Food web structure variability in the surface layer, at a fixed station influenced by the North Western Mediterranean Current

Urania Christaki (1, 2) , France van Wambeke (2) , Epaminondas D Christou (3) , Pascal Conan (1) , Raymond Gaudy (1)

1 COM - Centre d'océanologie de Marseille
2 Laboratoire de Microbiologie Marine
3 National Centre for Marine Research

The structure of the planktonic community and the influence of mesozooplankton migration on the microbial food web were investigated during six die' studies from June 92 to June 93 in the surface waters of a station in the NorthWestern Mediterranean Sea. Each die' study consisted of sampling at 5 and 40 m every 3 h over 24 h. Most of the times diel cycles did not show any convincing diel patterns in any of the variables studied. Clear zooplankton migration was evident in only two diel studies. The ratio of heterotrophic/autotrophic biomasses varied from 0 .68 to 3 .0, with a strong dominance of the heterotrophic biomass under oligotrophic conditions. Differences in food web structure were probably related to the influences of coastal water and the NorthWestern Mediterranean Current. Thus we found that the planktonic food web variability relatable to hydrodynamic variability, to be greater than die' variability. However, very large differences in food web structure among dates were evident. For example proportion of Chl a found in the < 10 tm fraction varied from 18 to 96% .

Mots clés: microbial food web; diel cycles; mesozooplankton; NW Mediterranean Sea

Domaines: Sciences de l'environnement; Océan, Atmosphère

Urania Christaki, France van Wambeke, Epaminondas D Christou, Pascal Conan, Raymond Gaudy. Food web structure variability in the surface layer, at a fixed station influenced by the North Western Mediterranean Current. Hydrobiologia, 1996, 321, pp.14 - 19. ⟨hal-01829994⟩