Coastal ecology and palaeoecology of the Baltic and adjacent seas
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Diatom taxonomy

High quality and detailed taxonomy is a prerequisite in the formation of reliable training sets. This becomes even more important when multiple analysts enumerate samples that will later be merged together. Within the MOLTEN and DEFINE projects the five diatom analysts work closely together and use slide exchanges, cross counting exercises and this web site as forums to further taxonomic harmonisation.

One of the original tools to be developed from these projects were the publicly available transfer functions to reconstruct nutrient histories based on counts that other diatom analysts might have made. For certain groups of taxa the demarcation of individual species is difficult, and accordingly, individual ideas of the species concept for taxa can vary widely. Such inconsistencies can affect the reliability of the results of transfer functions. In an attempt to mitigate such affects, a decision was taken to create aggregates for difficult species groups, where borders between species might be blurred and vary between the different analysts. The merges to create the aggregates are performed by a relational database, leaving each analyst free to enumerate samples at the taxonomic level they are comfortable with, but ensuring all samples are harmonised according to the agreed taxonomy. Formatting of other people’s count data to be in accordance with the MOLTEN and DEFINE taxonomic protocols is made available within the transfer function tool.

The aggregates (which all include at least two different species) are shown in the table below. It should be stressed that inclusion of a species in an aggregate does not indicate that the analysts disagree with the definition or validity of that species, the use of aggregates is purely practical.

There are other instances where varieties are not distinguished from each other, and all are reported under the nominate name, these instances are given here:

  • Cocconeis placentula includes C. placentula, C. Placentula v. euglypta, C. placentula v. lineata and C. Placentula v. pseudolineata
  • Denticula tenuis includes D. tenuis and D. tenuis v. crassula
  • Dimeregramma minor includes D. minor and D. minor v. nanum
  • Diploneis smithii includes D. smithii and D. smithii v. rhombica
  • Fragilaria capucina includes F. capucina, F. capucina v. gracilis and F. capucina v. mesolepta
  • Gomphonema olivaceum includes G. olivaceum and G. olivaceum v. salinarum
  • Melosira lineata includes M. lineata, M. lineata v. juergensii and M. lineata v. orichalcea
  • Pseudostaurosira brevistriata includes P. brevistriata and P. brevistriata v. inflata

A final word on the pictures from this website, more are indeed on their way to being made publicly available. In the meantime the references we give to floras can be used as a guide to the species concepts adopted by these projects.

Genera browse

This page lists all genera which have species with a maximum abundance >1% and found in more than one site.
Log in for full access to the database.
Click on a name to view a list of species found.

GenusNGenusNGenusN
Achnanthes11Diploneis9Pinnularia3
Achnanthidium1Encyonema1Plagiogramma1
Actinocyclus2Encyonopsis1Plagiogrammopsis3
Actinoptychus1Entomoneis2Plagiotropis1
Amphora14Epithemia3Planothidium2
Anaulus1Eunotia1Pleurosigma1
Astartiella1Fallacia11Porosira1
Asterionella1Fragilaria12Psammothidium1
Aulacoseira6Fragilariforma1Pseudo-Nitzschia1
Bacillaria1Fragilariopsis1Pseudostaurosira1
Berkeleya1Frustulia1Reimeria1
Biremis2Glyphodesmis2Rhabdonema1
Brachysira2Gomphonemopsis3Rhaphoneis1
Brockmanniella1Grammatophora1Rhoicosphenia1
Campylodiscus1Gyrosigma8Rhopalodia2
Catenula1Haslea1Stauroneis1
Cavinula1Hyalodiscus1Staurosira5
Cerataulina1Karayevia2Staurosirella3
Cocconeis14Martyana3Stephanodiscus5
Coscinodiscus2Mastogloia3Surirella1
Ctenophora1Melosira5Tabellaria1
Cyclostephanos1Minidiscus1Tabularia1
Cyclotella10Navicula55Thalassionema1
Cymatosira1Nitzschia23Thalassiosira22
Cymbella2Odontella2Trachyneis1
Delphineis2Opephora7Tryblionella6
Diatoma2Paralia1Unknown12
Dickieia1Pauliella1
Dimeregramma1Petroneis1