Marine benthic diatoms from Attica 

(Greece, Aegean Sea, sublittoral zone)


Collection of the samples

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 ; see bibliography).

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 : 57 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 :

Genera Amphora to Cocconeis
Several non-identified taxa are presented in :

Non-identified taxa

The genus Mastogloia Thwaites ex WM Smith :
The three samples have allowed to list 57 taxa belonging to the genus Mastogloia  (see liste of taxa). These taxa represent 30 % of the whole of the collected taxa. Thirteen Mastogloia taxa were not identified.

Fifteen taxa among the 44 identified taxa are also present in Dalmatie, Sardegna et Crete. One to four taxa (a total of 17) are present in only one or two of these 3 countries.
Only one non-identified Mastogloia taxa (M. sp. C) is also present in the 3 other countries, and only an other one is present in the French Lesser Antilles (M. sp. 15).

Some of the 57 Mastogloia taxa are presented in :

Genus Mastogloia (1)
Genus Mastogloia (2)
Genus Mastogloia (3)

Conclusions :

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 649 taxa (220 were not identified), was listed in the samples collected in Sardegna, in Dalmatie, in Greece and in Crete (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 and Sardegna, we have listed a total of 104 Mastogloia taxa  (see list Mastogloia from the Méditerranean Sea). Twenty eight among these taxa were not determined; six among them (identified by a number ) were also present in the French Lesser Antilles, while 22 others (identified by a letter) were present only in the mediterranean investigated countries.

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