Abundance of microzooplankton determined during the EisenEx cruise ANT-XVIII/2 to the South Atlantic

During the 21 day experiment, protozooplankton and small metazooplankton were sampled from the mixed layer inside and outside the patch using Niskin bottles. Aplastidic dinoflagellates increased threefold in abundance and biomass in the first 10 d of the experiment, but decreased thereafter to values twofold higher than pre-fertilisation values.

The decline after day 10 is attributed to increasing grazing pressure by copepods. They also constrained ciliate abundances and biomass which were higher inside the fertilised patch than outside but highly variable. Copepod nauplii abundance also remained stable whereas biomass doubled.