Three
samples were collected by schnorkelling between 3 and 4 meters deep, at the beginning of October 2013, at 4
km southward of
Marathon (38° 06'15.29" N, 23° 58 51.70" E; 2 samples) and at Egine Island (37° 44'52.87 N,23° 25'28.72 E;
1 sample). 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 populations :
The analysis of the 3 samples has allowed to list a total of 190 taxa, belonging to 44 genera (see list of taxa). Twenty seven genera were
represented by only one taxus. Thirty nine taxa were not identified, 13 of which belong to the genus Mastogloia et 11 belong to the genus Navicula. The genus of 1 taxa was not determined.
The most represented genera are :
Genus Mastogloia : 51 taxa, Genus Navicula : 19 taxa,
Genus Amphora (and Halamphora): 18 taxa, Genus Nitzschia : 13 taxa, Genus Diploneis : 12 taxa,
Genus Cocconeis: 10 taxa, Genus Pleurosigma : 5 taxa,
Genus Lyrella : 5 taxa.
Many taxa have measurements near or below the inferior limit indicated by the diagnoses.
Pictures of some of the collected species are presented in :
The three samples have allowed to list 51 taxa belonging to the genus Mastogloia (seeliste of taxa). These taxa represent 30 % of the whole of the collected taxa. Four Mastogloia taxa were not
identified. Only one non-identified Mastogloia taxa (M. sp. 15) is also
present in the French Lesser Antilles.
Some of the 51 Mastogloia taxa are presented in :
The
3 samples collected at the beginning of October in a very
restricted zone of the littoral of Greece have allowed to establish a
likely incomplete inventory of the benthic diatoms present in the first
meters of the sub-littoral zone of this coast. Nevertheless, they
allowed to evidence the great diversity of the diatom populations in
this zone, while in the supralittoral and eulittoral zones of the
Saronikos Gulf about three time less marine taxa (planktonic, benthic and brackish-marine) have been identified (Economou-Amilli 1980). In these zones the specific composition of the diatom populations differs conspicuously : only 17 taxa among the 190 taxa that we have collected have been identified by Economou-Amilli (1980).
The diatom population present in both greek stations
present less species than those that we have collected in Sardegna (271
taxa), Crete (344 taxa)
et Dalmatie (299 taxa). A total of 790 taxa (254 were not identified), was listed in the samples collected in Sardegna, in Dalmatie, in Greece, in Crete, in Corfu and in Menorca (list diatoms Mediterranean Sea).
Our inventory for the genus Mastogloia evidences the richness and diversity of this genus in the first meters of the sub-littoral zone on the coast of Attique (57 taxa),
as it is also the case on the coasts of Sardegna (48 taxa), Crete ( 67 taxa) and Dalmatia (55
taxa). Our results suggest that in the first meters of the mediterranean sub-littoral zone the specific diversity of the genus Mastogloia is far higher than in the littoral aquatic systems (Spain : Tomas 1982; Turkey : Colak Sabanci 2013) and in the eulittoral zone (Saronikos Gulf : only one taxus; Economou-Amilli 1980). In
the whole of the samples collected on the littoral of Crete, Damatie,
Greece, Sardegna, Corfu and Menorca 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). Twenty among these taxa were not determined.