School of Engineering and Science - Jacobs University

CHAPTER I
Figure 6: Comparison of cell concentration data on Myrionecta rubra [n L -1 ] between the 2.5 year
microzooplankton monitoring (a) and the long-term monitoring (b).
Besides the different counting frequencies deviations in the recordings of both species
resulted most probably from differences in counting methodology. While in the longterm
monitoring lower volumes are settled during blooms due to cell densities (usually
25 mL) and often stripes are counted for the smaller species, at least half of the
sedimentation chamber was counted during the microzooplankton monitoring and 50
mL were always used for sedimentation. Despite these minor differences data on N.
scintillans and M. rubra of both monitoring programs matched quite well.
Ecological implications of the microzooplankton monitoring data
Our results for ciliates are similar to results from monitoring programs in the Baltic Sea
and the Gulf of Maine (Montagnes et al., 1988) where they also form distinct spring
peaks (Smetacek, 1981, Johansson et al., 2004). Heterotrophic dinoflagellates are
generally directly related to the availability of larger phytoplankton prey (Hansen, 1991)
and often occur at high concentrations during diatom blooms (Sherr & Sherr, 2007)
especially in spring (Stelfox-Widdicombe et al., 2004). Hansen (1991) reported a close
relationship between dinoflagellate concentration and prey availability as also shown by
our results.
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