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217940.0 [No comment] 29.04.2005 10:18 Released

ID: 217940.0, MPI für Evolutionsbiologie / Ecophysiology
Impacts of copepods on marine seston, and resulting effects on Calanus finmarchicus RNA : DNA ratios in mesocosm experiments
Authors:Becker, C.; Brepohl, D.; Feuchtmayr, H.; Zöllner, E.; Sommer, F.; Clemmesen, C.; Sommer, U.; Boersma, M.
Date of Publication (YYYY-MM-DD):2005-02
Title of Journal:Marine Biology
Issue / Number:3
Start Page:531
End Page:541
Review Status:not specified
Audience:Not Specified
Abstract / Description:We investigated the impact of copepods on the seston community in a mesocosm set-up, and assessed how the changes in food quantity, quality and size affected the condition of the grazers, by measuring the RNA:DNA ratios in different developmental stages of Calanus finmarchicus. Manipulated copepod densities did not affect the particulate carbon concentration in the mesocosms. On the other hand, chlorophyll a content increased with higher copepod densities, and increasing densities had a positive effect on seston food quality in the mesocosms, measured as C:N ratios and omega3:omega6 fatty acid ratios. These food quality indicators were significantly correlated to the nutritional status of C. finmarchicus. In contrast to our expectations, these results suggest a lower copepod growth potential on higher quality food. However, in concordance with earlier studies, we found that when copepods were in high densities the large particles (>1000 mum(3)) decreased and that the smaller particles (<1000 mum(3)) increased in number. These patterns were closely linked to the condition of C. finmarchicus, which were of better condition (RNA:DNA ratios) with increasing biovolumes of large particles, and, conversely, lower RNA:DNA ratios with increasing biovolumes of smaller particles. Consequentially, the selective grazing by copepods stimulated increased biovolumes of smaller plankton, and this increase was responsible for the increased food quality, in terms of C:N and omega3:omega6 ratios. Thus, we conclude that the decreasing growth potentials of C. finmarchicus were a result of a decrease of favourably sized food particles, induced by copepod grazing.
External Publication Status:published
Document Type:Article
Affiliations:MPI für Limnologie/Abt. Ökophysiologie
External Affiliations:Michigan State Univ, Wk Kellogg Biol Stn, Hickory Corners, MI 49060 USA; IFM GEOMAR Marine Okol, Leibniz Inst Meereswissensch, Kiel, D-24105 Germany; Alfred Wegener Inst Polar & Marine Res, Biol Anstalt Helgoland, Helgoland, D-27483 Germany
Identifiers:ISSN:0025-3162 [ID-No:1]
DOI:10.1007/s00227-004-1459-7 [ID-No:2]
LOCALID:2375/S 38353 [Listen-Nummer/S-Nummer]
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