000K utf8 1100 $c2007 1500 eng 2050 urn:nbn:de:gbv:8-diss-19224 3000 Knotz, Susanna 4000 Trophic interactions in the pelagic$hChristian-Albrechts-Universität zu Kiel [Knotz, Susanna] 4030 Kiel$nChristian-Albrechts-Universität zu Kiel 4209 Physiological and nutritional factors that influence the population dynamics of North Sea copepods were identified. Five digestive enzymes were measured in individual copepods. Short-term starvation elicited complex enzyme reactions. Protease isozyme patterns did not change. Seston C:N and POP:TPP correlated with reproductive success. Grazing behaviour and digestive system mediated the effect. Copepods took up N:P in ratios matching their body ratios. C:N and POP ingestion followed the seston pattern. Compensatory feeding was observed. Food quality and stable isotope signatures changed over time (Helgoland, 2004-2005) and between GLOBEC-stations (southern North Sea). Seston d15N and d13C revealed major composition shifts in spring and a strong heterotroph component in summer. A. clausi and T. longicornis utilised different carbon sources despite similar high trophic levels. A low seston d13C (spring) was favourable. Chitobiase activity indicated C assimilation, the other enzymes N assimilation. A low body d13C may denote high turnover rates. Combining methods explains zooplankton- phytoplankton interactions better than only one approach. 4950 https://nbn-resolving.org/urn:nbn:de:gbv:8-diss-19224$xR$3Volltext$534 4961 https://macau.uni-kiel.de/receive/diss_mods_00001922 5051 550 5550 C:N:P 5550 digestive enzymes 5550 elemental uptake 5550 Ernährung 5550 GLOBEC 5550 grazing behaviour 5550 Helgoland 5550 Nordsee 5550 North Sea copepods 5550 protease isozymes 5550 Ruderfußkrebse 5550 seston quality 5550 stable isotope ratios