Microzooplankton is now recognized as the main consumer of daily primary production in the ocean (Landry et al. 1997; Calbet and Landry 2004). This status confers microzooplankton a key role in the carbon fluxes through planktonic food webs. However different phytoplankton groups may differ in their growth and grazing-caused mortality rates (Latasa et al 1997, 2005). Within this background this work aims to 1) Characterize growth and mortality dynamics of main phytoplankton groups determined by marker pigments, 2) Quantify the carbon fluxes derived from these dynamics, 3) Analyze links between initial composition of phytoplankton community and relative contribution of different phytoplankton groups to carbon fluxes. In order to answer these questions we monthly sampled an oligotrophic coastal system of the northwestern Mediterranean. This sampling included dilution experiments and primary production measurements. Preliminary results show a clear seasonality. Phytoplankton community present during spring-summer period was more dynamic, with higher growth and mortality rates than the community observed during autumn-winter period. On average microzooplankton consumed daily 76 % of the primary production (66% and 90% during spring-summer and autumn-winter respectively) and 77 % of the chlorophyll a standing stock (110 % and 34 %. for spring-summer and autumn-winter period respectively). Carbon cycling through microzooplankton grazing was much faster during the spring-summer than autumn-winter period. Calbet, A. and Landry, M.R. (2004) Phytoplankton growth, microzooplankton grazing and carbon cycling in marine systems, Limnol. Oceanogr., 49, 51-57. Landry, M.R., R.T Barber, R.R Bidigare, F. Chai, K.H. Coale, H.G. Dam, M.R. Lewis, S.T,Lindley, J.J. McCarthy, M.R. Roman, D.K. Stoecker, P.G,Verity, J.R. White (1997) Iron and grazing constraints on primary production in the central equatorial Pacific: an Eqpac synthesis. Limnol.Oceanogr. 42: 405-418. Latasa, M., M.R Landry, L. Schlüter, and R.R. Bidigare (1997) Pigment-specific growthand grazing rates in the equatorial Pacific as measured by the dilution technique. Limnol. Oceanogr. 42:289-298 Latasa, M., X.A. Moran, R. Scharek, M. Estrada (2005) Estimating the carbon flux through main phytoplankton groups in the northwestern Mediterranean. Limnol. Oceanogr., 50:1447-1458

Symposium GLOBEC-IMBER España celebrado del 28-30 marzo de 2007 en Valencia.-- 1 page

Peer reviewed