final Report Abstract
Bacteria in aquatic environments have primarily been regarded as free-living organisms responsible for degradation of dissolved organic matter although the importance of zooplankton and their carcasses for bacteria has been previously described. Our studies reveal that dead and live zooplankton selects for highly specific bacterial communities with potentially important physiological capabilities for aquatic organic matter and energy cycling. The major results are: • Zooplankton-associated bacterial communities significantly differ from those in the surrounding water in a large number of aquatic habitats. We show that - although zooplankton form unique microhabitats (islands) - bacteria associated to zooplankton are not independent from their environment and that their community composition greatly differs along a salinity gradient and with sampling depth. In addition microbial community composition changes over time in relation to temporal changes in environmental parameters. • Microbial communities on both live and dead zooplankton show active nirS gene expression and direct stable isotope measurements reveal denitrification rates which were inversely related to oxygen concentration. These findings indicate the particular importance of the zooplankton microhabitat for overall biogeochemical processes in aquatic systems. • Microbial symbionts allow for specific biogeochemical processes which cannot take place in the surrounding water. In particular, presence of nitrifying bacteria and cyanobacteria in the ciliate host, when nitrogen is limited in the environment, suggests that specific microbial symbionts have the potential to render the ciliate host less dependent from its environment. In conclusion, microbial interactions are of great importance for shaping the bacterial community structure and biogeochemical functioning of aquatic ecosystems. These interactions have been neglected for a long time but are substantial for microbial evolution, the identification of new bacterial (anaerobic) processes, and thus for the physiology of interacting partners. Better knowledge on these interactions could be a key for understanding aquatic microbial diversity and function in a rapidly changing world.
Publications
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(2012) Ciliate Epibionts Associated with Crustacean Zooplankton in German Lakes: Distribution, Motility, and Bacterivory. Spec. Issue Front Microbiol. 2012; 3(243): 1-11
Bickel, Samantha L.; Tang, Kam W. & Grossart, Hans-Peter
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(2012) Microbes in and on Organisms: Gain or Pain? Erweiterte Zusammenfassungen der Tagung in Koblenz 2012, Seiten 129-130, ISBN-Nr. 978-3-9813095-3-9
Grossart, H.-P. and Dziallas, C.
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(2013) Distinct Communities of Free-Living and Copepod-Associated Microorganisms along a Salinity Gradient in Godthabsfjord, West Greenland. Arctic, Antarctic, and Alpine Research, Vol. 45, (4): 471-480
Dziallas, Claudia; Grossart, Hans-Peter; Tang, Kam W. & Nielsen, Torkel Gissel
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(2013) Molecular and functional ecology of aquatic microbial symbionts. Front. Microb., 4:59
Grossart, Hans-Peter; Riemann, Lasse & Tang, Kam W.
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(2014) Structure and function of zooplanktonassociated bacterial communities in a temperate estuary change more with time than zooplankton species. Aquat. Microb. Ecol. 72: 1–15
Bickel, SL; Tang, KW & Grossart, HP
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(2014) Zooplankton carcasses and non-predatory mortality in freshwater and inland sea environments. J. Plankton Res. 36(3): 597–612
Tang, Kam W.; Gladyshev, Michail I.; Dubovskaya, Olgo P.; Kirillin, Georgiy & Grossart, Hans-Peter
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(2015) Copepod carcasses as microbial hot spots for pelagic denitrification. Limnology and Oceanography 60 (6), 2026-2037
Glud, Ronnie N.; Grossart, Hans‐Peter; Larsen, Morten; Tang, Kam W.; Arendt, Kristine E.; Rysgaard, Søren; Thamdrup, Bo & Gissel Nielsen, Torkel
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(2015) Estimating In Situ Zooplankton Non-Predation Mortality in an Oligo-Mesotrophic Lake from Sediment Trap Data: Caveats and Reality Check. PLoS ONE 07/2015; 10(7):e0131431
Dubovskaya, Olga P.; Tang, Kam W.; Gladyshev, Michail I.; Kirillin, Georgiy; Buseva, Zhanna; Kasprzak, Peter; Tolomeev, Aleksandr P. & Grossart, Hans-Peter
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(2015) Tube-dwelling invertebrates: tiny ecosystem engineers have large effects in lake ecosystems. Ecological Monographs 08/2015; 85(3):333–351
Hölker, Franz; Vanni, Michael J.; Kuiper, Jan J.; Meile, Christof; Grossart, Hans-Peter; Stief, Peter; Adrian, Rita; Lorke, Andreas; Dellwig, Olaf; Brand, Andreas; Hupfer, Michael; Mooij, Wolf M.; Nützmann, Gunnar & Lewandowski, Jörg
