Hansen, B. W. Roskilde University, bhansen@ruc.dk
Hygum, B. H. Roskilde University, hygum@ruc.dk
Brozek, M. Roskilde University,
Jensen, F. Roskilde University,
Rey, C. Université P. et M. Curie, Station Zoologique,

 
FOOD WEB INTERACTIONS IN A CALANUS FINMARCHICUS DOMINATED SYSTEM - A MESOCOSM STUDY
 
The significance as grazers of Calanus finmarchicus nauplii and copepodite stages were investigated during two periods of 7-8 d in experimental mesocosms (18,500 l) manipulated by additions of two different levels of inorganic nutrients. During the nauplii dominated period the phytoplankton bloomed with a mixture of diatoms and nanophytoplankton and during the copepodite period the phytoplankton was in a post-bloom phase characterized by mainly the flagellate Phaeocystis sp. All biomass pools of phytoplankton, bacteria, protozoans and copepods were determined, and additionally production as well as carbon demands. Grazing by copepods were obtained by three methods,gut fluorescense - chlorophyll clearance and growth method. Empirical carbon flow models were constructed and revealed that nauplii could not control- or cause any structuring effects upon the system. But the phytoplankton grazing was performed by the protozoans. In contrast, the copepodites grazed >100% of the daily primary production and additionally heavily upon the protozoans.The fate of the primary production in the two different copepod scenarios followed predicted schematic routes as suggested by Wassmann, 1998.
 
Day: Thursday, Feb. 4
Time: 10:30 - 10:45am
Location: Eldorado Hotel
 
Code: SS51TH1030E