A high-resolution diatom assemblage’s database was built on a 65 cm long sediment
core (Tó34f), obtained from the Siófok Basin of Lake Balaton in 2017. Light microscope
photo-documentation was developed out of 15,797 diatom valves. The pictures were arranged
according to taxonomy from centric diatoms via araphids, monoraphids to biraphid forms.
30 categories were established to group the diatom taxa instead of species level identification
requiring high level of expertise. Some (1) characteristic, and easily identifiable
taxa (Karayevia clevei, Cavinula scutelloides) were distinguished on species level,
(2) taxa were grouped at genus level (like Amphora, Aulacoseira, Neidium), while (3)
were joined based on their morphological features. Two large groups were created based
on this approach, the “light fragilarioids” and the “heavy fragilarioids”. Both groups
contain diatoms with taxonomic problems, e.g. Staurosira, Staurosirella genera and
other fragilarioids. This approach allowed us to make paleo-ecological reconstruction
on (1) rough taxonomic data and (2) apply trait-based methods. Diatom assemblage’s
zones were defined by CONISS clustering method, validated by the broken stick model.
Though the planktonic trait (referring the high lake level) is insignificant (< 5%)
in most of the studied record, but some peaks (>35%) point to high water level. The
most recent trend of increasing number of planktonic diatoms is hypothesized to be
due to the recent global warming. We demonstrated that traits are a good alternative
to time and expertise demanding species-level determination of diatoms, thus a quick
method is found for paleo-ecological reconstructions, while the photo-base good for
detailed taxonomic work at a future time.
