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Abstract:
The dynamics of diatoms and dinoflagellates have been monitored for many
decades at the Helgoland Roads Long-Term Ecological Research site and
are relatively well understood. In contrast, small-sized eukaryotic
microbes and their community changes are still much more elusive, mainly
due to their small size and uniform morphology, which makes them
difficult to identify microscopically. By using next-generation
sequencing, we wanted to shed light on the Helgoland planktonic
community dynamics, including nano- and picoplankton, during a spring
bloom. We took samples from March to May 2016 and sequenced the V4
region of the 18S rDNA. Our results showed that mixotrophic and
heterotrophic taxa were more abundant than autotrophic diatoms.
Dinoflagellates dominated the sequence assemblage, and several
small-sized eukaryotic microbes like Haptophyta, Choanoflagellata,
Marine Stramenopiles and Syndiniales were identified. A diverse
background community including taxa from all size classes was present
during the whole sampling period. Five phases with several communities
were distinguished. The fastest changes in community composition took
place in phase 3, while the communities from phases 1 to 5 were more
similar to each other despite contrasting environmental conditions.
Synergy effects of next-generation sequencing and traditional methods
may be exploited in future long-term observations.
