engleski

The diatom Nitzschia sicula (Castr.) Hust. and naupliar faecal minipellets in the Adriatic Sea

Nitzschia sicula (Castr.) Hust., a planktonic pennate diatom, dominated the microphyto-plankton (10^5 x 104 cells • H) in the central, oligotrophic Southern Adriatic Pit waters (20-50m layer) in May 1990. Nauplii dominated the microzooplankton (3 indiv. • H in the 0-50m layer, 130 mn mean body length) and produced a considerable amount of faecal (mini)pellets (1900 • H at 50m, mean diameter 47 nm), which were compactly filled with N. sicula frustules. The subsurface accumulation of diatoms and nauplii was probably the result of both productive activity under specific hydrographic conditions and the convergence in a relatively strong southern Adriatic cyclonic gyre ; the advective transport of populations along the shear zone, at the boundary between water masses of different thermo-haline characteristics may also have played a role. The amount of minipellets was high if compared with the data available from other seas. This was probably due to high production of minipellets, their slow sinking rate, and/or an absence of manipulation of the faecal material by zooplankton

Nitzschia sicula; phytoplankton; microzooplankton; nauplii; faecal pellets; minipellets; hydrography; Adriatic Sea

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