Marine benthic diatoms from Crete

(Mediterranean Sea, sublittoral zone)


Collection of the samples

Three samples were collected by schnorkelling at the beginning of October 2011, at the north-east of the island, northward of Agios Nicolaos (35° 14'21.32" N, 25° 44' 06.80 E) between 3 and 5 meters deep.
One sample was collected at the end of May 2019, at the north-west of the island, westward of Chania, at Agioi Apostoli (35° 30' 55.36 N, 23° 58' 42?12 E), bertween 2 and 3.5 meters deep.
The surface of the sediment was scraped on a thickness of 3-4 mm using 50 ml Falcon tubes. 
After dilution with 0.5 volume of sea water, the samples were shaken deeply and the diatoms were separated from the sediment by 2 or 3 differential sedimentations, then fixed with acidic Lugol solution. The frustules were treated and prepared according to Loir (2004a and 2004b ; see bibliography).

Composition of the collected diatom populations 

The analysis of the 3 samples collected in 2011 has allowed to list 344 taxa, représenting 60 genera.  Only 79 taxa belonging to 23 genera were found in the sample collected in 2019.

A total of 380 taxa belonging to 64 genera was found in the four samples (see list of taxa).

Ninety six taxa were not identified and the genus of 4 taxa was not determined.

The most represented genera in the 3 first samples are :

Genus Mastogloia : 53 taxa,

Genus Nitzschia : 47 taxa,
Genera Amphora and Halamphora: 38 taxa,
Genus Navicula : 34 taxa,
Genus Cocconeis: 25 taxa,
Genus Diploneis : 17 taxa,
Genus Lyrella : 10 taxa,
Genus Pleurosigma : 8 taxa,
Genus Licmophora : 7 taxa.

The most represented genera in the fourth sample are:

Genus Navicula : 16 taxa,
Genus Nitzschia : 16 taxa,
Genera Amphora and Halamphora : 13 taxa.

Many taxa have measurements near or below the inferior limit given by the diagnoses.

Pictures of some of the collected species are presented in  :

Genera Achnanthes à Amphora
Genera Ardissonia à Cocconeis
Genera Cylindrotheca à Licmophora
Genera Luticola à Navicula
Genus Nitzschia
Genera Opephora à Toxonidea

Several not identified taxa are presented in :

Non-identified taxa 1
Non-identified taxa 2

The genus Mastogloia Thwaites ex WM Smith :

The 3 samples collected in 2011 have allowed to list 53 taxa belonging to the genus Mastogloia  (see list of taxa). Seven taxa  have not been identified. Only 2 taxa, already found in 2011, were present in the sample collected in 2019.

 Forty four taxa are also present in the sub-littoral zone of the French Lesser Antilles. Four among the 7 non-identified Mastogloia taxa (M. sp. cf. exilis (named M. sp. 6), M. sp.3, M. sp. 8 and M. sp. 17) are  present in the sub-littoral zone of the French Lesser Antilles.

The valves of twenty six identified Mastogloia taxa have measurements near or below the inferior limits given by the diagnoses.

Some of the 53 Mastogloia taxa are presented in :

Genus Mastogloia 1
Genus Mastogloia 2

Conclusions :

The four samples collected in a very limited zone of the littoral of Crete have allowed  to establish a probably incomplete inventory of the diatom taxa present in the first meters of the sub-littoral zone on this coast. Nevertheless, they allow to highlight 1) a high specific diversity and 2) the presence of numerous taxa belonging to the genus Mastogloia.

A total of 790 taxa (254 were not identified), was listed in the samples collected in Sardegna, in Dalmatia, in Greece, in Crete, at Corfu and at Menorca (list diatoms from the Mediterranean Sea). In the whole of the samples collected on the littoral of these six countries, we have listed a total of 102 Mastogloia taxa (see A check-list of the Mastogloia species from the Mediterranean area and  list Mastogloia from the Méditerranean Sea)

It would be interesting to know if the presence of some diatom species does not result from a migration by the Suez canal, from the Red Sea to the Mediterranean Sea (this phenomenon bears the name of lesseptian migration).

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