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 ; seebibliography).
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 :
The 3 samples collected in 2011 have allowed to list 53 taxa belonging to the genus Mastogloia (seelist 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 :
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.
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).